diff --git "a/raw_rss_feeds/https___arxiv_org_rss_quant_ph.xml" "b/raw_rss_feeds/https___arxiv_org_rss_quant_ph.xml" --- "a/raw_rss_feeds/https___arxiv_org_rss_quant_ph.xml" +++ "b/raw_rss_feeds/https___arxiv_org_rss_quant_ph.xml" @@ -7,3428 +7,1238 @@ http://www.rssboard.org/rss-specification en-us - Wed, 21 Jan 2026 05:00:32 +0000 + Fri, 23 Jan 2026 05:00:05 +0000 rss-help@arxiv.org - Wed, 21 Jan 2026 00:00:00 -0500 + Fri, 23 Jan 2026 00:00:00 -0500 Saturday Sunday - $\ell$-Multiranks of Multipartite Quantum States via Tensor Flattening: A Mathematica Codebase - https://arxiv.org/abs/2601.11551 - arXiv:2601.11551v1 Announce Type: new -Abstract: We present a Mathematica codebase for computing $\ell$-multilinear ranks ($\ell$-multiranks) of multiqudit quantum states using tensor-flattening techniques. By calculating the ranks of all bipartition-induced matricizations, the method provides an efficient criterion for detecting Genuine Multipartite Entangled (GME) states in systems with local dimension $d$. The code automatically generates all required tensor reshapes and outputs the full $\ell$-multirank profile, offering a practical tool for characterizing entanglement in high-dimensional multiqudit systems. - oai:arXiv.org:2601.11551v1 + Precision limit under weak-coupling with ancillary qubit + https://arxiv.org/abs/2601.15354 + arXiv:2601.15354v1 Announce Type: new +Abstract: We propose a measurement-based quantum metrology protocol in a composite model, where the probe system (a spin ensemble) is coupled to an ancillary two-level system (qubit) with a general Heisenberg XXZ interaction. With an optimized and weak probe-ancilla coupling strength and a proper duration of joint evolution, the two parallel evolution paths of the probe system induced by the unconditional measurement on qubit can transform an eigenstate of the collective angular momentum operator of spin ensemble to be a two-component state with a large distance in eigenspace. The quantum Fisher information about the phase encoded in the probe system of polarized states or their superposition, that could be relaxed to mixed states, can therefore manifest an exact or asymptotic quadratic scaling with respect to the probe size (spin number) $N$. The quadratic scaling behavior is found to be insensitive to the imperfect encoding operator and coupling strength. By virtue of the parity detection on the ancillary qubit or the probe system, the phase sensitivity can approach the Heisenberg limit. We suggest that the unconditional measurement on qubit could become an efficient resource to replace Greenberger-Horne-Zeilinger-like states and squeezing Hamiltonian for exceeding the standard quantum limit in metrology precision. + oai:arXiv.org:2601.15354v1 quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 + Fri, 23 Jan 2026 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Masoud Gharahi + Peng Chen, Jun Jing - QDsiM: A Noise-Aware Simulation Toolkit for Quantum Diamond Microscope - https://arxiv.org/abs/2601.11649 - arXiv:2601.11649v1 Announce Type: new -Abstract: The nitrogen-vacancy (NV) center in diamond is a leading solid-state platform for room-temperature quantum magnetometry owing to its long spin coherence times, optical spin initialization and readout, and high sensitivity to magnetic, electric, and thermal perturbations. As NV-based optically detected magnetic resonance (ODMR) systems transition from controlled laboratory environments toward portable and field-deployable sensors, a detailed understanding of realistic noise sources and experimental imperfections becomes essential for optimizing performance and sensitivity. In this work, we present a comprehensive simulation framework, i.e., a digital twin, for continuous-wave wide-field ODMR in NV-center ensembles. The model is built upon a physically consistent seven-level description of the NV center and incorporates a broad range of experimentally relevant noise and imperfection mechanisms as modular, parameterized components. These include laser and microwave amplitude fluctuations, microwave phase noise, uncertainty in the NV gyromagnetic ratio, spin dephasing, temperature-induced shifts of the ground-state zero-field splitting, surface-induced magnetic field perturbations, and photon shot noise. Power broadening and contrast degradation arising from optical and microwave driving are captured self-consistently through linewidth calculations. Also, the spatial inhomogeneity is modeled via a Gaussian laser intensity profile across the sensing region... - oai:arXiv.org:2601.11649v1 + USDs: A universal stabilizer decoder framework using symmetry + https://arxiv.org/abs/2601.15361 + arXiv:2601.15361v1 Announce Type: new +Abstract: Quantum error correction is indispensable to achieving reliable quantum computation. When quantum information is encoded redundantly, a larger Hilbert space is constructed using multiple physical qubits, and the computation is performed within a designated subspace. When applying deep learning to the decoding of quantum error-correcting codes, a key challenge arises from the non-uniqueness between the syndrome measurements provided to the decoder and the corresponding error patterns that constitute the ground-truth labels. Building upon prior work that addressed this issue for the toric code by re-optimizing the decoder with respect to the symmetry inherent in the parity-check structure, we generalize this approach to arbitrary stabilizer codes. In our experiments, we employed multilayer perceptrons to approximate continuous functions that complement the syndrome measurements of the Color code and the Golay code. Using these models, we performed decoder re-optimization for each code. For the Color code, we achieved an improvement of approximately 0.8% in decoding accuracy at a physical error rate of 5%, while for the Golay code the accuracy increased by about 0.1%. Furthermore, from the evaluation of the geometric and algebraic structures in the continuous function approximation for each code, we showed that the design of generalized continuous functions is advantageous for learning the geometric structure inherent in the code. Our results also indicate that approximations that faithfully reproduce the code structure can have a significant impact on the effectiveness of reoptimization. This study demonstrates that the re-optimization technique previously shown to be effective for the Toric code can be generalized to address the challenge of label degeneracy that arises when applying deep learning to the decoding of stabilizer codes. + oai:arXiv.org:2601.15361v1 quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 + cs.LG + Fri, 23 Jan 2026 00:00:00 -0500 new - http://creativecommons.org/licenses/by-nc-sa/4.0/ - Satyam Pandey, Abhimanyu Magapu, Prabhat Anand, Ankit Khandelwal, M. Girish Chandra + http://creativecommons.org/licenses/by-nc-nd/4.0/ + Hoshitaro Ohnishi, Hideo Mukai - Experimental observation of dynamical blockade between transmon qubits via ZZ interaction engineering - https://arxiv.org/abs/2601.11714 - arXiv:2601.11714v1 Announce Type: new -Abstract: We report the experimental realization of strong longitudinal (ZZ) coupling between two superconducting transmon qubits achieved solely through capacitive engineering. By systematically varying the qubit frequency detuning, we measure cross-Kerr inter-qubit interaction strengths ranging from 10 MHz up to 350 MHz, more than an order of magnitude larger than previously observed in similar capacitively coupled systems. In this configuration, the qubits enter a strong-interaction regime in which the excitation of one qubit inhibits that of its neighbor, demonstrating a dynamical blockade mediated entirely by the engineered ZZ coupling. Circuit quantization simulations accurately reproduce the experimental results, while perturbative models confirm the theoretical origin of the energy shift as a hybridization between the computational states and higher-excitation manifolds. We establish a robust and scalable method to access interaction-dominated physics in superconducting circuits, providing a pathway towards solid-state implementations of globally controlled quantum architectures and cooperative many-body dynamics. - oai:arXiv.org:2601.11714v1 + The computational two-way quantum capacity + https://arxiv.org/abs/2601.15393 + arXiv:2601.15393v1 Announce Type: new +Abstract: Quantum channel capacities are fundamental to quantum information theory. Their definition, however, does not limit the computational resources of sender and receiver. In this work, we initiate the study of computational quantum capacities. These quantify how much information can be reliably transmitted when imposing the natural requirement that en- and decoding have to be computationally efficient. We focus on the computational two-way quantum capacity and showcase that it is closely related to the computational distillable entanglement of the Choi state of the channel. This connection allows us to show a stark computational capacity separation. Under standard cryptographic assumptions, there exists a quantum channel of polynomial complexity whose computational two-way quantum capacity vanishes while its unbounded counterpart is nearly maximal. More so, we show that there exists a sharp transition in computational quantum capacity from nearly maximal to zero when the channel complexity leaves the polynomial realm. Our results demonstrate that the natural requirement of computational efficiency can radically alter the limits of quantum communication. + oai:arXiv.org:2601.15393v1 quant-ph - cond-mat.mes-hall - cond-mat.other - cond-mat.supr-con - Wed, 21 Jan 2026 00:00:00 -0500 + cs.CC + cs.CR + cs.IT + math.IT + Fri, 23 Jan 2026 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Marco Riccardi, Aviv Glezer Moshe, Guido Menichetti, Riccardo Aiudi, Carlo Cosenza, Ashkan Abedi, Roberto Menta, Halima Giovanna Ahmad, Diego Nieri Orfatti, Francesco Cioni, Davide Massarotti, Francesco Tafuri, Vittorio Giovannetti, Marco Polini, Francesco Caravelli, Daniel Szombati + Johannes Jakob Meyer, Jacopo Rizzo, Asad Raza, Lorenzo Leone, Sofiene Jerbi, Jens Eisert - Entanglement Distribution over a Polarization-Stabilized Aerial Fiber - https://arxiv.org/abs/2601.11753 - arXiv:2601.11753v1 Announce Type: new -Abstract: We experimentally demonstrate the distribution of polarization-entangled photons across a 62-km, partially-aerial fiber. With polarization stabilization applied to the fiber link, we achieve a photon pair rate of approximately 1500 per second and observe a CHSH inequality violation with S=2.34. - oai:arXiv.org:2601.11753v1 + Quadratic tensors as a unification of Clifford, Gaussian, and free-fermion physics + https://arxiv.org/abs/2601.15396 + arXiv:2601.15396v1 Announce Type: new +Abstract: Certain families of quantum mechanical models can be described and solved efficiently on a classical computer, including qubit or qudit Clifford circuits and stabilizer codes, free-boson or free-fermion models, and certain rotor and GKP codes. We show that all of these families can be described as instances of the same algebraic structure, namely quadratic functions over abelian groups, or more generally over (super) Hopf algebras. Different kinds of degrees of freedom correspond to different "elementary" abelian groups or Hopf algebras: $\mathbb{Z}_2$ for qubits, $\mathbb{Z}_d$ for qudits, $\mathbb{R}$ for continuous variables, both $\mathbb{Z}$ and $\mathbb{R}/\mathbb{Z}$ for rotors, and a super Hopf algebra $\mathcal F$ for fermionic modes. Objects such as states, operators, superoperators, or projection-operator valued measures, etc, are tensors. For the solvable models above, these tensors are quadratic tensors based on quadratic functions. Quadratic tensors with $n$ degrees of freedom are fully specified by only $O(n^2)$ coefficients. Tensor networks of quadratic tensors can be contracted efficiently on the level of these coefficients, using an operation reminiscent of the Schur complement. Our formalism naturally includes models with mixed degrees of freedom, such as qudits of different dimensions. We also use quadratic functions to define generalized stabilizer codes and Clifford gates for arbitrary abelian groups. Finally, we give a generalization from quadratic (or 2nd order) to $i$th order tensors, which are specified by $O(n^i)$ coefficients but cannot be contracted efficiently in general. + oai:arXiv.org:2601.15396v1 quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 + math-ph + math.MP + Fri, 23 Jan 2026 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Yicheng Shi, Jing Su, Anouar Rahmouni, Pranish Shrestha, Mheni Merzouki, Gabriel Bello Portmann, Anne Lazenby, Mael Flament, Mehdi Namazi, Abdella Battou, Oliver Slattery, Thomas Gerrits + Andreas Bauer, Seth Lloyd - Generalized Shiraishi--Mori construction is exhaustive for ferromagnetic quantum many-body scars - https://arxiv.org/abs/2601.11806 - arXiv:2601.11806v1 Announce Type: new -Abstract: Quantum many-body scars (QMBS) constitute a subtle violation of ergodicity through a set of non-thermal eigenstates, referred to as scar states, which are embedded in an otherwise thermal spectrum. In a broad class of known examples, these scar states admit a simple interpretation: they are magnon excitations of fixed momentum on top of a ferromagnetic background. In this paper we prove that any Hamiltonian hosting such ``ferromagnetic scar states'' necessarily admits a structural decomposition into a Zeeman term and an ``annihilator'' that annihilates the entire scar manifold. Moreover, we show that this annihilator must itself decompose into a sum of terms built from local projectors that locally annihilate the scar states. This architecture is closely related to the Shiraishi--Mori construction, and our main theorem establishes that an appropriate generalization of that construction is in fact essentially exhaustive for this class of scar states. - oai:arXiv.org:2601.11806v1 + Dissipative Quantum Dynamics in Static Network with Different Topologies + https://arxiv.org/abs/2601.15439 + arXiv:2601.15439v1 Announce Type: new +Abstract: We investigate the dissipative dynamics of quantum population and coherence among different network topologies of a quantum network using a quantum spin model coupled to a thermal bosonic reservoir. Our study proceeds in two parts. First, we analyze a small network of Ising spins embedded in a large dissipative bath, modeled via the Lindblad master equation, where temperature arises naturally from system-bath coupling. This approach reveals how network topology shapes quantum dissipative dynamics, providing a basis for controlling quantum coherence through tailored network structures. Second, we propose a mean-field approach that extends the network to larger scales and captures dissipative dynamics in large-scale networks, connecting network topology to quantum coherence in complex systems and revealing the sensitivity of quantum coherence to network structure. Our results highlight how dissipative quantum dynamics depend on network topology, providing insight into the coherent dynamics of entangled states in networks. These results may be extended to dynamics in complex systems such as opinion propagation in social models, epidemiology, and various condensed-phase and biological systems. + oai:arXiv.org:2601.15439v1 quant-ph - cond-mat.str-el - math-ph - math.MP - Wed, 21 Jan 2026 00:00:00 -0500 + cond-mat.stat-mech + Fri, 23 Jan 2026 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Keita Omiya + Wei-Yang Liu, Hsuan-Wei Lee - Scalable and telecom single-erbium system with record-long room-temperature quantum coherence - https://arxiv.org/abs/2601.11879 - arXiv:2601.11879v1 Announce Type: new -Abstract: Eliminating cryogenic operating requirements while preserving microsecond-scale quantum coherence and enabling CMOS scalability remains a central challenge for telecom quantum technologies. Addressing this, we introduce a CMOS-compatible quantum system comprising single-erbium-(Er)-ion qudits (five-level systems) operating across the visible and telecom C-band. Through innovative nanofabrication, we achieve self-aligned ion placement, enabling spatial isolation of single-Er ions and suppressing dephasing. We realize individually addressable single-Er-devices with record-long optical coherence times in the telecom C-band exceeding 500 {\mu}s at ambient conditions, a performance previously limited to vacuum conditions at temperatures over 900 times lower. Furthermore, we present the first demonstration of background-free, upconversion-enabled single-photon Er-emissions providing coherent, high-contrast optical readouts. This work showcases the first room-temperature single-Er-qudit system with unprecedented properties enabling next-generation cryogen-free telecom quantum technologies. - oai:arXiv.org:2601.11879v1 + Check-weight-constrained quantum codes: Bounds and examples + https://arxiv.org/abs/2601.15446 + arXiv:2601.15446v1 Announce Type: new +Abstract: Quantum low-density parity-check (qLDPC) codes can be implemented by measuring only low-weight checks, making them compatible with noisy quantum hardware and central to the quest to build noise-resilient quantum computers. A fundamental open question is how constraints on check weight limit the achievable parameters of qLDPC codes. Here, we study stabilizer and subsystem codes with constrained check weight, combining analytical arguments with numerical optimization to establish strong upper bounds on their parameters. We show that stabilizer codes with checks of weight at most three cannot have nontrivial distance. We also prove tight tradeoffs between rate and distance for broad families of CSS stabilizer and subsystem codes with checks of weight at most four and two, respectively. Notably, our bounds are applicable to general qLDPC codes, as they rely only on check-weight constraints without assuming geometric locality or special graph connectivity. In the finite-size regime, we derive numerical upper bounds using linear programming techniques and identify explicit code constructions that approach these limits, delineating the landscape of practically relevant qLDPC codes with tens or hundreds of physical qubits. + oai:arXiv.org:2601.15446v1 quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 + Fri, 23 Jan 2026 00:00:00 -0500 new - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Alex Kaloyeros, Natasha Tabassum, Spyros Gallis + http://creativecommons.org/licenses/by/4.0/ + Lily Wang, Andy Zeyi Liu, Ray Li, Aleksander Kubica, Shouzhen Gu - Indoor Occupancy Classification using a Compact Hybrid Quantum-Classical Model Enabled by a Physics-Informed Radar Digital Twin - https://arxiv.org/abs/2601.11929 - arXiv:2601.11929v1 Announce Type: new -Abstract: Indoor occupancy classification enables privacy-preserving monitoring in settings such as remote elder care, where presence information helps triage alarms without cameras or wearables. Radar suits this role by sensing motion through occlusions and in darkness. Modern deep-learning pipelines are the standard for interpreting radar returns effectively; however, they are often parameter-heavy and sensitive at low signal-to-noise ratios (SNR), motivating compact alternatives like Hybrid Quantum Neural Networks (HQNNs). A two-qubit HQNN is benchmarked against convolutional neural networks (CNNs) using a physics-informed 60GHz digital twin and real radar measurements under matched training protocols. In clean conditions, the HQNN achieves high accuracy (99.7% synthetic; 97.0% real) with up to 170x fewer parameters (0.066M). Its parameter efficiency is shown to be structural, as an ablation of the parameterized quantum circuit (PQC) causes sharp performance drops on real data (to 68.5% and 31.5% for the control heads). A domain-dependent sensitivity emerges under additive-noise evaluation, where the HQNN begins recovery earlier in synthetic data while CNNs recover more steeply and peak higher on real measurements. In label-fraction ablations, CNNs prove more sample-efficient on real Range-Doppler Maps (RDMs), with the performance gap being most pronounced (at 50% labels, BA 0.89-0.99 vs. HQNN 0.75). On synthetic data, this gap narrows significantly, largely vanishing by the 50% label mark. Overall, the HQNN's value lies in parameter efficiency and a compact inductive bias that shapes its distinct sensitivity profile; this work establishes a rigorous baseline for hybrid quantum models in privacy-preserving radar occupancy sensing. - oai:arXiv.org:2601.11929v1 + NWQWorkflow: The Northwest Quantum Workflow + https://arxiv.org/abs/2601.15521 + arXiv:2601.15521v1 Announce Type: new +Abstract: This whitepaper presents NWQWorkflow, an end-to-end workflow for quantum application development, compilation, error correction, benchmarking, numerical simulation, control, and execution on a prototype superconducting testbed. NWQWorkflow integrates NWQStudio (programming GUI environment), NWQASM (intermediate representation), QASMTrans (compiler), NWQEC (quantum error correction), QASMBench (benchmarking and characterization), NWQSim (HPC simulation), NWQLib (algorithm library), NWQData (data sets), NWQControl (quantum control), and NWQSC (superconducting testbed). The system enables closed-loop software-hardware co-design and reflects the past eight years of quantum computing research the author has led at PNNL (2018-2026). By releasing most software components as open source or planning their open-source availability, we aim to cultivate a collaborative quantum information science (QIS) ecosystem and support the transition toward a scalable quantum supercomputing era. + oai:arXiv.org:2601.15521v1 quant-ph - eess.SP - Wed, 21 Jan 2026 00:00:00 -0500 + Fri, 23 Jan 2026 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Sebastian Ratto, Ahmed N. Sayed, Neda Rojhani, Arien P. Sligar, Jose R. Rosas-Bustos, Saasha Joshi, Luke C. G. Govia, Omar M. Ramahi, George Shaker + Ang Li - Impact of Circuit Depth versus Qubit Count on Variational Quantum Classifiers for Higgs Boson Signal Detection - https://arxiv.org/abs/2601.11937 - arXiv:2601.11937v1 Announce Type: new -Abstract: High-Energy Physics (HEP) experiments, such as those at the Large Hadron Collider (LHC), generate massive datasets that challenge classical computational limits. Quantum Machine Learning (QML) offers a potential advantage in processing high-dimensional data; however, finding the optimal architecture for current Noisy Intermediate-Scale Quantum (NISQ) devices remains an open challenge. This study investigates the performance of Variational Quantum Classifiers (VQC) in detecting Higgs Boson signals using the ATLAS Higgs Boson Machine Learning Challenge 2014 experiment dataset. We implemented a dimensionality reduction pipeline using Principal Component Analysis (PCA) to map 30 physical features into 4-qubit and 8-qubit latent spaces. We benchmarked three configurations: (A) a shallow 4-qubit circuit, (B) a deep 4-qubit circuit with increased entanglement layers, and (C) an expanded 8-qubit circuit. Experimental results demonstrate that increasing circuit depth significantly improves performance, yielding the highest accuracy of 56.2% (Configuration B), compared to a baseline of 51.9%. Conversely, simply scaling to 8 qubits resulted in a performance degradation to 50.6% due to optimization challenges associated with Barren Plateaus in the larger Hilbert space. These findings suggest that for near-term quantum hardware, prioritizing circuit depth and entanglement capability is more critical than increasing qubit count for effective anomaly detection in HEP data. - oai:arXiv.org:2601.11937v1 + A Sublinear-Time Quantum Algorithm for High-Dimensional Reaction Rates + https://arxiv.org/abs/2601.15523 + arXiv:2601.15523v1 Announce Type: new +Abstract: The Fokker-Planck equation models rare events across sciences, but its high-dimensional nature challenges classical computers. Quantum algorithms for such non-unitary dynamics often suffer from exponential {decay in} success probability. We introduce a quantum algorithm that overcomes this for computing reaction rates. Using a sum-of-squares representation, we develop a Gaussian linear combination of Hamiltonian simulations (Gaussian-LCHS) to represent the non-unitary propagator with $O\left(\sqrt{t\|H\|\log(1/\epsilon)}\right)$ queries to its block encoding. Crucially, we pair this with {a} novel technique to directly estimate matrix elements without exponential decay. For $\eta$ pairwise interacting particles discretized with $N$ plane waves per degree of freedom, we estimate reactive flux to error $\epsilon$ using $\widetilde{O}\left((\eta^{5/2}\sqrt{t\beta}\alpha_V + \eta^{3/2}\sqrt{t/\beta}N)/\epsilon\right)$ quantum gates, where $\alpha_V = \max_{r}|V'(r)/r|$. For non-convex potentials, the {sharpest classical} worst-case analytical bounds to simulate the related overdamped Langevin {equation} scale as $O(te^{\Omega(\eta)}/\epsilon^4)$. This {implies} an exponential separation in particle number $\eta$, a quartic speedup in $\epsilon$, and quadratic speedup in $t$. While specialized classical heuristics may outperform these bounds in practice, this demonstrates a rigorous route toward quantum advantage for high-dimensional dissipative dynamics. + oai:arXiv.org:2601.15523v1 quant-ph - cs.LG - hep-ex - Wed, 21 Jan 2026 00:00:00 -0500 + Fri, 23 Jan 2026 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - 10.5281/zenodo.18096724 - Fatih Maulana + Tyler Kharazi, Ahmad M. Alkadri, Kranthi K. Mandadapu, K. Birgitta Whaley - Contour-integral based quantum eigenvalue transformation: analysis and applications - https://arxiv.org/abs/2601.11959 - arXiv:2601.11959v1 Announce Type: new -Abstract: Eigenvalue transformations appear ubiquitously in scientific computation, ranging from matrix polynomials to differential equations, and are beyond the reach of the quantum singular value transformation framework. In this work, we study the efficiency of quantum algorithms based on contour integral representation for eigenvalue transformations from both theoretical and practical aspects. Theoretically, we establish a complete complexity analysis of the contour integral approach proposed in [Takahira, Ohashi, Sogabe, and Usuda. Quant. Inf. Comput., 22, 11\&12, 965--979 (2021)]. Moreover, we combine the contour integral approach and the sampling-based linear combination of unitaries to propose a quantum algorithm for estimating observables of eigenvalue transformations using only $3$ additional qubits. Practically, we design contour integral based quantum algorithms for Hamiltonian simulation, matrix polynomials, and solving linear ordinary differential equations, and show that the contour integral algorithm can outperform all the existing quantum algorithms in the case of solving asymptotically stable differential equations. - oai:arXiv.org:2601.11959v1 + Bidirectional teleportation using scrambling dynamics: a practical protocol + https://arxiv.org/abs/2601.15536 + arXiv:2601.15536v1 Announce Type: new +Abstract: We show that quantum information scrambling can enable a generic SWAP gate between collective degrees of freedom in systems without universal local control. Our protocol combines the Hayden-Preskill recovery scheme, associated with the black hole information paradox, with quantum teleportation and runs them in parallel and in opposite directions, enabling bidirectional exchange of quantum states through global interactions alone. This approach cleanly distinguishes the roles of information spreading, entanglement, and chaos for enabling both coherent state transfer and recovery. We propose an experimental realization using the Dicke model, which can be realized in cavity-QED and trapped-ion platforms, highlighting the utility of holography in designing practical quantum gates. + oai:arXiv.org:2601.15536v1 quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 + cond-mat.stat-mech + hep-th + nlin.CD + physics.atom-ph + Fri, 23 Jan 2026 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Shan Jiang, Dong An + Amit Vikram, Edwin Chaparro, Muhammad Miskeen Khan, Andrew Lucas, Chris Akers, Ana Maria Rey - Temperature effect on a kicked Tonks-Girardeau gas - https://arxiv.org/abs/2601.12071 - arXiv:2601.12071v1 Announce Type: new -Abstract: It is widely recognized that finite temperatures degrade quantum coherence and can induce thermalization. Here, we study the effect of finite temperature on a kicked Tonks--Girardeau gas, which is known to exhibit many--body dynamical localization and delocalization under periodic and quasiperiodic kicks, respectively. We find that many--body dynamical localization persists at finite--and even high--temperatures, although the coherence of the localized state is further degraded. In particular, we demonstrate a modified effective thermalization of the localized state by considering the initial temperature. Moreover, we show many--body dynamical localization transition at intermediate temperature. Our work extends the study of many--body dynamical localization and delocalization to the finite--temperature regime, providing comprehensive guidance for cold--atom experiments. - oai:arXiv.org:2601.12071v1 + Spectator-transition crosstalk in a spin-3/2 silicon vacancy qudit in silicon carbide revealed by broadband Ramsey interferometry + https://arxiv.org/abs/2601.15559 + arXiv:2601.15559v1 Announce Type: new +Abstract: Color center spins in 4H-SiC offer a rare combination of wafer-scale materials maturity with long spin coherence and chip-level photonics, making them promising building blocks for scalable quantum technologies. In particular, the silicon vacancy hosts an S=3/2 ground state, a native qudit that enables compact encodings and subspace-selective control, but also introduces spectator transitions: short, detuned pulses can coherently drive non-addressed level pairs and create crosstalk. Here we use broadband Ramsey interferometry to reveal and quantify such spectator-transition crosstalk. Experimentally, the Ramsey Fourier spectra display multiple lines beyond the addressed single-quantum transition. Analytically, we map each line to a pairwise energy difference between qudit levels of the rotating-frame Hamiltonian and assign its weight via compact amplitudes set by the prepared state and the microwave pulse parameters, predicting a deterministic six-branch structure. Numerical time-domain propagation with the experimental sampling reproduces the detuning map, and the measured peak positions coincide with the analytic branch lines without frequency fitting. Together these results provide a practical, spectator-aware framework for multilevel control in the silicon vacancy qudit. The approach offers clear guidance to suppress crosstalk or, conversely, to exploit spectator lines, for example as additional constraints for in situ pulse calibration and for phase-sensitive quantum state and process estimation. + oai:arXiv.org:2601.15559v1 quant-ph - cond-mat.quant-gas - Wed, 21 Jan 2026 00:00:00 -0500 + Fri, 23 Jan 2026 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Ang Yang, Yue Chen, Lei Ying + Jun-Jae Choi, Seung-Jae Hwang, Seoyoung Paik, Juhwan Kim, Jawad UI-Hassan, Nguyen Tien Son, Hiroshi Abe, Takeshi Oshima, Jaekwon Suk, Hyeon-Ho Jeong, Dong-Hee Kim, Sang-Yun Lee - Peres-type Criterion of Einstein-Podolsky-Rosen Steering for Two Qubits - https://arxiv.org/abs/2601.12085 - arXiv:2601.12085v1 Announce Type: new -Abstract: Quantum nonlocality manifests in multipartite systems through entanglement, Bell's nonlocality, and Einstein-Podolsky-Rosen (EPR) steering. While Peres's positive-partial-transpose criterion provides a simple and powerful test for entanglement, a comparably elegant spectral criterion for detecting EPR steering remains an open challenge. In this work, we systematically explore whether a Peres-type criterion can be established for EPR steering in the two-qubit system. Focusing on rank-2 (including rank-1) states and the two-qubit Werner state, we analyze the eigenvalues of their partially transposed density matrices and construct a significant steering criterion based on symmetric combinations of these eigenvalues. We prove that this criterion serves as a necessary and sufficient condition for steerability for the Werner state, all two-qubit pure states, all two-qubit rank-2 states. Furthermore, we validate the criterion for higher-rank states (rank-3 and rank-4) and show that the results align with known steering inequalities. Our findings suggest a more unified framework for detecting quantum nonlocality via partial transposition and open avenues for further theoretical and numerical investigations into steering detection. - oai:arXiv.org:2601.12085v1 + Bright Pulsed Squeezed Light for Quantum-Enhanced Precision Microscopy + https://arxiv.org/abs/2601.15565 + arXiv:2601.15565v1 Announce Type: new +Abstract: Squeezed states of light enable enhanced measurement precision by reducing noise below the standard quantum limit. A key application of squeezed light is nonlinear microscopy, where state-of-the-art performance is limited by photodamage and quantum-limited noise. Such microscopes require bright, pulsed light for optimal operation, yet generating and detecting bright pulsed squeezing at high levels remains challenging. In this work, we present an efficient technique to generate high levels of bright picosecond pulsed squeezed light using a $\chi^2$ optical parametric amplification process in a waveguide. We measure $-3.2~\mathrm{dB}$ of bright squeezing with optical power compatible with nonlinear microscopy, as well as $-3.6~\mathrm{dB}$ of vacuum squeezing. Corrected for losses, these squeezing levels correspond to $-15.4^{+2.7}_{-8.7}~\mathrm{dB}$ of squeezing generated in the waveguide. The measured level of bright amplitude pulsed squeezing is to our knowledge the highest reported to date, and will contribute to the broader adoption of quantum-enhanced nonlinear microscopy in biological studies. + oai:arXiv.org:2601.15565v1 quant-ph - math-ph - math.MP - Wed, 21 Jan 2026 00:00:00 -0500 - new - http://creativecommons.org/licenses/by/4.0/ - Yu-Xuan Zhang, Jing-Ling Chen - - - An unexpected theoretical structure that could explain quantum-mechanics postulates like the Born rule and the wave-function reduction - https://arxiv.org/abs/2601.12092 - arXiv:2601.12092v1 Announce Type: new -Abstract: A unique postulate is shown to underly the whole quantum mechanics theory: the invariance of the Heisenberg uncertainty inequality under a group of special nonlinear gauge transformations (NLGT). With this postulate, the quantum mechanics of a free particle is derived from classical mechanics, including the statements of the postulates of quantum mechanics, except for the wave-function-collapse postulate. An explanatory mechanism for the latter postulate is derived by performing an analytical continuation of the NLGTs. This extension results in a Schr\"odinger-bridge process, intertwined under the NLGT with the standard unitary quantum evolution, and revealing non-quantum (or beyond-quantum) phenomena. Mechanisms of that latter kind, like the ones associated to the quantum measurement process, occur in a new space-like dimension and hence are non causal in nature, in opposition to a time evolution. The present exercice focusses on the free particle in order to highlight the features of the performed derivation in the simplest possible way. Work is in progress to extend the performed derivation beyond that simple case. - oai:arXiv.org:2601.12092v1 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 + physics.optics + Fri, 23 Jan 2026 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - L\'eon Brenig, Marc Vincke + Alex Terrasson, Lars Madsen, Joel Grim, Warwick Bowen - Probing multiparameter quantum estimation in the process $e^+e^-\to J/\psi \to \text{B}\bar{\text{B}}$ at BESIII - https://arxiv.org/abs/2601.12097 - arXiv:2601.12097v1 Announce Type: new -Abstract: The quantum Fisher information matrix (QFIM) is the cornerstone of multiparameter quantum metrology. In this work, we investigate multiparameter quantum estimation in baryon-antibaryon (B bar-B) pairs produced via the e+ e- -> J/psi -> B bar-B process at the BESIII experiment, utilizing the symmetric logarithmic derivative (SLD) formalism. Moreover, the QFIM defines the quantum Cramer-Rao bound and dictates the choice of optimal probe states. We compare individual and simultaneous estimation strategies for two key physical parameters: the scattering angle phi and the decay parameter alpha_psi. The estimation variances are found to depend strongly on the explored region of the (phi, alpha_psi) parameter space and to display markedly different temporal dynamics. In general, higher true values of a parameter increase the system's sensitivity, thereby significantly reducing the associated variance. While both variances increase with evolution time, they do so at distinct rates, revealing parameter-dependent information loss driven by environmental decoherence. These findings demonstrate the utility of the QFIM framework for multiparameter quantum estimation in realistic open systems and provide new insights into the ultimate precision limits achievable for hyperon decay parameters. - oai:arXiv.org:2601.12097v1 + Optimized Slice-Phase Control of Mirror Pulse in Cold-Atom Interferometry with Finite Response Time + https://arxiv.org/abs/2601.15586 + arXiv:2601.15586v1 Announce Type: new +Abstract: Atom interferometers require both high efficiency and robust performance in their mirror pulses under experimental inhomogeneities. In this work, we demonstrated that quantum optimal control designed mirror pulse significantly enhance interferometer performance by using novel adaptive sliced structure. Using gradient ascent pulse engineering (GRAPE), optimized mirror pulse for a Mach-Zehnder light-pulse atom interferometer was designed by discretizing the control into non-uniform phase slices. This design broadened the tolerence to experimentally relevant variations in detuning $[-\Omega_0,\Omega_0]$ and Rabi frequency $[0.1\times\Omega_0,1.9\times\Omega_0]$ ($\Omega_0=2\pi\times25$ kHz), while maintaining high transfer efficiency even when the response-time delays up to 1.6 $\rm{\mu s}$. The optimized pulse was found to be robust to coupling inhomogeneity and velocity spread, offering a significant improvement in robustness over conventional pulse. The adaptive pulse slicing method provides a minimalist strategy that reduces experimental complexity while enhancing robustness and scalability, offering an innovative scheme for quantum optimal control in high precision atom interferometry. + oai:arXiv.org:2601.15586v1 quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 + Fri, 23 Jan 2026 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Elhabib Jaloum, Mohamed Amazioug + 10.1103/r62p-d86z + Xueting Fang, Doudou Wang, Kun Yuan, Jie Deng, Qin Luo, Xiaochun Duan, Minkang Zhou, Lushuai Cao, Zhongkun Hu - Quantum interference between spectral bandwidth mismatched photons - https://arxiv.org/abs/2601.12129 - arXiv:2601.12129v1 Announce Type: new -Abstract: Two-photon interference is a cornerstone of photonic quantum technologies. However, its practical implementation in promising hybrid architectures is severely constrained by the requirement of photon wavepacket indistinguishability, in particular, in terms of the photon linewidth and associated time scale. While narrowband filtering can improve interference visibility, it introduces significant photon loss - a critical limitation for applications. Here, we experimentally demonstrate an efficient approach to enable non-classical two-photon interference between spectral-bandwidth mismatched photons using an electro-optic time lens. We increase the visibility of Hong-Ou-Mandel interference between photons of 10-fold spectral bandwidth mismatch by more than 12 times, achieving non-classical two-photon interference visibility without spectral filtering. This result opens the possibility to efficiently integrate quantum systems operating at different time scales for hybrid quantum communication, teleportation, entanglement swapping, distributed sensing, and hybrid quantum computing. - oai:arXiv.org:2601.12129v1 + Tensor-based phase difference estimation on time series analysis + https://arxiv.org/abs/2601.15616 + arXiv:2601.15616v1 Announce Type: new +Abstract: We propose a phase-difference estimation algorithm based on the tensor-network circuit compression, leveraging time-evolution data to pursue scalability and higher accuracy on a quantum phase estimation (QPE)-type algorithm. Using tensor networks, we construct circuits composed solely of nearest-neighbor gates and extract time-evolution data by four-type circuit measurements. In addition, to enhance the accuracy of time-evolution and state-preparation circuits, we propose techniques based on algorithmic error mitigation and on iterative circuit optimization combined with merging into matrix product states, respectively. Verifications using a noiseless simulator for the 8-qubit one-dimensional Hubbard model using an ancilla qubit show that the proposed algorithm achieves accuracies with 0.4--4.7\% error from a true energy gap on an appropriate time-step size, and that accuracy improvements due to the algorithmic error mitigation are observed. We also confirm the enhancement of the overlap with matrix product states through iterative optimization. Finally, the proposed algorithm is demonstrated on IBM Heron devices with Q-CTRL error suppression for 8-, 36-, and 52-qubit models using more than 5,000 2-qubit gates. These largest-scale demonstrations for the QPE-type algorithm represent significant progress not only toward practical applications of near-term quantum computing but also toward preparation for the era of error-corrected quantum devices. + oai:arXiv.org:2601.15616v1 quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 + Fri, 23 Jan 2026 00:00:00 -0500 new - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Jan Krzy\.zanowski, Jerzy Szuniewicz, Sanjay Kapoor, Filip So\'snicki, Micha{\l} Karpi\'nski + http://creativecommons.org/licenses/by-nc-nd/4.0/ + Shu Kanno, Kenji Sugisaki, Rei Sakuma, Jumpei Kato, Hajime Nakamura, Naoki Yamamoto - Physical probability in the Everett interpretation and Bell inequalities - https://arxiv.org/abs/2601.12159 - arXiv:2601.12159v1 Announce Type: new -Abstract: I define a notion of locality LOC, closely modelled on the Bell principle of Local Causality, construed as the condition that single case probabilities cannot be modified by actions at spacelike separation. The new principle, like that of Bell, forces Bell inequalities, but with two loopholes: one is violation of measurement independence, known to Bell, but the other is non-uniqueness of remote outcomes, a loophole only for LOC, not for Local Causality. I also set out a theory of physical probability, applicable to the Everett interpretation, in which the Born rule is derived, and which therefore violates Bell inequalities. I show it is consistent with LOC. Surprisingly, both loopholes are exploited. I conclude not only that physical probability in the Everett interpretation involves no action at a distance, but that the observed violation of Bell inequalities is powerful evidence for many worlds. - oai:arXiv.org:2601.12159v1 + Machine Failure Detection Based on Projected Quantum Models + https://arxiv.org/abs/2601.15641 + arXiv:2601.15641v1 Announce Type: new +Abstract: Detecting machine failures promptly is of utmost importance in industry for maintaining efficiency and minimizing downtime. This paper introduces a failure detection algorithm based on quantum computing and a statistical change-point detection approach. Our method leverages the potential of projected quantum feature maps to enhance the precision of anomaly detection in machine monitoring systems. We empirically validate our approach on benchmark multi-dimensional time series datasets as well as on a real-world dataset comprising IoT sensor readings from operational machines, ensuring the practical relevance of our study. The algorithm was executed on IBM's 133-qubit Heron quantum processor, demonstrating the feasibility of integrating quantum computing into industrial maintenance procedures. The presented results underscore the effectiveness of our quantum-based failure detection system, showcasing its capability to accurately identify anomalies in noisy time series data. This work not only highlights the potential of quantum computing in industrial diagnostics but also paves the way for more sophisticated quantum algorithms in the realm of predictive maintenance. + oai:arXiv.org:2601.15641v1 quant-ph - physics.hist-ph - Wed, 21 Jan 2026 00:00:00 -0500 + cs.LG + Fri, 23 Jan 2026 00:00:00 -0500 new - http://creativecommons.org/licenses/by-nc-sa/4.0/ - Simon Saunders + http://creativecommons.org/licenses/by/4.0/ + Larry Bowden, Qi Chu, Bernard Cena, Kentaro Ohno, Bob Parney, Deepak Sharma, Mitsuharu Takeori - Single-shot Quantum State Classification via Nonlinear Quantum Amplification - https://arxiv.org/abs/2601.12168 - arXiv:2601.12168v1 Announce Type: new -Abstract: Quantum amplifiers are intrinsically nonlinear systems whose performance limits are set by quantum mechanics. In quantum measurement, amplifier operation is conventionally optimized in the linear regime by maximizing signal-to-noise ratio, an objective that is well-suited to parameter estimation but is typically insufficient for more general tasks such as arbitrary quantum state discrimination. Here we show that single-shot quantum state classification can benefit from operating a quantum amplifier outside the linear regime, when the measurement chain is optimized end-to-end for a task-specific cost function. We analyze a realistic superconducting readout architecture that includes state preparation, cryogenic nonlinear amplification, and room-temperature detection with finite noise. By introducing performance metrics tailored to state discrimination, we identify operating regimes in which nonlinear amplification provides a measurable advantage and clarify the trade-offs that ultimately limit classification fidelity. Our results propose the utility of practical nonlinear quantum amplifiers for quantum state discrimination, and are the first step in a broader research program aimed at developing a general framework for end-to-end, resource-limited optimization of nonlinear quantum amplifiers for such quantum information processing applications. - oai:arXiv.org:2601.12168v1 + Enhancing the Size of Phase-Space States Containing Sub-Planck-Scale Structures via Non-Gaussian Operations + https://arxiv.org/abs/2601.15654 + arXiv:2601.15654v1 Announce Type: new +Abstract: We observe a metrological advantage in phase-space sensitivity for photon-added cat and kitten states over their original forms, due to phase-space broadening from increased amplitude via photon addition, albeit with higher energy cost. Using accessible non-classical resources, weak squeezing and displacement, we construct a squeezed state and two superposed states: the squeezed cat state and the symmetrically squeezed state. Their photon-added variants are compared with parity-matched cat and KSs using quantum Fisher information and fidelity. The QFI isocontours reveal regimes where KS exhibit high fidelity and large amplitude, enabling their preparation via Gaussian operations and photon addition. Similar regimes are identified for cat states enhanced by squeezing and photon addition, demonstrating improved metrological performance. Moreover, increased amplitude and thus larger phase-space area reduces the size of interferometric fringes, enhancing the effectiveness of quantum error correction in cat codes. + oai:arXiv.org:2601.15654v1 quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 + physics.optics + Fri, 23 Jan 2026 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Elif C\"uce, Saeed A. Khan, Boris Mesits, Michael Hatridge, Hakan E. T\"ureci + Arman, Prasanta K. Panigrahi - State Engineering via Nonlinear Interferometry with Linear Spectral Phases - https://arxiv.org/abs/2601.12173 - arXiv:2601.12173v1 Announce Type: new -Abstract: Many protocols within quantum cryptography, communications, and computing require the ability to generate entangled states as well as spectral qudits. Nonlinear interferometry is a viable way to engineer these complex quantum states of light. However, it is difficult to achieve a high level of control over spectral correlations. Here, we present a protocol utilizing a nonlinear interferometer with linear spectral phases that can generate both high-dimensional spectral qudits and high-dimensional entangled states. We model the effect of loss and loss of overlap on interference visibility and thereby on the states generated. - oai:arXiv.org:2601.12173v1 + Quantum-HPC hybrid computation of biomolecular excited-state energies + https://arxiv.org/abs/2601.15677 + arXiv:2601.15677v1 Announce Type: new +Abstract: We develop a workflow within the ONIOM framework and demonstrate it on the hybrid computing system consisting of the supercomputer Fugaku and the Quantinuum Reimei trapped-ion quantum computer. This hybrid platform extends the layered approach for biomolecular chemical reactions to accurately treat the active site, such as a protein, and the large and often weakly correlated molecular environment. Our result marks a significant milestone in enabling scalable and accurate simulation of complex biomolecular reactions + oai:arXiv.org:2601.15677v1 quant-ph - physics.optics - Wed, 21 Jan 2026 00:00:00 -0500 + Fri, 23 Jan 2026 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Cody Charles Payne, Elaganuru Bashaiah, Markus Allgaier + Kentaro Yamamoto, Riku Masui, Takahito Nakajima, Miwako Tsuji, Mitsuhisa Sato, Peter Schow, Lukas Heidemann, Matthew Burke, Philipp Seitz, Oliver J. Backhouse, Juan W. Pedersen, John Children, Craig Holliman, Nathan Lysne, Daichi Okuno, Seyon Sivarajah, David Mu\~noz Ramo, Alex Chernoguzov, Ross Duncan - Non-Trivial Topological Majorana Architectures: Mobius and Trefoil Band Topologies evaluated by Signal to Noise Ratio and Coherence time mesuarements - https://arxiv.org/abs/2601.12182 - arXiv:2601.12182v1 Announce Type: new -Abstract: Topological quantum computing is expected to be less sensitive to noise because information is stored in global states rather than local features. To examine whether different device topologies show measurable differences, we study three geometries with distinct topological invariants: a Mobius strip, a loop, and a trefoil knot, which have been proposed in electronic-structure settings. From quantum capacitance measurements, we extract power versus frequency spectra and fit Lorentzian line shapes to obtain the linewidth, amplitude, signal-to-noise ratio, and coherence time. The signal-to-noise ratio quantifies the ratio of the parity measurement signal to background noise and serves as an indicator of readout quality, while the coherence time characterizes the timescale for decoherence of the quantum state. Across all three topologies, coherence times are similar, with no clear dependence on geometry. In contrast, the signal-to-noise ratio differs in the regime E0 = 10 micro-eV and Z = -1, following the ordering Trefoil, Mobius, and Loop. These results provide a reference point for future experiments aimed at separating genuine topological effects from device-level parameters. - oai:arXiv.org:2601.12182v1 + Fractional squeezing: spectra and dynamics from generalized squeezing Hamiltonian with fractional orders + https://arxiv.org/abs/2601.15693 + arXiv:2601.15693v1 Announce Type: new +Abstract: We generalize the generalized-squeezing problem to include fractional values of the squeezing order $n$. This approach allows us to determine the locations of critical points at which qualitative changes in behaviour occur and accurately predict the behaviour at these critical points, which are challenging for conventional computational methods. Based on our numerical calculations, we identify with a high degree of confidence the point at which the spectrum turns from continuous to discrete and the point at which oscillations turn from having asymptotically infinite amplitudes to finite amplitudes. Furthermore, we numerically investigate the behaviour in the large $n$ regime and provide an intuitive explanation that coincides with the numerical results. + oai:arXiv.org:2601.15693v1 quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 + Fri, 23 Jan 2026 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Spandan Das, Ennis Mawas + Sahel Ashhab - Maximum precision charging of multi-qubit quantum batteries - https://arxiv.org/abs/2601.12183 - arXiv:2601.12183v1 Announce Type: new -Abstract: Precision, robustness, and efficiency are crucial aspects in the design of quantum technologies. Here, we show how genuine quantum features, together with non-Gaussianity, can be the key elements to achieve the best of these three aspects during a quantum battery-charging process. Taking inspiration from a light-matter interaction paradigm, i.e., the Jaynes-Cummings model, we employ the Full Counting Statistics to study the stochastic exchanges of energy between an entire stack of qubits and a single-mode electromagnetic field (or mechanical oscillator). Our study allows to conclude that charging the battery through a sequential protocol involving a quantum non-Gaussian field state guarantees extremely high-performances in the charging process, whose precision is maximized even under sub-optimal operating conditions. These results highlight the potential of non-Gaussian quantum state charging to achieve a robust quantum precision advantage over Gaussian states of the field by suppressing detrimental quantum fluctuations, thus making it suitable to ultimate tasks for which a significant degree of accuracy is required. - oai:arXiv.org:2601.12183v1 + Unsplit Spreading: An Overlooked Signature of Long-Range Interaction + https://arxiv.org/abs/2601.15752 + arXiv:2601.15752v1 Announce Type: new +Abstract: In conventional lattice models, the dispersion relation $\omega(k)$ is assumed to be a smooth function. We prove that this smoothness implies the splitting of an initially localized excitation into counter-propagating wave packets. Consequently, unsplit spreading can occur only when $\omega(k)$ develops singular features, precisely what long-range interactions enable. Remarkably, this phenomenon was clearly visible in published quantum simulation experiments as early as 2014, yet it has remained unrecognized or discussed as a distinct physical effect. We show that unsplit spreading emerges in realistic open quantum systems, such as 1D and 2D subwavelength atomic arrays, where the long-lived subradiant states host effective dispersion with the required singularities. Our work establishes unsplit spreading as an experimentally accessible, smoking-gun signature of singular band structure induced by long-range physics. + oai:arXiv.org:2601.15752v1 quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 + Fri, 23 Jan 2026 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Davide Rinaldi, Radim Filip, Dario Gerace, Giacomo Guarnieri + Jian-Feng Wu, Yi Huang, Yu-Xiang Zhang - Inverse Quantum Simulation for Quantum Material Design - https://arxiv.org/abs/2601.12239 - arXiv:2601.12239v1 Announce Type: new -Abstract: Quantum simulation provides a powerful route for exploring many-body phenomena beyond the capabilities of classical computation. Existing approaches typically proceed in the forward direction: a model Hamiltonian is specified, implemented on a programmable quantum platform, and its phase diagram and properties are explored. Here we present a quantum algorithmic framework for inverse quantum simulation, enabling quantum material design with desired properties. Target material characteristics are encoded as a cost function, which is minimized on quantum hardware to prepare a many-body state with the desired properties in quantum memory. Hamiltonian learning is then used to reconstruct a low-energy Hamiltonian for which this state is an approximate ground state, yielding a physically interpretable model that can guide experimental synthesis. As illustrative applications, we outline how the method can be used to search for high-temperature superconductors within the fermionic Hubbard model, enhancing $d$-wave correlations over a broad range of dopings and temperatures, design quantum phases by stabilizing a topological order through continuous Hamiltonian modifications, and optimize dynamical properties relevant for photochemistry and frequency- and momentum-resolved condensed-matter data. These results extend the scope of quantum simulators from exploring quantum many-body systems to designing and discovering new quantum materials. - oai:arXiv.org:2601.12239v1 + Improving the efficiency of QAOA using efficient parameter transfer initialization and targeted-single-layer regularized optimization with minimal performance degradation + https://arxiv.org/abs/2601.15760 + arXiv:2601.15760v1 Announce Type: new +Abstract: Quantum approximate optimization algorithm (QAOA) have promising applications in combinatorial optimization problems (COPs). We investigated the MaxCut problem in three different families of graphs using QAOA ansats with parameter transfer initialization followed by targeted single layer optimization. For 3 regular (3R), Erdos Renyi (ER), and Barabasi Albert (BA) graphs, the parameter transfer approach achieved mean approximation ratios of 0.9443 for targeted-single layer optimization as compared to 0.9551 of full optimization. It represents 98.88 percent optimal performance, with 8.06 times computational speedup in unweighted graphs. But, in weighted graph families, optimal performance is relatively low (less than 90 percent) for higher nodes graph, suggesting parameter transfer followed by targeted-single-layer optimization is not ideal for weighted graph families, however, we find that for some weighted families (weighted 3-regular) this approach works perfectly. In 8.92 percent test cases, targeted single layer optimization outperformed the full optimization, indicating that complex parameter landscape can trap full optimization in sub-optimal local minima. To mitigate this inconsistency, ridge (L2) regularization is used to smoothen the solution landscape, which helps the optimizer to find better optimum parameters during full optimization and reduces these inconsistent test cases from 8.92 percent to 3.81 percent. This work demonstrates that efficient parameter initialization and targeted-single-layer optimization can improve the efficiency of QAOA with minimal performance degradation. + oai:arXiv.org:2601.15760v1 quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 + Fri, 23 Jan 2026 00:00:00 -0500 new - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Christian Kokail, Pavel E. Dolgirev, Rick van Bijnen, Daniel Gonzalez-Cuadra, Mikhail D. Lukin, Peter Zoller + http://creativecommons.org/licenses/by/4.0/ + Shubham Patel, Utkarsh Mishra - Measuring unconventional causal structures in monitored dynamics - https://arxiv.org/abs/2601.12271 - arXiv:2601.12271v1 Announce Type: new -Abstract: Causality underpins all logical reasoning. However, the causal structure in quantum processes can be far from intuitive, often differing from its classical counterpart in relativity, which is defined by the light cone. In particular, in systems with measurement and post-selection, causal influence can occur between spacelike separated regions. In this work, we study the causal structure and emergent "arrow of time" in monitored quantum dynamics, particularly their dependence on initial and final states. We propose a new measure, the cross-entropy quantum causal influence, to quantify the extent of causal influence, whose simulation demonstrates exotic causal structures, such as inverted light cones. This quantity can be measured in current quantum computing platforms. Additionally, we provide an analytical understanding of the relation between time arrow and entropy by studying two types of models that are analytically tractable: a quantum Brownian evolution model and a dual-unitary circuit model. - oai:arXiv.org:2601.12271v1 + Classical Simulation of Noiseless Quantum Dynamics without Randomness + https://arxiv.org/abs/2601.15770 + arXiv:2601.15770v1 Announce Type: new +Abstract: Simulating noiseless quantum dynamics classically faces a fundamental dilemma: tensor-network methods become inefficient as entanglement saturates, while Pauli-truncation approaches typically rely on noise or randomness. To close the gap, we propose the Low-weight Pauli Dynamics (LPD) algorithm that efficiently approximates local observables for short-time dynamics in the absence of noise. We prove that the truncation error admits an average-case bound without assuming randomness, provided that the state is sufficiently entangled. Counterintuitively, entanglement--usually an obstacle for classical simulation--alleviates classical simulation error. We further show that such entangled states can be generated either by tensor-network classical simulation or near-term quantum devices. Our results establish a rigorous synergy between existing classical simulation methods and provide a complementary route to quantum simulation that reduces circuit depth for long-time dynamics, thereby extending the accessible regime of quantum dynamics. + oai:arXiv.org:2601.15770v1 quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 + Fri, 23 Jan 2026 00:00:00 -0500 new - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Hong-Yi Wang, Haifeng Tang, Xiao-Liang Qi + http://creativecommons.org/licenses/by/4.0/ + Jue Xu, Chu Zhao, Xiangran Zhang, Shuchen Zhu, Qi Zhao - Hierarchy of quantum correlations in qubit-qutrit axially symmetric states - https://arxiv.org/abs/2601.12292 - arXiv:2601.12292v1 Announce Type: new -Abstract: We investigate quantum correlations in a hybrid qubit-qutrit system subject to both axial and planar single-ion anisotropies, dipolar spin-spin interactions, and Dzyaloshinskii-Moriya (DM) coupling. Using Negativity, Measurement-Induced Non-locality (MIN), Uncertainty-Induced Nonlocality (UIN), and Bell nonlocality (as quantified by the CHSH inequality) as measures, we analyze the interplay between anisotropy parameters, magnetic fields, and temperature on the survival of quantum correlations. Our results demonstrate that Bell nonlocality and entanglement (Negativity) are highly sensitive to temperature and anisotropy, exhibiting sudden death under thermal noise, whereas MIN and UIN are significantly more robust. In particular, these discord-like and information-theoretic measures provide the largest baseline and persist even in parameter regions where entanglement vanishes, highlighting their suitability as a quantumness witness in realistic conditions. Notably, our Bell nonlocality study is tailored to the asymmetric qubit-qutrit setting by exploiting a recently developed qubit-qudit CHSH maximization framework. However, Bell nonlocality is confirmed to be the most fragile, surviving only in narrow parameter windows at low temperature. A key finding of this work is that we observe the fragility hierarchy: Bell nonlocality < Negativity < UIN(MIN) in the qubit-qutrit setting. These results provide deeper insight into the relative robustness of distinct quantum resources in anisotropic qubit-qutrit models, suggesting that quantum discord-like measures, such as MIN and UIN, may serve as more practical resources than entanglement for quantum information tasks in thermally active spin systems. - oai:arXiv.org:2601.12292v1 + Fermion Doubling in Dirac Quantum Walks + https://arxiv.org/abs/2601.15885 + arXiv:2601.15885v1 Announce Type: new +Abstract: We consider discrete spacetime models known as quantum walks, which can be used to simulate Dirac particles. In particular we look at fermion doubling in these models, in which high momentum states yield additional low energy solutions which behave like Dirac particles. The presence of doublers carries over to the `second quantised' version of the walks represented by quantum cellular automata, which may lead to spurious solutions when introducing interactions. Moreover, we also consider pseudo-doublers, which have high energy but behave like low energy Dirac particles, and cause potential problems regarding the stability of the vacuum. To address these issues, we propose a family of quantum walks, that are free of these doublers and pseudo-doublers, but still simulate the Dirac equation in the continuum limit. However, there remain a small number of additional low energy solutions which do not directly correspond to Dirac particles. While the conventional Dirac walk always has a zero probability for the walker staying at the same point, we obtain the family of walks by allowing this probability to be non-zero. + oai:arXiv.org:2601.15885v1 quant-ph - physics.optics - Wed, 21 Jan 2026 00:00:00 -0500 + hep-lat + Fri, 23 Jan 2026 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Venkat Abhignan, R. Muthuganesan + Chaitanya Gupta, Anthony J. Short - Disentanglement by deranking and by suppression of correlation - https://arxiv.org/abs/2601.12344 - arXiv:2601.12344v1 Announce Type: new -Abstract: The spontaneous disentanglement hypothesis is motivated by some outstanding issues in standard quantum mechanics, including the problem of quantum measurement. The current study compares between some possible methods that can be used to implement the hypothesis. Disentanglement is formulated using a nonlinear operator, which can be used to modify both the Schr\"{o}dinger equation for the quantum state vector, and the master equation for the density operator. Two types of nonlinear disentanglement operators are explored. The first one gives rise to matrix deranking, and the second one to correlation suppression. Both types are demonstrated using a two spin system that is driven close to the Hartmann--Hahn double resonance. It is shown that limit cycle steady state solutions, which are excluded by standard quantum mechanics, become possible in the presence of disentanglement. - oai:arXiv.org:2601.12344v1 + Improved cryptographic security in teleportation with q-deformed non-maximal entangled states + https://arxiv.org/abs/2601.15902 + arXiv:2601.15902v1 Announce Type: new +Abstract: In this work the machinery of q-deformed algebras are used to enhance cryptographic security during teleportation. We use q-deformed harmonic oscillator states to develop a novel method of teleportation. The deformed states can be expressed in terms of standard oscillator states and the expressions contain certain arbitrary functions of $q$. It is the presence of these arbitrary functions that allows an enhancement of cryptographic security. The specifics are : + (a) q-deformed Bell-like states are constructed which reduce to the usual Bell states when the deformation parameter $q\rightarrow 1$. These deformed states form an orthonormal basis for q-deformed entangled bipartite states when certain arbitrary functions of $q$ satisfy a constraint. + (b) We discuss the generalisation of the usual teleportation protocol with non-maximally entangled states. This generalisation is then employed to construct two new protocols using q-deformed non-maximally entangled states. These states have additional parameters and these have to be shared for decryption after teleportation. Consequently, the cryptographic security is improved. + oai:arXiv.org:2601.15902v1 quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 + Fri, 23 Jan 2026 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Eyal Buks + Prabal Dasgupta, Debashis Gangopadhyay - Efficient classical simulation of time dynamics in Fermi-Hubbard models with imaginary interactions - https://arxiv.org/abs/2601.12368 - arXiv:2601.12368v1 Announce Type: new -Abstract: Using a map between the Lindbladian evolution of dephasing in free fermions and the time evolution of imaginary-interaction Fermi-Hubbard models in bipartite lattices, we present an efficient classical algorithm to solve the Schr\"{o}dinger equation in these interacting systems. This algorithm leverages the recently discovered algorithm for simulating Lindbladian evolution by sampling mixed unitary channels (Wang et al arXiv:2601.06298). We comment on the expected classical complexity of the problem for general complex values of the parameters and discuss some applications. - oai:arXiv.org:2601.12368v1 + Automated quantum circuit optimization with randomized replacements + https://arxiv.org/abs/2601.15934 + arXiv:2601.15934v1 Announce Type: new +Abstract: Quantum circuit optimization - the process of transforming a quantum circuit into an equivalent one with reduced time and space requirements - is crucial for maximizing the utility of current and near-future quantum devices. While most automated optimization techniques focus on transforming circuits into equivalent ones that implement the same unitary, we show that substantial new opportunities for resource reduction can be achieved by (1) allowing approximate local transformations and (2) employing mixed quantum channels to approximate pure circuits. Our novel automated protocol for approximate circuit rewriting is a refined evolution of automated optimization techniques based on the ZX-calculus, where we add a greedy strategy that selectively replaces ZX-diagrams with small phase angles with stochastic mixtures of the identity and carefully chosen over-rotations, which are designed to reduce the overall gate count in expectation while staying within a strict error budget. This approach yields modest two-qubit gate count reduction in random quantum circuits, and achieves a substantial reduction in structured circuits such as the quantum Fourier transform. Fundamentally, our protocol converts experimental noise due to gate applications into deliberately engineered random noise, outperforming many other approximation methods on average. These results highlight the potential of mixed-channel approximations to enhance future quantum circuit performance, suggesting new directions for resource-aware automated quantum compilation beyond pure unitary channels. + oai:arXiv.org:2601.15934v1 quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 + Fri, 23 Jan 2026 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Raul A. Santos + Marcin Szyniszewski, Aleks Kissinger, Noah Linden, Paul Skrzypczyk - Topological quantum color code model on infinite lattice - https://arxiv.org/abs/2601.12409 - arXiv:2601.12409v1 Announce Type: new -Abstract: The color code model is a crucial instance of a Calderbank--Shor--Steane (CSS)-type topological quantum error-correcting code, which notably supports transversal implementation of the full Clifford group. Its robustness against local noise is rooted in the structure of its topological excitations. From the perspective of quantum phases of matter, it is essential to understand these excitations in the thermodynamic limit. In this work, we analyze the color code model on an infinite lattice within the quasi-local $C^{*}$-algebra framework, using a cone-localized Doplicher-Haag-Roberts (DHR) analysis. We classify its irreducible anyon superselection sectors and construct explicit string operators that generate anyonic excitations from the ground state. We further examine the fusion and braiding properties of these excitations. Our results show that the topological order of the color code is described by $\mathsf{Rep}(D(\mathbb{Z}_2 \times \mathbb{Z}_2)) \simeq \mathsf{Rep}(D(\mathbb{Z}_2)) \boxtimes \mathsf{Rep}(D(\mathbb{Z}_2))$, which is equivalent to a double layer of the toric code and consistent with established analyses on finite lattices. - oai:arXiv.org:2601.12409v1 + Frictional work and entropy production in integrable and non-integrable spin chains + https://arxiv.org/abs/2601.15941 + arXiv:2601.15941v1 Announce Type: new +Abstract: The maximum work extractable from a quantum system is achieved when the system is driven adiabatically. Frictional work then quantifies the difference in work output between adiabatic and non-adiabatic driving. Here we show that frictional work in a non-integrable spin chain is well-described by the diagonal entropy production associated with the build up of quantum coherence. The relationship is characterized by an effective temperature of the final adiabatic state and holds for slow to moderate driving protocols. For fast protocols, the frictional work is instead described by the quantum relative entropy between the final non-adiabatic and adiabatic states. We compare our results to those obtained from an integrable spin chain, in which case the adiabatic state is no longer described by a single temperature. In this case, the frictional work is described by a sum of terms for each independent subspace of the spin chain, which are at different effective temperatures. We show how integrability breaking can enhance work extraction in the adiabatic limit, but degrade work extraction in sufficiently non-adiabatic regimes. + oai:arXiv.org:2601.15941v1 quant-ph - hep-th - math-ph - math.MP - math.QA - Wed, 21 Jan 2026 00:00:00 -0500 + cond-mat.stat-mech + Fri, 23 Jan 2026 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Shiyu Cao, Zhian Jia, Sheng Tan + Vishnu Muraleedharan Sajitha, Matthew J. Davis, L. A. Williamson - Operator delocalization in disordered spin chains via exact MPO marginals - https://arxiv.org/abs/2601.12446 - arXiv:2601.12446v1 Announce Type: new -Abstract: We investigate operator delocalization in disordered one-dimensional spin chains by introducing -- besides the already known operator mass -- a complementary measure of operator complexity: the operator length. Like the operator nonstabilizerness, both these quantities are defined from the expansion of time-evolved operators in the Pauli basis. They characterize, respectively, the number of sites on which an operator acts nontrivially and the spatial extent of its support. We show that both the operator mass and length can be computed efficiently and exactly within a matrix-product-operator (MPS) framework, providing direct access to their full probability distributions, without resorting to stochastic sampling. Applying this approach to the disordered XXZ spin-1/2 chain, we find sharply distinct behaviors in non-interacting and interacting regimes. In the Anderson-localized case, operator mass, length, and operator entanglement entropy rapidly saturate, signaling the absence of scrambling. By contrast, in the many-body localized (MBL) regime, for arbitrarily weak interactions, all quantities exhibit a robust logarithmic growth in time, consistent with the known logarithmic light cone of quantum-correlation propagation in MBL. We demonstrate that this behavior is quantitatively captured by an effective $\ell$-bit model and persists across system sizes accessible via tensor-network simulations. - oai:arXiv.org:2601.12446v1 + Renormalization Treatment of IR and UV Cutoffs in Waveguide QED and Implications to Numerical Model Simulation + https://arxiv.org/abs/2601.15945 + arXiv:2601.15945v1 Announce Type: new +Abstract: We present a non-perturbative, first-principles derivation of renormalization relations for waveguide-QED models, explicitly accounting for the infrared (IR) and ultraviolet (UV) cutoffs that are necessarily introduced in numerical simulations. By formulating the atomic dynamics in the time domain, we obtain explicit expressions linking the bare model parameters to the physically observable atomic frequency and decay rate, and verify their consistency with scattering theory. We further connect these results to standard Feynman diagrams, providing a transparent physical interpretation and ensuring the generality of the approach. Finally, we show how these renormalization relations can be used to parameterize simulations with a minimal frequency bandwidth, simultaneously preserving physical accuracy and reducing computational cost, thereby paving the way for efficient and reliable multi-photon light-matter simulations. + oai:arXiv.org:2601.15945v1 quant-ph - cond-mat.dis-nn - cond-mat.str-el - Wed, 21 Jan 2026 00:00:00 -0500 + Fri, 23 Jan 2026 00:00:00 -0500 new - http://creativecommons.org/licenses/by/4.0/ - Jonnathan Pineda, Mario Collura, Gianluca Passarelli, Procolo Lucignaon, Davide Rossini, Angelo Russomanno + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Romain Piron, Akihito Soeda - Stochastic Quantum Information Geometry and Speed Limits at the Trajectory Level - https://arxiv.org/abs/2601.12475 - arXiv:2601.12475v1 Announce Type: new -Abstract: Standard quantum metrology relies on ensemble-averaged quantities, such as the Quantum Fisher Information (QFI), which often mask the fluctuations inherent to single-shot realizations. In this work, we bridge the gap between quantum information geometry and stochastic thermodynamics by introducing the Conditional Quantum Fisher Information (CQFI). Defined via the Symmetric Logarithmic Derivative, the CQFI generalizes the classical stochastic Fisher information to the quantum domain. We demonstrate that the CQFI admits a decomposition into incoherent (population) and coherent (basis rotation) contributions, augmented by a transient interference cross-term absent at the ensemble level. Crucially, we show that this cross-term can be negative, signaling destructive interference between classical and quantum information channels along individual trajectories. Leveraging this framework, we construct a stochastic information geometry that defines thermodynamic length and action for single quantum trajectories. Finally, we derive fundamental quantum speed limits valid at the single-trajectory level and validate our results using the quantum jump unraveling of a driven thermal qubit. - oai:arXiv.org:2601.12475v1 + Universal Digitized Counterdiabatic Driving + https://arxiv.org/abs/2601.15972 + arXiv:2601.15972v1 Announce Type: new +Abstract: Counterdiabatic driving realizes parameter displacement of an energy eigenstate of a given parametrized Hamiltonian using the adiabatic gauge potential. In this paper, we propose a universal method of digitized counterdiabatic driving, constructing the adiabatic gauge potential in a digital way with the idea of universal counterdiabatic driving. This method has three advantages over existing universal counterdiabatic driving and/or digitized counterdiabatic driving: it does not introduce any many-body and/or nonlocal interactions to an original target Hamiltonian; it can incorporate infinite nested commutators, which constitute the adiabatic gauge potential; and it gives explicit expression of rotation angles for digital implementation. We show the consistency of our method to the exact theory in an analytical way and the effectiveness of our method with the aid of numerical simulations. + oai:arXiv.org:2601.15972v1 quant-ph cond-mat.stat-mech - Wed, 21 Jan 2026 00:00:00 -0500 - new - http://creativecommons.org/licenses/by/4.0/ - Pedro B. Melo, Pedro V. Paraguass\'u, S\'ilvio M. Duarte Queir\'os, Fernando Iemini, Mauro Paternostro, Welles A. M. Morgado - - - A Mixture of Experts Vision Transformer for High-Fidelity Surface Code Decoding - https://arxiv.org/abs/2601.12483 - arXiv:2601.12483v1 Announce Type: new -Abstract: Quantum error correction is a key ingredient for large scale quantum computation, protecting logical information from physical noise by encoding it into many physical qubits. Topological stabilizer codes are particularly appealing due to their geometric locality and practical relevance. In these codes, stabilizer measurements yield a syndrome that must be decoded into a recovery operation, making decoding a central bottleneck for scalable real time operation. Existing decoders are commonly classified into two categories. Classical algorithmic decoders provide strong and well established baselines, but may incur substantial computational overhead at large code distances or under stringent latency constraints. Machine learning based decoders offer fast GPU inference and flexible function approximation, yet many approaches do not explicitly exploit the lattice geometry and local structure of topological codes, which can limit performance. In this work, we propose QuantumSMoE, a quantum vision transformer based decoder that incorporates code structure through plus shaped embeddings and adaptive masking to capture local interactions and lattice connectivity, and improves scalability via a mixture of experts layer with a novel auxiliary loss. Experiments on the toric code demonstrate that QuantumSMoE outperforms state-of-the-art machine learning decoders as well as widely used classical baselines. - oai:arXiv.org:2601.12483v1 - quant-ph - cs.IT - cs.LG - math.IT - Wed, 21 Jan 2026 00:00:00 -0500 + Fri, 23 Jan 2026 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Hoang Viet Nguyen, Manh Hung Nguyen, Hoang Ta, Van Khu Vu, Yeow Meng Chee + Takuya Hatomura - Coherence Scaling in Quantum Communication Protocols - https://arxiv.org/abs/2601.12516 - arXiv:2601.12516v1 Announce Type: new -Abstract: We investigate how quantum coherence scales and is redistributed in quantum communication protocols, using superdense coding and quantum teleportation as paradigmatic case studies. Employing the relative entropy of coherence as a circuit-level resource measure, we show that multipartite resource states relevant to generalized superdense coding can enable scalable communication while exhibiting only logarithmic or even constant coherence growth, depending on their entanglement structure. In sharp contrast, quantum teleportation displays an unavoidable, protocol-induced coherence cost that grows linearly with the number of teleported qubits and is independent of the input state. Through a stage-resolved analysis of the teleportation circuit, we separate protocol-generated coherence from message-dependent contributions and identify a universal two-bit coherence offset per teleported qubit at the maximal-coherence stage. We further demonstrate explicitly that this extensive intermediate coherence generation is fully consistent with information-theoretic bounds, including the Holevo limit, and does not correspond to an increase in accessible classical information. - oai:arXiv.org:2601.12516v1 + Semiclassical entanglement entropy for spin-field interaction + https://arxiv.org/abs/2601.15986 + arXiv:2601.15986v1 Announce Type: new +Abstract: We study a general bipartite quantum system consisting of a spin interacting with a bosonic field, with the initial state prepared as the product of a spin coherent state and a canonical coherent state. Our goal is to develop a semiclassical framework to describe the entanglement dynamics between these two subsystems. Using appropriate approximations, we derive a semiclassical expression for the entanglement entropy that depends exclusively on the trajectories of the underlying classical description. By analytically extending the classical phase space into the complex domain, we identify additional complex trajectories that significantly improve the accuracy of the semiclassical description. The inclusion of these complex trajectories allows us to capture the entanglement dynamics with remarkable precision, even well beyond the Ehrenfest time. The approach is illustrated with a representative example, where the role of real and complex trajectories in reproducing the quantum entanglement entropy is explicitly demonstrated. + oai:arXiv.org:2601.15986v1 quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 + Fri, 23 Jan 2026 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Pedro H. Alvarez, Marcos C. de Oliveira + Matheus V. Scherer, Lea F. Santos, Alexandre D. Ribeiro - Quantum Filtering for Squeezed Noise Inputs - https://arxiv.org/abs/2601.12564 - arXiv:2601.12564v1 Announce Type: new -Abstract: We derive the quantum filter for a quantum open system undergoing quadrature measurements (homodyning) where the input field is in a general quasi-free state. This extends previous work for thermal input noise and allows for squeezed inputs. We introduce a convenient class of Bogoliubov transformations which we refer to as balanced and formulate the quantum stochastic model with squeezed noise as an Araki-Woods type representation. We make an essential use of the Tomita-Takesaki theory to construct the commutant of the C*-algebra describing the inputs and obtain the filtering equations using the quantum reference probability technique. The derived quantum filter must be independent of the choice of representation and this is achieved by fixing an independent quadrature in the commutant algebra. - oai:arXiv.org:2601.12564v1 + Engineering quantum Mpemba effect by Liouvillian skin effect + https://arxiv.org/abs/2601.16002 + arXiv:2601.16002v1 Announce Type: new +Abstract: We propose a new approach to engineer the quantum Mpemba effect (QME) -- wherein an initial state farther from system relaxes faster than a close one -- by the Liouvillian skin effect (LSE) in open quantum systems. Moreover, the LSE serves as an ideal platform for realizing the QME and the spatial profile of the LSE provides a straightforward pathway for the initial state preparation, thereby enabling readily accessible experimental preparation. Focusing on the quadratic Lindbladians, we consider two concrete cases to design the initial states, thereby realizing the QME. Interestingly, we uncover a new kind of QME (QME-III) that is distinct from the two typical scenarios, manifested as two reversals in the Hilbert-Schmidt distance at two different times. In particular, the LSE provides a physically more intuitive understanding of the QME. + oai:arXiv.org:2601.16002v1 quant-ph - math-ph - math.MP - Wed, 21 Jan 2026 00:00:00 -0500 + Fri, 23 Jan 2026 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - John Gough, Dylon Rees - - - Interpolation of unitaries with time-dependent Hamiltonians via Deep Learning - https://arxiv.org/abs/2601.12619 - arXiv:2601.12619v1 Announce Type: new -Abstract: Quantum systems governed by time-dependent Hamiltonians pose significant challenges for the accurate computation of unitary time-evolution operators, which are essential for predicting quantum state dynamics. In this work, we introduce a physics-informed deep learning approach based on Physics-Informed Neural Networks to estimate these operators over the full time domain. By incorporating physical constraints such as unitarity and leveraging the second-order Magnus expansion on the evolution operator, the proposed framework enables the estimation of unitary matrices at different time intervals. The model is trained using simulated unitary operators and evaluated on quantum systems ranging from 2 to 6 qubits. For larger many-body systems, specifically those with 7 and 8 qubits, the same methodology is employed to reconstruct an effective time-dependent Hamiltonian, from which the corresponding time-evolution operator is computed over the entire temporal domain. The proposed framework achieves fidelities exceeding 0.92 using a limited number of unitary samples, indicating a potential reduction in measurement and data acquisition costs. These results highlight the effectiveness of the approach for data-driven simulation and identification of quantum dynamical systems, with direct relevance to quantum computing and quantum simulation applications. - oai:arXiv.org:2601.12619v1 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - new - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Antonio Guerra, Daniel Uzcategui-Contreras, Aldo Delgado, Esteban S. G\'omez + Xiang Zhang Chen Sun, Fuxiang Li - Equation-Free Discovery of Open Quantum Systems via Paraconsistent Neural Networks - https://arxiv.org/abs/2601.12635 - arXiv:2601.12635v1 Announce Type: new -Abstract: Modeling the dynamics of open quantum systems on noisy intermediate-scale quantum (NISQ) devices constitutes a major challenge, as high noise levels and environmental degradations lead to the decay of pure quantum states (decoherence) and energy losses. This situation represents one of the most important problems in the field of quantum information technologies. While existing data-driven methods struggle to generalize beyond the training data (extrapolation), physics-informed neural networks (PINNs) require predefined governing equations, which limit their discovery capability when the underlying physics is incomplete or unknown. In this work, we present the ParaQNN (ParaQuantum neural network) architecture, an equation-free framework for physical discovery. ParaQNN disentangles multi-scale dynamics without relying on a priori laws by employing a dialetheist logic layer that models coherent signal and decoherent noise as independent yet interacting channels. Through extensive benchmark tests performed on Rabi oscillations, Lindblad dynamics, and particularly complex ``mixed regimes'' where relaxation and dephasing processes compete, we show that ParaQNN exhibits a consistent performance advantage compared to Random Forest, XGBoost, and PINN models with incomplete physical information. Unlike its competitors, ParaQNN succeeds in maintaining oscillatory and damping dynamics with high accuracy even in extrapolation regions where training data are unavailable, by ``discovering'' the underlying structural invariants from noisy measurements. These results demonstrate that paraconsistent logic provides a structurally more stable epistemic foundation than classical methods for learning quantum behavior in situations where mathematical equations prove insufficient. - oai:arXiv.org:2601.12635v1 + Wigner's Friend as a Circuit: Inter-Branch Communication Witness Benchmarks on Superconducting Quantum Hardware + https://arxiv.org/abs/2601.16004 + arXiv:2601.16004v1 Announce Type: new +Abstract: We implement and benchmark on IBM Quantum hardware the circuit family proposed by Violaris for estimating operational inter-branch communication witnesses, defined as correlations in classical measurement records produced by compiled Wigner's-friend-style circuits. We realize a five-qubit instance of the protocol as an inter-register message-transfer pattern within a single circuit, rather than physical signaling, and evaluate its behavior under realistic device noise and compilation constraints. The circuit encodes branch-conditioned evolution of an observer subsystem whose dynamics depend on a control qubit, followed by a controlled transfer operation that probes correlations between conditional measurement contexts. + Executing on the ibm_fez backend with 20000 shots, we observe population-based visibility of 0.877, coherence witnesses of 0.840 and -0.811 along orthogonal axes, and a phase-sensitive magnitude of approximately 1.17. While the visibility metric is insensitive to some classes of dephasing, the coherence witnesses provide complementary sensitivity to off-diagonal noise. + This work does not test or discriminate among interpretations of quantum mechanics. Instead, it provides a reproducible operational constraint pipeline for evaluating detectability of non-ideal channels relative to calibrated device noise. + oai:arXiv.org:2601.16004v1 quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 + cs.ET + Fri, 23 Jan 2026 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Aleyna Ceyran, Jair Minoro Abe - - - Learning at the Edge of Causality: Optimal Learning-Sample Complexity from No-Signaling Constraints - https://arxiv.org/abs/2601.12651 - arXiv:2601.12651v1 Announce Type: new -Abstract: What ultimately fixes the sample cost of quantum learning -- algorithmic ingenuity or physical law? We study this question in an arena where computation, learning, and causality collide. A twist on Grover's search that reflects about an a priori unknown state can collapse the query complexity from $O(\sqrt{N})$ to $O(\log N)$ over a search space $N$, i.e., an exponential speedup. Yet, standard quantum theory forbids such a unknown-state reflection (no-reflection theorem). We therefore build a state-learning-assisted architecture, called ``amplify-learn,'' which alternates the coherent amplitude amplification with state learning. Embedding this amplify-learn into the Bao-Bouland-Jordan no-signaling framework, we show that the logarithmic-round dream would open a super-luminal communication channel unless each round expends the learning-sample and reflection-circuit budgets scaling at least as $\Omega(\sqrt{N}/\log N)$. In parallel, we derive tight computational learning-theoretic sample bounds for learning circuit-generated pure states, revealing a state-universal ansatz ``lock'' at order $N$ in the worst case. The dramatic closure is that no-signaling does not merely veto the unphysical primitive, but it fixes the only consistent reflection-circuit complexity, and feeding this causality-enforced complexity into the computational learning bound makes it collapse onto the very same $\sqrt{N}/\log N$ scaling demanded by no-signaling alone. No-signaling thus acts as a regulator of learnability: a constraint that mediates between physics and computation, welding query, gate, and sample complexities into a single causality-compatible triangle. - oai:arXiv.org:2601.12651v1 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - new - http://creativecommons.org/licenses/by-nc-nd/4.0/ - Jeongho Bang, Kyoungho Cho, Jeongwoo Jae + Christopher Altman - Constructing the Hamiltonian for a free 1D KFGM particle in an interval - https://arxiv.org/abs/2601.12739 - arXiv:2601.12739v1 Announce Type: new -Abstract: We analyze the problem of a free 1D Klein-Fock-Gordon-Majorana (KFGM) particle in an interval. By free, we mean that there is no potential within the interval and that its walls are penetrable; hence, the pertinent energy current density does not vanish at the walls. Certainly, quantization in an interval is not trivial because certain restrictions imposed by the domains of the operators involved arise. Here, our objective is to obtain the Hamiltonian for these particles. In practice, the Feshbach-Villars (FV)--free Hamiltonian is the proper operator for characterizing them and is a function of the momentum operator. Additionally, a Majorana condition must also be imposed on the wavefunctions on which these two operators can act. Thus, we start by calculating the pseudo self-adjoint momentum operator. A three-parameter set of boundary conditions (BCs) constitutes its domain. Up to this point, the domain of the Hamiltonian is induced by the domain of the momentum operator; however, we ensure that only the BCs for which the energy current density has the same value at each end of the interval are in its domain. All these BCs essentially belong to a one-parameter set of BCs. Moreover, because the FV equation is invariant under the operation of parity, the parity-transformed wavefunction is also a solution of this equation, which further restricts the domain of the free FV Hamiltonian. Finally, knowing the most general three-parameter set of BCs for the pseudo self-adjoint FV Hamiltonian for a 1D KFGM particle in an interval, we find that only two BCs can remain within the domain of the FV--free Hamiltonian: the periodic BC and the antiperiodic BC. These BCs are satisfied by both the two-component FV wavefunction, with these components being related, and the one-component KFG wavefunction, which can be real or imaginary. - oai:arXiv.org:2601.12739v1 + Echoed Random Quantum Metrology + https://arxiv.org/abs/2601.16026 + arXiv:2601.16026v1 Announce Type: new +Abstract: Quantum metrology typically demands the preparation of exotic quantum probe states, such as entangled or squeezed states, to surpass classical limits. However, the need for carefully calibrated system parameters and finely optimized quantum controls imposes limitations on scalability and robustness. Here, we circumvent these limitations by introducing an echoed random process that achieves sensitivity approaching the Heisenberg limit while remaining blind to the random probe state. We demonstrate that by simply driving a Kerr nonlinear mode with random pulses, the emergence of sub-Planck phase-space structures grants high sensitivity, eliminating the need for complex quantum control. The protocol is statistically robust, yielding high performance across broad driving parameter ranges while exhibiting resilience to control fluctuations and photon loss. Broadly applicable to both bosonic and qubit platforms, our work reveals a practical, hardware-efficient, scalable, and optimization-free route to quantum-enhanced metrology in high-dimensional Hilbert spaces. + oai:arXiv.org:2601.16026v1 quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 + Fri, 23 Jan 2026 00:00:00 -0500 new - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Techapon Kampu, Salvatore De Vincenzo + http://creativecommons.org/licenses/by/4.0/ + Dong-Sheng Liu, Zi-Jie Chen, Ziyue Hua, Yilong Zhou, Qing-Xuan Jie, Weizhou Cai, Ming Li, Luyan Sun, Chang-Ling Zou, Xi-Feng Ren, Guang-Can Guo - Connecting Magic Dynamics in Thermofield Double States to Spectral Form Factors - https://arxiv.org/abs/2601.12787 - arXiv:2601.12787v1 Announce Type: new -Abstract: Under unitary evolution, chaotic quantum systems initialized in simple states rapidly develop high complexity, precluding any efficient classical description. Quantum chaos is traditionally characterized by spectral properties of the Hamiltonian, most notably through the spectral form factor, while the hardness of classical simulation within the stabilizer formalism, commonly referred to as quantum magic, can be quantified by the stabilizer R\'enyi entropy. In this Letter, we propose a relation between the dynamics of the stabilizer R\'enyi entropy for thermofield double states and the spectral form factor, based on general arguments for chaotic systems with all-to-all interactions. This relation implies that the saturation of the stabilizer R\'enyi entropy is governed by a first-order dynamical transition. We then demonstrate this relation explicitly in the Sachdev-Ye-Kitaev model, using an auxiliary-spin representation of the stabilizer R\'enyi entropy that exhibits an emergent $Z_2$ symmetry. We further find that, in the high-temperature regime of the SYK model, the transition occurs at a finite time, with the long-time phase marked by spontaneous $Z_2$ symmetry breaking. In contrast, at low temperatures, the transition is pushed to times exponentially long in the system size. Our results reveal an intriguing interplay between quantum chaos and quantum magic. - oai:arXiv.org:2601.12787v1 + Robust Quantum Algorithmic Binary Decision-Making on Displacement Signals + https://arxiv.org/abs/2601.16081 + arXiv:2601.16081v1 Announce Type: new +Abstract: A relevant signal in the quantum domain may manifest as a displacement or a phase shift operator in the bosonic phase space. For a real parameter $\beta$ embedded in such a displacement operator, the task of determining if $\beta \in [\beta_{-th}, \beta_{+th}]$ for real asymmetric thresholds $(\beta_{-th} \ne -\beta_{+th})$ is a binary decision problem. We propose a framework based on generalized quantum signal processing interferometry (GQSPI) on hybrid qubit-bosonic oscillator systems that addresses this parameter detection problem by recasting the practical task of active binary hypothesis testing on quantum systems to that of a polynomial approximation. We achieve a small decision error probability $p_{err}$ on the order of $O(\frac{1}{d}\log{(d)})$, with $d$ as the circuit depth. We analyze the protocol when (i) $\beta$ is a deterministic parameter, and (ii) when $\beta$ is drawn randomly from a known prior distribution. The performance of the sensing protocol under dephasing noise is also shown to be robust. We further extend our protocol from two thresholds to more general multi-threshold cases as well. Overall, the proposed framework enables decision-making over arbitrary thresholds for any general displacement signal in a single or a few shots. + oai:arXiv.org:2601.16081v1 quant-ph - cond-mat.str-el - Wed, 21 Jan 2026 00:00:00 -0500 + Fri, 23 Jan 2026 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Ning Sun, Pengfei Zhang + Aishwarya Majumdar, Yuan Liu - Revealing the non-classicality of a molecular nanomagnet - https://arxiv.org/abs/2601.12832 - arXiv:2601.12832v1 Announce Type: new -Abstract: Molecular nanomagnets are compounds characterized by a high-spin magnetic core that is protected by organic ligands. They have recently gained attention as potential quantum information carriers in solid-state quantum computing platforms, simultaneously exhibiting classical macroscopic properties and quantum features in light of their complex nature and configuration. Addressing the condition when they manifest unquestionable quantum behavior is key to guarantee their effectiveness as resources for quantum information processing. We address the quantumness of molecular nanomagnets using a recently formulated criterion [cf. Krisnanda et al., Phys. Rev. Lett. 119, 120402 (2017)] demonstrating that these systems exhibit an intrinsic quantum nature, as evidenced by their ability to generate and enhance quantum correlations between two non-interacting probes. Our analysis, which is performed addressing various dynamical regimes, paves the way to the design of experimentally viable tests of non-classicality in multipartite registers consisting of ensembles of molecular nanomagnets. - oai:arXiv.org:2601.12832v1 + Quantum Metrology under Coarse-Grained Measurement + https://arxiv.org/abs/2601.16106 + arXiv:2601.16106v1 Announce Type: new +Abstract: While quantum metrology enables measurement precision beyond classical limits, its performance is often susceptible to experimental imperfections. Most prior studies have focused on imperfections in quantum states and operations. Here, we investigate the effect of coarse graining in quantum measurement through both theoretical analysis and experimental demonstration. Using an interferometer with a squeezed vacuum and a laser input, we analyze how coarse graining in homodyne detection affects the precision of phase estimation. We evaluate the Fisher information under various coarse-graining conditions and determine, in each case, an optimal estimation strategy that saturates the Cram\'{e}r-Rao bound. Remarkably, even extremely coarse-grained measurement -- with only two bins -- enables phase estimation beyond the standard quantum limit and even achieves a precision that follows the Heisenberg scaling. We experimentally demonstrate quantum-enhanced phase estimation under coarse-grained homodyne detection. To determine an optimal estimation strategy, we employ the method of moments and present calibration procedures that enable its application to general experimental settings. Using only two bins, we observe a quantum enhancement of 1.2 dB compared to the classical method using the ideal measurement, improving towards 3.8 dB as the bin number increases. These results highlight a practical pathway to achieving quantum enhancement under the presence of severe experimental imperfections. + oai:arXiv.org:2601.16106v1 quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 + Fri, 23 Jan 2026 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Alessandra Cammarata, Steve Campbell, Mauro Paternostro + Byeong-Yoon Go, Geunhee Gwak, Young-Do Yoon, Sungho Lee, Nicolas Treps, Jiyong Park, Young-Sik Ra - Nonreciprocity of intense light field and weak quantum signal in optomechanical systems with three-mode parametric interactions - https://arxiv.org/abs/2601.12855 - arXiv:2601.12855v1 Announce Type: new -Abstract: We demonstrate nonreciprocal optical transmission for both intense classical fields and weak quantum signals within a reconfigurable optomechanical platform driven by three-mode parametric interactions. The platform is modular, where each three-mode optomechanical system serves as a fundamental building block. Operating independently, a single block achieves nonreciprocity for classical fields. Specifically, asymmetric radiation pressure from intrinsic optomechanical nonlinearity induces nonreciprocal mechanical displacement, modulating the cavity intensity through optomechanical feedback. This enables full isolation of backward transmission without requiring parameter initialization. Alternatively, for quantum signals, the platform is reconfigured by activating photonic and phononic exchange channels between the two blocks. In this configuration, nonreciprocity arises from quantum interference between direct photon hopping and indirect conversion pathways. Constructive interference enables unidirectional low-loss transmission, while destructive interference completely suppresses the reverse direction. After adiabatically eliminating the auxiliary modes, the optimal nonreciprocal frequency and the trade-off between insertion loss and nonreciprocal bandwidth can be controlled by engineering optomechanically induced mechanical dissipation. Additionally, the three-mode-based device requires less control-field power than two-mode systems under resolved-sideband conditions, demonstrating versatile potential for optical nonreciprocity applications across classical and quantum domains. - oai:arXiv.org:2601.12855v1 + Experimental prime factorization via a feedback quantum control + https://arxiv.org/abs/2601.16116 + arXiv:2601.16116v1 Announce Type: new +Abstract: Prime factorization on quantum processors is typically implemented either via circuit-based approaches such as Shor's algorithm or through Hamiltonian optimization methods based on adiabatic, annealing, or variational techniques. While Shor's algorithm demands high-fidelity quantum gates, Hamiltonian optimization schemes, with prime factors encoded as degenerate ground states of a problem Hamiltonian, generally require substantial classical post-processing to determine control parameters. We propose an all-quantum, measurement-based feedback approach that iteratively steers a quantum system toward the target ground state, eliminating the need for classical computation of drive parameters once the problem Hamiltonian is determined and realized. As a proof of principle, we experimentally factor the biprime 551 using a three-qubit NMR quantum register and numerically analyze the robustness of the method against control field-errors. We further demonstrate scalability by numerically implementing the FALQON factorization of larger biprimes, 9,167 and 2,106,287, using 5 and 9 qubits, respectively. + oai:arXiv.org:2601.16116v1 quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 + Fri, 23 Jan 2026 00:00:00 -0500 new - http://creativecommons.org/publicdomain/zero/1.0/ - 10.1103/8kg8-brsx - Phys. Rev. A 113, 013513 (2026) - Yao Dong, Xin-Yao Huang, Guo-Feng Zhang + http://creativecommons.org/licenses/by/4.0/ + Hari Krishnan KB, Vishal Varma, T. S. Mahesh - Exact dynamics and bound states of a cavity coupled to a two-dimensional reservoir - https://arxiv.org/abs/2601.12880 - arXiv:2601.12880v1 Announce Type: new -Abstract: We demonstrate a robust scheme for quantum information storage based on bound states in a two-dimensional coupled-cavity array. When a target cavity is tuned to resonance with the array, a bound state in the continuum (BIC) emerges, coexisting with two conventional bound states outside the band. The resulting dynamics reflects a delicate interplay between these bound states, which can be fully captured through exact analytical solutions. In the weak-coupling regime, the BIC dominates, enabling perfect and persistent information storage. At stronger coupling, all bound states contribute, leading to oscillatory behavior and reduced storage fidelity. These results, valid at both zero and finite reservoir temperatures and further supported by a single-particle framework, reveal distinctive non-Markovian features in continuous-variable systems and highlight the potential of photonic lattices for scalable all-optical decoherence-free quantum memory platforms. - oai:arXiv.org:2601.12880v1 + Exceptional points in Gaussian channels: diffusion gauging and drift-governed spectrum + https://arxiv.org/abs/2601.16121 + arXiv:2601.16121v1 Announce Type: new +Abstract: McDonald and Clerk [Phys.\ Rev.\ Research 5, 033107 (2023)] showed that for linear open quantum systems the Liouvillian spectrum is independent of the noise strength. We first make this noise-independence principle precise in continuous time for multimode bosonic Gaussian Markov semigroups: for Hurwitz drift, a time-independent Gaussian similarity fixed by the Lyapunov equation gauges away diffusion for all times, so eigenvalues and non-diagonalizability are controlled entirely by the drift, while diffusion determines steady states and the structure of eigenoperators. We then extend the same separation to discrete time for general stable multimode bosonic Gaussian channels: for any stable Gaussian channel, we construct an explicit Gaussian similarity transformation that gauges away diffusion at the level of the channel parametrization. We illustrate the method with a single-mode squeezed-reservoir Lindbladian and with a non-Markovian family of single-mode Gaussian channels, where the exceptional-point manifolds and the associated gauging covariances can be obtained analytically. + oai:arXiv.org:2601.16121v1 quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 + math-ph + math.MP + Fri, 23 Jan 2026 00:00:00 -0500 new http://creativecommons.org/licenses/by-nc-nd/4.0/ - Heng-Na Xiong, Da-Wei Ye, Yang Yang, Hongli Zhu, Yixiao Huang, Stefano Longhi, Fanxin Liu + Frank Ernesto Quintela Rodr\'iguez - No-Signalling Fixes the Hilbert-Space Inner Product - https://arxiv.org/abs/2601.13012 - arXiv:2601.13012v1 Announce Type: new -Abstract: We investigate whether the inner product structure of quantum mechanics can be modified without violating fundamental physical principles. We consider a generalized inner product defined by a positive operator and assume local unitary dynamics, existence of entangled states and the no-signalling principle. We show that any nontrivial choice of inner product different from standard one inevitably leads to superluminal signalling, in contradiction with relativistic causality. Therefore, the standard Hilbert-space inner product is uniquely enforced by no-signalling. - oai:arXiv.org:2601.13012v1 + Calibration-Conditioned FiLM Decoders for Low-Latency Decoding of Quantum Error Correction Evaluated on IBM Repetition-Code Experiments + https://arxiv.org/abs/2601.16123 + arXiv:2601.16123v1 Announce Type: new +Abstract: Real-time decoding of quantum error correction (QEC) is essential for enabling fault-tolerant quantum computation. A practical decoder must operate with high accuracy at low latency, while remaining robust to spatial and temporal variations in hardware noise. We introduce a hardware-conditioned neural decoder framework designed to exploit the natural separation of timescales in superconducting processors, where calibration drifts occur over hours while error correction requires microsecond-scale responses. By processing calibration data through a graph-based encoder and conditioning a lightweight convolutional backbone via feature-wise linear modulation (FiLM), we decouple the heavy processing of device statistics from the low-latency syndrome decoding. + We evaluate this approach using the 1D repetition code as a testbed on IBM Fez, Kingston, and Pittsburgh processors, collecting over 2.7 million experimental shots spanning distances up to d = 11. We demonstrate that a single trained model generalizes to unseen qubit chains and new calibration data acquired days later without retraining. On these unseen experiments, the FiLM-conditioned decoder achieves up to an 11.1x reduction in logical error rate relative to modified minimum-weight perfect matching. We observe that by employing a network architecture that exploits the highly asynchronous nature of system calibration and decoding, hardware-conditioned neural decoding demonstrates promising, adaptive performance with negligible latency overhead relative to unconditioned baselines. + oai:arXiv.org:2601.16123v1 quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 + Fri, 23 Jan 2026 00:00:00 -0500 new - http://creativecommons.org/licenses/by/4.0/ - Arun Kumar Pati + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Samuel Stein, Shuwen Kan, Chenxu Liu, Adrian Harkness, Sean Garner, Zefan Du, Yufei Ding, Ying Mao, Ang Li - Failure of the mean-field Hartree approximation for a bosonic many-body system with non-Hermitian Hamiltonian - https://arxiv.org/abs/2601.13038 - arXiv:2601.13038v1 Announce Type: new -Abstract: Mean-field Hartree theory is a central tool for reducing interacting many-body dynamics to an effective nonlinear one-particle evolution. This approximation has been employed also when the Hamiltonian that governs the many-body dynamics is not Hermitian. Indeed, non-Hermitian Hamiltonians model particle gain/loss or the evolution of open quantum systems between consecutive quantum jumps. Furthermore, the validity of the Hartree approximation for generic non-Hermitian Hamiltonians lies at the basis of a quantum algorithm for nonlinear differential equations. In this work, we show that this approximation can fail. We analytically solve a model of $N$ bosonic qubits with two-body interactions generated by a purely anti-Hermitian Hamiltonian, determine an analytic expression for the limit for $N\to\infty$ of the one-particle marginal state and show that such a limit does not agree with the solution of the non-Hermitian Hartree evolution equation. We further show that there exists an initial condition such that the exact one-particle marginal state undergoes a finite-time transition to a mixed state, a phenomenon that is completely absent in the case of Hermitian Hamiltonians. Our findings challenge the validity of the mean-field Hartree approximation for non-Hermitian Hamiltonians, and call for additional conditions for the validity of the mean-field regime to model the dynamics of particle gain and loss and the open-system dynamics in bosonic many-body systems. - oai:arXiv.org:2601.13038v1 + Quantum Dimension Reduction of Hidden Markov Models + https://arxiv.org/abs/2601.16126 + arXiv:2601.16126v1 Announce Type: new +Abstract: Hidden Markov models (HMMs) are ubiquitous in time-series modelling, with applications ranging from chemical reaction modelling to speech recognition. These HMMs are often large, with high-dimensional memories. A recently-proposed application of quantum technologies is to execute quantum analogues of HMMs. Such quantum HMMs (QHMMs) are strictly more expressive than their classical counterparts, enabling the construction of more parsimonious models of stochastic processes. However, state-of-the-art techniques for QHMM compression, based on tensor networks, are only applicable for a restricted subset of HMMs, where the transitions are deterministic. In this work we introduce a pipeline by which \emph{any} finite, ergodic HMM can be compressed in this manner, providing a route for effective quantum dimension reduction of general HMMs. We demonstrate the method on both a simple toy model, and on a speech-derived HMM trained from data, obtaining favourable memory--accuracy trade-offs compared to classical compression approaches. + oai:arXiv.org:2601.16126v1 quant-ph cond-mat.stat-mech - math-ph - math.MP - Wed, 21 Jan 2026 00:00:00 -0500 + Fri, 23 Jan 2026 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Matias Ginzburg, Giacomo De Palma, Simone Rademacher + Rishi Sundar, Thomas Elliott - Quantitative wave-particle duality in uniform multipath interferometers with symmetric which-path detector states - https://arxiv.org/abs/2601.13083 - arXiv:2601.13083v1 Announce Type: new -Abstract: A quantum system (quanton) traverses an interferometer with $N$ equally probable paths and interacts with another quantum system (detector) that stores path information in a set of symmetric states. In this interferometric framework, we present entropic wave-particle duality relations between quantum coherence, characterized by the relative entropy of coherence of the quanton state, and which-path knowledge, quantified by the mutual information obtained through detector-state discrimination. By applying a general optimal discrimination measurement, which has a closed-form solution and encompasses other fundamental strategies as special cases, we provide an exact quantification of which-path knowledge in a variety of scenarios. This measurement is carried out in two steps. First, an optimal separation map with a prescribed separation level $\xi\in [0,1]$ probabilistically reduces the overlaps between the input detector states with maximum success rate, or increases them in case of failure. Then, a minimum-error (ME) measurement discriminates either only the successful outputs (standard approach) or both the successful and failure outputs (concatenated approach). We show that the duality relation is tighter at $\xi=0$, where both approaches reduce to the ME measurement. For $\xi>0$, each approach yields a distinct relation that becomes less tight as $\xi$ increases, with the concatenated one providing the tighter bound. Finally, by using the discrete uncertainty principle, we determine the sets of detector states that lead to saturation of the duality relation, showing that they span $n$-dimensional subspaces of the detector space, where $n$ divides $N$. As a result, nontrivial saturation occurs only for interferometers with a nonprime number of paths. From the identified saturating sets, we highlight how the quanton-detector correlations underlie this phenomenon. - oai:arXiv.org:2601.13083v1 + Fair sampling with temperature-targeted QAOA based on quantum-classical correspondence theory + https://arxiv.org/abs/2601.16144 + arXiv:2601.16144v1 Announce Type: new +Abstract: In combinatorial optimization problems with degenerate ground states, fair sampling of degenerate solutions is essential. However, the quantum approximate optimization algorithm (QAOA) with a standard transverse-field mixer induces biases among degenerate states as circuit depth increases. Based on quantum-classical correspondence theory, we propose SBO-QAOA, which employs a temperature-dependent Hamiltonian encoding a Gibbs distribution as its ground state. Numerical simulations show that, unlike standard QAOA, SBO-QAOA yields ground-state probabilities converging to finite-temperature values with uniform distribution among degenerate states. These fairness and temperature-targeting properties are preserved even with only four variational parameters under a linear schedule. + oai:arXiv.org:2601.16144v1 quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 + cond-mat.stat-mech + Fri, 23 Jan 2026 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - L. F. Melo, O. Jim\'enez, L. Neves - - - Comparison between explicit and implicit discretization strategies for a dissipative thermal environment - https://arxiv.org/abs/2601.13103 - arXiv:2601.13103v1 Announce Type: new -Abstract: We investigate strategies for simulating open quantum systems coupled to dissipative baths by comparing explicit wave function-based discretization [via multi-layer multi-configuration time-dependent Hartree (ML-MCTDH)] and the implicit density matrix-based master equation method [via tree tensor network hierarchical equations of motion (TTN-HEOM)]. For dissipative baths characterized by exponentially decaying bath correlation functions, the implicit discretization approach of HEOM -- rooted in bath correlation function decompositions -- proves significantly more efficient than explicit discretization of the bath into discrete harmonic modes. Explicit methods, like ML-MCTDH, require extensive mode discretization to approximate continuum baths, leading to computational bottlenecks. Case studies for two-level systems and a Fenna--Matthews--Olson complex model highlight TTN-HEOM's superiority in capturing dissipative dynamics with relaxations with a minimal number of auxiliary modes, while the explicit methods are as exact as the HEOM in pure dephasing regimes. This comparison is enabled by the TENSO package, which has both ML-MCTDH and TTN-HEOM implemented using the same computational structure and propagation strategy. - oai:arXiv.org:2601.13103v1 - quant-ph - physics.chem-ph - Wed, 21 Jan 2026 00:00:00 -0500 - new - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - 10.1063/5.0307152 - Xinxian Chen, Ignacio Franco + Tetsuro Abe, Shu Tanaka - Product-State Approximation Algorithms for the Transverse Field Ising Model - https://arxiv.org/abs/2601.13106 - arXiv:2601.13106v1 Announce Type: new -Abstract: We study classical polynomial-time approximation algorithms for the transverse-field Ising model (TFIM) Hamiltonian, allowing a mixture of ferromagnetic and anti-ferromagnetic interactions between pairs of qbits, alongside transverse field terms with arbitrary non-negative weights. - Our main results are a series of approximation algorithms (all approximation ratios with respect to the true quantum optimum): (i) a simple maximum of two product state rounding algorithm achieving an approximation ratio $\gamma\approx 0.71$ , (ii) a strengthened rounding, inspired by the anticommutation property of the two $X_i, Z_iZ_j$ observables achieving ratio $\gamma\approx 0.7860$, and (iii) a further improvement by interpolation achieving ratio $\gamma \approx 0.8156$. We also give an explicit (purely ferromagnetic) TFIM instance on three qbits for which every product state achieves at most $169/180\approx 0.9389$ of the true optimum, yielding an upper bound for all algorithms producing product state approximations, even in the purely ferromagnetic case. - oai:arXiv.org:2601.13106v1 + Polynomial-time thermalization and Gibbs sampling from system-bath couplings + https://arxiv.org/abs/2601.16154 + arXiv:2601.16154v1 Announce Type: new +Abstract: Many physical phenomena, including thermalization in open quantum systems and quantum Gibbs sampling, are modeled by Lindbladians approximating a system weakly coupled to a bath. Understanding the convergence speed of these Lindbladians to their steady states is crucial for bounding algorithmic runtimes and thermalization timescales. We study two such families of processes: one characterizing a repeated-interaction Gibbs sampling algorithm, and another modeling open many-body quantum thermalization. We prove that both converge in polynomial time for several non-commuting systems, including high-temperature local lattices, weakly interacting fermions, and 1D spin chains. These results demonstrate that simple dissipative quantum algorithms can prepare complex Gibbs states and that Lindblad dynamics accurately capture thermal relaxation. Our proofs rely on a novel technical result that extrapolates spectral gap lower bounds from quasi-local Lindbladians to the non-local generators governing these dynamics. + oai:arXiv.org:2601.16154v1 quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 + Fri, 23 Jan 2026 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Vincenzo Lipardi, David Mestel, Georgios Stamoulis + Samuel Slezak, Matteo Scandi, \'Alvaro M. Alhambra, Daniel Stilck Fran\c{c}a, Cambyse Rouz\'e - Noncontextual versus contextual interferometry - https://arxiv.org/abs/2601.13109 - arXiv:2601.13109v1 Announce Type: new -Abstract: Feynman famously said that single-particle interference is ``a phenomenon which is impossible to explain in any classical way, and which has in it the heart of quantum mechanics.'' In this paper we show that some of the phenomenology of interference can be reproduced in a ``classical'' way, by reproducing the Elitzur-Vaidman Bomb Tester (including their improved version) using an extension of the quantum simulation logic (QSL) formalism. Our result improves and simplifies a previous result by Catani \emph{et al}, which relies on a much more complicated extension involving a ``toy field theory.'' We also show that not all single-particle interference can be explained by such a simple extension (including that of Catani et al), by showing that Hofmann's three-path interferometer is ``nonclassical'' in a very specific sense: it violates a Kochen-Specker-noncontextual inequality. Given that both our extension of QSL and Catani et al's extension are \emph{noncontextual} -- so do not reproduce the contextual behaviour of Hofmann's three-path interferometer -- the behaviour of that interferometer is a proper example of a phenomenon that has in it the heart of quantum mechanics, according to Feynman. - oai:arXiv.org:2601.13109v1 + Stabilizer Thermal Eigenstates at Infinite Temperature + https://arxiv.org/abs/2601.16177 + arXiv:2601.16177v1 Announce Type: new +Abstract: Understanding how to analyze highly entangled thermal eigenstates is a central challenge in the study of quantum many-body systems. In this Letter, we introduce a stabilizer-based approach to construct analytically tractable energy eigenstates of nonintegrable many-body Hamiltonians. Focusing on zero-energy eigenstates at infinite temperature, we prove a sharp no-go theorem: stabilizer eigenstates of two-body Hamiltonians cannot satisfy $k$-body microscopic thermal equilibrium for any $k\ge4$. We further show that this bound is tight by explicitly constructing two-body nonintegrable Hamiltonians whose stabilizer eigenstates reproduce thermal expectation values for all two-body and all three-body observables. Finally, we identify the structural origin of this limitation by characterizing the conditions under which a stabilizer state can appear as a zero-energy eigenstate of a Hamiltonian, thereby revealing a fundamental constraint imposed by the few-body nature of interactions. + oai:arXiv.org:2601.16177v1 quant-ph - physics.hist-ph - physics.optics - Wed, 21 Jan 2026 00:00:00 -0500 + cond-mat.stat-mech + Fri, 23 Jan 2026 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Jonte R. Hance, Jakov Krnic, Jan-{\AA}ke Larsson + Akihiro Hokkyo - Quantum Data Structure for Range Minimum Query - https://arxiv.org/abs/2601.13195 - arXiv:2601.13195v1 Announce Type: new -Abstract: Given an array $a[1..n]$, the Range Minimum Query (RMQ) problem is to maintain a data structure that supports RMQ queries: given a range $[l, r]$, find the index of the minimum element among $a[l..r]$, i.e., $\operatorname{argmin}_{i \in [l, r]} a[i]$. In this paper, we propose a quantum data structure that supports RMQ queries and range updates, with an optimal time complexity $\widetilde \Theta(\sqrt{nq})$ for performing $q = O(n)$ operations without preprocessing, compared to the classical $\widetilde\Theta(n+q)$. As an application, we obtain a time-efficient quantum algorithm for $k$-minimum finding without the use of quantum random access memory. - oai:arXiv.org:2601.13195v1 + Studying energy-resolved transport with wavepacket dynamics on quantum computers + https://arxiv.org/abs/2601.16180 + arXiv:2601.16180v1 Announce Type: new +Abstract: Probing energy-dependent transport in quantum simulators requires preparing states with tunable energy and small energy variance. Existing approaches often study quench dynamics of simple initial states, such as computational basis states, which are far from energy eigenstates and therefore limit the achievable energy resolution. In this work, we propose using wavepackets to probe transport properties with improved energy resolution. To demonstrate the utility of this approach, we prepare and evolve wavepackets on Quantinuum's H2-2 quantum computer and identify an energy-dependent localization transition in the Anderson model on an 8x7 lattice--a finite-size mobility edge. We observe that a wavepacket initialized at low energy remains spatially localized under time evolution, while a high-energy wavepacket delocalizes, consistent with the presence of a mobility edge. Crucial to our experiments is an error mitigation strategy that infers the noiseless output bit string distribution using maximum-likelihood estimation. Compared to post-selection, this method removes systematic errors and reduces statistical uncertainty by up to a factor of 5. We extend our methods to the many-particle regime by developing a quantum algorithm for preparing quasiparticle wavepackets in a one-dimensional model of interacting fermions. This technique has modest quantum resource requirements, making wavepacket-based studies of transport in many-body systems a promising application for near-term quantum computers. + oai:arXiv.org:2601.16180v1 quant-ph - cs.DS - Wed, 21 Jan 2026 00:00:00 -0500 + cond-mat.dis-nn + Fri, 23 Jan 2026 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - 10.1016/j.jcss.2026.103756 - Journal of Computer and System Sciences, 103756, 2026 - Qisheng Wang, Zhean Xu, Zhicheng Zhang + Melody Lee, Roland C. Farrell - All-Dielectric Resonant Cavity Electro-Optic Transduction Between Microwave and Telecom - https://arxiv.org/abs/2601.13199 - arXiv:2601.13199v1 Announce Type: new -Abstract: We present a resonant electro-optic transducer for efficient conversion between microwave and telecom wavelength photons. Our platform employs a bulk lithium niobate crystal whose large dielectric constant creates wavelength-scale confinement of microwave photons. By incorporating this crystal within a high-finesse Fabry - Perot optical cavity, microwave photons couple to optical photons through the electro-optic effect. We demonstrate the ability to tune our system into triply resonant operation, where microwave photons, optical pump photons, and upconverted optical photons are simultaneously resonant with high quality factor electromagnetic modes of the system. The device achieves photon number conversion efficiency at the percent level, comparable to state-of-the-art devices at room temperature -- sufficient to resolve the thermal occupation of the microwave mode -- while avoiding the noise and loss associated with metal electrodes. These results establish our all-dielectric devices as a promising platform for high-precision sensing of optically detected microwave fields and as a viable route toward single-photon-level microwave - optical quantum transduction. - oai:arXiv.org:2601.13199v1 + Robust Bell Nonlocality from Gottesman-Kitaev-Preskill States + https://arxiv.org/abs/2601.16189 + arXiv:2601.16189v1 Announce Type: new +Abstract: Bell tests based on homodyne detection are strongly constrained in continuous-variable systems. Can Gottesman-Kitaev-Preskill (GKP) encoding turn homodyne detection into a practical tool for revealing Bell nonlocality? We consider a physically motivated model in which each party performs homodyne detection and digitizes the continuous outcome via a fixed periodic binning, corresponding to logical Pauli measurements. Within this framework, we derive a bipartite no-go: CHSH cannot be violated for Bell-pair states. Moving beyond two parties, we show that finitely squeezed GKP-encoded GHZ and W states nevertheless exhibit strong multipartite nonlocality, violating multipartite Bell inequalities with homodyne-only readout. We quantify the required squeezing thresholds and robustness to loss, providing a route toward homodyne-based Bell tests in continuous-variable systems. + oai:arXiv.org:2601.16189v1 quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - new - http://creativecommons.org/licenses/by-nc-sa/4.0/ - Mihir Khanna, Yang Hu, Thomas P. Purdy - - - Towards Simple and Useful One-Time Programs in the Quantum Random Oracle Model - https://arxiv.org/abs/2601.13258 - arXiv:2601.13258v1 Announce Type: new -Abstract: We construct simulation-secure one-time memories (OTM) in the random oracle model, and present a plausible argument for their security against quantum adversaries with bounded and adaptive depth. Our contributions include: (1) A simple scheme where we use only single-qubit Wiesner states and conjunction obfuscation (constructible from LPN): no complex entanglement or quantum cryptography is required. (2) A new POVM bound where e prove that any measurement achieving $(1 - \epsilon)$ success on one basis has conjugate-basis guessing probability at most $\frac{1}{2m} + O(\epsilon^\frac{1}{4})$. (3) Simultation-secure OTMs in the quantum random oracle model where an adversary can only query the random oracle classically. (4) Adaptive depth security where, via an informal application of a lifting theorem from Arora et al., we conjecture security against adversaries with polynomial quantum circuit depth between random oracle queries. - Security against adaptive, depth-bounded, quantum adversaries captures many realistic attacks on OTMs built from single-qubit states; our work thus paves the way for practical and truly secure one-time programs. Moreover, depth bounded adaptive adversarial models may allow for encoding one-time memories into error corrected memory states, opening the door to implementations of one-time programs which persist for long periods of time. - oai:arXiv.org:2601.13258v1 - quant-ph - cs.CR - Wed, 21 Jan 2026 00:00:00 -0500 + Fri, 23 Jan 2026 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Lev Stambler + Xiaotian Yang, Santiago Zamora, Rafael Chaves, Ulrik L. Andersen, Jonatan Bohr Brask, A. de Oliveira Junior - Microscopic Quantum Friction - https://arxiv.org/abs/2601.13265 - arXiv:2601.13265v1 Announce Type: new -Abstract: We report on a microscopic theory of quantum friction. Our approach investigates the interplay between the dispersive response and the relative center-of-mass motion of two ground-state atoms. This coupling yields a quantum force, which can be expressed as a power series in the velocity. The significance of each contribution depends on its order parity: while even-order terms are reversible, odd-order terms are irreversible and only survive in the presence of an internal dissipation mechanism. In addition, we obtain general, model-independent properties for the work performed by these contributions for arbitrary scattering trajectories. These results enable an unambiguous identification of odd-parity terms with microscopic quantum friction. At room temperature, the dominant microscopic quantum friction is of first order in the velocity and presents a strong quantum character. Our microscopic theory reveals that several properties of quantum friction obtained in specific settings -- such as the cubic dependence on velocity at zero temperature -- are indeed universal features already present at the atomic scale. - oai:arXiv.org:2601.13265v1 + Quantum scientists for disarmament: a manifesto + https://arxiv.org/abs/2601.14282 + arXiv:2601.14282v1 Announce Type: cross +Abstract: We, as researchers in quantum science and technology, are publishing this manifesto to express our deep concerns about the current geopolitical situation and the global race to rearm. We firmly oppose all forms of militarization in our societies and, in particular, within the academic world. We categorically reject the use of our research for military applications, population control, or surveillance. We stand against the practice of military funding for research. This manifesto is a call to action: to confront the elephant in the room of quantum research, and to unite all researchers who share our views. Our main goals are: i) To express, as a unified collective, our rejection of the use of our research for military purposes; ii) To open a debate in our community about the ethical implications of quantum research for military purposes; iii) To create a forum where concerned scientists can share their opinions and join forces in support of demilitarized research; iv) To advocate for the establishment of a public database listing all research projects at public universities funded by military or defense agencies. In what follows, we lay out our concerns and the rationale behind our opposition to the militarization of quantum research. + oai:arXiv.org:2601.14282v1 + physics.soc-ph quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - new - http://creativecommons.org/licenses/by/4.0/ - Pedro H. Pereira, F. Impens, C. Farina, P. A. Maia Neto, R. de Melo e Souza + Fri, 23 Jan 2026 00:00:00 -0500 + cross + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Quantum Scientists for Disarmament - Implementation of Leaking Quantum Walks on a Photonic Processor - https://arxiv.org/abs/2601.13269 - arXiv:2601.13269v1 Announce Type: new -Abstract: Quantum walks represent pillars of quantum dynamics and information processing. They provide a powerful framework for simulating quantum transport, designing search algorithms, and achieving universal quantum computation. Several physical platforms have been employed to implement QWs, such as trapped atoms, trapped ions, nuclear magnetic resonance systems and photonic quantum systems either in bulk optics or waveguide structures and fiber-loop networks. Here we focus on the most promising approach, that is photonic integrated circuits. We will review how the employment of this versatile experimental platform has allowed to explore several phenomena related to QW-based protocols, e.g. the evolution in presence of different kinds of noise. In this landscape, to the best of our knowledge, few examples report on the introduction of absorbing centers and their effects on the coherence of the dynamics. Here we present and discuss the results related to absorbing boundaries in QWs obtained through theoretical simulations and experiments conducted with the universal photonic quantum processors realized by Quix Quantum. - oai:arXiv.org:2601.13269v1 + Beyond the Einstein-Bohr Debate: Cognitive Complementarity and the Emergence of Quantum Intuition + https://arxiv.org/abs/2601.15314 + arXiv:2601.15314v1 Announce Type: cross +Abstract: Recent high-precision experimental confirmations of quantum complementarity have revitalized foundational debates about measurement, description, and realism. This article argues that complementarity is most productively interpreted as an epistemic principle--constraining what can be simultaneously accessed and represented--rather than as an ontological claim about quantum reality. Reexamining the Einstein-Bohr debate through this lens reveals a persistent tension between descriptive completeness and contextual meaning, a tension experiments clarify but do not dissolve. Building on this analysis, we introduce cognitive complementarity as a structural principle governing reasoning under non-classical uncertainty, where mutually constraining representations cannot be jointly optimized. Within this framework, we propose quantum intuition as a testable cognitive capacity: the ability to sustain representational plurality, regulate commitment timing, and resolve perspective-incompatibilities in a context-sensitive manner. Formulated as a naturalistic construct grounded in shared informational constraints, quantum intuition offers a principled bridge between quantum measurement theory and cognition. This work reframes the historical debate, extends epistemic lessons from quantum foundations into cognitive science, and outlines empirical pathways for studying decision-making in contexts of irreducible uncertainty. + oai:arXiv.org:2601.15314v1 + q-bio.NC + cs.AI quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - new + Fri, 23 Jan 2026 00:00:00 -0500 + cross http://creativecommons.org/licenses/by/4.0/ - E. Stefanutti, J. Phillips, J. Buetow, A. Guidara, M. Nuvoli, A. Chiuri, L. Sansoni + Lalit Kumar Shukla - Rethinking Quantum Noise in Quantum Machine Learning: When Noise Improves Learning - https://arxiv.org/abs/2601.13275 - arXiv:2601.13275v1 Announce Type: new -Abstract: Quantum noise is conventionally viewed as a fundamental obstacle in near-term quantum computing, motivating extensive error correction and mitigation strategies. We present numerical evidence that challenges this consensus. Through experiments on quantum graph neural networks for molecular property prediction, we discover that quantum noise induces heterogeneous, initialization-dependent responses. Among randomly initialized models with identical architecture, approximately one-third show performance improvement under moderate noise, while a smaller fraction deteriorate and the remainder are marginally affected. We identify a strong negative correlation ($r = -0.62$) between baseline model performance and noise benefit, suggesting that noise acts as an implicit regularizer for under-optimized models while disrupting well-converged ones. The observed optimal noise level falls below theoretical predictions, indicating error cancellation in structured quantum circuits. These findings demonstrate that quantum noise effects depend critically on initialization quality and need not be uniformly detrimental, suggesting a shift from universal noise mitigation toward structure- and noise-aware optimization strategies. - oai:arXiv.org:2601.13275v1 + Non-zero Momentum Implies Long-Range Entanglement When Translation Symmetry is Broken in 1D + https://arxiv.org/abs/2601.15345 + arXiv:2601.15345v1 Announce Type: cross +Abstract: A result by Gioia and Wang [Phys Rev X 12, 031007 (2022)] showed that translationally symmetric states having nonzero momentum are necessarily long range entangled (LRE). Here, we consider the question: can a notion of momentum for non-translation symmetric states directly encode the nature of their entanglement, as it does for translation symmetric states? We show the answer is affirmative for 1D systems, while higher dimensional extensions and topologically ordered systems require further work. While Gioia and Wang's result applies to states connected via finite depth quantum circuits to a translation symmetric state, it is often impractical to find such a circuit to determine the nature of the entanglement of states that break translation symmetry. Here, instead of translation eigenstates, we focus on the many-body momentum distribution and the expectation value of the translation operator in many-body states of systems having broken translation symmetry. We show that in the continuum limit the magnitude of the expectation value of the translation operator $|<T>|$ necessarily goes to $1$ for delocalized states, a proxy for LRE states in 1D systems. This result can be seen as a momentum-space version of Resta's formula for the localization length. We investigate how accurate our results are in different lattice models with and without well-defined continuum limits. To that end, we introduce two models: a deterministic version of the random dimer model, illustrating the role of the thermodynamic and continuum limits for our result at a lattice level, and a simplified version of the Aubry-Andre model, with commensurate hopping for both momentum and position space. Finally, we use the random dimer model as a test case for the accuracy of $|<T>|$ as a localization (and thus entanglement) probe for 1D periodic lattice models without a well-defined continuum limit. + oai:arXiv.org:2601.15345v1 + cond-mat.dis-nn quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - new - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Linghua Zhu, Yulong Dong, Ziyu Zhang, Xiaosong Li + Fri, 23 Jan 2026 00:00:00 -0500 + cross + http://creativecommons.org/licenses/by/4.0/ + Amanda Gatto Lamas, Taylor L. Hughes - Quantum eigenvalues and eigenfunctions of an electron confined between conducting planes - https://arxiv.org/abs/2601.13278 - arXiv:2601.13278v1 Announce Type: new -Abstract: Two of the most iconic systems of quantum physics are the particle in a box and the Coulomb potential (the third is, of course, the harmonic oscillator). In this expository paper, we consider the quantum solution to the problem of an electron confined between the grounded planes of an infinite capacitor. The potential arises from the image charges that form in the grounded planes, along with the added condition that at x = 0, L, where L is the distance between the planes, the wavefunction must be zero. This effectively couples a hydrogen like system to a particle-in-a-box (PIB) based on L, the distance between the planes. The problem of finding the electrostatic potential of this infinite series of image charges is an old one, going back to at least 1929. Here, we give a short derivation for one of the limiting cases that yields a compact expression and show how the Kellogg infinite summation formula converges to that value. We note here that this potential is a symmetric double well potential, so there will be many familiar properties of its solutions. Then using that potential, we solve Schr\"odinger's equation using a spectral technique. The limiting forms of a particle in a box for small L (and high E), and that of a (degenerate) bound image charge at large L and small energy are recovered. We also discuss the tunneling level splitting that occurs in the transition from the large L to the small L regime. - oai:arXiv.org:2601.13278v1 - quant-ph + In-Substrate Imaging of Diamond hBN FET Current via Widefield Quantum Diamond Microscopy + https://arxiv.org/abs/2601.15355 + arXiv:2601.15355v1 Announce Type: cross +Abstract: We demonstrate widefield magnetic imaging of current flow in hydrogen terminated diamond field effect transistors (FETs) through in-substrate nitrogen vacancy (NV) centers. Hydrogen termination of the diamond surface induces a two dimensional hole gas (2DHG), while an ensemble of near surface NV centers located $ \sim 1~\mu m$ below the surface enables noninvasive magnetic imaging of current flow with micrometer scale spatial resolution. The FETs were electrically characterized over a range of drain source biases $V_{ds}= 0$ to $-15V$ and gate voltages,$V_{gs}= +3$ to $-9V$ followed by in situ widefield NV magnetometry during device operation. Magnetic field maps and reconstructed current density distributions directly visualize current injection at the source drain contacts and transport beneath the hBN gated channel. Magnetic field maps reveal current density variations in the channel region owing to non-uniformities or defects in the gate dielectric. In addition, we observe a pronounced enhancement of the drain current ($\sim 600-900 \mu A$) and a shift in the apparent threshold voltage during laser illumination, reflecting photo induced changes in channel electrostatics. By correlating gate dependent magnetic images with simultaneous electrical measurements, we directly link spatial current distributions to FET transfer characteristics, providing new insight into buried interface transport and non-uniform gating effects in the transistor channel. As the methodology is compatible with top gated FETs, it can be used to map channel current distributions with micrometer resolution in emerging channel materials, such as 2D materials and wide bandgap channels, and establish widefield NV magnetometry as a powerful platform for probing charge transport in transistors and Van der Waals dielectric heterostructures. + oai:arXiv.org:2601.15355v1 cond-mat.mes-hall - Wed, 21 Jan 2026 00:00:00 -0500 - new + quant-ph + Fri, 23 Jan 2026 00:00:00 -0500 + cross http://creativecommons.org/licenses/by/4.0/ - Don MacMillen + Anuj Bathla, Subrat Kumar Pradhan, Ajit Kumar Dash, Prabhat Anand, M. Girish Chandra, Kenji Watanabe, Takashi Taniguchi, Akshay Singh, Veeresh Deshpande, Kasturi Saha - The table maker's quantum search - https://arxiv.org/abs/2601.13306 - arXiv:2601.13306v1 Announce Type: new -Abstract: We show that quantum search can be used to compute the hardness to round an elementary function, that is, to determine the minimum working precision required to compute the values of an elementary function correctly rounded to a target precision of $n$ digits for all possible precision-$n$ floating-point inputs in a given interval. For elementary functions $f$ related to the exponential function, quantum search takes time $\tilde O(2^{n/2} \log (1/\delta))$ to return, with probability $1-\delta$, the hardness to round $f$ over all $n$-bit floating-point inputs in a given binade. For periodic elementary functions in large binades, standalone quantum search yields an asymptotic speedup over the best known classical algorithms and heuristics. - oai:arXiv.org:2601.13306v1 + Exploring Quantumness at Long-Baseline Neutrino Experiments + https://arxiv.org/abs/2601.15375 + arXiv:2601.15375v1 Announce Type: cross +Abstract: Violations of classicality can be probed through measurements performed on a system at different times, as proposed by Leggett and Garg. Specifically, violations of Leggett-Garg inequalities suggest the presence of quantum effects in macroscopic systems. Long-baseline neutrino experiments provide some of the longest available propagation distances over which such tests can be performed. Previous studies of Leggett-Garg tests in the neutrino sector have largely focused on showing that the oscillation probabilities can violate classical bounds for certain parameter choices. In this work, we develop a more complete and data-driven framework that treats both the distributions representing the classical and quantum behavior, as well as the experimental uncertainties. We consider MINOS, T2K, NOvA, as well as the upcoming DUNE, and present the respective statistical significance for distinguishing quantum behavior from classical scenarios at these long-baseline neutrino experiments. Among them, we find that T2K yields the most significant violation of classicality, at the level of $\sim 14 \sigma$, with NOvA and projections for DUNE also resulting in a significance of more than $5\sigma$. + oai:arXiv.org:2601.15375v1 + hep-ph + hep-ex quant-ph - cs.NA - math.NA - Wed, 21 Jan 2026 00:00:00 -0500 - new + Fri, 23 Jan 2026 00:00:00 -0500 + cross http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Stefanos Kourtis + Murshed Alam, Vedran Brdar, Dibya S. Chattopadhyay - Synthesis of Fault-tolerant State Preparation Circuits using Steane-type Error Detection - https://arxiv.org/abs/2601.13313 - arXiv:2601.13313v1 Announce Type: new -Abstract: Fault-tolerant state preparation is essential for reliable quantum error correction, particularly in Steane-type error correction, which relies on robust ancilla states for syndrome readout. One method of fault-tolerant state preparation is to initialize multiple ancilla states and check them against each other to detect problematic errors. In the worst case, the number of states required for successful initialization grows polynomially with the code distance, but it has been shown that this can be reduced to constant ancilla overhead-in the best case, only four states are required. However, existing techniques for finding low-overhead initialization schemes are limited to codes with large symmetry groups, such as the Golay code. In this work, we propose a general, automated synthesis methodology for Steane-type fault-tolerant state preparation circuits that applies to arbitrary Calderbank-Shor-Steane (CSS) codes and does not rely on code symmetries. We apply the proposed methods to various CSS codes up to a distance of seven and simulate the successful fault-tolerant initialization of logical basis states under circuit-level depolarizing noise. The circuits synthesized using the proposed methodology provide an important step towards experimental realizations of high-fidelity ancilla states for near-term demonstration of fault-tolerant quantum computation. - oai:arXiv.org:2601.13313v1 + Exactly solvable topological phase transition in a quantum dimer model + https://arxiv.org/abs/2601.15377 + arXiv:2601.15377v1 Announce Type: cross +Abstract: We introduce a family of generalized Rokhsar-Kivelson (RK) Hamiltonians, which are reverse-engineered to have an arbitrary edge-weighted superposition of dimer coverings as their exact ground state at the RK point. We then focus on a quantum dimer model on the triangular lattice, with doubly-periodic edge weights. For simplicity we consider a $2\times1$ periodic model in which all weights are set to one except for a tunable horizontal edge weight labeled $\alpha$. We analytically show that the model exhibits a continuous quantum phase transition at $\alpha=3$, changing from a topological $\mathbb{Z}_2$ quantum spin liquid ($\alpha<3$) to a columnar ordered state ($\alpha>3$). The dimer-dimer correlator decays exponentially on both sides of the transition with the correlation length $\xi\propto1/|\alpha-3|$ and as a power-law at criticality. The vison correlator exhibits an exponential decay in the spin liquid phase, but becomes a constant in the ordered phase. We explain the constant vison correlator in terms of loops statistics of the double-dimer model. Using finite-size scaling of the vison correlator, we extract critical exponents consistent with the 2D Ising universality class. + oai:arXiv.org:2601.15377v1 + cond-mat.str-el + cond-mat.stat-mech + math-ph + math.MP quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - new + Fri, 23 Jan 2026 00:00:00 -0500 + cross http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Erik Weilandt, Tom Peham, Robert Wille + Laura Shou, Jeet Shah, Matthew Lerner-Brecher, Amol Aggarwal, Alexei Borodin, Victor Galitski - Quantum Circuit Pruning: Improving Fidelity via Compilation-Aware Circuit Approximation - https://arxiv.org/abs/2601.13322 - arXiv:2601.13322v1 Announce Type: new -Abstract: This work presents a routing-aware pruning strategy for quantum circuits executed on Noisy Intermediate-Scale Quantum (NISQ) devices. We propose a method to remove parametric controlled rotations whose small rotation angles do not justify the routing overhead required for their implementation. By selectively pruning such gates, the method mitigates fidelity loss arising from additional SWAP operations introduced during compilation. Our approach evaluates whether executing a gate leads to greater fidelity loss than omitting it. Simulations on benchmark circuits with realistic noise models show that the method reduces two-qubit gate counts (up to 48.6%) while improving final state fidelity (up to 47.7%), especially for larger circuits where routing costs dominate. - oai:arXiv.org:2601.13322v1 + Stabilizer-Code Channel Transforms Beyond Repetition Codes for Improved Hashing Bounds + https://arxiv.org/abs/2601.15505 + arXiv:2601.15505v1 Announce Type: cross +Abstract: The quantum hashing bound guarantees that rates up to $1-H(p_I, p_X, p_Y, p_Z)$ are achievable for memoryless Pauli channels, but it is not generally tight. A known way to improve achievable rates for certain asymmetric Pauli channels is to apply a small inner stabilizer code to a few channel uses, decode, and treat the resulting logical noise as an induced Pauli channel; reapplying the hashing argument to this induced channel can beat the baseline hashing bound. We generalize this induced-channel viewpoint to arbitrary stabilizer codes used purely as channel transforms. Given any $ [\![ n, k ]\!] $ stabilizer generator set, we construct a full symplectic tableau, compute the induced joint distribution of logical Pauli errors and syndromes under the physical Pauli channel, and obtain an achievable rate via a hashing bound with decoder side information. We perform a structured search over small transforms and report instances that improve the baseline hashing bound for a family of Pauli channels with skewed and independent errors studied in prior work. + oai:arXiv.org:2601.15505v1 + cs.IT + math.IT quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - new + Fri, 23 Jan 2026 00:00:00 -0500 + cross http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Pau Escofet, Santiago Rodrigo, Rohit Sarma Sarkar, Carmen G. Almud\'ever, Eduard Alarc\'on, Sergi Abadal + Tyler Kann, Matthieu R. Bloch, Shrinivas Kudekar, Ruediger Urbanke - Polynomial-time certification of fidelity for many-body mixed states and mixed-state universality classes - https://arxiv.org/abs/2601.13333 - arXiv:2601.13333v1 Announce Type: new -Abstract: Computation of Uhlmann fidelity between many-body mixed states generally involves full diagonalization of exponentially large matrices. In this work, we introduce a polynomial-time algorithm to compute certified lower and upper bounds for the fidelity between matrix product density operators (MPDOs). Our method maps the fidelity estimation problem to a variational optimization of sequential quantum circuits, allowing for systematic improvement of the lower bounds by increasing the circuit depth. Complementarily, we obtain certified upper bounds on fidelity by variational lower bounds on the trace distance through the same framework. We demonstrate the power of this approach with two examples: fidelity correlators in critical mixed states, and codeword distinguishability in an approximate quantum error-correcting code. Remarkably, the variational lower bound accurately track the universal scaling behavior of the fidelity with a size-consistent relative error, allowing for the extraction of previously unknown critical exponents. Our results offer an exponential improvement in precision over known moment-based bounds and establish a scalable framework for the verification of many-body quantum systems. - oai:arXiv.org:2601.13333v1 + Quantum Coherence Spaces Revisited: A von Neumann (Co)Algebraic Approach + https://arxiv.org/abs/2601.15832 + arXiv:2601.15832v1 Announce Type: cross +Abstract: We describe a categorical model of MALL (Multiplicative Additive Linear Logic) inspired by the Heisenberg-Schr\"odinger duality of finite-dimensional quantum theory. Proofs of formulas with positive logical polarity correspond to CPTP (completely positive trace-preserving) maps in our model, i.e. the quantum operations in the Schr\"odinger picture, whereas proofs of formulas with negative logical polarity correspond to CPU (completely positive unital) maps, i.e. the quantum operations in the Heisenberg picture. The mathematical development is based on noncommutative geometry and finite-dimensional von Neumann (co)algebras, which can be defined as special kinds of (co)monoid objects internal to the category of finite-dimensional operator spaces. + oai:arXiv.org:2601.15832v1 + math.CT + cs.LO + math.FA + math.OA quant-ph - cond-mat.str-el - Wed, 21 Jan 2026 00:00:00 -0500 - new - http://creativecommons.org/licenses/by/4.0/ - Yuhan Liu, Yijian Zou + Fri, 23 Jan 2026 00:00:00 -0500 + cross + http://creativecommons.org/licenses/by-nc-nd/4.0/ + Thea Li, Vladimir Zamdzhiev - Stochastic resetting induces quantum non-Markovianity - https://arxiv.org/abs/2601.13367 - arXiv:2601.13367v1 Announce Type: new -Abstract: Stochastic resetting describes dynamics which are reinitialized to a reference state at random times. These protocols are attracting significant interest: they can stabilize nonequilibrium stationary states, generate correlations in noninteracting systems, and enable optimal search strategies. While a constant reset probability results in a Markovian dynamics, much less is known about non-Markovian effects in quantum stochastic resetting. Here, we analyze memory effects in these processes -- examining the evolution of quantum states and of observables -- through witnesses of non-Markovianity for open quantum systems. We focus on discrete-time reset processes, which are of particular interest as they can be implemented on existing gate-operated quantum devices. We show that these processes are generically described by non-divisible maps and, in non-classical scenarios where the effective reset probability can become negative, can feature revivals in the state distinguishability. Our results reveal non-Markovian effects in quantum stochastic resetting and show that a time-dependent reset may be exploited to engineer enhanced stationary quantum correlations. - oai:arXiv.org:2601.13367v1 + Magic of discrete lattice gauge theories + https://arxiv.org/abs/2601.15842 + arXiv:2601.15842v1 Announce Type: cross +Abstract: Simulation of quantum field theories and fundamental interactions are one of the most challenging tasks in modern particle physics. Classical computers generally fail to reproduce accurate results when it comes to strongly coupled theories such as QCD. Recent developments in quantum technologies open up the possibility of simulating such physical regimes by using quantum computers. In this paper, we study the quantum resource related to the simulability of a quantum theory, i.e. non-stabilizerness for Lattice Gauge Theory (LGT) with discrete symmetry gauge groups. We show that enforcing gauge constraints for $\mathbb{Z}_l$ LGTs has no cost in terms of this resource and discuss the relation between non-abelianity of the gauge group with the average non-stabilizerness of the gauge invariant Hilbert space. + oai:arXiv.org:2601.15842v1 + hep-lat quant-ph - cond-mat.stat-mech - Wed, 21 Jan 2026 00:00:00 -0500 - new + Fri, 23 Jan 2026 00:00:00 -0500 + cross http://creativecommons.org/licenses/by/4.0/ - Federico Carollo, Sascha Wald + 10.1142/S0219887825500033 + International Journal of Geometric Methods in Modern Physics Vol. 22, No. 06, 2550003 (2025) + Gianluca Esposito, Simone Cepollaro, Luigi Cappiello, Alioscia Hamma - Type-I and Type-II Fusion Protocols for Weighted Graph States - https://arxiv.org/abs/2601.13381 - arXiv:2601.13381v1 Announce Type: new -Abstract: Weighted graph states extend standard graph states by associating phases with entangling edges, and may serve as resources for measurement-based quantum computation (MBQC). We analyze how the two main fusion operations, Type-I and Type-II, act on weighted graph states. Type-I fusion operates identically to the unweighted case, merging two one-dimensional weighted graphs, while preserving edge weights and success probabilities. In addition, the pool of 2-qubit weighted graph states can be generated easily by GHZ states or Bell pairs. In contrast, Type-II fusion requires a logical qubit, which can be formed only for specific weight configurations, and with success probability below one-half, which is an obstacle one can avoid. When successful, it fuses the states correctly, but its failure outcomes destroy the structure of the graphs, removing the good-failure feature, known from ordinary graph states. We compute the entanglement reduction of the resulting link due to the fused states being weighted graph states (for generalized fusion), and classify the resulting states of a general non-Bell projection. These results define the practical limits of the fusion-based construction of weighted graph states for MBQC. - oai:arXiv.org:2601.13381v1 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - new - http://creativecommons.org/licenses/by-nc-nd/4.0/ - N. Rimock, Y. Oz - - - Precise estimation of the coupling strength between two nanomechanical modes from four Ramsey fringes - https://arxiv.org/abs/2601.13415 - arXiv:2601.13415v1 Announce Type: new -Abstract: We experimentally determine the coupling strength between two strongly coupled nanomechanical modes using a Ramsey-inspired technique optimized for signals as short as four fringes. The method is applied to precisely probe the change of the coupling rate induced by a modification of the microwave-cavity readout field. It opens a pathway towards sensing electrostatic field fluctuations approaching single-charge resolution. - oai:arXiv.org:2601.13415v1 + Reaching the intrinsic performance limits of superconducting strip photon detectors up to 0.1 mm wide + https://arxiv.org/abs/2601.15971 + arXiv:2601.15971v1 Announce Type: cross +Abstract: Superconducting nanowire single-photon detectors (SNSPDs) have emerged as the highest performing photon-counting detectors, making them a critical technology in quantum photonics and photon-starved optical sensing. However, the performance of SNSPDs is limited not by the intrinsic properties of the superconducting film, but by edge-induced current crowding. Despite extensive materials optimization and increasingly demanding fabrication strategies aimed at mitigating this edge-limited behavior, the device edges continue to limit the maximum device operating current, thereby degrading key performance metrics. Here, we demonstrate for the first time in situ tuning of a detector from an edge-limited to a bulk-limited regime, allowing the device to reach its intrinsic performance limit. Our approach is based on current-biased superconducting "rails" placed on either side of the detector to suppress current crowding at the edges. We show that activation of the rails reduces the dark count rate by nine orders of magnitude and extends the photon detection plateau at 1550 nm by more than 40%. These results are demonstrated on detectors up to 0.1 mm wide, establishing an entirely new class of ultra-wide strip detectors that we call superconducting strip photon detectors (SSPD). Moreover, the ability to suppress edge current crowding using the rails provides a pathway toward SSPDs with strip widths extending into the mm-scale. Such devices will enable large-area, high efficiency SSPD arrays with infrared sensitivity and open new opportunities in applications ranging from biomedical imaging to deep space optical communication. + oai:arXiv.org:2601.15971v1 + cond-mat.supr-con + physics.app-ph + physics.ins-det + physics.optics quant-ph - cond-mat.mes-hall - Wed, 21 Jan 2026 00:00:00 -0500 - new + Fri, 23 Jan 2026 00:00:00 -0500 + cross http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Anh Tuan Le, Avishek Chowdhury, Hugo Ribeiro, Eva M. Weig + Kristen M. Parzuchowski, Eli Mueller, Bakhrom G. Oripov, Benedikt Hampel, Ravin A. Chowdhury, Sahil R. Patel, Daniel Kuznesof, Emma K. Batson, Ryan Morgenstern, Robert H. Hadfield, Varun B. Verma, Matthew D. Shaw, Jason P. Allmaras, Martin J. Stevens, Alex Gurevich, Adam N. McCaughan - Efficient and compact quantum network node based on a parabolic mirror on an optical chip - https://arxiv.org/abs/2601.13420 - arXiv:2601.13420v1 Announce Type: new -Abstract: We demonstrate a neutral atom networking node that combines high photon collection efficiency with high atom photon entanglement fidelity in a compact, fiber integrated platform. A parabolic mirror is used both to form the trap and to collect fluorescence from a single rubidium atom, intrinsically mode matching $\sigma$ polarized emitted photons to the fiber and rendering the system largely insensitive to small imperfections or drifts. The core optics consist of millimeter scale components that are pre aligned, rigidly bonded on a monolithic invacuum assembly, and interfaced entirely via optical fibers. With this design, we measure an overall photon collection and detection efficiency of $3.66\%$, from which we infer an overall collection efficiency of $6.6\%$ after the single--mode fiber coupling. We generate atom photon entangled states with a raw Bell state fidelity of 0.93 and an inferred fidelity of 0.98 after correcting for atom readout errors. The same node design has been realized in two independent setups with comparable performance and is compatible with adding high NA objective lenses to create and control atomic arrays at each node. Our results establish a robust, cavity free neutral atom interface that operates near the limit set by the collection optics numerical aperture and provides a practical building block for scalable quantum network nodes and repeaters. - oai:arXiv.org:2601.13420v1 + Quantum Hall Effect at 0.002T + https://arxiv.org/abs/2601.16015 + arXiv:2601.16015v1 Announce Type: cross +Abstract: Graphene enables precise carrier-density control via gating, making it an ideal platform for studying electronic interactions. However, sample inhomogeneities often limit access to the low-density regimes where these interactions dominate. Enhancing carrier mobility is therefore crucial for exploring fundamental properties and developing device applications. Here, we demonstrate a significant reduction in external inhomogeneity using a double-layer graphene architecture separated by an ultra-thin hexagonal boron nitride layer. Mutual screening between the layers reduces scattering from random Coulomb potentials, resulting in a quantum mobility exceeding. Shubnikov de-Haas oscillations emerge at magnetic fields below 1 mT, while integer quantum Hall features are observed at 0.002T. Furthermore, we identify a fractional quantum Hall plateau at a filling factor of at 2T. These results demonstrate the platform's suitability for investigating strongly correlated electronic phases in graphene-based heterostructures. + oai:arXiv.org:2601.16015v1 + cond-mat.mes-hall quant-ph - physics.atom-ph - Wed, 21 Jan 2026 00:00:00 -0500 - new + Fri, 23 Jan 2026 00:00:00 -0500 + cross http://creativecommons.org/licenses/by/4.0/ - A. Safari, E. Oh, P. Huft, G. Chase, J. Zhang, M. Saffman + Alexander S. Mayorov, Ping Wang, Xiaokai Yue, Biao Wu, Jianhong He, Di Zhang, Fuzhuo Lian, Siqi Jiang, Jiabei Huang, Zihao Wang, Qian Guo, Kenji Watanabe, Takashi Taniguchi, Renjun Du, Rui Wang, Baigeng Wang, Lei Wang, Kostya S. Novoselov, Geliang Yu - Quantum Entanglement, Stratified Spaces, and Topological Matter: Towards an Entanglement-Sensitive Langlands Correspondence - https://arxiv.org/abs/2601.13467 - arXiv:2601.13467v1 Announce Type: new -Abstract: Recently, quantum entanglement has been presented as a cohomological obstruction to reconstructing a global quantum state from locally compatible information, where sheafification provides a functor that is forgetful with regards to global-from-local signatures while acting faithfully with respect to within-patch multipartite structures. Nontrivial connections to Hecke modifications and the geometric Langlands program are explored in the process. The aim of this work is to validate and extend a number of the claims made in [arXiv:2511.04326] through both theoretical analysis and numerical simulations, employing concrete perspectives from condensed matter physics. - oai:arXiv.org:2601.13467v1 - quant-ph + Helical Current of Propagating Dirac Electrons and Geometric Coupling to Chiral Environments + https://arxiv.org/abs/2601.16066 + arXiv:2601.16066v1 Announce Type: cross +Abstract: We show that a propagating Dirac electron with intrinsic spin generically carries a real--space helical conserved current, even in the absence of orbital angular momentum. Using exact Dirac eigenstates in cylindrical confinement, we demonstrate that this helical structure possesses definite handedness, persists into evanescent regions, and is characterized by a geometric helix pitch independent of the longitudinal de~Broglie wavelength. This intrinsic helical geometry enables a local geometric coupling between a propagating electron and a chiral environment, yielding chirality--dependent spin selectivity through current geometry rather than through a spin--orbit coupling term. + oai:arXiv.org:2601.16066v1 cond-mat.mes-hall - math-ph - math.MP - math.RT - Wed, 21 Jan 2026 00:00:00 -0500 - new - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Kazuki Ikeda, Steven Rayan - - - Symmetric Informationally Complete Positive Operator Valued Measure and Zauner conjecture - https://arxiv.org/abs/2601.13475 - arXiv:2601.13475v1 Announce Type: new -Abstract: In this paper, we show that in Hilbert space of any finite dimension N, there are N^2 pure states which constitute Symmetric Informationally Complete Positive Operator Valued Measure (SIC-POVM). - oai:arXiv.org:2601.13475v1 quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - new + Fri, 23 Jan 2026 00:00:00 -0500 + cross http://creativecommons.org/licenses/by/4.0/ - Stefan Joka + Ju Gao, Fang Shen - Confined non-Hermitian skin effect in a semi-infinite Fock-state lattice - https://arxiv.org/abs/2601.13540 - arXiv:2601.13540v1 Announce Type: new -Abstract: In this paper, we investigate the non-Hermitian skin effect in a semi-infinite Fock-state lattice, where the inherent coupling scales as \sqrt{n}. By analytically solving a non-uniform, non-reciprocal SSH model, we demonstrate that the intrinsic inhomogeneous coupling, in combination with nonreciprocity, fundamentally modifies the conventional skin effect. Instead of accumulating at the physical boundary, all eigenmodes become compressed and skewed within a finite spatial range determined by the inhomogeneous profile-a phenomenon we term the confined non-Hermitian skin effect. Consequently, the evolution of the probability distribution on the lattice starting from a single site is doubly confined: it is spatially bounded to a finite range by the inhomogeneous coupling, and further restricted to a one-sided trajectory at the edge of this range by the non-reciprocity. Moreover, a feasible experimental scheme based on a single trapped ion is also proposed. This work reveals how engineered coupling profiles in synthetic dimensions can reshape non-Hermitian properties and enable new protocols for quantum state manipulation. - oai:arXiv.org:2601.13540v1 + A pseudo-bosonic Klein-Gordon field with finite two-points function + https://arxiv.org/abs/2601.16131 + arXiv:2601.16131v1 Announce Type: cross +Abstract: We introduce a class of pseudo-bosonic Klein-Gordon fields in 1+1 dimensions and we discuss some of their properties. This work originates from non Hermitian quantum mechanics and deformed canonical commutation relations. We show that, within this class of fields, there exist a specific subclass with the interesting feature of having finite equal space-time two-points function, contrarily to what happens for {\em standard} Klein-Gordon fields. This, in our opinion, is a relevant aspect of our proposal which is a good motivation to undertake a deeper analysis of this (and related) quantum fields. + oai:arXiv.org:2601.16131v1 + math-ph + hep-th + math.MP quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - new + Fri, 23 Jan 2026 00:00:00 -0500 + cross http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Zhi Jiao Deng, Xing Yao Mi, Ruo Kun Cai, Chun Wang Wu, Ping Xing Chen + Fabio Bagarello - Fundamental Limits of Continuous Gaussian Quantum Metrology - https://arxiv.org/abs/2601.13554 - arXiv:2601.13554v1 Announce Type: new -Abstract: Continuous quantum metrology holds promise for realizing high-precision sensing by harnessing information progressively carried away by the radiation quanta emitted into the environment. Despite recent progress, a comprehensive understanding of the fundamental precision limits of continuous metrology with bosonic systems is currently lacking. We develop a general theoretical framework for quantum metrology with multimode free bosons under continuous Gaussian measurements. We derive analytical expressions for the asymptotic growth rates of the global quantum Fisher information (QFI) and the environmental QFI, which quantify the total information encoded in the joint system-environment state and the information accessible from the emitted radiation, respectively. We derive fundamental bounds on these quantities, showing that while Heisenberg-type scaling with the number of modes is attainable, the precision scales at most linearly with time and a meaningful energy resource. To illustrate our findings, we analyze several concrete setups, including coupled cavity arrays and trapped particle arrays. While a local setup yields a standard linear scaling with resources, a globally coupled setup can achieve the optimal quadratic scaling in terms of the mode number. Furthermore, we demonstrate that a nonreciprocal setup can leverage the non-Hermitian skin effect to realize an exponentially enhanced global QFI. Notably, however, this enhancement cannot be reflected in the environmental QFI, highlighting a fundamental distinction between the information stored within the joint state and the information radiated into the environment. These findings establish an understanding of the resource trade-offs and scaling behaviors in continuous bosonic sensing. - oai:arXiv.org:2601.13554v1 + On the structural properties of Lie algebras via associated labeled directed graphs + https://arxiv.org/abs/2601.16161 + arXiv:2601.16161v1 Announce Type: cross +Abstract: We present a method for associating labeled directed graphs to finite-dimensional Lie algebras, thereby enabling rapid identification of key structural algebraic features. To formalize this approach, we introduce the concept of graph-admissible Lie algebras and analyze properties of valid graphs given the antisymmetry property of the Lie bracket as well as the Jacobi identity. Based on these foundations, we develop graph-theoretic criteria for solvability, nilpotency, presence of ideals, simplicity, semisimplicity, and reductiveness of an algebra. Practical algorithms are provided for constructing such graphs and those associated with the lower central series and derived series via an iterative pruning procedure. This visual framework allows for an intuitive understanding of Lie algebraic structures that goes beyond purely visual advantages, since it enables a simpler and swifter grasping of the algebras of interest beyond computational-heavy approaches. Examples, which include the Schr\"odinger and Lorentz algebra, illustrate the applicability of these tools to physically relevant cases. We further explore applications in physics, where the method facilitates computation of similtude relations essential for determining quantum mechanical time evolution via the Lie algebraic factorization method. Extensions to graded Lie algebras and related conjectures are discussed. Our approach bridges algebraic and combinatorial perspectives, offering both theoretical insights and computational tools into this area of mathematical physics. + oai:arXiv.org:2601.16161v1 + math-ph + math.MP quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - new - http://creativecommons.org/licenses/by/4.0/ - Kazuki Yokomizo, Aashish A. Clerk, Yuto Ashida + Fri, 23 Jan 2026 00:00:00 -0500 + cross + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Tim Heib, David Edward Bruschi - A scalable near-visible integrated photon-pair source for satellite quantum science - https://arxiv.org/abs/2601.13617 - arXiv:2601.13617v1 Announce Type: new -Abstract: Quantum state distribution over vast distances is essential for global-scale quantum networks and fundamental test of quantum physics at space scale. While satellite platforms have demonstrated thousand-kilometer entanglement distribution, quantum key distribution and quantum teleportation with ground, future constellations and deep-space missions demand photon sources that are robust, compact, and power-efficient. Integrated photonics offers a scalable solution, yet a critical spectral gap persists. Although telecom-band integrated photon-pair sources are well established, near-visible photons offer distinct advantages for satellite-to-ground links by mitigating diffraction loss and maximizing the collection efficiency of optical telescopes. Scalable integrated sources in this regime have remained elusive due to the fundamental challenge of achieving anomalous dispersion in materials transparent at visible wavelengths. Here we bridge this gap by demonstrating an integrated near-visible photon-pair source based on a wide-bandgap, ultralow-loss, silicon nitride (Si$_3$N$_4$) microresonator. By engineering the dispersion of higher-order waveguide modes, we overcome the intrinsic normal dispersion limit to achieve efficient phase matching. The device exhibits a spectral brightness of 4.87$\times$10$^7$ pairs/s/mW$^2$/GHz and a narrow photon linewidth of 357 MHz. We report high-purity heralded single-photon generation with a heralding rate up to 2.3 MHz and a second-order correlation function as low as 0.0041. Furthermore, we observe energy-time entanglement with 98.4% interference visibility, violating the CHSH limit even at flux exceeding 40.6 million pairs/s. Combined with the proven radiation hardness of Si$_3$N$_4$, this source constitutes a flight-ready hardware foundation for daylight quantum communications and protocols requiring on-orbit multiphoton interference. - oai:arXiv.org:2601.13617v1 + String Breaking and Glueball Dynamics in $2+1$D Quantum Link Electrodynamics + https://arxiv.org/abs/2601.16166 + arXiv:2601.16166v1 Announce Type: cross +Abstract: At the heart of quark confinement and hadronization, the physics of flux strings has recently become a focal point in the field of quantum simulation of high-energy physics (HEP). Despite considerable progress, a detailed understanding of the behavior of flux strings in quantum simulation-relevant lattice formulations of gauge theories has remained limited to the lowest truncations of the gauge field, which are severely limited in their ability to draw conclusions about the quantum field theory limit. Here, we employ tensor network simulations to investigate the behavior of flux strings in a quantum link formulation of $2+1$D quantum electrodynamics (QED) with a spin-$1$ representation of the gauge field. We first map out the ground-state phase diagram of this model in the presence of two spatially separated static charges, revealing distinct microscopic processes responsible for string breaking, including a two-stage breaking mechanism not possible in the spin-$\frac{1}{2}$ formulation. Starting in different initial product state string configurations, we then explore far-from-equilibrium quench dynamics across various parameter regimes, demonstrating genuine $2+1$D real-time string breaking and glueball-like bound state formation, with the latter not possible in the spin-$\frac{1}{2}$ formulation. In and out of equilibrium, we consider different values and placements of the static charges. Finally, we provide efficient qudit circuits for a quantum simulation experiment in which our results can be observed in state-of-the-art ion-trap setups. Our findings lay the groundwork for quantum simulations of flux strings towards the quantum field theory limit. + oai:arXiv.org:2601.16166v1 + hep-lat + cond-mat.quant-gas + nucl-th quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - new - http://creativecommons.org/licenses/by/4.0/ - Yi-Han Luo, Yuan Chen, Ruiyang Chen, Zeying Zhong, Sicheng Zeng, Baoqi Shi, Sanli Huang, Chen Shen, Hui-Nan Wu, Yuan Cao, Junqiu Liu + Fri, 23 Jan 2026 00:00:00 -0500 + cross + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Jiahao Cao, Rohan Joshi, Yizhuo Tian, N. S. Srivatsa, Jad C. Halimeh - Theory for Entangled-Photons Stimulated Raman Scattering versus Nonlinear Absorption for Polyatomic Molecules - https://arxiv.org/abs/2601.13646 - arXiv:2601.13646v1 Announce Type: new -Abstract: Quantum entanglement offers an incredible resource for enhancing the sensing and spectroscopic probes. Here we develop a microscopic theory for the stimulated Raman scattering (SRS) using entangled photons. We demonstrate that the time-energy correlation of the photon pairs can optimize the signal for polyatomic molecules. Our results show that the spectral-line intensity of the entangled-photon SRS (ESRS) is of the same order of magnitude as the one for the entangled two-photon absorption (ETPA); the parameter window is thus identified to do so. Moreover, the vibrational coherence is found to play an important role for enhancing the ESRS against the ETPA intensity. Our work paves a firm road for extending the schemes of molecular spectroscopy with quantum light, based on the observation of the ETPA in experiments. - oai:arXiv.org:2601.13646v1 + Majorization theoretical approach to entanglement enhancement via local filtration + https://arxiv.org/abs/2312.02066 + arXiv:2312.02066v2 Announce Type: replace +Abstract: From the perspective of majorization theory, we study how to enhance the entanglement of a two-mode squeezed vacuum (TMSV) state by using local filtration operations. We present several schemes achieving entanglement enhancement with photon addition and subtraction, and then consider filtration as a general probabilistic procedure consisting in acting with local (non-unitary) operators on each mode. From this, we identify a sufficient set of two conditions for these filtration operators to successfully enhance the entanglement of a TMSV state, namely the operators must be Fock-orthogonal (i.e., preserving the orthogonality of Fock states) and Fock-amplifying (i.e., giving larger amplitudes to larger Fock states). Our results notably prove that ideal photon addition, subtraction, and any concatenation thereof always enhance the entanglement of a TMSV state in the sense of majorization theory. We further investigate the case of realistic photon addition (subtraction) and are able to upper bound the distance between a realistic photon-added (-subtracted) TMSV state and a nearby state that is provably more entangled than the TMSV, thus extending entanglement enhancement to practical schemes via the use of a notion of approximate majorization. Finally, we consider the state resulting from $k$-photon addition (on each of the two modes) on a TMSV state. We prove analytically that the state corresponding to $k=1$ majorizes any state corresponding to $2\leq k \leq 8$ and we conjecture the validity of the statement for all $k\geq 9$. + oai:arXiv.org:2312.02066v2 quant-ph - physics.chem-ph - Wed, 21 Jan 2026 00:00:00 -0500 - new - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Mingran Zhang, Jiahao Joel Fan, Frank Schlawin, Zhedong Zhang + Fri, 23 Jan 2026 00:00:00 -0500 + replace + http://creativecommons.org/licenses/by-nc-sa/4.0/ + 10.1103/PhysRevA.110.042430 + Phys. Rev. A 110, 042430 (2024) + Zacharie Van Herstraeten, Nicolas J. Cerf, Saikat Guha, Christos N. Gagatsos - 3D Stacked Surface-Code Architecture for Measurement-Free Fault-Tolerant Quantum Error Correction - https://arxiv.org/abs/2601.13648 - arXiv:2601.13648v1 Announce Type: new -Abstract: Mid-circuit measurements are a major bottleneck for superconducting quantum processors because they are slower and noisier than gates. Measurement-free quantum error correction (mfec) replaces repeated measurements and classical feed-forward by coherent quantum feedback, but existing mfec protocols suffer from severe connectivity overhead when mapped to planar surface-code architectures: transversal interactions between logical patches require SWAP chains of length $O(d)$ in the code distance, which increase depth and generate hook errors. This work introduces a 3D stacked surface-code architecture for measurement-free fault-tolerant quantum error correction that removes this connectivity bottleneck. Vertical transversal couplers between aligned surface-code patches enable coherent parity mapping and feedback with zero SWAP overhead, realizing constant-depth $O(1)$ inter-layer operations in d while preserving local 2D stabilizer checks. A fault-tolerant mfec protocol for the surface code is constructed that suppresses hook errors under realistic noise. An analytical performance model shows that the 3D architecture overcomes the readout error floor and achieves logical error rates orders of magnitude below both standard measurement-based surface codes and 2D mfec variants in regimes with slow, noisy measurements, identifying 3D integration as a key enabler for scalable measurement-free fault tolerance. - oai:arXiv.org:2601.13648v1 + Classical capacity of quantum non-Gaussian attenuator and amplifier channels + https://arxiv.org/abs/2312.15623 + arXiv:2312.15623v2 Announce Type: replace +Abstract: We consider a quantum bosonic channel that couples the input mode via a beam splitter or two-mode squeezer to an environmental mode that is prepared in an arbitrary state. We investigate the classical capacity of this channel, which we call a non-Gaussian attenuator or amplifier channel. If the environment state is thermal, we of course recover a Gaussian phase-covariant channel whose classical capacity is well known. Otherwise, we derive both a lower and an upper bound to the classical capacity of the channel, drawing inspiration from the classical treatment of the capacity of non-Gaussian additive-noise channels. We show that the lower bound to the capacity is always achievable and give examples where the non-Gaussianity of the channel can be exploited so that the communication rate beats the capacity of the Gaussian-equivalent channel (i.e., the channel where the environment state is replaced by a Gaussian state with the same covariance matrix). Finally, our upper bound leads us to formulate and investigate conjectures on the input state that minimizes the output entropy of non-Gaussian attenuator or amplifier channels. Solving these conjectures would be a main step towards accessing the capacity of a large class of non-Gaussian bosonic channels. + oai:arXiv.org:2312.15623v2 quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - new - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - GunSik Min, IlKwon Sohn, Jun Heo + Fri, 23 Jan 2026 00:00:00 -0500 + replace + http://creativecommons.org/licenses/by-nc-sa/4.0/ + 10.1142/S0219749924400033 + Int. J. Quantum Inf. 22, 2440003 (2024) + Zacharie Van Herstraeten, Saikat Guha, Nicolas J. Cerf - Spectral stability of cavity-enhanced single-photon emitters in silicon - https://arxiv.org/abs/2601.13666 - arXiv:2601.13666v1 Announce Type: new -Abstract: The unrivaled maturity of its nanofabrication makes silicon a promising hardware platform for quantum information processing. To this end, efficient single-photon sources and spin-photon interfaces have been implemented by integrating color centers or erbium dopants into nanophotonic resonators. However, the optical emission frequencies in this approach are subject to temporal fluctuations on both long and short timescales, which hinders the development of quantum applications. Here, we investigate this limitation and demonstrate that it can be alleviated by integrating the emitters into Fabry-Perot instead of nanophotonic resonators. Their larger optical mode volume enables both increasing the distance to crystal surfaces and operating at a lower dopant concentration, which reduces implantation-induced crystal damage and interactions between emitters. As a result, we observe a fivefold reduction of the spectral diffusion linewidth down to 4.0(2) MHz. Calculations and experimental investigations of isotopically purified 28-Si crystals suggest that the remaining spectral instability is caused by laser-induced electric-field fluctuations. In direct comparison with a nanophotonic device, the instability is significantly reduced at the same intracavity power, enabling a tenfold increase of the optical coherence time up to 20(1) microseconds. These findings represent a key step towards spectrally stable spin-photon interfaces in silicon and their potential applications in quantum networking and distributed quantum information processing. - oai:arXiv.org:2601.13666v1 + Third-quantized master equations as a classical Ornstein-Uhlenbeck process + https://arxiv.org/abs/2408.11893 + arXiv:2408.11893v3 Announce Type: replace +Abstract: Third quantization is used in open quantum systems to construct a superoperator basis in which quadratic Lindbladians can be turned into a normal form. From it follows the spectral properties of the Lindbladian, including eigenvalues and eigenvectors. However, the connection between third quantization and the semiclassical representations usually employed to obtain the dynamics of open quantum systems remains opaque. We introduce an alternative basis for third quantization that bridges this gap between third quantization and the $Q$ representation by projecting the master equation onto a superoperator coherent-state basis. The equation of motion reduces to a multidimensional complex Ornstein-Uhlenbeck process. + oai:arXiv.org:2408.11893v3 quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - new - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Johannes Fr\"uh, Fabian Salamon, Andreas Gritsch, Alexander Ulanowski, Andreas Reiserer + cond-mat.quant-gas + math-ph + math.MP + physics.class-ph + Fri, 23 Jan 2026 00:00:00 -0500 + replace + http://creativecommons.org/licenses/by-nc-nd/4.0/ + 10.1103/ntv6-jzvb + Phys. Rev. A 112, 063724 (2025) + L\'eonce Dupays - Generative Adversarial Networks for Resource State Generation - https://arxiv.org/abs/2601.13708 - arXiv:2601.13708v1 Announce Type: new -Abstract: We introduce a physics-informed Generative Adversarial Network framework that recasts quantum resource-state generation as an inverse-design task. By embedding task-specific utility functions into training, the model learns to generate valid two-qubit states optimized for teleportation and entanglement broadcasting. Comparing decomposition-based and direct-generation architectures reveals that structural enforcement of Hermiticity, trace-one, and positivity yields higher fidelity and training stability than loss-only approaches. The framework reproduces theoretical resource boundaries for Werner-like and Bell-diagonal states with fidelities exceeding ~98%, establishing adversarial learning as a lightweight yet effective method for constraint-driven quantum-state discovery. This approach provides a scalable foundation for automated design of tailored quantum resources for information-processing applications, exemplified with teleportation and broadcasting of entanglement, and it opens up the possibility of using such states in efficient quantum network design. - oai:arXiv.org:2601.13708v1 + Parallel Logical Measurements via Quantum Code Surgery + https://arxiv.org/abs/2503.05003 + arXiv:2503.05003v3 Announce Type: replace +Abstract: Quantum code surgery is a flexible and low overhead technique for performing logical measurements on quantum error-correcting codes, which generalises lattice surgery. In this work, we present a code surgery scheme, applicable to any qubit stabiliser low-density parity check (LDPC) code, that fault-tolerantly measures many logical Pauli operators in parallel. For a collection of logically disjoint Pauli product measurements supported on $t$ logical qubits, our scheme uses $O\big(t \omega (\log t + \log^3\omega)\big)$ ancilla qubits, where $\omega \geq d$ is the maximum weight of the single logical Pauli representatives involved in the measurements, and $d$ is the code distance. This is all done in time $O(d)$ independent of $t$. Our proposed scheme preserves both the LDPC property and the fault-distance of the original code, without requiring ancillary logical codeblocks which may be costly to prepare. This addresses a shortcoming of several recently introduced surgery schemes which can only be applied to measure a limited number of logical operators in parallel if they overlap on data qubits. + oai:arXiv.org:2503.05003v3 quant-ph - cs.LG - Wed, 21 Jan 2026 00:00:00 -0500 - new - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Shahbaz Shaik, Sourav Chatterjee, Sayantan Pramanik, Indranil Chakrabarty + Fri, 23 Jan 2026 00:00:00 -0500 + replace + http://creativecommons.org/licenses/by/4.0/ + Alexander Cowtan, Zhiyang He, Dominic J. Williamson, Theodore J. Yoder - Quantum Box-Muller Transform - https://arxiv.org/abs/2601.13718 - arXiv:2601.13718v1 Announce Type: new -Abstract: The Box-Muller transform is a widely used method to generate Gaussian samples from uniform samples. Quantum amplitude encoding methods encode the multi-variate normal distribution in the amplitudes of a quantum state. This work presents the Quantum Box-Muller transform which creates a superposition of binary-encoded grid points representing the multi-variate normal distribution. The gate complexity of our method depends on quantum arithmetic operations and, using a specific set of known implementations, the complexity is quadratic in the number of qubits. We apply our method to Monte-Carlo integration, in particular to the estimation of the expectation value of a function of Gaussian random variables. Our method implies that the state preparation circuit used multiple times in amplitude estimation requires only quantum arithmetic circuits for the grid points and the function, in addition to a single controlled rotation. We show how to provide the expectation value estimate with an error that is exponentially small in the number of qubits, similar to the amplitude-encoding setting with error-free encoding. - oai:arXiv.org:2601.13718v1 + Variational Perturbation Theory in Open Quantum Systems for Efficient Steady State Computation + https://arxiv.org/abs/2504.00085 + arXiv:2504.00085v2 Announce Type: replace +Abstract: Determining the steady state of an open quantum system is crucial for characterizing quantum devices and studying various physical phenomena. Often, computing a single steady state is insufficient, and it is necessary to explore its dependence on multiple external parameters. In such cases, calculating the steady state independently for each combination of parameters quickly becomes intractable. Perturbation theory (PT) can mitigate this challenge by expanding steady states around reference parameters, minimizing redundant computations across neighboring parameter values. However, PT has two significant limitations: it relies on the pseudo-inverse -- a numerically costly operation -- and has a limited radius of convergence. In this work, we remove both of these roadblocks. First, we introduce a variational perturbation theory (VPT) and its multipoint generalization that significantly extends the radius of convergence even in the presence of non-analytic effects such as dissipative phase transitions. Then, we develop two numerical strategies that eliminate the need to compute pseudo-inverses. The first relies on a single LU decomposition to efficiently construct the steady state within the convergence region, while the second reformulates VPT as a Krylov space recycling problem and uses preconditioned iterative methods. We benchmark these approaches across various models, demonstrating their broad applicability and significant improvements over standard PT. + oai:arXiv.org:2504.00085v2 quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - new + Fri, 23 Jan 2026 00:00:00 -0500 + replace http://creativecommons.org/licenses/by/4.0/ - Dinh-Long Vu, Hitomi Mori, Patrick Rebentrost + Andr\'e Melo, Gaspard Beugnot, Fabrizio Minganti - On-Chip Generation of Co-Polarized and Spectrally Separable Photon Pairs - https://arxiv.org/abs/2601.13740 - arXiv:2601.13740v1 Announce Type: new -Abstract: On-chip generation of high-purity single photons is essential for scalable photonic quantum technologies. Spontaneous parametric down-conversion (SPDC) is widely used to generate photon pairs for heralded single-photon sources, but intrinsic spectral correlations of the pairs often limit the purity and interference visibility of the heralded photons. Existing approaches to suppress these correlations rely on narrowband spectral filtering, which introduces loss, or exploiting different polarizations, which complicates on-chip integration. Here, we demonstrate a new strategy for generating spectrally separable photon pairs in thin-film lithium niobate nanophotonic circuits by harnessing higher-order spatial modes, with all interacting fields residing in the same polarization. Spectral separability is achieved by engineering group-velocity matching using higher-order transverse-electric modes, combined with a Gaussian-apodized poling profile to further suppress residual correlations inherent to standard periodic poling. Subsequent on-chip mode conversion with efficiency exceeding 95\% maps the higher-order mode to the fundamental mode and routes the photons into distinct output channels. The resulting heralded photons exhibit spectral purities exceeding 94\% inferred from joint-spectral intensity and 89\% from unheralded $g^{(2)}$ measurement. This approach enables flexible spectral and temporal engineering of on-chip quantum light sources for quantum computing and quantum networking. - oai:arXiv.org:2601.13740v1 + Entropy-based analysis of single-qubit Otto and Carnot heat engines + https://arxiv.org/abs/2505.01567 + arXiv:2505.01567v2 Announce Type: replace +Abstract: From an entropy-based formulation of the first law of thermodynamics in the quantum regime, we investigate the performance of Otto-like and Carnot-like engines for a single-qubit working medium. Within this framework, the first law includes an additional contribution -- coherence work -- that quantifies the energetic cost of deviating the quantum trajectory from its natural unitary evolution. We focus on the efficiency of the heat-to-coherence work conversion and show that the Carnot cycle achieves the classical Carnot efficiency, while the performance of the Otto cycle is upper-bounded by the Carnot efficiency corresponding to the extreme temperatures of the cycle. We identify entropy generation during the isochoric stages as the key source of irreversibility limiting the Otto cycle's efficiency. + oai:arXiv.org:2505.01567v2 quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - new + cond-mat.stat-mech + Fri, 23 Jan 2026 00:00:00 -0500 + replace http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Xiaojie Wang, Lin Zhou, Yue Li, Sakthi Sanjeev Mohanraj, Xiaodong Shi, Zhuoyang Yu, Ran Yang, Xu Chen, Guangxing Wu, Hao Hao, Sihao Wang, Veerendra Dhyani, Di Zhu + Andr\'es Vallejo, Catty Lissardy, Santiago Silva-Gallo, Alejandro Romanelli, Raul Donangelo - Limits of multimode bunching for boson sampling validation: anomalous bunching induced by time delays - https://arxiv.org/abs/2601.13792 - arXiv:2601.13792v1 Announce Type: new -Abstract: The multimode bunching probability is expected to provide a useful criterion for validating boson sampling experiments. Its applicability, however, is challenged by the existence of anomalous bunching, namely paradoxical situations in which partially distinguishable particles exhibit a higher bunching probability in two or more modes than perfectly indistinguishable ones. Using multimode bunching as a reliable criterion of genuine indistinguishability, therefore, requires a clear identification of the interferometric configurations in which anomalous bunching can or cannot occur. In particular, since uncontrolled small time delays between single-photon pulses constitute a common source of mode mismatch in current photonic platforms, it is essential to determine whether the resulting photon distinguishability might lead to anomalous bunching. Here, we first identify a broad class of interferometric configurations in which anomalous bunching is rigorously excluded, thereby establishing regimes where multimode bunching-based validation remains valid. Then, we find that, quite unexpectedly, temporal mode mismatch does not belong to this class. We exhibit a specific interferometric setup in which temporal distinguishability enhances multimode bunching, demonstrating that time delays can induce an anomalous behavior. These results help clarify the conditions under which multimode bunching remains a reliable validation tool. - oai:arXiv.org:2601.13792v1 + Numerical Optimization Strategies for the Variational Hamiltonian Ansatz in Noisy Quantum Environments + https://arxiv.org/abs/2505.22398 + arXiv:2505.22398v4 Announce Type: replace +Abstract: The prevalence of variational methods in near-term quantum computing makes optimizer choice critical, yet selection is frequently intuition-based. We therefore present a systematic benchmark of eight classical optimization algorithms for variational quantum chemistry using the truncated Variational Hamiltonian Ansatz. Performance is evaluated on H$_2$, H$_4$, and LiH in both full and active-space representations under noiseless and finite-shot sampling noise. Sampling noise substantially reshapes cost landscapes, induces wandering near minima, and flips optimizer rankings: gradient-based methods perform best in noiseless simulations, whereas population-based optimizers, particularly CMA-ES, show greater robustness under finite-shot noise. Optimizer performance is strongly problem dependent: Hartree-Fock initialization aids small systems, but its advantage diminishes with system size. Also, we observe that finite shot sampling frequently violates the lower bound given by the variational principle, a principle that cannot be strictly held in the presence of noise. By exploiting the guaranteed convergence of Evolution Strategies to a steady state distribution defined by the noise floor, we utilize the symmetry of these violations to achieve energy estimation precision beyond the intrinsic sampling limit. + oai:arXiv.org:2505.22398v4 quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - new + cs.NA + math.NA + Fri, 23 Jan 2026 00:00:00 -0500 + replace http://creativecommons.org/licenses/by/4.0/ - L\'eo Pioge, Leonardo Novo, Nicolas J. Cerf + S. Ill\'esov\'a, V. Nov\'ak, T. Bezd\v{e}k, C. Possel, M. Beseda - Composing $p$-adic qubits: from representations of SO(3)$_p$ to entanglement and universal quantum logic gates - https://arxiv.org/abs/2601.13808 - arXiv:2601.13808v1 Announce Type: new -Abstract: In the context of $p$-adic quantum mechanics, we investigate composite systems of $p$-adic qubits and $p$-adically controlled quantum logic gates. We build on the notion of a single $p$-adic qubit as a two-dimensional irreducible representation of the compact $p$-adic special orthogonal group SO(3)$_p$. We show that the classification of these representations reduces to the finite case, as they all factorise through some finite quotient SO(3)$_p$ mod $p^k$. Then, we tackle the problem of $p$-adic qubit composition and entanglement, fundamental for a $p$-adic formulation of quantum information processing. We classify the representations of SO(3)$_p$ mod $p$, and analyse tensor products of two $p$-adic qubit representations lifted from SO(3)$_p$ mod $p$. We solve the Clebsch-Gordan problem for such systems, revealing that the coupled bases decompose into singlet and doublet states. We further study entanglement arising from those stable subsystems. For $p=3$, we construct a set of gates from $4$-dimensional irreducible representations of SO(3)$_p$ mod $p$ that we prove to be universal for quantum computation. - oai:arXiv.org:2601.13808v1 + Erasure cost of a quantum process: A thermodynamic meaning of the dynamical min-entropy + https://arxiv.org/abs/2506.05307 + arXiv:2506.05307v4 Announce Type: replace +Abstract: The erasure of information is fundamentally an irreversible logical operation, carrying profound consequences for the energetics of computation and information processing. We investigate the thermodynamic costs associated with erasing (and preparing) quantum processes. Specifically, we analyze an arbitrary bipartite unitary gate acting on logical and ancillary input-output systems, where the ancillary input is always initialized in the ground state. We focus on the adversarial erasure cost of the reduced dynamics -- that is, the minimal thermodynamic work cost to erase the logical output of the gate for any logical input, assuming full access to the ancilla but no access to any purifying reference of the logical input state. We determine that this adversarial erasure cost is directly proportional to the negative min-entropy of the reduced dynamics, thereby giving the dynamical min-entropy a clear operational meaning. The dynamical min-entropy can take positive and negative values, depending on the underlying quantum dynamics. The negative value of the erasure cost implies that the extraction of thermodynamic work is possible instead of its consumption during the process. A key foundation of this result is the quantum process decoupling theorem, which quantitatively relates the decoupling ability of a process with its min-entropy. This insight bridges thermodynamics, information theory, and the fundamental limits of quantum computation. + oai:arXiv.org:2506.05307v4 quant-ph math-ph math.MP - math.RT - Wed, 21 Jan 2026 00:00:00 -0500 - new - http://creativecommons.org/licenses/by/4.0/ - Ilaria Svampa, Sonia L'Innocente, Stefano Mancini, Andreas Winter + Fri, 23 Jan 2026 00:00:00 -0500 + replace + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + 10.1088/2058-9565/ae34e2 + Quantum Science and Technology, vol. 11, no. 1, page 015038, January 2026 + Himanshu Badhani, Dhanuja GS, Swati Choudhary, Vishal Anand, Siddhartha Das - Squeezed-Light-Enhanced Multiparameter Quantum Estimation in Cavity Magnonics - https://arxiv.org/abs/2601.13814 - arXiv:2601.13814v1 Announce Type: new -Abstract: Improving multiparameter quantum estimation in magnonic systems via quantum noise suppression is a well-established and critical research objective. In this work, we propose an experimentally realistic scheme to improve the precision of simultaneously estimating different parameters in a cavity-magnon system by utilizing a degenerate optical parametric amplifier (OPA). The OPA enhances the estimation precision by decreasing the most informative quantum Cram\'er-Rao bound, calculated employing the symmetric logarithmic derivative (SLD) and the right logarithmic derivative (RLD). We show that when nonlinearity is introduced into the system, quantum noise is significantly suppressed. Our results show how different physical parameters influence multiparameter estimation precision and provide a detailed discussion of the associated physical mechanisms in the steady state. Our results focus on exploring practical Gaussian measurement schemes that can be realized experimentally. Besides, we further analyze the system's dynamics, comparing both the SLD quantum Fisher information (QFI) and the classical Fisher information (CFI) for both homodyne and heterodyne detection. This approach provides a robust foundation for multiparameter quantum estimation, offering significant potential for application in hybrid magnomechanical and optomechanical systems. - oai:arXiv.org:2601.13814v1 + Einstein Electron and Local Branching: Unitarity without Many Worlds --Local Hilbert spaces, boundaries, and quantum nonlocality + https://arxiv.org/abs/2507.16123 + arXiv:2507.16123v2 Announce Type: replace +Abstract: Traditional interpretations of quantum mechanics often present a dichotomy: either the wavefunction collapses upon measurement (Copenhagen), violating unitarity, or the entire universe branches into countless parallel worlds (Many-Worlds), with significant ontological proliferation. The Branched Hilbert Subspace Interpretation (BHSI) resolves this tension by introducing branching strictly within local Hilbert spaces. This framework reinterprets scenarios such as the Einstein 1927 electron-diffraction thought experiment, in which all quantum events are confined to a local Hilbert space, allowing the Born rule to emerge naturally from branch weights. Crucially, BHSI treats branching as a dynamical process tied to information recording. This leads to a testable proposal: a dual-layer experiment in which the particle transit time between layers is shorter than the sensor response time, enabling a direct probe of measurement timing and mismatched or uncommitted outcomes. We argue that a quantum system behaves as a unified whole, an island of coherence, within which unitary branching is confined to the system boundary, without observable correlations with distant, unentangled systems. Finally, we show that quantum nonlocality (e.g., in Bell tests or tunneling) arises naturally from the intrinsic vector-space structure of local Hilbert spaces, rather than from superluminal signaling. + oai:arXiv.org:2507.16123v2 quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - new + math-ph + math.MP + Fri, 23 Jan 2026 00:00:00 -0500 + replace http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Hamza Harraf, Mohamed Amazioug, Rachid Ahl Laamara + Xing M. Wang - Nonclassical photocounting statistics with a single on-off detector - https://arxiv.org/abs/2601.13869 - arXiv:2601.13869v1 Announce Type: new -Abstract: Any single on-off photocounter, which can only detect the presence or absence of photons without discriminating their number, is not capable of identifying nonclassical nature of light. This limitation arises because any photocounting statistics obtained with such a detector can be easily reproduced with coherent states of a light mode. We show that a simple modification of an on-off detector -- introducing controlled attenuation as a tunable setting -- enables such detectors to reveal nonclassical properties of radiation fields. - oai:arXiv.org:2601.13869v1 + Local-available quantum correlation swapping in one-parameter X states + https://arxiv.org/abs/2507.23142 + arXiv:2507.23142v3 Announce Type: replace +Abstract: Although introduced for entanglement, quantum repeaters and swapping protocols have been analyzed for other quantum correlations (QC), such as quantum discord. In 2015, Mundarain and Ladr\'on de Guevara [Quantum Inf. Process. 14, 4493 (2015)] introduced local-available quantum correlations (LAQC), which are a promising yet understudied quantum correlation. Recently, Bellorin et al. [Int. J. Mod. Phys. B 36, 22500990 (2022), Int. J. Mod. Phys. B 36, 2250154 (2022)] obtained exact analytical results for the LAQC quantifier of general 2-qubit X states. Building up from those results, we analyzed the LAQC swapping for 2-qubit X states. As expected, we find that if the initial states are non-classical and the one used for the projective measurement is entangled, the final state will generally have non-zero LAQC. Using the properties of this quantum correlation, we establish the conditions for a QCS scheme that leads to a final state with a non-zero LAQC measure. We illustrate these results by analyzing five families of one-parameter 2-qubit X states, including families where the projective measure leads to a separable state, but whose LAQC measure is non-zero. This feature opens the possibility for this quantum correlation to be considered a genuine resource in quantum information technology. + oai:arXiv.org:2507.23142v3 quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - new + physics.app-ph + Fri, 23 Jan 2026 00:00:00 -0500 + replace http://creativecommons.org/licenses/by/4.0/ - V. S. Kovtoniuk, M. Bohmann, A. A. Semenov + Hermann L. Albrecht - A phase space approach to the wavefunction and operator spreading in the Krylov basis - https://arxiv.org/abs/2601.13872 - arXiv:2601.13872v1 Announce Type: new -Abstract: In the Wigner-Weyl phase space formulation of quantum mechanics, we analyse the problem of the spreading of an initial state or an initial operator under time evolution when described in terms of the Krylov basis. After constructing the phase space representations of the Krylov basis states generated by a Hamiltonian from a given initial state by using the Weyl transformation, we subsequently use them to cast the Krylov state complexity as an integral over the phase space in terms of the Wigner function of the time-evolved initial state, so that the contribution of the classical Liouville equation and higher-order quantum corrections to the Wigner function time evolution equation towards the Krylov state complexity can be identified. Next, we construct the double phase space functions associated with the Krylov basis for the operators by using a suitable generalisation of the Weyl transformation applicable for superoperators, and use them to rewrite the Krylov operator complexity as an integral over the double phase space in terms of a generalisation of the usual Wigner function. These results, in particular, show that the complexity measures based on the expansion of a time-evolved state (or an operator) in the Krylov basis can be thought to belong to a general class of complexity measures constructed from the expansion coefficients of the time-dependent Wigner function in an orthonormal basis in the phase space, and help us to connect these complexity measures with measures of complexity of time-evolved state based on harmonic expansion of the time-dependent Wigner function. - oai:arXiv.org:2601.13872v1 + Can a Quantum Computer Simulate Nuclear Magnetic Resonance Spectra Better than a Classical One? + https://arxiv.org/abs/2508.06448 + arXiv:2508.06448v2 Announce Type: replace +Abstract: The simulation of the spectra measured in nuclear magnetic resonance (NMR) spectroscopy experiments is a computationally non-trivial problem which, due to its natural interpretation as a quantum spin problem, maps in a straightforward way to a quantum computer. As such, it represents a problem for which such a device may provide some practical advantage over traditional computing methods. In order to understand the extent to which such problems may indeed provide examples of useful quantum advantage, it is important to understand the limitations of existing classical simulation methods. In this work, we benchmark our own classical solver designed to study such problems. This solver uses a clustering approximation to achieve a resource scaling which is linear in the total number of nuclear spins in a given molecule, for a fixed cluster size. The success of such an approximation would present a stark repudiation to the common claim that such problems require an exponential scaling of resources, the very claim which makes simulating an NMR spectra a candidate for quantum advantage. Our benchmarking results indicate that our approximation performs well throughout, and even somewhat beyond, the more typical experimental regimes. We discuss what implications this may have for future efforts to demonstrate quantum advantage in the context of NMR. + oai:arXiv.org:2508.06448v2 quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - new + physics.chem-ph + Fri, 23 Jan 2026 00:00:00 -0500 + replace http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Kunal Pal, Kuntal Pal, Keun-Young Kim + Keith R. Fratus, Nicklas Enenkel, Sebastian Zanker, Jan-Michael Reiner, Michael Marthaler, Peter Schmitteckert - On spooky action at a distance and conditional probabilities - https://arxiv.org/abs/2601.13875 - arXiv:2601.13875v1 Announce Type: new -Abstract: The aim of this expos\'e is to make explicit the analogy between the classical notion of non-independent probability distribution and the quantum notion of entangled state. - To bring that analogy forth, we consider a classical systems with two dependent random variables and a quantum system with two components. In the classical case, afet observing one of the random variables, the underlying sample space and the probability distribution change. In the quantum case, when and event pertaining to one of the components is observed, the post-measurement state captures, both, the change in the state of the system and implicitly the new probability distribution. - The predictions after a measurement in the classical case and in the quantum case, have to be computed with the conditional distribution given the value of the observed variable. - oai:arXiv.org:2601.13875v1 + Gradients, parallelism, and variance of quantum estimates + https://arxiv.org/abs/2509.11214 + arXiv:2509.11214v2 Announce Type: replace +Abstract: Computation of observables and their gradients on near-term quantum hardware is a central aspect of any quantum algorithm. In this work, we first review standard approaches to the estimation of observables with and without quantum amplitude estimation for both cost functions and gradients, discuss sampling problems, and analyze variance propagation on quantum circuits with and without Linear Combination of Unitaries (LCU). Afterwards, we systematically analyze the standard approaches to gradient computation with LCU circuits. Finally, we develop a LCU gradient framework for the most general gradients based on n-qubit gates and for time-dependent quantum control gradient, analyze the convergence behaviour of the circuit estimators, and provide detailed circuit representations of both for near-term and fault-tolerant hardware. + oai:arXiv.org:2509.11214v2 quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - new - http://creativecommons.org/licenses/by-sa/4.0/ - Henryk Gzyl + Fri, 23 Jan 2026 00:00:00 -0500 + replace + http://creativecommons.org/publicdomain/zero/1.0/ + Francesco Preti, Michael Schilling, J\'ozsef Zsolt Bern\'ad, Tommaso Calarco, Francisco C\'ardenas-L\'opez, Felix Motzoi - Low-Resource Quantum Energy Gap Estimation via Randomization - https://arxiv.org/abs/2601.13881 - arXiv:2601.13881v1 Announce Type: new -Abstract: Estimating the energy spectra of quantum many-body systems is a fundamental task in quantum physics, with applications ranging from chemistry to condensed matter. Algorithmic shadow spectroscopy is a recent method that leverages randomized measurements on time-evolved quantum states to extract spectral information. However, implementing accurate time evolution with low-depth circuits remains a key challenge for near-term quantum hardware. In this work, we propose a hybrid quantum-classical protocol that integrates Time Evolution via Probabilistic Angle Interpolation (TE-PAI) into the shadow spectroscopy framework. TE-PAI enables the simulation of time evolution using shallow stochastic circuits while preserving unbiased estimates through quasiprobability sampling. We construct the combined estimator and derive its theoretical properties. Through numerical simulations, we demonstrate that our method accurately resolves energy gaps and exhibits enhanced robustness to gate noise compared to standard Trotter-based shadow spectroscopy. We further validate the protocol experimentally on up to 20 qubits using IBM quantum hardware. This makes TE-PAI shadow spectroscopy a promising tool for spectral analysis on noisy intermediate-scale quantum (NISQ) devices. - oai:arXiv.org:2601.13881v1 + Triple-Tone Microwave Control for Sensitivity Optimization in Compact Ensemble Nitrogen-Vacancy Magnetometers + https://arxiv.org/abs/2510.00913 + arXiv:2510.00913v3 Announce Type: replace +Abstract: Ensembles of nitrogen-vacancy (NV) centers in diamond are a well-established platform for quantum magnetometry under ambient conditions. One challenge arises from the hyperfine structure of the NV, which, for the common $^{14}$N isotope, results in a threefold reduction of contrast and thus sensitivity. By addressing each of the NV hyperfine transitions individually, triple-tone microwave (MW) control can mitigate this sensitivity loss. Here, we experimentally and theoretically investigate the regimes in which triple-tone excitation offers an advantage over standard single-tone MW control for two DC magnetometry protocols: pulsed optically detected magnetic resonance (ODMR) and Ramsey interferometry. We validate a master equation model of the NV dynamics against ensemble NV measurements, and use the model to explore triple-tone vs single-tone sensitivity for different MW powers and NV dephasing rates. For pulsed ODMR, triple-tone driving improves sensitivity by up to a factor of three in the low-dephasing regime, with diminishing gains when dephasing rates approach the hyperfine splitting. In contrast, for Ramsey interferometry, triple-tone excitation only improves sensitivity if MW power is limited. Our results delineate the operating regimes where triple-tone control provides a practical strategy for enhancing NV ensemble magnetometry in portable and power-limited sensors. + oai:arXiv.org:2510.00913v3 quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - new + Fri, 23 Jan 2026 00:00:00 -0500 + replace http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Hugo Pages, Chusei Kiumi, Yuto Morohoshi, B\'alint Koczor, Kosuke Mitarai + Ankita Chakravarty, Romain Ruhlmann, Vincent Halde, David Roy-Guay, Michel Pioro-Ladri\`ere, Lilian Childress, Yves B\'erub\'e-Lauzi\`ere - Bright Heralded Single-Photon Superradiance in a High-Density Thin Vapor Cell - https://arxiv.org/abs/2601.13909 - arXiv:2601.13909v1 Announce Type: new -Abstract: Superradiance is a hallmark of cooperative quantum emission, where radiative decay is collectively enhanced by coherence among emitters. Here, extending superradiant effects to photon pair generation from multi-level atoms, two-photon process offers a pathway to novel quantum light sources and a useful case for practical superradiance. We report bright heralded single-photon superradiance via spontaneous four-wave mixing in a 1-mm-long, high-density cesium vapor cell. By reducing the average distance between atoms in the atomic vapor to 0.29 times the idler photon wavelength, we observe a dramatic narrowing of the temporal two-photon wavefunction. This compression of temporal two-photon wavefunction evidences the superradiance of heralded photons in the collective two-photon emission dynamics. Furthermore, our heralded single-photon superradiance is accompanied by a coincidence-to-accidental ratio of 200 and the detected photon-pair counting exceeding 10^6 pairs/s. These findings establish dense thin atomic vapors as a practical, robust medium for realizing superradiant photon sources, with immediate relevance for quantum optics and the development of efficient photonic quantum technologies. - oai:arXiv.org:2601.13909v1 + Non-stabilizerness in quantum-enhanced metrological protocols + https://arxiv.org/abs/2510.01380 + arXiv:2510.01380v2 Announce Type: replace +Abstract: Non-stabilizerness (colloquially "magic") characterizes genuinely quantum (beyond-Clifford) operations necessary for preparation of quantum states, and can be measured by stabilizer R\'enyi entropy (SRE). For permutationally symmetric states, we show that the SRE depends, for sufficiently large systems, only on a constant number of expectation values of collective spin operators. This compact description is leveraged for analysis of spin-squeezing protocols, which inherently generate non-stabilizerness. Under one-axis twisting (OAT), the generation of optimal squeezing is accompanied by a logarithmic divergence of SRE with system system size. Continued time evolution under OAT produces metrologically useful "kitten" states-superpositions of rotated GHZ states-that feature many-body Bell correlations but exhibit a smaller, system-size-independent SRE that decreases with increasing Bell-correlation strength. Our results reveal connections between non-stabilizerness, multipartite correlations, and quantum metrology, and provide a practical route to quantify non-stabilizerness in experiments for precision sensing. + oai:arXiv.org:2510.01380v2 quant-ph - physics.atom-ph - physics.optics - Wed, 21 Jan 2026 00:00:00 -0500 - new - http://creativecommons.org/licenses/by-nc-nd/4.0/ - Heewoo Kim, Bojeong Seo, Han Seb Moon + cond-mat.quant-gas + Fri, 23 Jan 2026 00:00:00 -0500 + replace + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + 10.1103/tmf9-fyc2 + Phys. Rev. A 113, 012416 (2026) + Tanaus\'u Hern\'andez-Yanes, Piotr Sierant, Jakub Zakrzewski, Marcin P{\l}odzie\'n - Universal composite phase gates with tunable target phase - https://arxiv.org/abs/2601.13923 - arXiv:2601.13923v1 Announce Type: new -Abstract: We present a systematic method for constructing universal composite phase gates with a continuously tunable target phase. Using a general Cayley--Klein parametrization of the single-pulse propagator, we design gates from an even number of nominal $\pi$ pulses and derive analytic phase families by canceling, order by order in a small deviation parameter, the leading contributions to the undesired off-diagonal element of the composite propagator, independently of the dynamical phase. The resulting sequences provide intrinsic robustness against generic control imperfections and parameter fluctuations and remain valid for arbitrary pulse shapes. Numerical simulations in a standard two-level model confirm high-order error suppression and demonstrate broad, flat high-fidelity plateaus over wide ranges of simultaneous pulse-area and detuning errors, highlighting the efficiency of the proposed universal composite phase gates for resilient phase control in quantum information processing. - oai:arXiv.org:2601.13923v1 + Quantum matrix arithmetics with Hamiltonian evolution + https://arxiv.org/abs/2510.06316 + arXiv:2510.06316v2 Announce Type: replace +Abstract: The efficient implementation of matrix arithmetic operations underpins the speedups of many quantum algorithms. We develop a suite of methods to perform matrix arithmetics -- with the result encoded in the off-diagonal blocks of a Hamiltonian -- using Hamiltonian evolutions of input operators. We show how to maintain this $\textit{Hamiltonian block encoding}$, so that matrix operations can be composed one after another, and the entire quantum computation takes $\leq 2$ ancilla qubits. We achieve this for matrix multiplication, matrix addition, matrix inversion, Hermitian conjugation, fractional scaling, integer scaling, complex phase scaling, as well as singular value transformation for both odd and even polynomials. We also present an overlap estimation algorithm to extract classical properties of Hamiltonian block encoded operators, analogous to the well known Hadmard test, at no extra cost of qubit. Our Hamiltonian matrix multiplication uses the Lie group commutator product formula and its higher-order generalizations due to Childs and Wiebe. Our Hamiltonian singular value transformation employs a dominated polynomial approximation, where the approximation holds within the domain of interest, while the constructed polynomial is upper bounded by the target function over the entire unit interval. We describe a circuit for simulating a class of sum-of-squares Hamiltonians, attaining a commutator scaling in step count, while leveraging the power of matrix arithmetics to reduce the cost of each simulation step. In particular, we apply this to the doubly factorized tensor hypercontracted Hamiltonians from recent studies of quantum chemistry, obtaining further improvements for initial states with a fixed number of particles. We achieve this with $1$ ancilla qubit. + oai:arXiv.org:2510.06316v2 quant-ph - physics.atom-ph - Wed, 21 Jan 2026 00:00:00 -0500 - new + cs.DS + cs.NA + math.NA + physics.chem-ph + Fri, 23 Jan 2026 00:00:00 -0500 + replace http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Peter Chernev, Mouhamad Al-Mahmoud, Andon A. Rangelov + Christopher Kang, Yuan Su - Ultra Compact low cost two mode squeezed light source - https://arxiv.org/abs/2601.13939 - arXiv:2601.13939v1 Announce Type: new -Abstract: Quantum-correlated states of light, such as squeezed states, constitute a fundamental resource for quantum technologies, enabling enhanced performance in quantum metrology, quantum information processing, and quantum communications. The practical deployment of such technologies requires squeezed-light sources that are compact, efficient, low-cost, and robust. Here we report a compact narrowband source of two-mode squeezed light at 795 nm based on four-wave mixing in hot 85Rb atomic vapor. The source is implemented in a small, modular architecture featuring a single fiber-coupled input, an electro-optic phase modulator combined with a single Fabry-Perot etalon for probe generation, and two free-space output modes corresponding to the signal and conjugate fields. Optimized for low pump power, the system achieves up to -8 dB of intensity-difference squeezing at an analysis frequency of 0.8 MHz with a pump power of only 300 mW. The intrinsic narrowband character of the generated quantum states makes this source particularly well suited for atomic-based quantum sensing and quantum networking, including interfaces with atomic quantum memories. Our results establish a versatile and portable platform for low-SWaP squeezed-light generation, paving the way toward deployable quantum-enhanced technologies. - oai:arXiv.org:2601.13939v1 + Verifiable blind observable estimation + https://arxiv.org/abs/2510.08548 + arXiv:2510.08548v2 Announce Type: replace +Abstract: Cryptographic verification is essential for establishing trust in quantum-computing-as-a-service. However, a fundamental gap exists in the current verification landscape: existing efficient protocols are largely restricted to decision problems where correctness is boosted by classical majority voting. This excludes observable estimation, the statistical task underpinning nearly all near-term quantum advantage applications. For such tasks, current verification techniques face a prohibitive trade-off: either weak security guarantees or massive space overhead that exceeds the capacity of near-term hardware. To resolve this, we introduce the Secure Delegated Observable Estimation (SDOE) ideal resource, the first formal cryptographic framework for trustworthy expectation-value estimation within Abstract Cryptography. We then present the Verifiable Blind Observable Estimation (VBOE) protocol, which efficiently constructs this resource. VBOE circumvents the limitations inherent in prior methodologies by enabling the sequential collection of samples with negligible security error, requiring zero extra qubit overhead. By directly averaging computation rounds in classical post-processing, our protocol provides the only known path to rigorous, composable verification for the most common class of near-term quantum-classical hybrid algorithms. This work bridges foundational cryptographic theory with practical quantum tasks, enabling the certification of quantum utility on current and near-future devices. + oai:arXiv.org:2510.08548v2 quant-ph - physics.atom-ph - physics.optics - Wed, 21 Jan 2026 00:00:00 -0500 - new + Fri, 23 Jan 2026 00:00:00 -0500 + replace http://creativecommons.org/licenses/by/4.0/ - Shahar Monsa, Shmuel Sternklar, Eliran Talker + Bo Yang, Elham Kashefi, Harold Ollivier - Tensor Network Assisted Distributed Variational Quantum Algorithm for Large Scale Combinatorial Optimization Problem - https://arxiv.org/abs/2601.13956 - arXiv:2601.13956v1 Announce Type: new -Abstract: Although quantum computing holds promise for solving Combinatorial Optimization Problems (COPs), the limited qubit capacity of NISQ hardware makes large-scale instances intractable. Conventional methods attempt to bridge this gap through decomposition or compression, yet they frequently fail to capture global correlations of subsystems, leading to solutions of limited quality. We propose the Distributed Variational Quantum Algorithm (DVQA) to overcome these limitations, enabling the solution of 1,000-variable instances on constrained hardware. A key innovation of DVQA is its use of the truncated higher-order singular value decomposition to preserve inter-variable dependencies without relying on complex long-range entanglement, leading to a natural form of noise localization where errors scale with subsystem size rather than total qubit count, thus reconciling scalability with accuracy. Theoretical bounds confirm the algorithm's robustness for p-local Hamiltonians. Empirically, DVQA achieves state-of-the-art performance in simulations and has been experimentally validated on the Wu Kong quantum computer for portfolio optimization. This work provides a scalable, noise-resilient framework that advances the timeline for practical quantum optimization algorithms. - oai:arXiv.org:2601.13956v1 + Thermodynamics of quantum processes: An operational framework for free energy and reversible athermality + https://arxiv.org/abs/2510.12790 + arXiv:2510.12790v3 Announce Type: replace +Abstract: We explore the thermodynamics of quantum processes (quantum channels) by axiomatically introducing the free energy for channels, defined via the quantum relative entropy with an absolutely thermal channel whose fixed output is in equilibrium with a thermal reservoir. This definition finds strong support through its operational interpretations in designated quantum information and thermodynamic tasks. We construct a resource theory of athermality for quantum processes, where free operations are Gibbs preserving superchannels and golden units are unitary channels with respect to absolutely thermal channel having fully degenerate output Hamiltonian. We exactly characterize the one-shot distillation and formation of quantum channels using hypothesis-testing and max-relative entropy with respect to the absolutely thermal channel. These rates converge asymptotically to the channel free energy (up to a multiplicative factor of half the inverse temperature), establishing its operational meaning and proving the asymptotic reversibility of the athermality. We show the direct relation between the resource theory of athermality and quantum information tasks such as private randomness and purity distillation, and thermodynamic tasks of erasure and work extraction. Our work connects the core thermodynamic concepts of free energy, energy, entropy, and maximal extractable work of quantum processes to their information processing capabilities. + oai:arXiv.org:2510.12790v3 quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - new - http://creativecommons.org/licenses/by-nc-nd/4.0/ - Yuhan Huang, Siyuan Jin, Yichi Zhang, Qi Zhao, Jun Qi, Qiming Shao - - - A Converse Bound via the Nussbaum-Szko{\l}a Mapping for Quantum Hypothesis Testing - https://arxiv.org/abs/2601.13970 - arXiv:2601.13970v1 Announce Type: new -Abstract: Quantum hypothesis testing concerns the discrimination between quantum states. This paper introduces a novel lower bound for asymmetric quantum hypothesis testing that is based on the Nussbaum-Szko{\l}a mapping. The lower bound provides a unified recovery of converse results across all major asymptotic regimes, including large-, moderate-, and small-deviations. Unlike existing bounds, which either rely on technically involved information-spectrum arguments or suffer from fixed prefactors and limited applicability in the non-asymptotic regime, the proposed bound arises from a single expression and enables, in some cases, the direct use of classical results. It is further demonstrated that the proposed bound provides accurate approximations to the optimal quantum error trade-off function at small blocklengths. Numerical comparisons with existing bounds, including those based on fidelity and information spectrum methods, highlight its improved tightness and practical relevance. - oai:arXiv.org:2601.13970v1 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - new - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Jorge Lizarribar-Carrillo, Gonzalo Vazquez-Vilar, Tobias Koch - - - Experimental Evidence-Based Sub-Rayleigh Source Discrimination - https://arxiv.org/abs/2601.13972 - arXiv:2601.13972v1 Announce Type: new -Abstract: We propose a Bayesian evidence-based inference framework based on relative belief ratios and apply it to discriminating between one and two incoherent optical point sources using spatial-mode demultiplexing (SPADE). Unlike the Helstrom measurement, SPADE require no collective detection and its optimal for asymptotically large samples. Our method avoids ad hoc statistical constructs and relies solely on the information contained in the data, with all assumptions entering only through the likelihood model and prior beliefs. Using experimental evidence, we demonstrate the superior resolving performance of SPADE over direct imaging from a new and extensible perspective; one that naturally generalizes to multiple sources and offers a practical robust approach to analyzing quantum-enhanced superresolution. - oai:arXiv.org:2601.13972v1 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - new - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Saurabh U. Shringarpure, Yong Siah Teo, Hyunseok Jeong, Michael Evans, Luis L. Sanchez-Soto, Antonin Grateau, Alexander Boeschoten, Nicolas Treps - - - Optimal Construction of Two-Qubit Gates using the Symmetries of B Gate Equivalence Class - https://arxiv.org/abs/2601.13983 - arXiv:2601.13983v1 Announce Type: new -Abstract: Two applications of gates from the B gate equivalence class can generate all two-qubit gates. This local equivalence class is invariant under the mirror (multiplication with the SWAP gate) operation, inverse (Hermitian conjugate) operation, and the combined inverse and mirror operations. The last two symmetries are associated with the ability of a two-qubit gate to generate the two-qubit local gates and the SWAP gate in two applications. No single local equivalence class of two-qubit gates, except the B gate equivalence class, has these two symmetries. Only the planar regions of the Weyl chamber, describing the mirror operation, contain the local equivalence classes with either one of the two symmetries. We show that there exist one-parameter families of local equivalence classes on these planes, with and without the B gate equivalence class, such that each of them can be used to construct a parameterized universal two-qubit quantum circuit that involves only two nonlocal two-qubit gates. We also discuss the implementation of the gates from a few families of local equivalence classes on superconducting quantum computers for optimal generation of all two-qubit gates. - oai:arXiv.org:2601.13983v1 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - new - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - M. Karthick Selvan, S. Balakrishnan - - - Tripartite quantum correlations obtained by post-selection from twin beams - https://arxiv.org/abs/2601.14017 - arXiv:2601.14017v1 Announce Type: new -Abstract: Spatially-resolved photon counting of a twin beam performed by an iCCD camera allows for versatile tailoring the properties of the beams formed by parts of the original twin beam. Dividing the idler beam of the twin beam into three equally-intense parts and post-selecting by detecting a given number of photocounts in the whole signal beam we arrive at the idler fields exhibiting high degrees of nonclassicality and being endowed with tripartite quantum correlations. Nonclassicality is analyzed with the help of suitable nonclassicality witnesses and their corresponding nonclassicality depths. Suitable parameters are introduced to quantify quantum correlations. These parameters are analyzed as they depend on the field intensity. The experimental photocount histograms are reconstructed by the maximum-likelihood approach and the obtained photon-number distributions are compared with a suitable model in which the original twin beam is approximated by an appropriate multi-mode Gaussian field and undergoes the corresponding beams' transformations. - oai:arXiv.org:2601.14017v1 - quant-ph - physics.optics - Wed, 21 Jan 2026 00:00:00 -0500 - new - http://creativecommons.org/licenses/by/4.0/ - Pavel Pavlicek, Jan Perina Jr., Vaclav Michalek, Radek Machulka, Ondrej Haderka - - - The rate of purification of quantum trajectories - https://arxiv.org/abs/2601.14023 - arXiv:2601.14023v1 Announce Type: new -Abstract: We investigate the behavior of quantum trajectories conditioned on measurement outcomes. Under a condition related to the absence of so-called dark subspaces, K\"{u}mmerer and Maassen had shown that such trajectories almost surely purify in the long run. In this article, we first present a simple alternative proof of this result using Lyapunov methods. We then strengthen the conclusion by proving that purification actually occurs at an exponential rate in expectation, again using a Lyapunov approach. Furthermore, we address the quantum state estimation problem by propagating two trajectories under the same measurement record--one from the true initial state and the other from an arbitrary initial guess--and show that the estimated trajectory converges exponentially fast to the true one, thus quantifying the rate at which information is progressively revealed through the measurement process. - oai:arXiv.org:2601.14023v1 - quant-ph - math-ph - math.MP - Wed, 21 Jan 2026 00:00:00 -0500 - new - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Ma\"el Bompais, Nina H. Amini, Juan P. Garrahan, M\u{a}d\u{a}lin Gu\c{t}\u{a} - - - Performance enhancing of hybrid quantum-classical Benders approach for MILP optimization - https://arxiv.org/abs/2601.14024 - arXiv:2601.14024v1 Announce Type: new -Abstract: Mixed-integer linear programming problems are extensively used in industry for a wide range of optimization tasks. However, as they get larger, they present computational challenges for classical solvers within practical time limits. Quantum annealers can, in principle, accelerate the solution of problems formulated as quadratic unconstrained binary optimization instances, but their limited scale currently prevents achieving practical speedups. Quantum-classical algorithms have been proposed to take advantage of both paradigms and to allow current quantum computers to be used in larger problems. In this work, a hardware-agnostic Benders' decomposition algorithm and a series of enhancements with the goal of taking the most advantage of quantum computing are presented. The decomposition consists of a master problem with integer variables, which is reformulated as a quadratic unconstrained binary optimization problem and solved with a quantum annealer, and a linear subproblem solved by a classical computer. The enhancements consist, among others, of different embedding processes that substantially reduce the pre-processing time of the embedding computation without compromising solution quality, a conservative handling of cut constraints, and a stopping criterion that accounts for the limited size of current quantum computers and their heuristic nature. The proposed algorithm is benchmarked against classical approaches using a D-Wave quantum annealer for a scalable family of transmission network expansion planning problems. - oai:arXiv.org:2601.14024v1 - quant-ph - math.OC - Wed, 21 Jan 2026 00:00:00 -0500 - new - http://creativecommons.org/licenses/by/4.0/ - Sergio L\'opez-Ba\~nos, Elisabeth Lobe, Ontje L\"unsdorf, Oriol Ravent\'os - - - Generalised contextuality of continuous variable quantum theory can be revealed with a single projective measurement - https://arxiv.org/abs/2601.14067 - arXiv:2601.14067v1 Announce Type: new -Abstract: Generalized contextuality is a possible indicator of non-classical behaviour in quantum information theory. In finite-dimensional systems, this is justified by the fact that noncontextual theories can be embedded into some simplex, i.e. into a classical theory. We show that a direct application of the standard definition of generalized contextuality to continuous variable systems does not envelope the statistics of some basic measurements, such as the position observable. In other words, we construct families of fully classical, i.e. commuting, measurements that nevertheless can be used to show contextuality of quantum theory. To overcome the apparent disagreement between the two notions of classicality, that is commutativity and noncontextuality, we propose a modified definition of generalised contextuality for continuous-variable systems. The modified definition is based on a physically-motivated approximation procedure, that uses only finite sets of measurement effects. We prove that in the limiting case this definition corresponds exactly to an extension of noncontextual models that benefits from non-constructive response functions. In the process, we discuss the extension of a known connection between contextuality and no-broadcasting to the continuous-variable scenario, and prove structural results regarding fixed points of infinite-dimensional entanglement breaking channels. - oai:arXiv.org:2601.14067v1 - quant-ph - math-ph - math.MP - Wed, 21 Jan 2026 00:00:00 -0500 - new - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Pauli Jokinen, Mirjam Weilenmann, Martin Pl\'avala, Juha-Pekka Pellonp\"a\"a, Jukka Kiukas, Roope Uola - - - Quantum Pontus-Mpemba Effect Enabled by the Liouvillian Skin Effect - https://arxiv.org/abs/2601.14083 - arXiv:2601.14083v1 Announce Type: new -Abstract: We unveil a quantum Pontus-Mpemba effect enabled by the Liouvillian skin effect in a dissipative tight-binding chain with asymmetric incoherent hopping and coherent boundary coupling. The skin effect, induced by non-reciprocal dissipation, localizes relaxation modes near the system boundaries and gives rise to non-orthogonal spectral geometry. While such non-normality is often linked to slow relaxation, we show that it can instead accelerate relaxation through a two-step protocol - realizing a quantum Pontus-Mpemba effect. Specifically, we consider a one-dimensional open chain with coherent hopping $J$, asymmetric incoherent hoppings $J_{\rm R} \neq J_{\rm L}$, and a controllable end-to-end coupling $\epsilon$. For $\epsilon=0$, the system exhibits the Liouvillian skin effect, with left and right eigenmodes localized at opposite edges. We compare two relaxation protocols toward the same stationary state: (i) a direct relaxation with $\epsilon=0$, and (ii) a two-step (Pontus) protocol where a brief coherent evolution transfers the excitation across the lattice before relaxation. Although both share the same asymptotic decay rate, the two-step protocol relaxes significantly faster due to its reduced overlap with the slow boundary-localized Liouvillian mode. The effect disappears when $J_{\rm R}=J_{\rm L}$, i.e., when the skin effect vanishes. Our results reveal a clear connection between boundary-induced non-normality and protocol-dependent relaxation acceleration, suggesting new routes for controlling dissipation and transient dynamics in open quantum systems. - oai:arXiv.org:2601.14083v1 - quant-ph - cond-mat.dis-nn - Wed, 21 Jan 2026 00:00:00 -0500 - new - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Stefano Longhi - - - Information transport and transport-induced entanglement in open fermion chains - https://arxiv.org/abs/2601.14153 - arXiv:2601.14153v1 Announce Type: new -Abstract: Understanding the entanglement dynamics in quantum many-body systems under steady-state transport conditions is an actively pursued challenging topic. Hydrodynamic equations, akin to transport equations for charge or heat, would be of great interest but face severe challenges because of the inherent nonlocality of entanglement and the difficulty of identifying conservation laws. We show that progress is facilitated by using information as key quantity related to - but distinct from - entanglement. Employing the recently developed "information lattice" framework, we characterize spatially and scale-resolved information currents in nonequilibrium open quantum systems. Specifically, using Lindblad master equations, we consider noninteracting fermion chains coupled to dissipative reservoirs. By relating the information lattice to a noise lattice constructed from particle-number fluctuations, we show that information is experimentally accessible via noise easurements. Similarly, local information currents can be obtained by measuring particle currents, onsite occupations, and covariances of particle numbers and/or particle currents. Using the fermionic negativity to quantify bipartite entanglement, we also study transport-induced entanglement and its relation to information currents. For a clean particle-hole symmetric chain, we find that information currents are shielded from entering the information lattice. Impurities or particle-hole asymmetry break this effect, causing information current flow and entanglement between end segments of the chain. Our work opens the door to systematic investigations of information transport and entanglement generation in driven open quantum systems far from equilibrium. - oai:arXiv.org:2601.14153v1 - quant-ph - cond-mat.stat-mech - Wed, 21 Jan 2026 00:00:00 -0500 - new - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Andrea Nava, Claudia Artiaco, Yuval Gefen, Igor Gornyi, Mikheil Tsitsishvili, Alex Zazunov, Reinhold Egger - - - Sharp Inequalities for Schur-Convex Functionals of Partial Traces over Unitary Orbits - https://arxiv.org/abs/2601.14158 - arXiv:2601.14158v1 Announce Type: new -Abstract: While many bounds have been proved for partial trace inequalities over the last decades for a large variety of quantities, recent problems in quantum information theory demand sharper bounds. In this work, we study optimal bounds for partial trace quantities in terms of the spectrum; equivalently, we determine the best bounds attainable over unitary orbits of matrices. We solve this question for Schur-convex functionals acting on a single partial trace in terms of eigenvalues for self-adjoint matrices and then we extend these results to singular values of general matrices. We subsequently extend the study to Schur-convex functionals that act on several partial traces simultaneously and present sufficient conditions for sharpness. In cases where closed-form maximizers cannot be identified, we present quadratic programs that yield new computable upper bounds for any Schur-convex functional. We additionally present examples demonstrating improvements over previously known bounds. Finally, we conclude with the study of optimal bounds for an $n$-qubit system and its subsystems of dimension $2$. - oai:arXiv.org:2601.14158v1 - quant-ph - math-ph - math.MP - Wed, 21 Jan 2026 00:00:00 -0500 - new - http://creativecommons.org/licenses/by-nc-nd/4.0/ - Pablo Costa Rico, Pavel Shteyner - - - Localizable Entanglement as an Order Parameter for Measurement-Induced Phase Transitions - https://arxiv.org/abs/2601.14185 - arXiv:2601.14185v1 Announce Type: new -Abstract: We identify localizable entanglement (LE) as an order parameter for measurement-induced phase transitions (MIPT). LE exhibits universal finite-size scaling with critical exponents that match previous MIPT results and gives a nice operational interpretation connecting MIPTs to classical percolation. Remarkably, we find that LE decays exponentially with distance in the area-law phase as opposed to being essentially constant for the volume-law phase thereby, discover an intrinsic length scale $\xi_E$ that diverges at the critical measurement probability $p_c$. While classical percolation transition captures successful transport across a network, MIPT as characterized by LE can be interpreted as quantifying the amount of quantum teleportation between two given nodes in a quantum circuit. Building on this insight, we propose a two-ancilla protocol that provides an experimentally accessible readout of entanglement redistribution across the transition. - oai:arXiv.org:2601.14185v1 - quant-ph - cond-mat.stat-mech - Wed, 21 Jan 2026 00:00:00 -0500 - new - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Sourav Manna, Arul Lakshminarayan, Vaibhav Madhok - - - Device-independent quantum memory certification in two-point measurement experiments - https://arxiv.org/abs/2601.14191 - arXiv:2601.14191v1 Announce Type: new -Abstract: Quantum memories are key components of emerging quantum technologies. They are designed to store quantum states and retrieve them on demand without losing features such as superposition and entanglement. Verifying that a memory preserves these features is indispensable for applications such as quantum computation, cryptography and networks, yet no general and assumption-free method has been available. Here, we present a device-independent approach for certifying black-box quantum memories, requiring no trust in any part of the experimental setup. We do so by probing quantum systems at two points in time and then confronting the observed temporal correlations against classical causal models through violations of causal inequalities. We perform a proof-of-principle experiment in a trapped-ion quantum processor, where we certify 35 ms of a qubit memory. Our method establishes temporal correlations and causal modelling as practical and powerful tool for benchmarking key ingredients of quantum technologies, such as quantum gates or implementations of algorithms. - oai:arXiv.org:2601.14191v1 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - new - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Leonardo S. V. Santos, Peter Tirler, Michael Meth, Lukas Gerster, Manuel John, Keshav Pareek, Tim Gollerthan, Martin Ringbauer, Otfried G\"uhne - - - Native linear-optical protocol for efficient multivariate trace estimation - https://arxiv.org/abs/2601.14204 - arXiv:2601.14204v1 Announce Type: new -Abstract: The Hong-Ou-Mandel test estimates the overlap between spectral functions characterizing the internal degrees of freedom of two single photons. It can be viewed as a photon-native protocol that implements the well-known quantum SWAP test. Here, we propose a native linear-optical protocol that efficiently estimates multivariate traces of quantum states called Bargmann invariants, which are ubiquitous in quantum mechanics. Our protocol may be understood as a photon-native version of the cycle test in the circuit model, which encompasses many-photon multimode quantum states. We show the protocol is sample-efficient and discuss applications, such as generalized suppression laws, efficient quantum kernel estimation for quantum machine learning, eigenspectrum estimation, and the characterization of multiphoton indistinguishability. - oai:arXiv.org:2601.14204v1 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - new - http://creativecommons.org/licenses/by/4.0/ - Leonardo Novo, Marco Robbio, Ernesto F. Galv\~ao, Nicolas J. Cerf - - - Locality forces equal energy spacing of quantum many-body scar towers - https://arxiv.org/abs/2601.14206 - arXiv:2601.14206v1 Announce Type: new -Abstract: Quantum many-body scars are non-thermal eigenstates embedded in the spectra of otherwise non-integrable Hamiltonians. Paradigmatic examples often appear as quasiparticle towers of states, such as the maximally ferromagnetic spin-1/2 states, also known as Dicke states. A distinguishing feature of quantum many-body scars is that they admit multiple local "parent" Hamiltonians for which they are exact eigenstates. In this work, we show that the locality of such parent Hamiltonians strongly constrains the relative placement of these states within the energy spectrum. In particular, we prove that if the full set of Dicke states are exact eigenstates of an extensive local Hamiltonian, then their energies must necessarily be equally spaced. Our proof builds on recent results concerning parent Hamiltonians of the $W$ state, together with general algebraic structures underlying such quasiparticle towers. We further demonstrate that this equal spacing property extends to local Hamiltonians defined on arbitrary bounded-degree graphs, including regular lattices in any spatial dimension and expander graphs. Hamiltonians with $k$-local interactions and a bounded number of interaction terms per site are also encompassed by our proof. On the same classes of graphs, we additionally establish equal spacing for towers constructed from multi-site quasiparticles on top of product states. For the towers considered here, an immediate corollary of the equal spacing property is that any state initialized entirely within the quantum many-body scar manifold exhibits completely frozen entanglement dynamics under any local Hamiltonian for which those scars are exact eigenstates. Overall, our results reveal a stringent interplay between locality and the structure of quantum many-body scars. - oai:arXiv.org:2601.14206v1 - quant-ph - cond-mat.stat-mech - Wed, 21 Jan 2026 00:00:00 -0500 - new - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Nicholas O'Dea, Lei Gioia, Sanjay Moudgalya, Olexei I. Motrunich - - - Group Fourier filtering of quantum resources in quantum phase space - https://arxiv.org/abs/2601.14225 - arXiv:2601.14225v1 Announce Type: new -Abstract: Recently, it has been shown that group Fourier analysis of quantum states, i.e., decomposing them into the irreducible representations (irreps) of a symmetry group, enables new ways to characterize their resourcefulness. Given that quantum phase spaces (QPSs) provide an alternative description of quantum systems, and thus of the group's representation, one may wonder how such harmonic analysis changes. In this work we show that for general compact Lie-group quantum resource theories (QRTs), the entire family of Stratonovich-Weyl quantum phase space representations-characterized by the Cahill-Glauber parameter $s$-has a clear resource-theoretic and signal-processing meaning. Specifically, changing $s$ implements a group Fourier filter that can be continuously tuned to favor low-dimensional irreps where free states have most of their support ($s=-1$), leave the spectrum unchanged ($s=0$), or highlight resourceful, high-dimensional irreps ($s=1$). As such, distinct QPSs constitute veritable group Fourier filters for resources. Moreover, we show that the norms of the QRT's free state Fourier components completely characterize all QPSs. Finally, we uncover an $s$-duality relating the phase space spectra of free states and typical (Haar-random) highly resourceful states through a shift in $s$. Overall, our results provide a new interpretation of QPSs and promote them to a signal-processing framework for diagnosing, filtering, and visualizing quantum resources. - oai:arXiv.org:2601.14225v1 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - new - http://creativecommons.org/licenses/by/4.0/ - Luke Coffman, N. L. Diaz, Martin Larocca, Maria Schuld, M. Cerezo - - - Deep Learning Approaches to Quantum Error Mitigation - https://arxiv.org/abs/2601.14226 - arXiv:2601.14226v1 Announce Type: new -Abstract: We present a systematic investigation of deep learning methods applied to quantum error mitigation of noisy output probability distributions from measured quantum circuits. We compare different architectures, from fully connected neural networks to transformers, and we test different design/training modalities, identifying sequence-to-sequence, attention-based models as the most effective on our datasets. These models consistently produce mitigated distributions that are closer to the ideal outputs when tested on both simulated and real device data obtained from IBM superconducting quantum processing units (QPU) up to five qubits. Across several different circuit depths, our approach outperforms other baseline error mitigation techniques. We perform a series of ablation studies to examine: how different input features (circuit, device properties, noisy output statistics) affect performance; cross-dataset generalization across circuit families; and transfer learning to a different IBM QPU. We observe that generalization performance across similar devices with the same architecture works effectively, without needing to fully retrain models. - oai:arXiv.org:2601.14226v1 - quant-ph - cs.LG - Wed, 21 Jan 2026 00:00:00 -0500 - new - http://creativecommons.org/licenses/by/4.0/ - Leonardo Placidi, Ifan Williams, Enrico Rinaldi, Daniel Mills, Cristina C\^irstoiu, Vanya Eccles, Ross Duncan - - - Homogeneous Microwave Delivery for Quantum Sensing with Nitrogen-Vacancy Centers at High Pressures - https://arxiv.org/abs/2601.11725 - arXiv:2601.11725v1 Announce Type: cross -Abstract: Nitrogen vacancy (NV) centers have been demonstrated as a useful tool in high pressure environments. However, the geometry and small working area of the diamond anvil cells (DACs) used to apply pressure present a challenge to effective delivery of microwave (mw) fields. We designed and characterized a novel slotted design for mw transmission to nitrogen-vacancy centers (NVs) in a diamond anvil cell via zero-field and in-field optically detected magnetic resonance (ODMR) measurements across pressures between 1 and 48 GPa. The mw fields experienced by NVs across the diamond culet was calculated from Rabi frequency and found to be higher and more uniform than those generated by an equivalent simple mw line, which will improve performance for wide-field, high-pressure measurements to probe spatial variations across samples under pressure. - oai:arXiv.org:2601.11725v1 - cond-mat.mtrl-sci - cond-mat.mes-hall - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - cross - http://creativecommons.org/licenses/by/4.0/ - Timothy A. Elmslie, Luca Basso, Adam Dodson, Jacob Henshaw, Andrew M. Mounce - - - Quantum Kernel Machine Learning for Autonomous Materials Science - https://arxiv.org/abs/2601.11775 - arXiv:2601.11775v1 Announce Type: cross -Abstract: Autonomous materials science, where active learning is used to navigate large compositional phase space, has emerged as a powerful vehicle to rapidly explore new materials. A crucial aspect of autonomous materials science is exploring new materials using as little data as possible. Gaussian process-based active learning allows effective charting of multi-dimensional parameter space with a limited number of training data, and thus is a common algorithmic choice for autonomous materials science. An integral part of the autonomous workflow is the application of kernel functions for quantifying similarities among measured data points. A recent theoretical breakthrough has shown that quantum kernel models can achieve similar performance with less training data than classical models. This signals the possible advantage of applying quantum kernel machine learning to autonomous materials discovery. In this work, we compare quantum and classical kernels for their utility in sequential phase space navigation for autonomous materials science. Specifically, we compute a quantum kernel and several classical kernels for x-ray diffraction patterns taken from an Fe-Ga-Pd ternary composition spread library. We conduct our study on both IonQ's Aria trapped ion quantum computer hardware and the corresponding classical noisy simulator. We experimentally verify that a quantum kernel model can outperform some classical kernel models. The results highlight the potential of quantum kernel machine learning methods for accelerating materials discovery and suggest complex x-ray diffraction data is a candidate for robust quantum kernel model advantage. - oai:arXiv.org:2601.11775v1 - cond-mat.mtrl-sci - cs.LG - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - cross - http://creativecommons.org/licenses/by/4.0/ - Felix Adams (University of Maryland College Park), Daiwei Zhu (IonQ), David W. Steuerman (IonQ), A. Gilad Kusne (University of Maryland College Park, National Institute for Standards and Technology), Ichiro Takeuchi (University of Maryland College Park, University of Maryland Quantum Materials Center) - - - Trainability-Oriented Hybrid Quantum Regression via Geometric Preconditioning and Curriculum Optimization - https://arxiv.org/abs/2601.11942 - arXiv:2601.11942v1 Announce Type: cross -Abstract: Quantum neural networks (QNNs) have attracted growing interest for scientific machine learning, yet in regression settings they often suffer from limited trainability under noisy gradients and ill-conditioned optimization. We propose a hybrid quantum-classical regression framework designed to mitigate these bottlenecks. Our model prepends a lightweight classical embedding that acts as a learnable geometric preconditioner, reshaping the input representation to better condition a downstream variational quantum circuit. Building on this architecture, we introduce a curriculum optimization protocol that progressively increases circuit depth and transitions from SPSA-based stochastic exploration to Adam-based gradient fine-tuning. We evaluate the approach on PDE-informed regression benchmarks and standard regression datasets under a fixed training budget in a simulator setting. Empirically, the proposed framework consistently improves over pure QNN baselines and yields more stable convergence in data-limited regimes. We further observe reduced structured errors that are visually correlated with oscillatory components on several scientific benchmarks, suggesting that geometric preconditioning combined with curriculum training is a practical approach for stabilizing quantum regression. - oai:arXiv.org:2601.11942v1 - cs.LG - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - cross - http://creativecommons.org/publicdomain/zero/1.0/ - Qingyu Meng, Yangshuai Wang - - - Measurement-induced crossover in quantum first-detection times - https://arxiv.org/abs/2601.12102 - arXiv:2601.12102v1 Announce Type: cross -Abstract: The quantum first-detection problem concerns the statistics of the time at which a system, subject to repeated measurements, is observed in a prescribed target state for the first time. Unlike its classical counterpart, the measurement back action intrinsic to quantum mechanics may profoundly alter the system dynamics. Here we show that it induces a distinct change in the statistics of the first-detection time. For a quantum particle in one spatial dimension subject to stroboscopic measurements, we observe an algebraic decay of the probability of the first-detection time if the particle is free, an exponential decay in the presence of a confining potential, and a time-dependent crossover between these behaviors if the particle is partially confined. This crossover reflects the purely quantum nature of the detection process, which fundamentally distinguishes it from the first-passage problem in classical systems. - oai:arXiv.org:2601.12102v1 - cond-mat.stat-mech - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - cross - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Giovanni Di Fresco, Aldo Coraggio, Alessandro Silva, Andrea Gambassi - - - Wave Phenomena and Wave Equations - https://arxiv.org/abs/2601.12176 - arXiv:2601.12176v1 Announce Type: cross -Abstract: For any kind of wave phenomenon one can find ways to derive the respective dispersion relation from experimental observations and measurements. This dispersion relation determines the structure of the wave equation and thus characterizes the dynamics of the respective wave. Different wave phenomena are thus governed by different differential equations. Here we want to emphasize the experimental approach to matter waves, but before doing so we will discuss and test the procedure for other types of waves, in particular water waves. - oai:arXiv.org:2601.12176v1 - physics.flu-dyn - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - cross - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Gerd Leuchs, Mojdeh S. Najafabadi - - - Classical-Quantum Channel Resolvability Using Matrix Multiplicative Weight Update Algorithm - https://arxiv.org/abs/2601.12230 - arXiv:2601.12230v1 Announce Type: cross -Abstract: We study classical-quantum (C-Q) channel resolvability. C-Q channel resolvability has been proved by only random coding in the literature. In our previous study, we proved channel resolvability by deterministic coding, using multiplicative weight update algorithm. We extend this approach to C-Q channels and prove C-Q channel resolvability by deterministic coding, using the matrix multiplicative weight update algorithm. This is the first approach to C-Q channel resolvability using deterministic coding. - oai:arXiv.org:2601.12230v1 - cs.IT - math.IT - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - cross - http://creativecommons.org/licenses/by/4.0/ - Koki Takahashi, Shun Watanabe - - - Non-intersecting Squared Bessel Process: Spectral Moments and Dynamical Entanglement Entropy - https://arxiv.org/abs/2601.12484 - arXiv:2601.12484v1 Announce Type: cross -Abstract: Statistical ensembles of reduced density matrices of bipartite quantum systems play a central role in entanglement estimation, but do not capture the non-stationary nature of entanglement relevant to realistic quantum information processing. To address this limitation, we propose a dynamical extension of the Hilbert-Schmidt ensemble, a baseline statistical model for entanglement estimation, arising from non-intersecting squared Bessel processes and perform entanglement estimation via average entanglement entropy and quantum purity. The investigation is enabled by finding spectral moments of the proposed dynamical ensemble, which serves as a new approach for systematic computation of entanglement metrics. Along the way, we also obtain new results for the underlying multiple orthogonal polynomials of modified Bessel weights, including structure and recurrence relations, and a Christoffel-Darboux formula for the correlation kernels. - oai:arXiv.org:2601.12484v1 - math-ph - math.MP - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - cross - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Youyi Huang, Lu Wei - - - Semidefinite Programming for Quantum Channel Learning - https://arxiv.org/abs/2601.12502 - arXiv:2601.12502v1 Announce Type: cross -Abstract: The problem of reconstructing a quantum channel from a sample of classical data is considered. When the total fidelity can be represented as a ratio of two quadratic forms (e.g., in the case of mapping a mixed state to a pure state, projective operators, unitary learning, and others), Semidefinite Programming (SDP) can be applied to solve the fidelity optimization problem with respect to the Choi matrix. A remarkable feature of SDP is that the optimization is convex, which allows the problem to be efficiently solved by a variety of numerical algorithms. We have tested several commercially available SDP solvers, all of which allowed for the reconstruction of quantum channels of different forms. A notable feature is that the Kraus rank of the obtained quantum channel typically comprises less than a few percent of its maximal possible value. This suggests that a relatively small Kraus rank quantum channel is typically sufficient to describe experimentally observed classical data. The theory was also applied to the problem of reconstructing projective operators from data. Finally, we discuss a classical computational model based on quantum channel transformation, performed and calculated on a classical computer, possibly hardware-optimized. - oai:arXiv.org:2601.12502v1 - cs.LG - cs.NA - math.NA - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - cross - http://creativecommons.org/licenses/by/4.0/ - Mikhail Gennadievich Belov, Victor Victorovich Dubov, Vadim Konstantinovich Ivanov, Alexander Yurievich Maslov, Olga Vladimirovna Proshina, Vladislav Gennadievich Malyshkin - - - AlphaSyndrome: Tackling the Syndrome Measurement Circuit Scheduling Problem for QEC Codes - https://arxiv.org/abs/2601.12509 - arXiv:2601.12509v1 Announce Type: cross -Abstract: Quantum error correction (QEC) is essential for scalable quantum computing, yet repeated syndrome-measurement cycles dominate its spacetime and hardware cost. Although stabilizers commute and admit many valid execution orders, different schedules induce distinct error-propagation paths under realistic noise, leading to large variations in logical error rate. Outside of surface codes, effective syndrome-measurement scheduling remains largely unexplored. We present AlphaSyndrome, an automated synthesis framework for scheduling syndrome-measurement circuits in general commuting-stabilizer codes under minimal assumptions: mutually commuting stabilizers and a heuristic decoder. AlphaSyndrome formulates scheduling as an optimization problem that shapes error propagation to (i) avoid patterns close to logical operators and (ii) remain within the decoder's correctable region. The framework uses Monte Carlo Tree Search (MCTS) to explore ordering and parallelism, guided by code structure and decoder feedback. Across diverse code families, sizes, and decoders, AlphaSyndrome reduces logical error rates by 80.6% on average (up to 96.2%) relative to depth-optimal baselines, matches Google's hand-crafted surface-code schedules, and outperforms IBM's schedule for the Bivariate Bicycle code. - oai:arXiv.org:2601.12509v1 - cs.ET - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - cross - http://creativecommons.org/licenses/by/4.0/ - Yuhao Liu, Shuohao Ping, Junyu Zhou, Ethan Decker, Justin Kalloor, Mathias Weiden, Kean Chen, Yunong Shi, Ali Javadi-Abhari, Costin Iancu, Gushu Li - - - Artificial Intelligence in Materials Science and Engineering: Current Landscape, Key Challenges, and Future Trajectorie - https://arxiv.org/abs/2601.12554 - arXiv:2601.12554v1 Announce Type: cross -Abstract: Artificial Intelligence is rapidly transforming materials science and engineering, offering powerful tools to navigate complexity, accelerate discovery, and optimize material design in ways previously unattainable. Driven by the accelerating pace of algorithmic advancements and increasing data availability, AI is becoming an essential competency for materials researchers. This review provides a comprehensive and structured overview of the current landscape, synthesizing recent advancements and methodologies for materials scientists seeking to effectively leverage these data-driven techniques. We survey the spectrum of machine learning approaches, from traditional algorithms to advanced deep learning architectures, including CNNs, GNNs, and Transformers, alongside emerging generative AI and probabilistic models such as Gaussian Processes for uncertainty quantification. The review also examines the pivotal role of data in this field, emphasizing how effective representation and featurization strategies, spanning compositional, structural, image-based, and language-inspired approaches, combined with appropriate preprocessing, fundamentally underpin the performance of machine learning models in materials research. Persistent challenges related to data quality, quantity, and standardization, which critically impact model development and application in materials science and engineering, are also addressed. - oai:arXiv.org:2601.12554v1 - cond-mat.mtrl-sci - cs.AI - physics.comp-ph - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - cross - http://creativecommons.org/licenses/by-sa/4.0/ - 10.1016/j.compstruct.2025.119419 - Iman Peivaste, Salim Belouettar, Francesco Mercuri, Nicholas Fantuzzi, Hamidreza Dehghani, Razieh Izadi, Halliru Ibrahim, Jakub Lengiewicz, Ma\"el Belouettar-Mathis, Kouider Bendine, Ahmed Makradi, Martin H\"orsch, Peter Klein, Mohamed El Hachemi, Heinz A. Preisig, Yacine Rezgui, Natalia Konchakova, Ali Daouadji - - - Quantum State Preparation of Ferromagnetic Magnons by Parametric Driving - https://arxiv.org/abs/2601.12833 - arXiv:2601.12833v1 Announce Type: cross -Abstract: We propose a method to prepare and certify Gaussian quantum states of the ferromagnetic resonance spin-wave modes in ferromagnets using a longitudinal drive. Contrary to quantum optics-based strategies, our approach harnesses a purely magnonic feature - the spin-wave nonlinearity - to generate magnon squeezing. This resource is used to prepare vacuum-squeezed states, as well as entangled states between modes of different magnets coupled via a microwave cavity. We propose methods to detect such states with classical methods, such as ferromagnetic resonance or local pickup coils, and quantify the required detection efficiency. We analytically solve the case of ellipsoidal yttrium iron garnet ferrimagnets, but our method applies to a vast range of shapes and sizes. Our work enables quantum magnonics experiments without single-magnon sources or detectors (qubits), thus bringing the quantum regime within reach of the wider magnonics community. - oai:arXiv.org:2601.12833v1 - cond-mat.mes-hall - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - cross - http://creativecommons.org/licenses/by/4.0/ - Monika E. Mycroft, Rostyslav O. Serha, Andrii V. Chumak, Carlos Gonzalez-Ballestero - - - Anisotropic Collective Excitations of Bose Gases in Modified Newtonian Dynamics - https://arxiv.org/abs/2601.12848 - arXiv:2601.12848v1 Announce Type: cross -Abstract: Collective excitations are fundamental in quantum many-body physics, yet their spectra have traditionally been studied within Newtonian dynamics. In this Letter, we investigate collective excitations in Bose gases under Modified Newtonian Dynamics (MOND). We derive an anisotropic excitation spectrum in the MOND regime. This anisotropy arises directly from the intrinsic nonlinear structure of the MOND Poisson equation, forming a distinctive signature of the modified gravitational response. We then analyze the Jeans instability, obtaining analytic expressions for the direction-dependent critical wavelength and mass. These results advance our understanding of collective behavior in quantum systems under modified dynamics and establish clear theoretical signatures for testing MOND-like effects in quantum simulators. - oai:arXiv.org:2601.12848v1 - cond-mat.quant-gas - astro-ph.GA - cond-mat.stat-mech - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - cross - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Ning Liu - - - Anomalous diffusion and localization in a disorder-free atomic mixture - https://arxiv.org/abs/2601.13226 - arXiv:2601.13226v1 Announce Type: cross -Abstract: The concept of random walk, in which particles or waves undergo multiple collisions with the microscopic constituents of a surrounding medium, is central to understanding diffusive transport across many research areas. However, this paradigm may break down in complex systems, where quantum interference and memory effects render the particle propagation anomalous, often fostering localization. Here we report on the observation of such anomalous dynamics in a minimal setting: an ultracold mass-imbalanced mixture of two fermionic gases in three dimensions. We release light impurities into a gas of heavier atoms and follow their evolution across different collisional regimes. Under strong interspecies interactions, by lowering the temperature we unveil a crossover from normal diffusion to subdiffusion. Simultaneously, a localized fraction of the light gas emerges, displaying no discernible dynamics over hundreds of collisions. Our findings, incompatible with the conventional Fermi-liquid picture, are instead captured by a model of an atom propagating through a (quasi-)static disordered landscape of point-like scatterers. These results highlight the key role of quantum interference in our mixture, which emerges as a versatile platform for exploring disorder-free localization phenomena. - oai:arXiv.org:2601.13226v1 - cond-mat.quant-gas - physics.atom-ph - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - cross - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Stefano Finelli, Beatrice Restivo, Alessio Ciamei, Andreas Trenkwalder, Massimo Inguscio, Dmitry S. Petrov, Sergey E. Skipetrov, Matteo Zaccanti - - - The Anderson impurity model from a Krylov perspective: Lanczos coefficients in a quadratic model - https://arxiv.org/abs/2601.13255 - arXiv:2601.13255v1 Announce Type: cross -Abstract: We study the Lanczos coefficients in a quadratic model given by an impurity interacting with a multi-mode field of fermions, also known as single impurity Anderson model. We analytically derive closed expressions for the Lanczos coefficients of Majorana fermion operators of the impurity for different structures of the coupling to the hybridisation band at zero temperature. While the model remains quadratic, we find that the growth of the Lanczos coefficients structurally depends strongly on the chosen coupling. Concretely, we find $(i)$ approximately constant, $(ii)$ exactly constant, $(iii)$ square root-like as well $(iv)$ linear growth in the same model. We further argue that in fact through suitably chosen couplings, essentially arbitrary Lanczos coefficients can be obtained in this model. These altogether evince the inadequacy of the Lanczos coefficients as a reliable criterion for classifying the integrability or chaoticity of the systems. Eventually, in the wide-band limit, we find exponential decay of autocorrelation functions in all the settings $(i)-(iv)$, which demonstrates the different structures of the Lanczos coefficients not being indicative of different physical behavior. - oai:arXiv.org:2601.13255v1 - cond-mat.str-el - cond-mat.stat-mech - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - cross - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Merlin F\"ullgraf, Jiaozi Wang, Jochen Gemmer, Stefan Kehrein - - - Two-Point Stabilizer R\'enyi Entropy: a Computable Magic Proxy of Interacting Fermions - https://arxiv.org/abs/2601.13314 - arXiv:2601.13314v1 Announce Type: cross -Abstract: Quantifying non-stabilizerness (``magic'') in interacting fermionic systems remains a formidable challenge, particularly for extracting high order correlations from quantum Monte Carlo simulations. In this Letter, we establish the two-point stabilizer R\'enyi entropy (SRE) and its mutual counterpart as robust, computationally accessible probes for detecting magic in diverse fermionic phases. By deriving local estimators suitable for advanced numerical methods, we demonstrate that these metrics effectively characterize quantum phase transitions: in the one-dimensional spinless $t$-$V$ model, they sharply identify the Luttinger liquid to charge density wave transition, while in the two-dimensional honeycomb lattice via determinant quantum Monte Carlo, they faithfully capture the critical exponents of the Gross-Neveu-Ising universality class. Furthermore, extending our analysis to the fractional quantum Hall regime, we unveil a non-trivial spatial texture of magic in the Laughlin state, revealing signatures of short-range exclusion correlations. Our results validate the two-point SRE as a versatile and sensitive diagnostic, forging a novel link between quantum resource theory, critical phenomena, and topological order in strongly correlated matter. - oai:arXiv.org:2601.13314v1 - cond-mat.str-el - hep-lat - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - cross - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Jun Qi Fang, Fo-Hong Wang, Xiao Yan Xu - - - Inferring rotations using a bosonic Josephson junction - https://arxiv.org/abs/2601.13344 - arXiv:2601.13344v1 Announce Type: cross -Abstract: Rotation and quantum tunneling are fundamental concepts in physics, and their interplay in the ultracold atomic systems is of particular interest. In this theoretical work, we explore how tunneling dynamics in a bosonic Josephson junction are modified when the system is placed in a rotating, non-inertial frame. We show that the tunneling dynamics of ultracold bosons in a two-dimensional double-well potential offer an alternative pathway for inferring the rotation frequency. Using the mean-field and many-body analyses, we demonstrate that rotation strongly modifies the tunneling time period as well as the momentum and angular momentum dynamics. When the rotation axis passes through the center of the double well, the observables show distinct dynamical responses with increasing rotation frequency, enabling the rotation frequency to be assessed from changes in the tunneling dynamics. When the potential is displaced from the rotation axis, the rotation induces asymmetric tunneling and partial self-trapping, allowing both the rotation frequency and the displacement to be inferred. We further show that for an off-centered double well, the tunneling dynamics exhibit a pronounced orientation dependence, enabling the orientation of the double well to be inferred from the observed dynamics. The many-body analysis further shows that the depletion dynamics are strongly influenced by rotation, providing an additional tool for assessing the rotation frequency. Finally, we study the effect of time-dependent rotation in which the double well is gradually set into motion in the laboratory frame and identify distinct dynamical signatures that depend sensitively on the switching time. Together, these results establish a comprehensive framework for inferring the rotation frequency, radial displacement, and orientation directly from the tunneling dynamics. - oai:arXiv.org:2601.13344v1 - cond-mat.quant-gas - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - cross - http://creativecommons.org/licenses/by/4.0/ - Rhombik Roy, Ofir E. Alon - - - Loopless multiterminal quantum circuits at odd parity - https://arxiv.org/abs/2601.13369 - arXiv:2601.13369v1 Announce Type: cross -Abstract: We theoretically investigate loopless multiterminal hybrid superconducting devices at odd fermion parity with time-reversal symmetry. We find that the energy-phase relationship has a double minimum corresponding to opposite windings of the superconducting phases. Spin-orbit coupling adds multi-axial spin splittings, which contrasts with two-terminal devices where spin dependence is uniaxial. Capacitive shunting localizes quantum circuit states in the wells and exponentially suppresses their splitting. For weak spin-orbit strength, the system has a four-dimensional spin-chirality low-energy subspace which can be universally controlled with electric fields only. - oai:arXiv.org:2601.13369v1 - cond-mat.mes-hall - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - cross - http://creativecommons.org/licenses/by/4.0/ - Antonio Manesco, Anton Akhmerov, Valla Fatemi - - - High Field Diamond Magnetometry Towards Tokamak Diagnostics - https://arxiv.org/abs/2601.13413 - arXiv:2601.13413v1 Announce Type: cross -Abstract: Nitrogen vacancy centres (NVC) in diamond have been widely used for near-dc magnetometry. The intrinsic properties of diamonds make them potential candidates for tokamak fusion power diagnostics, where radiation-hard magnetometers will be essential for efficient control. An NVC magnetometer placed in a tokamak will need to operate within a $\geq$ 1 T magnetic field. In this work, we demonstrate fibre-coupled ensemble NVC optically detected magnetic resonance (ODMR) and magnetometry measurements at magnetic fields up to 1.2 T. Sensitivities of approximately 240 to 600 nT/$\sqrt{\textrm{Hz}}$ and 110 nT/$\sqrt{\textrm{Hz}}$ are achieved in a (10-150) Hz frequency range, for non-degenerate and near-$\langle$111$\rangle$ field alignments respectively. - oai:arXiv.org:2601.13413v1 - physics.app-ph - physics.ins-det - physics.optics - physics.plasm-ph - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - cross - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - S. M. Graham, C. J. Stephen, A. J. Newman, A. M. Edmonds, M. L. Markham, G. W. Morley - - - Quantum Qualifiers for Neural Network Model Selection in Hadronic Physics - https://arxiv.org/abs/2601.13463 - arXiv:2601.13463v1 Announce Type: cross -Abstract: As quantum machine-learning architectures mature, a central challenge is no longer their construction, but identifying the regimes in which they offer practical advantages over classical approaches. In this work, we introduce a framework for addressing this question in data-driven hadronic physics problems by developing diagnostic tools - centered on a quantitative quantum qualifier - that guide model selection between classical and quantum deep neural networks based on intrinsic properties of the data. Using controlled classification and regression studies, we show how relative model performance follows systematic trends in complexity, noise, and dimensionality, and how these trends can be distilled into a predictive criterion. We then demonstrate the utility of this approach through an application to Compton form factor extraction from deeply virtual Compton scattering, where the quantum qualifier identifies kinematic regimes favorable to quantum models. Together, these results establish a principled framework for deploying quantum machine-learning tools in precision hadronic physics. - oai:arXiv.org:2601.13463v1 - cs.LG - hep-ph - nucl-th - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - cross - http://creativecommons.org/licenses/by/4.0/ - Brandon B. Le, D. Keller - - - Onset of thermalization of q-deformed SU(2) Yang-Mills theory on a trapped-ion quantum computer - https://arxiv.org/abs/2601.13530 - arXiv:2601.13530v1 Announce Type: cross -Abstract: Nonequilibrium dynamics of quantum many-body systems is one of the main targets of quantum simulations. This focus - together with rapid advances in quantum-computing hardware - has driven increasing applications in high-energy physics, particularly in lattice gauge theories. However, most existing experimental demonstrations remain restricted to (1+1)-dimensional and/or abelian gauge theories, such as the Schwinger model and the toric code. It is essential to develop quantum simulations of nonabelian gauge theories in higher dimensions, addressing realistic problems in high-energy physics. To fill the gap, we demonstrate a quantum simulation of thermalization dynamics in a (2+1)-dimensional $q$-deformed $\mathrm{SU}(2)_3$ Yang-Mills theory using a trapped-ion quantum computer. By restricting the irreducible representations of the gauge fields to the integer-spin sector of $\mathrm{SU}(2)_3$, we obtain a simplified yet nontrivial model described by Fibonacci anyons, which preserves the essential nonabelian fusion structure of the gauge fields. We successfully simulate the real-time dynamics of this model using quantum circuits that explicitly implement $F$-moves. In our demonstrations, the quantum circuits execute up to 47 sequential $F$-moves. We identify idling errors as the dominant error source, which can be effectively mitigated using dynamical decoupling combined with a parallelized implementation of $F$-moves. - oai:arXiv.org:2601.13530v1 - hep-lat - cond-mat.str-el - hep-th - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - cross - http://creativecommons.org/licenses/by/4.0/ - Tomoya Hayata, Yoshimasa Hidaka, Yuta Kikuchi - - - Kaleidoscope Yang-Baxter Equation for Gaudin's Kaleidoscope models - https://arxiv.org/abs/2601.13596 - arXiv:2601.13596v1 Announce Type: cross -Abstract: Recently, researchers have proposed the Asymmetric Bethe ansatz method - a theoretical tool that extends the scope of Bethe ansatz-solvable models by "breaking" partial mirror symmetry via the introduction of a fully reflecting boundary. Within this framework, the integrability conditions which were originally put forward by Gaudin have been further generalized. In this work, building on Gaudin's generalized kaleidoscope model, we present a detailed investigation of the relationship between DN symmetry and its integrability. We demonstrate that the mathematical essence of integrability in this class of models is characterized by a newly proposed Kaleidoscope Yang-Baxter Equation. Furthermore, we show that the solvability of a model via the coordinate Bethe ansatz depends not only on the consistency relations satisfied by scattering matrices, but also on the model's boundary conditions and the symmetry of the subspace where solutions are sought. Through finite element method based numerical studies, we further confirm that Bethe ansatz integrability arises in a specific symmetry sector. Finally, by analyzing the algebraic structure of the Kaleidoscope Yang-Baxter Equation, we derive a series of novel quantum algebraic identities within the framework of quantum torus algebra. - oai:arXiv.org:2601.13596v1 - nlin.SI - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - cross - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Wen-Jie Qiu, Xi-Wen Guan, Yi-Cong Yu - - - Recent progress on disorder-induced topological phases - https://arxiv.org/abs/2601.13619 - arXiv:2601.13619v1 Announce Type: cross -Abstract: Topological states of matter in disordered systems without translation symmetry have attracted great interest in recent years. These states with topological characters are not only robust against certain disorders, but also can be counterintuitively induced by disorders from a topologically trivial phase in the clean limit. In this review, we summarize the current theoretical and experimental progress on disorder-induced topological phases in both condensed-matter and artificial systems. We first introduce the topological Anderson insulators (TAIs) induced by random disorders and their topological characterizations and experimental realizations. We then discuss various extensions of TAIs with unique localization phenomena in quasiperiodic and non-Hermitian systems. We also review the theoretical and experimental studies on the disorder-induced topology in dynamical and many-body systems, including topological Anderson-Thouless pumps, disordered correlated topological insulators and average-symmetry protected topological orders acting as interacting TAI phases. Finally, we conclude the review by highlighting potential directions for future explorations. - oai:arXiv.org:2601.13619v1 - cond-mat.dis-nn - cond-mat.mes-hall - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - cross - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Dan-Wei Zhang, Ling-Zhi Tang - - - Topological Anderson insulator and reentrant topological transitions in a mosaic trimer lattice - https://arxiv.org/abs/2601.13760 - arXiv:2601.13760v1 Announce Type: cross -Abstract: We study the topological properties of a one-dimensional quasiperiodic-potential-modulated mosaic trimer lattice. To begin with, we first investigate the topological properties of the model in the clean limit free of quasiperiodic disorder based on analytical derivation and numerical calculations of the Zak phase $Z$ and the polarization $P$. Two nontrivial topological phases corresponding to the $1/3$ filling and $2/3$ filling, respectively, are revealed. Then we incorporate the mosaic modulation and investigate the influence of quasiperiodic disorder on the two existing topological phases. Interestingly, it turns out that quasiperiodic disorder gives rise to multiple distinct effects for different fillings. At $2/3$ filling, the topological phase is significantly enhanced by the quasiperiodic disorder and topological Anderson insulator emerges. Based on the calculations of polarization and energy gap, we explicitly present corresponding topological phase diagram in the $\lambda-J$ plane. While for the $1/3$ filling case, % the topological phase is dramatically suppressed by the same quasiperiodic disorder. the quasiperiodic disorder dramatically compresses the topological phase, and strikingly, further induces the emergence of reentrant topological phase transitions instead. Furthermore, we verify the topological phase diagrams by computing the many-body ground state fidelity susceptibility for both the $1/3$ filling and $2/3$ filling cases. Our work exemplifies the diverse roles of quasiperiodic disorder in the modulation of topological properties, and will further inspire more research on the competitive and cooperative interplay between topological properties and quasiperiodic disorder. - oai:arXiv.org:2601.13760v1 - cond-mat.dis-nn - cond-mat.mes-hall - cond-mat.other - cond-mat.quant-gas - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - cross - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Xiatao Wang, Li Wang, Shu Chen - - - Quantum Entanglement Geometry on Severi-Brauer Schemes: Subsystem Reductions of Azumaya Algebras - https://arxiv.org/abs/2601.13764 - arXiv:2601.13764v1 Announce Type: cross -Abstract: We formulate pure-state entanglement in families as a geometric obstruction. In standard quantum information, entanglement is defined relative to a chosen tensor-product factorization of a fixed Hilbert space. In contrast, for a twisted family of pure-state spaces, which can be described by Azumaya algebras $A$ of degree $n$ on $X$ and their Severi-Brauer schemes \[ SB(A)=P\times^{PGL_n}\mathbb{P}^{n-1}\to X, \] such a subsystem choice may fail to globalize. We formalize this algebro-geometrically: fixing a factorization type $\mathbf d=(d_1,\dots,d_s)$ with $n=\prod_i d_i$, the existence of a global product-state locus of type $\mathbf d$ is equivalent to a reduction of the underlying $PGL_n$-torsor $P\to X$ to the stabilizer $G_{\mathbf d}\subset PGL_n$. Thus, entanglement is the obstruction to the existence of a relative Segre subscheme inside $SB(A)$. - Writing $\Sigma_{\mathbf d}\subset \mathbb{P}^{n-1}$ for the Segre variety, we call a reduction to $G_{\mathbf d}$ a $\mathbf d$-subsystem structure. Our first main result identifies the moduli of $\mathbf d$-subsystem structures with the quotient $P/G_{\mathbf d}$. Moreover, we realize naturally $P/G_{\mathbf d}$ as a locally closed subscheme of the relative Hilbert scheme, \[ \text{Hilb}^{\Sigma_{\mathbf d}}\!\bigl(SB(A)/X\bigr)\ \subset\ \text{Hilb}\bigl(SB(A)/X\bigr), \] parametrizing relative closed subschemes fppf-locally isomorphic to $\Sigma_{\mathbf d}\times X$. - oai:arXiv.org:2601.13764v1 - math.AG - hep-th - math-ph - math.MP - math.RA - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - cross - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Kazuki Ikeda - - - Quantum simulation of general spin-1/2 Hamiltonians with parity-violating fermionic Gaussian states - https://arxiv.org/abs/2601.13811 - arXiv:2601.13811v1 Announce Type: cross -Abstract: We introduce equations of motion for a parity-violating fermionic mean-field theory (PV-FMFT): a numerically efficient fermionic mean-field theory based on parity-violating fermionic Gaussian states (PV-FGS). This work provides explicit equations of motion for studying the real- and imaginary-time evolution of spin-1/2 Hamiltonians with arbitrary geometries and interactions. We extend previous formulations of parity-preserving fermionic mean-field theory (PP-FMFT) by including fermionic displacement operators in the variational Ansatz. Unlike PP-FMFT, PV-FMFT can be applied to general spin-1/2 Hamiltonians, describe quenches from arbitrary initial spin-1/2 product states, and compute local and non-local observables in a straight-forward manner at the same modest computational cost as PP-FMFT -- scaling as $O(N^3)$ in the worst case for a system of $N$ spins or fermionic modes. We demonstrate that PV-FMFT can exactly capture the imaginary- and real-time dynamics of non-interacting spin-1/2 Hamiltonians. We then study the post quench-dynamics of the one- and two-dimensional Ising model in presence of longitudinal and transversal fields with PV-FMFT and compute the single site magnetization and correlation functions, and compare them against results from other state-of-the-art numerical approaches. In two-dimensional spin systems, we show that the employed spin-to-fermion mapping can break rotational symmetry within the PV-FMFT description, and we discuss the resulting consequences for the calculated correlation functions. Our work introduces PV-FMFT as a benchmark for other numerical techniques and quantum simulators, and it outlines both its capabilities and its limitations. - oai:arXiv.org:2601.13811v1 - cond-mat.str-el - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - cross - http://creativecommons.org/licenses/by/4.0/ - Michael Kaicher, Joseph Vovrosh, Alexandre Dauphin, Simon B. J\"ager - - - Dimensional Constraints from SU(2) Representation Theory in Graph-Based Quantum Systems - https://arxiv.org/abs/2601.13828 - arXiv:2601.13828v1 Announce Type: cross -Abstract: We investigate dimensional constraints arising from representation theory when abstract graph edges possess internal degrees of freedom but lack geometric properties. We prove that such internal degrees of freedom can only encode directional information, necessitating quantum states in $\mathbb{C}^2$ (qubits) as the minimal representation. Any geometrically consistent projection of these states maps necessarily to $\mathbb{R}^3$ via the Bloch sphere. This dimensional constraint $d=3$ emerges through self-consistency: edges without intrinsic geometry force directional encoding ($\mathbb{C}^2$), whose natural symmetry group $SU(2)$ has three-dimensional Lie algebra, yielding emergent geometry that validates the hypothesis via Bloch sphere correspondence ($S^2 \subset \mathbb{R}^3$). We establish uniqueness (SU($N>2$) yields $d>3$) and robustness (dimensional saturation under graph topology changes). The Euclidean metric emerges canonically from the Killing form on $\mathfrak{su}(2)$. A global gauge consistency axiom is justified via principal bundle trivialization for finite graphs. Numerical simulations verify theoretical predictions. This result demonstrates how dimensional structure can be derived from information-theoretic constraints, with potential relevance to quantum information theory, discrete geometry, and quantum foundations. - oai:arXiv.org:2601.13828v1 - math-ph - math.MP - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - cross - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Jo\~ao P. da Cruz - - - Confinement-Induced Floquet Engineering and Non-Abelian Geometric Phases in Driven Quantum Wire Qubits - https://arxiv.org/abs/2601.13859 - arXiv:2601.13859v1 Announce Type: cross -Abstract: This work theoretically demonstrates that a spin qubit in a parabolic quantum wire driven by a bichromatic field exhibits a confinement-tunable synthetic gauge field, leading to novel Floquet topological phenomena. The study presents the underlying mechanism for topological protection of qubit states against time-periodic perturbations. The analysis reveals a confinement-induced topological Landau-Zener transition, marked by a shift from preserved symmetries to chiral interference patterns in Landau-Zener-St$\ddot{u}$ckelberg-Majorana interferometry. Notably, the emergence of non-Abelian geometric phases under cyclic evolution in curved confinement and phase-parameter space is identified, enabling holonomic quantum computation. Additionally, the prediction of unconventional Floquet-Bloch oscillations in the quasi-energy and resonance transition probability spectra as a function of the biharmonic phase indicates exotic properties, including fractal spectra and fractional Floquet tunneling. These phenomena provide direct evidence of coherent transport in the synthetic dimension. Collectively, these findings position quantum wire materials has a versatile platform for Floquet engineering, topological quantum control, and fault-tolerant quantum information processing. - oai:arXiv.org:2601.13859v1 - cond-mat.mes-hall - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - cross - http://creativecommons.org/licenses/by/4.0/ - Feulefack Ornela Claire, Dongmo Tedo Lynsia Saychele, Danga Jeremie Edmond, Keumo Tsiaze Roger Magloire, Fridolin Melong, Kenfack-Sadem Christian, Fotue Alain Jerve, Mahouton Norbert Hounkonnou, Lukong Cornelius Fai - - - To infinity and back -- $1/N$ graph expansions of light-matter systems - https://arxiv.org/abs/2601.13860 - arXiv:2601.13860v1 Announce Type: cross -Abstract: We present a method for performing a full graph expansion for light-matter systems, utilizing the linked-cluster theorem. This method enables us to explore $1/N$ corrections to the thermodynamic limit $N\to \infty$ in the number of particles, giving us access to the mesoscopic regime. While this regime is yet largely unexplored due to the challenges of studying it with established approaches, it incorporates intriguing features, such as entanglement between light and matter that vanishes in the thermodynamic limit. As a representative application, we calculate physical quantities of the low-energy regime for the paradigmatic Dicke-Ising chain in the paramagnetic normal phase by accompanying the graph expansion with both exact diagonalization (NLCE) and perturbation theory (\pcst), benchmarking our approach against other techniques. We investigate the ground-state energy density and photon density, showing a smooth transition from the microscopic to the macroscopic regime up to the thermodynamic limit. Around the quantum critical point, we extract the $1/N$ corrections to the ground-state energy density to obtain the critical point and critical exponent using extrapolation techniques. - oai:arXiv.org:2601.13860v1 - cond-mat.str-el - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - cross - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Andreas Schellenberger, Kai P. Schmidt - - - The $O(n\to\infty)$ Rotor Model and the Quantum Spherical Model on Graphs - https://arxiv.org/abs/2601.14119 - arXiv:2601.14119v1 Announce Type: cross -Abstract: We show that the large $n$ limit of the $O(n)$ quantum rotor model defined on a general graph has the same critical behavior as the corresponding quantum spherical model and that the critical exponents depend solely on the spectral dimension $d_s$ of the graph. To this end, we employ a classical to quantum mapping and use known results for the large $n$ limit of the classical $O(n)$ model on graphs. Away from the critical point, we discuss the interplay between the Laplacian and the Adjacency matrix in the whole parameter plane of the quantum Hamiltonian. These results allow us to paint the full picture of the $O(n)$ quantum rotor model on graphs in the large $n$ limit. - oai:arXiv.org:2601.14119v1 - cond-mat.stat-mech - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - cross - http://creativecommons.org/licenses/by/4.0/ - Nikita Titov, Andrea Trombettoni - - - Fundamental trade-off relation in probabilistic entanglement generation - https://arxiv.org/abs/2112.03233 - arXiv:2112.03233v3 Announce Type: replace -Abstract: We investigate the generation of entanglement between two non-interacting systems by synthesizing a new quantum process from the superposition of distinct processes characterized by local-only operations. Our analysis leads to the derivation of a universal trade-off relation, $P_{\text{succ}}(1+\mathcal{C})\le1$, that fundamentally bounds the success probability ($P_{\text{succ}}$) and the generated entanglement (concurrence $\mathcal{C}$). The derivation of this trade-off relation is inspired by indefinite causal order, but applies for a broader class of quantum processes. Next, we show that the mathematical structure of this bound predicts the existence of a "quasi-deterministic" mode of operation, a surprising phenomenon which we then confirm with concrete entanglement generation protocols, where a maximally entangled state is guaranteed to be produced. In this mode of operation, both outcomes of the post-selection measurement on the auxiliary control system result in a maximally entangled state of the target system. Furthermore, we demonstrate how this general principle can be realized using a quantum switch, which leverages an indefinite causal order as a physical resource, and explore the rich variety of dynamical behaviors governed by the universal trade-off. Our results establish a general principle for entanglement generation with superposition of quantum processes and introduce a novel way of controlling entanglement generation. - oai:arXiv.org:2112.03233v3 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Yuanbo Chen, Yoshihiko Hasegawa - - - Generalising Aumann's Agreement Theorem - https://arxiv.org/abs/2202.02156 - arXiv:2202.02156v3 Announce Type: replace -Abstract: According to Aumann's celebrated theorem, rational agents cannot agree to disagree. In other words, agents who once shared a common prior probability distribution and who have common knowledge about their posteriors cannot assign different probability distributions to a given proposition. Common knowledge imposes strong restrictions on assigned probabilities. In fact, Aumann's agreement theorem was one of the first attempts to formalise and explore the role played by common knowledge in decision theory. Recently, the debate over possible (quantum) extensions of Aumann's results has resurfaced. This paper contributes to this discussion. First, we argue that agreeing to disagree is impossible in quantum theory. Secondly, by building on the quantum argument, we show that agreeing to disagree is also forbidden in any generalised probability theory. The upshot is that in its probabilistic version, the agreement theorem is a direct consequence of how we choose to condition upon acquiring new information. - oai:arXiv.org:2202.02156v3 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Matthew Leifer, Cristhiano Duarte - - - Establishing trust in quantum computations - https://arxiv.org/abs/2204.07568 - arXiv:2204.07568v2 Announce Type: replace -Abstract: Quantum computing hardware has grown sufficiently complex that it often can no longer be simulated by classical computers, but its computational power remains limited by errors. These errors corrupt the results of quantum algorithms, and it is no longer always feasible to use classical simulations to directly check the correctness of quantum computations. Without practical methods for quantifying the accuracy with which a quantum algorithm has been executed, it is difficult to establish trust in the results of a quantum computation. Here we solve this problem, by introducing a simple and efficient technique for measuring the fidelity with which an as-built quantum computer can execute an algorithm. Our technique converts the algorithm's quantum circuits into a set of closely related ``mirror circuits'' whose success rates can be efficiently measured. It enables measuring the fidelity of quantum algorithm executions both in the near-term, with algorithms run on hundreds or thousands of physical qubits, and into the future, with algorithms run on logical qubits protected by quantum error correction. - oai:arXiv.org:2204.07568v2 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Timothy Proctor, Stefan Seritan, Erik Nielsen, Kenneth Rudinger, Kevin Young, Robin Blume-Kohout, Mohan Sarovar - - - Two convergent NPA-like hierarchies for the quantum bilocal scenario - https://arxiv.org/abs/2210.09065 - arXiv:2210.09065v5 Announce Type: replace -Abstract: Characterising the correlations that arise from locally measuring a single part of a joint quantum system is one of the main problems of quantum information theory. The seminal work [M. Navascu\'es et al., New J. Phys. 10, 073013 (2008)], known as the Navascu\'es-Pironio-Ac\'in (NPA) hierarchy, reformulated this question as a polynomial optimisation problem over noncommutative variables and proposed a convergent hierarchy of necessary conditions, each testable using semidefinite programming. More recently, the problem of characterising the quantum network correlations, which arise when locally measuring several independent quantum systems distributed in a network, has received considerable interest. Several generalisations of the NPA hierarchy, such as the scalar extension [A. Pozas-Kerstjens et al., Phys. Rev. Lett. 123, 140503 (2019)], were introduced while their converging sets remain unknown. In this work, we introduce a new bilocal factorisation NPA hierarchy, prove its equivalence to a modified bilocal scalar extension NPA hierarchy, and characterise its convergence in the case of the simplest network, the bilocal scenario. We further explore its relations with the other known generalisations. - oai:arXiv.org:2210.09065v5 - quant-ph - math-ph - math.MP - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - 10.1063/5.0211008 - J. Math. Phys. 67, 012203 (2026) - Marc-Olivier Renou, Xiangling Xu, Laurens T. Ligthart - - - Nonadiabatic transitions in non-Hermitian $\mathcal{PT}$-symmetric two-level systems - https://arxiv.org/abs/2301.10382 - arXiv:2301.10382v3 Announce Type: replace -Abstract: We systematically characterize the dynamical evolution of time-parity (PT )-symmetric two-level systems with spin-dependent dissipations. If the control parameters of the gap are linearly tuned with time, the dynamical evolution can be characterized with parabolic cylinder equations which can be analytically solved. We find that the asymptotic behaviors of particle probability on the two levels show initial-state-independent redistribution in the slow-tuning-speed limit as long as the system is nonadiabatically driven across exceptional points. Equal distributions appear when the nondissipative Hamiltonian shows gap closing. So long as the nondissipative Hamiltonian displays level anticrossing, the final distribution becomes unbalanced. The ratios between the occupation probabilities are given analytically. These results are confirmed with numerical simulations. The predicted equal distribution phenomenon may be used to identify the closing of the energy gap from anti-crossing between two energy bands. - oai:arXiv.org:2301.10382v3 - quant-ph - cond-mat.mes-hall - cond-mat.quant-gas - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by-nc-nd/4.0/ - 10.1103/PhysRevA.109.022245 - Phys. Rev. A 109, 022245 (2024) - Jian-Song Pan, Fan Wu - - - Spectral Gaps via Imaginary Time - https://arxiv.org/abs/2303.02124 - arXiv:2303.02124v2 Announce Type: replace -Abstract: The spectral gap occupies a role of central importance in many open problems in physics. We present an approach for evaluating the spectral gap of a Hamiltonian from a simple ratio of two expectation values, both of which are evaluated using a quantum state that is evolved in imaginary time. In principle, the only requirement is that the initial state is supported on both the ground and first excited states. We demonstrate this approach for the Fermi-Hubbard and transverse-field Ising models through numerical simulation. We then go on to explore avenues for its implementation on quantum computers using imaginary-time quantum dynamical emulation. - oai:arXiv.org:2303.02124v2 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by/4.0/ - Jacob M. Leamer, Alicia B. Magann, Gerard McCaul, Denys I. Bondar - - - A Computational Tsirelson's Theorem for the Value of Compiled XOR Games - https://arxiv.org/abs/2402.17301 - arXiv:2402.17301v3 Announce Type: replace -Abstract: Nonlocal games are a foundational tool for understanding entanglement and constructing quantum protocols in settings with multiple spatially separated quantum devices. In this work, we continue the study initiated by Kalai et al. (STOC '23) of compiled nonlocal games, played between a classical verifier and a single cryptographically limited quantum device. Our main result is that the compiler proposed by Kalai et al. is sound for any two-player XOR game. A celebrated theorem of Tsirelson shows that for XOR games, the quantum value is exactly given by a semidefinite program, and we obtain our result by showing that the SDP upper bound holds for the compiled game up to a negligible error arising from the compilation. This answers a question raised by Natarajan and Zhang (FOCS '23), who showed soundness for the specific case of the CHSH game. Using our techniques, we obtain several additional results, including (1) tight bounds on the compiled value of parallel-repeated XOR games, (2) operator self-testing statements for any compiled XOR game, and (3) a ``nice'' sum-of-squares certificate for any XOR game, from which operator rigidity is manifest. - oai:arXiv.org:2402.17301v3 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by/4.0/ - David Cui, Giulio Malavolta, Arthur Mehta, Anand Natarajan, Connor Paddock, Simon Schmidt, Michael Walter, Tina Zhang - - - Feedback-Based Quantum Algorithm for Excited States Calculation - https://arxiv.org/abs/2404.04620 - arXiv:2404.04620v2 Announce Type: replace -Abstract: Recently, feedback-based quantum algorithms have been introduced to calculate the ground states of Hamiltonians, inspired by quantum Lyapunov control theory. This paper aims to generalize these algorithms to the problem of calculating an eigenstate of a given Hamiltonian, assuming that the lower energy eigenstates are known. To this aim, we propose a new design methodology that combines the layer-wise construction of the quantum circuit in feedback-based quantum algorithms with a new feedback law based on a new Lyapunov function to assign the quantum circuit parameters. We present two approaches for evaluating the circuit parameters: one based on the expectation and overlap estimation of the terms in the feedback law and another based on the gradient of the Lyapunov function. We demonstrate the algorithm through an illustrative example and through an application in quantum chemistry. To assess its performance, we conduct numerical simulations and execution on IBM's superconducting quantum computer. - oai:arXiv.org:2404.04620v2 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by/4.0/ - 10.1109/TQE.2026.3654528 - Salahuddin Abdul Rahman, \"Ozkan Karabacak, Rafal Wisniewski - - - High-precision and low-depth quantum algorithm design for eigenstate problems - https://arxiv.org/abs/2406.04307 - arXiv:2406.04307v2 Announce Type: replace -Abstract: Estimating the eigenstate properties of quantum systems is a long-standing, challenging problem for both classical and quantum computing. Existing universal quantum algorithms typically rely on ideal and efficient query models (e.g. time evolution operator or block encoding of the Hamiltonian), which, however, become suboptimal for actual implementation at the quantum circuit level. Here, we present a full-stack design of quantum algorithms for estimating the eigenenergy and eigenstate properties, which can achieve high precision and good scaling with system size. The gate complexity per circuit for estimating generic Hamiltonians' eigenstate properties is $\tilde{O} (\log \varepsilon^{-1})$, which has a logarithmic dependence on the inverse precision $\varepsilon$. For lattice Hamiltonians, the circuit depth of our design achieves near-optimal system-size scaling, even with local qubit connectivity. Our full-stack algorithm has low overhead in circuit compilation, which thus results in a small actual gate count (CNOT and non-Clifford gates) for lattice and molecular problems compared to advanced eigenstate algorithms. The algorithm is implemented on IBM quantum devices using up to 2,000 two-qubit gates and 20,000 single-qubit gates, and achieves high-precision eigenenergy estimation for Heisenberg-type Hamiltonians, demonstrating its noise robustness. - oai:arXiv.org:2406.04307v2 - quant-ph - cond-mat.str-el - physics.comp-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by/4.0/ - 10.1126/sciadv.aeb1622 - Science Advances 12.3 (2026): eaeb1622 - Jinzhao Sun, Pei Zeng, Tom Gur, M. S. Kim - - - Improving the trainability of VQE on NISQ computers for solving portfolio optimization using convex interpolation - https://arxiv.org/abs/2407.05589 - arXiv:2407.05589v3 Announce Type: replace -Abstract: Solving combinatorial optimization problems using variational quantum algorithms (VQAs) might be a promise application in the NISQ era. However, the limited trainability of VQAs could hinder their scalability to large problem sizes. In this paper, we improve the trainability of variational quantum eigensolver (VQE) by utilizing convex interpolation to solve portfolio optimization. Based on convex interpolation, the location of the ground state can be evaluated by learning the property of a small subset of basis states in the Hilbert space. This enlightens naturally the proposals of the strategies of close-to-solution initialization, regular cost function landscape, and recursive ansatz equilibrium partition. The successfully implementation of a $40$-qubit experiment using only $10$ superconducting qubits demonstrates the effectiveness of our proposals. Furthermore, the quantum inspiration has also spurred the development of a prototype greedy algorithm. Extensive numerical simulations indicate that the hybridization of VQE and greedy algorithms achieves a mutual complementarity, combining the advantages of both global and local optimization methods. Our proposals can be extended to improve the trainability for solving other large-scale combinatorial optimization problems that are widely used in real applications, paving the way to unleash quantum advantages of NISQ computers in the near future. - oai:arXiv.org:2407.05589v3 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Shengbin Wang, Guihui Li, Zhimin Wang, Zhaoyun Chen, Peng Wang, Yongjian Gu, Yu-Chun Wu, Guo-Ping Guo - - - Discretized Quantum Exhaustive Search for Variational Quantum Algorithms - https://arxiv.org/abs/2407.17659 - arXiv:2407.17659v2 Announce Type: replace -Abstract: Quantum computers promise a great computational advantage over classical computers, yet currently available quantum devices have only a limited amount of qubits and a high level of noise, limiting the size of problems that can be solved accurately with those devices. Variational Quantum Algorithms (VQAs) have emerged as a leading strategy to address these limitations by optimizing cost functions based on measurement results of shallow-depth circuits. However, the optimization process usually suffers from severe trainability issues as a result of the exponentially large search space, mainly local minima and barren plateaus. Here we propose a novel method that can improve variational quantum algorithms -- ``discretized quantum exhaustive search''. On classical computers, exhaustive search, also named brute force, solves small-size NP complete and NP hard problems. Exhaustive search and efficient partial exhaustive search help designing heuristics and exact algorithms for solving larger-size problems by finding easy subcases or good approximations. We adopt this method to the quantum domain, by relying on mutually unbiased bases for the $2^n$-dimensional Hilbert space. We define a discretized quantum exhaustive search that works well for small size problems. We provide an example of an efficient partial discretized quantum exhaustive search for larger-size problems, in order to extend classical tools to the quantum computing domain, for near future and far future goals. Our method enables obtaining intuition on NP-complete and NP-hard problems as well as on Quantum Merlin Arthur (QMA)-complete and QMA-hard problems. We demonstrate our ideas in many simple cases, providing the energy landscape for various problems and presenting two types of energy curves via VQAs. - oai:arXiv.org:2407.17659v2 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by/4.0/ - Ittay Alfassi, Dekel Meirom, Tal Mor - - - Gibbs Sampling gives Quantum Advantage at Constant Temperatures with O(1)-Local Hamiltonians - https://arxiv.org/abs/2408.01516 - arXiv:2408.01516v4 Announce Type: replace -Abstract: Sampling from Gibbs states -- states corresponding to system in thermal equilibrium -- has recently been shown to be a task for which quantum computers are expected to achieve super-polynomial speed-up compared to classical computers, provided the locality of the Hamiltonian increases with the system size (Bergamaschi et al., arXiv: 2404.14639). We extend these results to show that this quantum advantage still occurs for Gibbs states of Hamiltonians with O(1)-local interactions at constant temperature by showing classical hardness-of-sampling and demonstrating such Gibbs states can be prepared efficiently using a quantum computer. In particular, we show hardness-of-sampling is maintained even for 5-local Hamiltonians on a 3D lattice. We additionally show that the hardness-of-sampling is robust when we are only able to make imperfect measurements. - oai:arXiv.org:2408.01516v4 - quant-ph - cond-mat.other - math-ph - math.MP - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by/4.0/ - Joel Rajakumar, James D. Watson - - - Time Derivatives of Weak Values - https://arxiv.org/abs/2409.01460 - arXiv:2409.01460v4 Announce Type: replace -Abstract: The time derivative of a physical property often gives rise to another meaningful property. Since weak values provide empirical insights that cannot be derived from expectation values, this paper explores what physical properties can be obtained from the time derivative of weak values. It demonstrates that, in general, the time derivative of a gauge-invariant weak value is neither a weak value nor a gauge-invariant quantity. Two conditions are presented to ensure that the left- or right-time derivative of a weak value is also a gauge-invariant weak value. Under these conditions, a local Ehrenfest-like theorem can be derived for weak values giving a natural interpretation for the time derivative of weak values. Notably, a single measured weak value of the system's position provides information about two additional unmeasured weak values: the system's local velocity and acceleration, through the first- and second-order time derivatives of the initial weak value, respectively. These findings also offer guidelines for experimentalists to translate the weak value theory into practical laboratory setups, paving the way for innovative quantum technologies. An example illustrates how the electromagnetic field can be determined at specific positions and times from the first- and second-order time derivatives of a weak value of position. - oai:arXiv.org:2409.01460v4 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by/4.0/ - 10.1038/s41598-025-28260-7 - Scientific Reports (Nature Portfolio) 15, 45707 (2025) - Xavier Oriols - - - Fast-forwarding quantum algorithms for linear dissipative differential equations - https://arxiv.org/abs/2410.13189 - arXiv:2410.13189v2 Announce Type: replace -Abstract: We establish improved complexity estimates of quantum algorithms for linear dissipative ordinary differential equations (ODEs) and show that the time dependence can be fast-forwarded to be sub-linear. Specifically, we show that a quantum algorithm based on truncated Dyson series can prepare history states of dissipative ODEs up to time $T$ with cost $\widetilde{\mathcal{O}}(\log(T) (\log(1/\epsilon))^2 )$, which is an exponential speedup over the best previous result. For final state preparation at time $T$, we show that its complexity is $\widetilde{\mathcal{O}}(\sqrt{T} (\log(1/\epsilon))^2 )$, achieving a polynomial speedup in $T$. We also analyze the complexity of simpler lower-order quantum algorithms, such as the forward Euler method and the trapezoidal rule, and find that even lower-order methods can still achieve $\widetilde{\mathcal{O}}(\sqrt{T})$ cost with respect to time $T$ for preparing final states of dissipative ODEs. As applications, we show that quantum algorithms can simulate dissipative non-Hermitian quantum dynamics and heat processes with fast-forwarded complexity sub-linear in time. - oai:arXiv.org:2410.13189v2 - quant-ph - cs.NA - math.NA - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by-nc-sa/4.0/ - Dong An, Akwum Onwunta, Gengzhi Yang - - - Typical Quantum States of the Universe are Observationally Indistinguishable - https://arxiv.org/abs/2410.16860 - arXiv:2410.16860v3 Announce Type: replace -Abstract: We establish three impossibility results regarding our knowledge of the quantum state of the universe. Suppose the universal quantum state is a typical unit vector in a high-dimensional subspace $\mathscr{H}_0$ of Hilbert space $\mathscr{H}$, such as the low-entropy subspace defined by the Past Hypothesis. We show that: (1) Any particular observation is incapable of identifying the universal state vector in $\mathscr{H}_0$ or substantially reducing the set of possibilities. In other words, the overwhelming majority of possible state vectors are observationally indistinguishable from each other. (2) For any reasonably probable measurement outcome and for most pairs of vectors in $\mathscr{H}_0$, that outcome will not appreciably favor one vector over the other. (3) Bayesian updating on any measurement result, unless it is extraordinarily improbable, has a negligible effect on the initial uniform probability distribution over the states in $\mathscr{H}_0$. These findings represent the most stringent epistemic constraints known for a quantum universe and are derived from a typicality theorem in quantum statistical mechanics. We close by considering how theoretical considerations beyond empirical evidence might inform our understanding of this fact and our knowledge of the universal quantum state. - oai:arXiv.org:2410.16860v3 - quant-ph - cond-mat.stat-mech - physics.hist-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by/4.0/ - Eddy Keming Chen, Roderich Tumulka - - - A Geometric Substructure for Quantum Dynamics - https://arxiv.org/abs/2411.08230 - arXiv:2411.08230v5 Announce Type: replace -Abstract: The description of a closed quantum system is extended with the identification of an underlying substructure enabling an expanded formulation of dynamics in the Heisenberg picture. Between measurements a ``state point" moves in an underlying multi-dimensional complex projective space with constant velocity determined by the quantum state vector. Following a measurement the point changes direction and moves with new constant velocity along one of several possible new orthogonal paths with probabilities determined by the Born Interpretation of the state vector. From this previously hidden substructure a new picture of quantum dynamics and quantum measurements emerges without violating existing no-gotheorems regarding hidden variables. A natural generalisation to a Riemannian substructure is proposed, determined by the entropy of the background environment. This leads to a suggestedinteraction between the substructure of quantum dynamics and the background gravitational field. - oai:arXiv.org:2411.08230v5 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by/4.0/ - Anthony John Bracken - - - Recurrent convolutional neural networks for modeling non-adiabatic dynamics of quantum-classical systems - https://arxiv.org/abs/2412.06631 - arXiv:2412.06631v3 Announce Type: replace -Abstract: Recurrent neural networks (RNNs) have recently been extensively applied to model the time-evolution in fluid dynamics, weather predictions, and even chaotic systems thanks to their ability to capture temporal dependencies and sequential patterns in data. Here we present a RNN model based on convolution neural networks for modeling the nonlinear non-adiabatic dynamics of hybrid quantum-classical systems. The dynamical evolution of the hybrid systems is governed by equations of motion for classical degrees of freedom and von Neumann equation for electrons. The physics-aware recurrent convolution (PARC) neural network structure incorporates a differentiator-integrator architecture that inductively models the spatiotemporal dynamics of generic physical systems. We apply our RNN approach to learn the space-time evolution of a one-dimensional semi-classical Holstein model after an interaction quench. For shallow quenches (small changes in electron-lattice coupling), the deterministic dynamics can be accurately captured using a single-CNN-based recurrent network. In contrast, deep quenches induce chaotic evolution, making long-term trajectory prediction significantly more challenging. Nonetheless, we demonstrate that the PARC-CNN architecture can effectively learn the statistical climate of the Holstein model under deep-quench conditions. - oai:arXiv.org:2412.06631v3 - quant-ph - physics.comp-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Alex P. Ning, Lingyu Yang, Gia-Wei Chern - - - Restricted Monte Carlo wave function method and Lindblad equation for identifying entangling open-quantum-system dynamics - https://arxiv.org/abs/2412.08735 - arXiv:2412.08735v2 Announce Type: replace -Abstract: We develop an extension of the Monte Carlo wave function approach that unambiguously identifies dynamical entanglement in general composite, open systems. Our algorithm performs tangential projections onto the set of separable states, leading to classically correlated quantum trajectories. By comparing this restricted evolution with the unrestricted one, we can characterize the entangling capabilities of quantum channels without making use of input-output relations. Moreover, applying this method is equivalent to solving the nonlinear master equation in Lindblad form introduced in \cite{PAH24} for two-qubit systems. We here extend these equations to multipartite systems of qudits, describing non-entangling dynamics in terms of a stochastic differential equation. We identify the impact of dynamical entanglement in open systems by applying our approach to several correlated decay processes. Therefore, our methodology provides a complete and ready-to-use framework to characterize dynamical quantum correlations caused by arbitrary open-system processes. - oai:arXiv.org:2412.08735v2 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by/4.0/ - 10.1103/hcj7-8zlg - Phys. Rev. A 113, 012220 (2026) - Laura Ares, Julien Pinske, Benjamin Hinrichs, Martin Kolb, Jan Sperling - - - Optimal Hamiltonian recognition of unknown quantum dynamics - https://arxiv.org/abs/2412.13067 - arXiv:2412.13067v2 Announce Type: replace -Abstract: Identifying unknown Hamiltonians from their quantum dynamics is a pivotal challenge in quantum technologies. In this paper, we introduce Hamiltonian recognition, a framework that bridges quantum hypothesis testing and quantum metrology, aiming to identify the Hamiltonian governing quantum dynamics from a known set of Hamiltonians. To identify $H$ for an unknown qubit quantum evolution $\exp(-iH\theta)$ with unknown $\theta$, from two or three orthogonal Hamiltonians, we develop a quantum algorithm for coherent function simulation, built on two quantum signal processing (QSP) structures. It can simultaneously realize a target polynomial based on measurement results regardless of the chosen signal unitary for the QSP. Utilizing semidefinite optimization and group representation theory, we prove that our methods achieve the optimal average success probability, taken over possible Hamiltonians $H$ and parameters $\theta$, decays as $O(1/k)$ with $k$ queries of the unknown unitary transformation. Furthermore, we demonstrate the validity of our protocol on a superconducting quantum processor. We also investigate a physically motivated recognition task for Heisenberg Hamiltonians, providing numerical evidence for effective multi-qubit quantum system recognition. This work presents an efficient method to recognize Hamiltonians from limited queries of the dynamics, opening new avenues in composite channel discrimination and quantum metrology. - oai:arXiv.org:2412.13067v2 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by/4.0/ - Chengkai Zhu, Shuyu He, Yu-Ao Chen, Lei Zhang, Xin Wang - - - Characterisation of individual gates using twirling circuits - https://arxiv.org/abs/2412.15466 - arXiv:2412.15466v2 Announce Type: replace -Abstract: We present a method to characterise qubit gates. Utilising the supermap formalism, we create a scheme for deterministic single-qubit gate analysis. Our approach introduces a new twirling process that is applied directly through fixed circuits. This method removes the requirement to average over random gates. The results enhance randomised benchmarking techniques and are suitable for experimental setups with multi-qubit control, focusing on the precise characterisation of single-qubit gates. - oai:arXiv.org:2412.15466v2 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by-nc-sa/4.0/ - 10.1142/S1230161225500167 - D Amaro-Alcal\'a Open Syst. Inf. Dyn. 32 (04), 2550016, 2025 - David Amaro-Alcal\'a - - - Quantum particle in the wrong box (or: the perils of finite-dimensional approximations) - https://arxiv.org/abs/2412.15889 - arXiv:2412.15889v3 Announce Type: replace -Abstract: When numerically simulating the unitary time evolution of an infinite-dimensional quantum system, one is usually led to treat the Hamiltonian $H$ as an "infinite-dimensional matrix" by expressing it in some orthonormal basis of the Hilbert space, and then truncate it to some finite dimensions. However, the solutions of the Schr\"odinger equations generated by the truncated Hamiltonians need not converge, in general, to the solution of the Schr\"odinger equation corresponding to the actual Hamiltonian. - In this paper we demonstrate that, under mild assumptions, they converge to the solution of the Schr\"odinger equation generated by a specific Hamiltonian which crucially depends on the particular choice of basis: the Friedrichs extension of the restriction of $H$ to the space of finite linear combinations of elements of the basis. Importantly, this is generally different from $H$ itself; in all such cases, numerical simulations will unavoidably reproduce the wrong dynamics in the limit, and yet there is no numerical test that can reveal this failure, unless one has the analytical solution to compare with. - As a practical demonstration of such results, we consider the quantum particle in the box, and we show that, for a wide class of bases (which include associated Legendre polynomials as a concrete example) the dynamics generated by the truncated Hamiltonians will always converge to the one corresponding to the particle with Dirichlet boundary conditions, regardless the initial choice of boundary conditions. Other such examples are discussed. - oai:arXiv.org:2412.15889v3 - quant-ph - math-ph - math.MP - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by/4.0/ - Felix Fischer, Daniel Burgarth, Davide Lonigro - - - Dissipating quartets of excitations in a superconducting circuit - https://arxiv.org/abs/2501.05960 - arXiv:2501.05960v3 Announce Type: replace -Abstract: Over the past decade, autonomous stabilization of bosonic qubits has emerged as a promising approach for hardware-efficient protection of quantum information. However, applying these techniques to more complex encodings than the Schr\"odinger cat code requires exquisite control of high-order wave mixing processes. The challenge is to enable specific multiphotonic dissipation channels while avoiding unintended non-linear interactions. In this work, we leverage a genuine six-wave mixing process enabled by a near Kerr-free Josephson element to enforce dissipation of quartets of excitations in a high-impedance superconducting resonator. Owing to residual non-linearities stemming from stray inductances in our circuit, this dissipation channel is only effective when the resonator holds a specific number of photons. Applying it to the fourth excited state of the resonator, we show an order of magnitude enhancement of the state decay rate while only marginally impacting the relaxation and coherence of lower energy states. Given that stray inductances could be strongly reduced through simple modifications in circuit design and that our methods can be adapted to activate even higher-order dissipation channels, these results pave the way toward the dynamical stabilization of four-component Schr\"odinger cat qubits and even more complex bosonic qubits. - oai:arXiv.org:2501.05960v3 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by/4.0/ - Aron Vanselow, Brieuc Beauseigneur, Louis Lattier, Marius Villiers, Anne Denis, Pascal Morfin, Zaki Leghtas, Philippe Campagne-Ibarcq - - - QSteed: A Resource-Virtualized and Hardware-Aware Quantum Compilation Framework for Real Quantum Computing Processors - https://arxiv.org/abs/2501.06993 - arXiv:2501.06993v2 Announce Type: replace -Abstract: As quantum computing systems continue to scale up and become more clustered, efficiently compiling user quantum programs into high fidelity executable sequences on real hardware remains a key challenge for current quantum compilation systems. In this study, we introduce a system software framework that integrates resource virtualization and hardware aware compilation for real quantum computing processors, termed QSteed. QSteed virtualizes quantum processors through a four layer abstraction hierarchy comprising the Real Quantum Processing Unit (QPU), Standard QPU (StdQPU), Substructure of the QPU (SubQPU), and Virtual QPU (VQPU). These abstractions, together with calibration data, device topology, and noise descriptors, are maintained in a dedicated database to enable unified and fine grained management across superconducting quantum platforms. At run time, the modular compiler queries the database to match each incoming circuit with the most suitable VQPU, after which it confines layout, routing, gate resynthesis, and noise adaptive optimizations to that virtual subregion. The complete stack has been deployed on the Quafu superconducting cluster, where experimental runs confirm the correctness of the virtualization model and the efficacy of the compiler without requiring modifications to user code. By integrating resource virtualization with a select-then-compile workflow, QSteed demonstrates a robust architecture for compiling programs on noisy superconducting processors. This architectural approach offers a promising path towards efficient compilation needs across various superconducting quantum computing platforms in the noisy intermediate scale quantum (NISQ) era. - oai:arXiv.org:2501.06993v2 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by-nc-sa/4.0/ - 10.34133/research.0947 - Research 8, 0947 (2025) - Hong-Ze Xu, Zheng-An Wang, Yu-Long Feng, Yu Chen, Xinpeng Zhang, Jingbo Wang, Xu-Dan Chai, Wei-Feng Zhuang, Yu-Xin Jin, Yirong Jin, Haifeng Yu, Heng Fan, Meng-Jun Hu, Dong E. Liu - - - Unifying quantum stochastic methods using Wick's theorem on the Keldysh contour - https://arxiv.org/abs/2501.09544 - arXiv:2501.09544v2 Announce Type: replace -Abstract: We present a method, based on the Keldysh formalism, for deriving stochastic master equations that describe the non-Markovian dynamics of a quantum system coupled to a Gaussian environment. This approach yields a compact expression for the system's propagator, which we show to be equivalent to existing formulations, such as the stochastic von Neumann equation (SVNE). A key advantage of our method is its generality: It can be extended to describe any open-system evolution defined on a suitable ordering contour. As a result, we adapt it to derive generalized versions of the SVNE that account for initial system-environment correlations, as well as stochastic equations that incorporate information about the statistics of energy flows in the environment. The insights offered by our technique further allow us to examine the nature of the noise processes appearing in the SVNE. We prove that its solution can be expressed in terms of a single physical noise, without any loss of information. Finally, we propose a semiclassical scenario in which this noise can be interpreted as arising from an initial measurement process on the environment. - oai:arXiv.org:2501.09544v2 - quant-ph - cond-mat.stat-mech - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - 10.1103/cnvm-w8cy - Phys. Rev. Research 7, 043262 (2025) - Vasco Cavina, Antonio D'Abbruzzo, Vittorio Giovannetti - - - Decoherence of Schr\"odinger cat states in light of wave/particle duality - https://arxiv.org/abs/2501.12328 - arXiv:2501.12328v3 Announce Type: replace -Abstract: We challenge the standard picture of decohering Schr\"odinger cat states as an ensemble average obeying a Lindblad master equation, brought about locally from an irreversible interaction with an environment. We generate self-consistent collections of pure system states correlated with specific environmental records, corresponding to the function of the wave-particle correlator first introduced in Carmichael et al. [Phys. Rev. Lett. 85, 1855 (2000)]. In the spirit of Carmichael et al. [Coherent States: Past, Present and Future, pp. 75-91, World Scientific (1994)], we find that the complementary unravelings evince a pronounced disparity when the ``position'' and ``momentum'' of the damped cavity mode - an explicitly open quantum system - are measured. Intensity-field correlations may largely deviate from a monotonic decay, while Wigner functions of the cavity state display contrasting manifestations of quantum interference when conditioned on photon counts sampling a continuous photocurrent. In turn, the conditional photodetection events mark the contextual diffusion of both the net charge generated at the homodyne detector, and the electromagnetic field amplitude in the resonator. - oai:arXiv.org:2501.12328v3 - quant-ph - cond-mat.mes-hall - physics.optics - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - 10.5802/crphys.271 - Comptes Rendus. Physique, Vol. 27, p.17-40 (2026) - Th. K. Mavrogordatos - - - On the distinguishability of geometrically uniform quantum states - https://arxiv.org/abs/2501.12376 - arXiv:2501.12376v2 Announce Type: replace -Abstract: A geometrically uniform (GU) ensemble is a uniformly weighted quantum state ensemble generated from a fixed state by a unitary representation of a finite group $G$. In this work we analyze the problem of discriminating GU ensembles from various angles. Assuming that the representation of $G$ is irreducible, we first show that a particular optimal measurement can be understood as the limit of weighted `pretty good measurements' (PGM). This naturally provides examples of state discrimination for which the unweighted PGM is provably sub-optimal. We extend this analysis to certain reducible representations, and use Schur-Weyl duality to discuss two particular examples of GU ensembles in terms of Werner-type and permutation-invariant generator states. For the case of pure-state GU ensembles we give a streamlined proof of optimality of the PGM first proved in [Eldar et al., 2004]. We use this result to give simplified proofs of the optimality of the PGM, along with expressions for the corresponding success probabilities, for two tasks: the hidden subgroup problem over semidirect product groups (first proved in [Bacon et al., 2005]), and port-based teleportation (first proved in [Mozrzymas et al., 2019] and [Leditzky, 2022]). Finally, we consider the $n$-copy setting and adapt a result of [Montanaro, 2007] to derive a compact and easily evaluated lower bound on the success probability of the PGM for this task. This result can be applied to the hidden subgroup problem to obtain a new proof for an upper bound on the sample complexity by [Hayashi et al., 2006]. - oai:arXiv.org:2501.12376v2 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - 10.1088/1751-8121/ae0a95 - Journal of Physics A: Mathematical and Theoretical 58, 415303 (2025) - Juntai Zhou, Stefano Chessa, Eric Chitambar, Felix Leditzky - - - Exceptional-Point-Induced Nonequilibrium Entanglement Dynamics in Bosonic Networks - https://arxiv.org/abs/2502.04639 - arXiv:2502.04639v2 Announce Type: replace -Abstract: Exceptional points (EPs), arising in non-Hermitian systems, have garnered significant attention in recent years, enabling advancements in sensing, wave manipulation, and mode selectivity. However, their role in quantum systems, particularly in influencing quantum correlations, remains underexplored. In this work, we investigate how EPs control multimode entanglement in bosonic chains. Using a Bogoliubov-de Gennes (BdG) framework to describe the Heisenberg equations, we identify EPs of varying orders and uncover spectral transitions between purely real, purely imaginary, and mixed eigenvalue spectra. These spectral regions, divided by EPs, correspond to three distinct entanglement dynamics: oscillatory, exponential, and hybrid. Remarkably, we demonstrate that higher-order EPs, realized by non-integer-pi hopping phases or nonuniform interaction strengths, significantly enhance the degree of multimode entanglement compared to second-order EPs. Our findings provide a pathway to leveraging EPs for entanglement control and exhibit the potential of non-Hermitian physics in advancing quantum technologies. - oai:arXiv.org:2502.04639v2 - quant-ph - physics.optics - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by-nc-nd/4.0/ - Chenghe Yu, Mingsheng Tian, Ningxin Kong, Matteo Fadel, Xinyao Huang, Qiongyi He - - - Exact non-Markovian master equations: a generalized derivation for Gaussian systems - https://arxiv.org/abs/2502.14364 - arXiv:2502.14364v3 Announce Type: replace -Abstract: We derive an exact master equation that captures the dynamics of a quadratic quantum system linearly coupled to a Gaussian environment of the same statistics: the Gaussian Master Equation (GME). Unlike previous approaches, our formulation applies universally to both bosonic and fermionic setups, and remains valid even in the presence of initial system-environment correlations, allowing for the exact computation of the system's reduced density matrix across all parameter regimes. Remarkably, the GME shares the same operatorial structure as the Redfield equation and depends on a single kernel - a dressed environment correlation function accounting for all virtual interactions between the system and the environment. This simple structure grants a clear physical interpretation and makes the GME easy to simulate numerically, as we show by applying it to an open system based on two fermions coupled via superconductive pairing. - oai:arXiv.org:2502.14364v3 - quant-ph - cond-mat.stat-mech - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - 10.1103/cb7c-5f66 - Phys. Rev. Lett. 135, 240401 (2025) - Antonio D'Abbruzzo, Vittorio Giovannetti, Vasco Cavina - - - Quantum state exclusion for group-generated ensembles of pure states - https://arxiv.org/abs/2503.02568 - arXiv:2503.02568v2 Announce Type: replace -Abstract: Quantum state exclusion is the task of determining which states from a given set a system was not prepared in. We provide a complete solution to optimal quantum state exclusion for arbitrary sets of pure states generated by finite groups, establishing necessary and sufficient conditions for perfect (zero-error conclusive) exclusion. When perfect exclusion is impossible, we introduce two natural extensions: minimum-error and unambiguous exclusion. For both, we derive the optimal protocols and present analytical expressions for the corresponding failure probabilities and measurements, providing additional insight into how quantum states encode information. - oai:arXiv.org:2503.02568v2 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by/4.0/ - 10.1103/2k5d-bprn - Phys. Rev. Research 8, L012001 (2026) - Arnau Diebra, Santiago Llorens, Emili Bagan, Gael Sent\'is, Ramon Mu\~noz-Tapia - - - Scalable quantum simulator with an extended gate set in giant atoms - https://arxiv.org/abs/2503.04537 - arXiv:2503.04537v3 Announce Type: replace -Abstract: Quantum computation and quantum simulation require a versatile gate set to optimize circuit compilation for practical applications. However, existing platforms are often limited to specific gate types or rely on parametric couplers to extend their gate set, which compromises scalability. Here, we propose a scalable quantum simulator with an extended gate set based on giant-atom three-level systems, which can be implemented with superconducting circuits. Unlike conventional small atoms, giant atoms couple to the environment at multiple points, introducing interference effects that allow exceptional tunability of their interactions. By leveraging this tunability, our setup supports both CZ and iSWAP gates through simple frequency adjustments, eliminating the need for parametric couplers. This dual-gate capability enhances circuit efficiency, reducing the overhead for quantum simulation. As a demonstration, we showcase the simulation of spin dynamics in dissipative Heisenberg XXZ spin chains, highlighting the setup's ability to tackle complex open quantum many-body dynamics. Finally, we discuss how a two-dimensional extension of our system could enable fault-tolerant quantum computation, paving the way for a universal quantum processor. - oai:arXiv.org:2503.04537v3 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by/4.0/ - Guangze Chen, Anton Frisk Kockum - - - A Multilevel Framework for Partitioning Quantum Circuits - https://arxiv.org/abs/2503.19082 - arXiv:2503.19082v4 Announce Type: replace -Abstract: Executing quantum algorithms over distributed quantum systems requires quantum circuits to be divided into sub-circuits which communicate via entanglement-based teleportation. Naively mapping circuits to qubits over multiple quantum processing units (QPUs) results in large communication overhead, increasing both execution time and noise. This can be minimised by optimising the assignment of qubits to QPUs and the methods used for covering non-local operations. Formulations that are general enough to capture the spectrum of teleportation possibilities lead to complex problem instances which can be difficult to solve effectively. This highlights a need to exploit the wide range of heuristic techniques used in the graph partitioning literature. This paper formalises and extends existing constructions for graphical quantum circuit partitioning and designs a new objective function that captures further possibilities for non-local operations via nested state teleportation. We adapt the well-known Fiduccia-Mattheyses heuristic to the constraints and problem objective and explore multilevel techniques that coarsen hypergraphs and partition at multiple levels of granularity. We find that this reduces runtime and improves solution quality of standard partitioning. We place these techniques within a larger framework, through which we can extract full distributed quantum circuits including teleportation instructions. We compare the entanglement requirements and runtimes with state-of-the-art methods, finding that we achieve the lowest entanglement costs in most cases. Averaging over a wide range of circuits, we reduce the entanglement requirements by 35% compared with the next best-performing method. We also find that our techniques can scale to much larger circuit sizes than competing methods, provided the number of partitions is not too large. - oai:arXiv.org:2503.19082v4 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by/4.0/ - Felix Burt, Kuan-Cheng Chen, Kin K. Leung - - - Covert Entanglement Generation and Secrecy - https://arxiv.org/abs/2503.21002 - arXiv:2503.21002v4 Announce Type: replace -Abstract: We determine the covert capacity for entanglement generation over a noisy quantum channel. While secrecy guarantees that the transmitted information remains inaccessible to an adversary, covert communication ensures that the transmission itself remains undetectable. The entanglement dimension follows a square root law (SRL) in the covert setting, i.e., $O(\sqrt{n})$ EPR pairs can be distributed covertly and reliably over $n$ channel uses. We begin with covert communication of classical information under a secrecy constraint. We then leverage this result to construct a coding scheme for covert entanglement generation. - oai:arXiv.org:2503.21002v4 - quant-ph - cs.IT - math.IT - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Ohad Kimelfeld, Boulat A. Bash, Uzi Pereg - - - Dissipation and non-thermal states in cryogenic cavities - https://arxiv.org/abs/2504.00591 - arXiv:2504.00591v3 Announce Type: replace -Abstract: We study the properties of photons in a cryogenic cavity, made by cryo-cooled mirrors surrounded by a room temperature environment. We model such a system as a multimode cavity coupled to two thermal reservoirs at different temperatures. Using a Lindblad master equation approach, we derive the photon distribution and the statistical properties of the cavity modes, finding an overall non-thermal state described by a mode-dependent effective temperature. We also calculate the dissipation rates arising from the interaction of the cavity field with the external environment and the mirrors, relating such rates to measurable macroscopic quantities. These results provide a simple theory to calculate the dissipative properties and the effective temperature of a cavity coupled to different thermal reservoirs, offering potential pathways for engineering dissipations and photon statistics in cavity settings. - oai:arXiv.org:2504.00591v3 - quant-ph - cond-mat.mes-hall - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by-nc-sa/4.0/ - Zeno Bacciconi, Giulia Piccitto, Alessandro Maria Verga, Giuseppe Falci, Elisabetta Paladino, Giuliano Chiriac\`o - - - Dynamically stable two-mode squeezing in cavity optomechanics - https://arxiv.org/abs/2504.03247 - arXiv:2504.03247v5 Announce Type: replace -Abstract: Bosonic two-mode squeezed states are paradigmatic entangled states with broad applications in quantum information processing and quantum metrology. In this work, we propose a two-mode squeezing scheme in a hybrid three-mode cavity optomechanical system, where a mechanical resonator couples to two microwave (or optical) photon modes. By applying and modulating strong driving pulses to the photon modes, we construct an effective Hamiltonian that describes two-photon squeezing mediated by the mechanical mode. This effective Hamiltonian is validated through diagonalization of the full system's transition matrix in the Heisenberg picture. With the effective Hamiltonian, we provide a rigorous theoretical solution for the dynamical process of squeezing generation within the framework of open quantum system. Our analysis reveals that stable two-mode squeezing can be obtained by optimizing the squeezing quadrature operator, even in unsteady system states. Remarkably, the squeezing level can exceed the maximum achievable under system stability conditions. Furthermore, we show that our protocol is robust against systematic errors in both driving intensity and frequency, as well as against thermal Markovian noises. Our work provides an extendable approach for generating two-mode squeezed states between indirectly coupled Gaussian modes. - oai:arXiv.org:2504.03247v5 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/publicdomain/zero/1.0/ - 10.1016/j.physleta.2026.131372 - Physics Letters A 573 (2026) 131372 - Chen Wang, Shi-fan Qi - - - Fault-tolerant protocols through spacetime concatenation - https://arxiv.org/abs/2504.08918 - arXiv:2504.08918v4 Announce Type: replace -Abstract: We introduce a framework called spacetime concatenation for fault-tolerant compilation of syndrome extraction circuits of stabilizer codes. Spacetime concatenation enables efficient compilation of syndrome extraction circuits into dynamical codes through structured gadget layouts and encoding matrices, facilitating low-weight measurements while preserving logical information. Our framework uses conditions that are sufficient for fault-tolerance of the dynamical code, including not measuring logical operators and preserving the spacetime distance. We construct explicit examples of dynamical codes using this framework, including the dynamical bivariate bicycle code and a dynamical Haah code, while illustrating their fault-tolerant properties. Furthermore, we analyze the classification and resource trade-offs of dynamical codes, demonstrating their adaptability to hardware constraints, including fabrication defects and qubit dropout scenarios. - oai:arXiv.org:2504.08918v4 - quant-ph - cond-mat.str-el - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by/4.0/ - Yichen Xu, Arpit Dua - - - Adaptive Entanglement Distillation - https://arxiv.org/abs/2504.11670 - arXiv:2504.11670v2 Announce Type: replace -Abstract: Quantum network applications impose a variety of requirements on entanglement resources in terms of rate, fidelity, latency, and more. The repeaters in the quantum network must combine good methods for entanglement generation, effective entanglement distillation, and smart routing protocols to satisfy these application requirements. In this work, we focus on entanglement distillation in a linear chain of quantum repeaters. While conventional approaches reuse the same distillation scheme over multiple hop lengths after entanglement swaps, we propose a novel adaptive quantum error correction (QEC) scheme that boosts end-to-end metrics. Specifically, depending on the network operating point, we adapt the code used in distillation over successive rounds to monotonically increase the rate while also improving fidelity. We demonstrate the effectiveness of this strategy using three codes, with parameters [[9,1,3]], [[9,2,3]], [[9,3,3]], and a new performance metric, efficiency, that incorporates both overall rate and fidelity. Since the minimum input fidelity for QEC-based distillation is high, we then extend our study to include non-QEC-based purification protocols, specifically DEJMPS since it outperforms others. We compare the performance of end-to-end DEJMPS against adapting from DEJMPS to QEC once DEJMPS improves the initial fidelity to the threshold for QEC. Through a refined efficiency metric, we illuminate the regime where QEC is beneficial. These results provide a detailed outlook for entanglement purification and distillation in first and second generation quantum repeaters. - oai:arXiv.org:2504.11670v2 - quant-ph - cs.IT - math.IT - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Sijie Cheng, Narayanan Rengaswamy - - - Micromagnons and long-range entanglement in ferrimagnetic ground states - https://arxiv.org/abs/2504.18724 - arXiv:2504.18724v2 Announce Type: replace -Abstract: While significant attention has been devoted to studying entanglement in photonic systems, solid-state spin lattices remain relatively underexplored. Motivated by this gap, we investigate the entanglement structure of one-dimensional ferrimagnetic chains composed of alternating spin-1/2 and spin-3/2 particles. We characterize the ground-state correlations using exact diagonalization and the Density Matrix Renormalization Group method. Although the bipartite entanglement is restricted to nearest neighbors, we reveal the presence of long-range genuine multipartite entanglement between spatially separated spin pairs. These findings advance our understanding of quantum correlations in ferrimagnetic materials. The micromagnon description allows to provide fast approximation of ground states of ferrimagnets and emphasizes presence of multipartite correlations not widely discussed thus far. - oai:arXiv.org:2504.18724v2 - quant-ph - cond-mat.str-el - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by/4.0/ - 10.1103/wwr6-l3dq - Phys. Rev. B 112, 134425 (2025) - Marcin Wie\'sniak, Ankit Kumar, Idriss Hank Nkouatchoua Ngueya - - - Algebraic Topology Principles behind Topological Quantum Error Correction - https://arxiv.org/abs/2505.06082 - arXiv:2505.06082v2 Announce Type: replace -Abstract: Quantum error correction (QEC) is crucial for realizing scalable quantum technologies, and topological quantum error correction (TQEC) has emerged as the most experimentally advanced paradigm of QEC. Existing homological and topological code constructions, however, are largely confined to orientable two-manifolds with simple boundary conditions. In this work, we develop a unified algebraic-topological framework for TQEC based on homology, cohomology, and intersection theory, which characterizes exactly when an arbitrary-dimensional manifold (with or without boundary) can serve as a quantum memory, thereby extending the standard 2D homological-code picture to arbitrary dimension and to manifolds with boundary via Poincar\'e-Lefschetz duality. Building on this classification, we introduce concrete code families that exploit nontrivial topology beyond the planar and toric settings. These include ``3-torus code'' and higher-dimensional ``volume codes'' on compact manifolds with mixed $X$- and $Z$-type boundaries. We further give a topological construction of qudit TQEC codes on general two-dimensional cell complexes using group presentation complexes, which unifies and extends several known quantum LDPC and homological-product-like constructions within a single geometric language. Finally, we combine the theoretical framework with numerical simulations to demonstrate that changing only the global topology can yield improved logical performance at fixed entanglement resources. Taken together, our results provide a systematic set of topological design principles for constructing and analyzing TQEC codes across dimensions and boundaries, and they open new avenues for topology-aware fault-tolerant quantum architectures. - oai:arXiv.org:2505.06082v2 - quant-ph - math-ph - math.MP - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Xiang Zou, Hoi-Kwong Lo - - - Fermion Doubling in Quantum Cellular Automata - https://arxiv.org/abs/2505.07900 - arXiv:2505.07900v3 Announce Type: replace -Abstract: A Quantum Cellular Automaton (QCA) is essentially an operator driving the evolution of particles on a lattice, through local unitaries. Because $\Delta_t=\Delta_x = \epsilon$, QCAs constitute a privileged framework to cast the digital quantum simulation of relativistic quantum particles and their interactions with gauge fields, e.g., $(3+1)$D Quantum Electrodynamics (QED). But before they can be adopted, simulation schemes for high-energy physics need prove themselves against specific numerical issues, of which the most infamous is Fermion Doubling (FD). FD is well understood in particular in the real-time, discrete-space \emph{but} continuous-time settings of Hamiltonian Lattice Gauge Theories (LGTs), as the appearance of spurious solutions for all $\Delta_x=\epsilon\neq 0$. We rigorously extend this analysis to the real-time, discrete-space \emph{and} discrete-time schemes that QCAs are. We demonstrate the existence of FD issues in QCAs for $\Delta_t =\Delta_x = \epsilon \neq 0$. By applying a covering map on the Brillouin zone, we provide a flavor-staggering-only way of fixing FD that does not break the chiral symmetry of the massless scheme. We explain how this method coexists with the Nielsen-Ninomiya no-go theorem, and give an example of neutrino-like QCA showing that our model allows to put chiral fermions interacting via the weak interaction on a spacetime lattice, without running into any FD problem. - oai:arXiv.org:2505.07900v3 - quant-ph - hep-lat - math-ph - math.MP - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by-nc-nd/4.0/ - Dogukan Bakircioglu, Pablo Arnault, Pablo Arrighi - - - High-Temperature Fermionic Gibbs States are Mixtures of Gaussian States - https://arxiv.org/abs/2505.09730 - arXiv:2505.09730v2 Announce Type: replace -Abstract: Efficient simulation of a quantum system generally relies on structural properties of the quantum state. Motivated by the recent results by Bakshi et al. on the sudden death of entanglement in high-temperature Gibbs states of quantum spin systems, we study the high-temperature Gibbs states of bounded-degree local fermionic Hamiltonians, which include the special case of geometrically local fermionic systems. We prove that at a sufficiently high temperature that is independent of the system size, the Gibbs state is a probabilistic mixture of fermionic Gaussian states. This forms the basis of an efficient classical algorithm to prepare the Gibbs state by sampling from a distribution of fermionic Gaussian states. As a contrasting example, we show that high-temperature Gibbs states of the Sachdev-Ye-Kitaev (SYK) model are not convex mixtures of Gaussian states. - oai:arXiv.org:2505.09730v2 - quant-ph - cs.DS - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by/4.0/ - Akshar Ramkumar, Yiyi Cai, Yu Tong, Jiaqing Jiang - - - Experimental robustness benchmarking of quantum neural networks on a superconducting quantum processor - https://arxiv.org/abs/2505.16714 - arXiv:2505.16714v2 Announce Type: replace -Abstract: Quantum machine learning (QML) models, like their classical counterparts, are vulnerable to adversarial attacks, hindering their secure deployment. Here, we report the first systematic experimental robustness benchmark for 20-qubit quantum neural network (QNN) classifiers executed on a superconducting processor. Our benchmarking framework features an efficient adversarial attack algorithm designed for QNNs, enabling quantitative characterization of adversarial robustness and robustness bounds. From our analysis, we verify that adversarial training reduces sensitivity to targeted perturbations by regularizing input gradients, significantly enhancing QNN's robustness. Additionally, our analysis reveals that QNNs exhibit superior adversarial robustness compared to classical neural networks, an advantage attributed to inherent quantum noise. Furthermore, the empirical upper bound extracted from our attack experiments shows a minimal deviation ($3 \times 10^{-3}$) from the theoretical lower bound, providing strong experimental confirmation of the attack's effectiveness and the tightness of fidelity-based robustness bounds. This work establishes a critical experimental framework for assessing and improving quantum adversarial robustness, paving the way for secure and reliable QML applications. - oai:arXiv.org:2505.16714v2 - quant-ph - cs.LG - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by-sa/4.0/ - Hai-Feng Zhang, Zhao-Yun Chen, Peng Wang, Liang-Liang Guo, Tian-Le Wang, Xiao-Yan Yang, Ren-Ze Zhao, Ze-An Zhao, Sheng Zhang, Lei Du, Hao-Ran Tao, Zhi-Long Jia, Wei-Cheng Kong, Huan-Yu Liu, Athanasios V. Vasilakos, Yang Yang, Yu-Chun Wu, Ji Guan, Peng Duan, Guo-Ping Guo - - - Probing the quantum motion of a macroscopic mechanical oscillator with a radio-frequency superconducting qubit - https://arxiv.org/abs/2505.21481 - arXiv:2505.21481v2 Announce Type: replace -Abstract: Long-lived mechanical resonators like drums oscillating at MHz frequencies and operating in the quantum regime are a powerful platform for quantum technologies and tests of fundamental physics. Yet, quantum control of such systems remains challenging, owing to their low energy scale and the difficulty of achieving efficient coupling to other well-controlled quantum devices. Here, we demonstrate repeated coherent interactions between a 4 MHz suspended silicon nitride membrane and a resonant superconducting heavy-fluxonium qubit. The qubit is initialized at an effective temperature of $21~\mathrm{\mu K}$ and read out with 77% single-shot fidelity. During the $6~\mathrm{ms}$ lifetime of the membrane the two systems swap excitations more than 300 times. After each interaction, a state-selective qubit detection is performed, implementing a stroboscopic series of weak measurements that provide information about the mechanical state. The accumulated records reconstruct the position noise spectrum of the membrane, revealing both its thermal occupation $n_\mathrm{th}\approx47$ at $10~\mathrm{mK}$ and the qubit-induced back-action. By preparing the qubit either in its ground or excited state before each interaction, we observe an imbalance between the emission and absorption spectra, proportional to $n_\mathrm{th}$ and $n_\mathrm{th}+1$, respectively-a hallmark of the non-commutation of phonon creation and annihilation operators. Since the predicted Di\'osi-Penrose gravitational collapse time is comparable to the measured mechanical decoherence time, our architecture enters a regime where gravity-induced decoherence could be tested directly. - oai:arXiv.org:2505.21481v2 - quant-ph - cond-mat.mes-hall - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by/4.0/ - Kyrylo Gerashchenko, R\'emi Rousseau, L\'eo Balembois, Himanshu Patange, Paul Manset, Tristan Briant, Pierre-Fran\c{c}ois Cohadon, Antoine Heidmann, W. Clarke Smith, Antoine Tilloy, Zaki Leghtas, Emmanuel Flurin, Thibaut Jacqmin, Samuel Del\'eglise - - - Flagged Extensions and Numerical Simulations for Quantum Channel Capacity: Bridging Theory and Computation - https://arxiv.org/abs/2506.03429 - arXiv:2506.03429v2 Announce Type: replace -Abstract: I will investigate the capacities of noisy quantum channels through a combined analytical and numerical approach. First, I introduce novel flagged extension techniques that embed a channel into a higher-dimensional space, enabling single-letter upper bounds on quantum and private capacities. My results refine previous bounds and clarify noise thresholds beyond which quantum transmission vanishes. Second, I present a simulation framework that uses coherent information to estimate channel capacities in practice, focusing on two canonical examples: the amplitude damping channel (which we confirm is degradable and thus single-letter) and the depolarizing channel (whose capacity requires multi-letter superadditivity). By parameterizing input qubit states on the Bloch sphere, I numerically pinpoint the maximum coherent information for each channel and validate the flagged extension bounds. Notably, I capture the abrupt transition to zero capacity at high noise and observe superadditivity for moderate noise levels. - oai:arXiv.org:2506.03429v2 - quant-ph - cs.IT - math.IT - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by/4.0/ - Vahid Nourozi - - - Evolution of a twisted electron wave packet perturbed by an inhomogeneous electric field - https://arxiv.org/abs/2506.06548 - arXiv:2506.06548v3 Announce Type: replace -Abstract: Laguerre-Gaussian (LG) wave packets, known for their vortex structure and nonzero orbital angular momentum (OAM), are of great interest in various scientific fields. Here we study the nonrelativistic dynamics of a spatially-localized electron LG wave packet interacting with an inhomogeneous external electric field that violates the axial symmetry of the initial wave function. We focus on the analysis of the electron density and demonstrate how it is affected by the external field. Within the first order of perturbation theory, we calculate the electron wave function and reveal that the electric field may significantly alter the wave packet's structure and distort its qualitative form. We demonstrate that due to the interaction with the external field, the degenerate zeros of the initial wave function located on the $z$ axis split into multiple nondegenerate nodes in the transverse plane representing separate single-charge vortices. This mechanism resembles the analogous effects known in topological optics. These findings provide new insights into controlling and manipulating twisted matter beams and into their possible instabilities. - oai:arXiv.org:2506.06548v3 - quant-ph - physics.optics - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by/4.0/ - A. Kudlis, I. A. Aleksandrov, N. N. Rosanov - - - Generalized momentum operators from Fourier transform correspondence - https://arxiv.org/abs/2506.10950 - arXiv:2506.10950v2 Announce Type: replace -Abstract: In this work we take a closer look at the algebraic-operator correspondence between the momentum space and the position space which defines the form of the canonical momentum operator in position space in Quantum Mechanics (QM). Starting from the Fourier transform (FT) relationship, we present a Hermitian generalization of the canonical momentum operator in position space. The action of the generalized operator is found to generate a local flow accompanied by position-dependent rescaling, rather than a global translation. Explicit eigenfunctions are obtained for representative cases and are shown to possess a well-defined limit to the plane-wave solution in QM. As an illustration, the infinite square well problem is solved using the generalized operator, yielding a deformed spectrum that has a smooth limit to the standard QM result. - oai:arXiv.org:2506.10950v2 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by/4.0/ - Siddharth Dwivedi - - - Learning quantum tomography from incomplete measurements - https://arxiv.org/abs/2506.19428 - arXiv:2506.19428v4 Announce Type: replace -Abstract: We revisit quantum tomography in an informationally incomplete scenario and propose improved state reconstruction methods using deep neural networks. In the first approach, the trained network predicts an optimal linear or quadratic reconstructor with coefficients depending only on the collection of (already taken) measurement operators. This effectively refines the undercomplete tomographic reconstructor based on pseudoinverse operation. The second, based on an LSTM recurrent network performs state reconstruction sequentially. It can also optimize the measurement sequence, which suggests a no-free-lunch theorem for tomography: by narrowing the state space, we gain the possibility of more efficient tomography by learning the optimal sequence of measurements. Numerical experiments for a 2-qubit system show that both methods outperform standard maximum likelihood estimation and also scale to larger 3- and 4-qubit systems. Our results demonstrate that neural networks can effectively learn the underlying geometry of multi-qubit states using this for their reconstruction. - oai:arXiv.org:2506.19428v4 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by-sa/4.0/ - Mateusz Krawczyk, Pavel Bal\'a\v{z}, Katarzyna Roszak, Jaros{\l}aw Paw{\l}owski - - - Free Electron Paths from Dirac's Wave Equation Elucidating Zitterbewegung and Spin - https://arxiv.org/abs/2506.20857 - arXiv:2506.20857v3 Announce Type: replace -Abstract: The worldline of a free electron is revealed by applying Dirac's velocity operator to its Dirac wave function whose space-time arguments are expressed in a proper time by a Lorentz transformation. This motion can be decomposed into two parts: the electron's global motion of its inertia (or spin) center and an inherent local periodic motion about this point that produces the electron's spin and has the zitterbewegung frequency found by Schr\"{o}dinger in his operator analysis of Dirac's wave equation. This zitter motion corresponds to the so-called polarization and magnetization currents in Gordon's decomposition of Dirac's current. In an inertial "rest"-frame fixed at the inertia center, Dirac's wave function for a free electron with its spin in a specified direction implies that the zitter motion is a perpetual circular motion about the inertia center in a plane orthogonal to this spin direction with a radius one half of the Compton radius and moving at the speed of light. The electron continuously accelerates about the spin center without any external force because the inertia is effective at the spin center, rather than at its charge center where the electron interacts with the electro-magnetic field. This analysis confirms the nature of zitterbewegung directly from Dirac's wave equation, agreeing with the conclusions of Barut and Zanghi, Beck, Hestenes, Rivas and Salesi from their classical Dirac particle models of the electron. Furthermore, these five classical models are equivalent and express the same free electron dynamics as Dirac's equation. - oai:arXiv.org:2506.20857v3 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - James L Beck - - - Topologically noise robust network steering without inputs - https://arxiv.org/abs/2506.23637 - arXiv:2506.23637v2 Announce Type: replace -Abstract: Quantum networks with independent sources allow observing quantum nonlocality or steering with just a single measurement per node of the network, or without any inputs. Inspired by the recently introduced notion of swap-steering, we consider here the triangle network scenario without inputs, where one of the parties is trusted to perform a well-calibrated measurement. In this scenario, we first propose a linear witness to detect triangle network swap-steering. Then, by using the correlations that achieve the maximum value of this inequality, and assuming that all the sources are the same, we can self-test the state generated by the sources and the measurements of the untrusted party. We then extend this framework to ring networks with an arbitrary number of nodes with one of them being trusted. Interestingly, this is the first example of a topologically robust, that is, one can observe steerability without assuming the network structure of the network, as well as noise-robust quantum advantage in a network. Additionally, by allowing the trusted party to perform tomography of their subsystems, we demonstrate that every bipartite entangled state will result in swap-steerable correlations in the ring network. For this purpose, we construct linear witnesses to detect ring network swap-steering corresponding to every bipartite entangled state. - oai:arXiv.org:2506.23637v2 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by/4.0/ - 10.1103/r9py-kcgj - Dhruv Baheti, Shubhayan Sarkar - - - Small Quantum Low Density Parity Check Codes for Near-Term Experiments - https://arxiv.org/abs/2507.09690 - arXiv:2507.09690v3 Announce Type: replace -Abstract: It is widely accepted that quantum error correction is essential for realizing large-scale fault-tolerant quantum computing. Recent experiments have demonstrated error correction codes operating below threshold, primarily using local planar codes such as the surface code and color code. In parallel, theoretical advances in quantum low-density parity-check (LDPC) codes promise significantly lower overheads, albeit at the cost of requiring non-local parity checks. While these results are encouraging, implementing such codes remains challenging for near-term experiments, creating obstacles to holistic benchmarking of hardware architectures capable of supporting long-range couplers. In this work, we present a simple construction recipe for small quantum LDPC codes based on recent developments in the field. Our codes are approximately twice as efficient as comparable surface codes, yet require only weight-four parity checks, which simplifies experimental realization compared to other quantum LDPC codes. We provide concrete proposals for implementations with superconducting qubits in flip-chip architectures and with semiconductor spin qubits using shuttling-based approaches. - oai:arXiv.org:2507.09690v3 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Christian Kraglund Andersen, Eli\v{s}ka Greplov\'a - - - A Simple Method of Evaluating Laser Diode Suitability for Phase-Noise Based QRNG - https://arxiv.org/abs/2507.17471 - arXiv:2507.17471v2 Announce Type: replace -Abstract: Quantum random number generators (QRNGs) based on semiconductor laser phase noise are an inexpensive and efficient resource for true random numbers. Commercially available technology allows for designing QRNG setups tailored to specific use cases. However, it is important to constantly monitor whether the QRNG is performing according to the desired security standards in terms of independence and uniform distribution of the generated numbers. This is especially important in cryptographic applications. This paper presents a test scheme that helps to assess the acceptable operating conditions of a semiconductor laser for QRNG operation, using commonly accessible methods. This can be used for system monitoring, but crucially also to help the user choose the laser diode which better suits their needs. Two specific quality measurements, ensuring proper operation of the device, are explained and discussed. Setup-specific approaches for setting an acceptance boundary for these measures are presented and exemplary measurement data showing their effectiveness is given. By following the comprehensible procedure described here, a QRNG qualification environment tailored to specific security requirements can be reproduced. - oai:arXiv.org:2507.17471v2 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by/4.0/ - 10.1364/OE.584527 - Matthias Ostner, Innocenzo De Marco, Christian Roubal - - - Quantum Advantage in Identifying the Parity of Permutations with Certainty - https://arxiv.org/abs/2508.04310 - arXiv:2508.04310v2 Announce Type: replace -Abstract: We establish a sharp quantum advantage in determining the parity (even/odd) of an unknown permutation applied to any number $n \ge 3$ of particles. Classically, this is impossible with fewer than $n$ labels, being that the success is limited to random guessing. Quantum mechanics does it with certainty with as few as $\lceil \sqrt{n}\, \rceil$ distinguishable states per particle, thanks to entanglement. Below this threshold, not even quantum mechanics helps: both classical and quantum success are limited to random guessing. For small $n$, we provide explicit expressions for states that ensure perfect parity identification. We also assess the minimum entanglement these states need to carry, finding it to be close to maximal, and even maximal in some cases. The task requires no oracles or contrived setups and provides a simple, rigorous example of genuine quantum advantage. - oai:arXiv.org:2508.04310v2 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by/4.0/ - 10.1103/yhyv-xnwq - Phys. Rev. Lett. 135, 260603 (2025) - Arnau Diebra, Santiago Llorens, David Gonz\'alez-Lociga, Albert Rico, John Calsamiglia, Mark Hillery, Emili Bagan - - - Robust Control and Entanglement of Qudits in Neutral Atom Arrays - https://arxiv.org/abs/2508.16294 - arXiv:2508.16294v2 Announce Type: replace -Abstract: Quantum devices comprised of elementary components with more than two stable levels - so-called qudits - enrich the accessible Hilbert space, enabling applications ranging from fault-tolerant quantum computing to simulating complex many-body models. While several quantum platforms are built from local elements that are equipped with a rich spectrum of stable energy levels, schemes for the efficient control and entanglement of qudits are scarce. Importantly, no experimental demonstration of multi-qudit control has been achieved to date in neutral atom arrays. Here, we propose a general scheme for controlling and entangling qudits and perform a full analysis for the case of qutrits, encoded in ground and metastable states of alkaline earth atoms. We find an efficient implementation of single-qudit gates via the simultaneous driving of multiple transition frequencies. For entangling operations, we provide a concrete and intuitive recipe for the controlled-Z (CZ) gate for any local dimension d, realized through alternating single qudit and entangling pulses that simultaneously drive up to two Rydberg transitions. We further prove that two simultaneous Rydberg tones are, in general, the minimum necessary for implementing the CZ gate with a global drive. The pulses we use are optimally-controlled, smooth, and robust to realistic experimental imperfections, as we demonstrate using extensive noise simulations. This amounts to a minimal, resource-efficient, and practical protocol for realizing a universal set of gates. Our scheme for the native control of qudits in a neutral atom array provides a high-fidelity route toward qudit-based quantum computation, ready for implementation on near-term devices. - oai:arXiv.org:2508.16294v2 - quant-ph - physics.atom-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - 10.1103/4xcd-wyxx - Phys. Rev. Research 8, 013055 (2026) - Amir Burshtein, Shachar Fraenkel, Moshe Goldstein, Ran Finkelstein - - - Optimal Hamiltonian for a quantum state with finite entropy - https://arxiv.org/abs/2508.16575 - arXiv:2508.16575v3 Announce Type: replace -Abstract: We consider the following task: how for a given quantum state $\rho$ to find a grounded Hamiltonian $H$ satisfying the condition $\mathrm{Tr} H\rho\leq E_0<+\infty$ in such a way that the von Neumann entropy of the Gibbs state $\gamma_H(E)$ corresponding to a given energy $E>0$ be as small as possible. - We show that for any mixed state $\rho$ with finite entropy and any $E>0$ there exists a solution $H(\rho,E_0,E)$ of the above problem (unique in the non-degenerate case) which we call optimal Hamiltonian for the state $\rho$. Explicit expressions for $H(\rho,E_0,E)$, $\gamma_{H(\rho,E_0,E)}(E)$ and $S(\gamma_{H(\rho,E_0,E)}(E))$ are obtained. Analytical properties of the function $E\mapsto S(\gamma_{H(\rho,E_0,E)}(E))$ are explored. Several examples are considered. - We also consider a modification of the above task in which arbitrary Hamiltonians (not necessarily grounded) are considered. - The basic application motivated this research is described. As examples, new semicontinuity bounds for the von Neumann entropy and for the entanglement of formation are obtained and briefly discussed (with the intention to give a detailed analysis in a separate article). - oai:arXiv.org:2508.16575v3 - quant-ph - cs.IT - math-ph - math.IT - math.MP - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - M. E. Shirokov - - - Coherent Two-State Oscillations in False Vacuum Decay Regimes - https://arxiv.org/abs/2509.04272 - arXiv:2509.04272v2 Announce Type: replace -Abstract: Coherent two-state oscillations are observed in numerical simulations of the one-dimensional transverse-longitudinal-field Ising model (TLFIM) within false vacuum decay regimes. Starting from the false vacuum (a nearly fully polarized ferromagnetic state), we show that in moderate-sized systems, at resonances $h\approx 2J/n$ (with longitudinal field $h$, transverse field $J$, and an integer $n$), the expected decay can give way to coherent oscillations between the false vacuum and a symmetric resonant state. The oscillation frequency, i.e., the tunneling splitting, is observed notably to exhibit a superradiant-like $\sqrt{L}$ enhancement, as confirmed by a Schrieffer-Wolff analysis. In large chains, coherence remains for $n\gtrsim L/2$ due to bubble-size blockade and is robust against stronger transverse fields; for small $n$, long-range interactions can stabilize the oscillations by lifting multi-bubble degeneracies, establishing a robust many-body coherence mechanism beyond perturbative and finite-size limits. - oai:arXiv.org:2509.04272v2 - quant-ph - physics.atom-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Peiyun Ge, Xiao Wang, Yu-Xin Chao, Rong Lu, Li You - - - Quantum spatial best-arm identification via quantum walks - https://arxiv.org/abs/2509.05890 - arXiv:2509.05890v2 Announce Type: replace -Abstract: Quantum reinforcement learning has emerged as a framework combining quantum computation with sequential decision-making, and applications to the multi-armed bandit (MAB) problem have been reported. The graph bandit problem extends the MAB setting by introducing spatial constraints, yet quantum approaches remain limited. We propose a quantum algorithmic framework for best-arm identification in graph bandits, termed Quantum Spatial Best-Arm Identification (QSBAI), which is applicable to general graph structures. The method employs quantum walks to encode superpositions over graph-constrained actions, extending amplitude amplification and generalizing the Quantum BAI algorithm via Szegedy's walk framework. This establishes a link between Grover-type search and reinforcement learning tasks with structural restrictions. We focus our theoretical analysis on complete and bipartite graphs, deriving the maximal success probability of identifying the best arm and the time step at which it is achieved. Our results highlight the potential of quantum walks to accelerate exploration in constrained environments and extend the applicability of quantum algorithms for decision-making. - oai:arXiv.org:2509.05890v2 - quant-ph - cs.AI - cs.LG - math-ph - math.MP - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by/4.0/ - Tomoki Yamagami, Etsuo Segawa, Takatomo Mihana, Andr\'e R\"ohm, Atsushi Uchida, Ryoichi Horisaki - - - Tuning of SiV quantum emission in nitrogen-doped nanodiamonds by dual-color excitation - https://arxiv.org/abs/2509.06500 - arXiv:2509.06500v2 Announce Type: replace -Abstract: The charge dynamics of silicon-vacancy (SiV) centers have been investigated for the first time in high-pressure high-temperature nanodiamonds (NDs) with varying concentrations of substitutional nitrogen (Ns). We demonstrate a controlled sixfold enhancement of SiV- photoluminescence (PL) under dual-color excitation, consisting of strong red (~660 nm) illumination combined with weak green (~530 nm) excitation. The measured dependencies of SiV- PL lifetime and intensity on excitation wavelength, together with the enhancement dependence on Ns concentration in the studied nanodiamonds, provide unambiguous evidence of the involvement of donor nitrogen in SiV-emission dynamics. Saturation curves and second-order PL intensity correlation measurements further indicate suppression of the population of the optically inactive SiV2- state upon the addition of green excitation. These results unlock a practical pathway toward engineering optically-controlled and scalable quantum emitters based on SiV-luminescent diamond nanoparticles. - oai:arXiv.org:2509.06500v2 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - A. A. Zhivopistsev, A. M. Romshin, A. V. Gritsienko, D. G. Pasternak, R. K. Bagramov, V. P. Filonenko, F. M. Maksimov, A. I. Chernov, A. M. Skomorokhov, N. I. Kargin, I. I. Vlasov - - - Universal quantum control over bosonic network - https://arxiv.org/abs/2509.06560 - arXiv:2509.06560v2 Announce Type: replace -Abstract: Perfect transfer of {\em unknown} states across distinct nodes is a basic function in bosonic quantum networks. Here we develop a general theory to construct an $N$-node bosonic network governed by the time-dependent Hamiltonian, as the universal quantum control theory for continuous-variable systems. In particular, we can activate nonadiabatic passages superposed of initial and target modes by the commutation condition about the Hamiltonian's coefficient matrix and projection operator in the representation of time-independent ancillary modes, which serves as the necessary and sufficient condition to solve the time-dependent Schr\"odinger equation of the full Hamiltonian. To exemplify the versatility of our theory on the Heisenberg-picture passages, we perform arbitrary state exchange between two nodes, chiral entanglement transfer among three bosonic nodes, and chiral Fock-state transfer among three of four bosonic nodes. Our work provides a promising avenue toward the universal control of any pair of nodes or modes as well as the entire bosonic network. - oai:arXiv.org:2509.06560v2 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by/4.0/ - 10.1103/ghqr-ydxs - Phys. Rev. A 113, 012426 (2026) - Zhu-yao Jin, Jun Jing - - - Robustness of quantum algorithms: Worst-case fidelity bounds and implications for design - https://arxiv.org/abs/2509.08481 - arXiv:2509.08481v2 Announce Type: replace -Abstract: Errors occurring on noisy hardware pose a key challenge to reliable quantum computing. Existing techniques such as error correction, mitigation, or suppression typically separate the error handling from the algorithm analysis and design. In this paper, we develop an alternative, algorithm-centered framework for understanding and improving the robustness against errors. For a given quantum algorithm and error model, we derive worst-case fidelity bounds which can be efficiently computed to certify the robustness. We consider general error models including coherent and (Markovian) incoherent errors and allowing for set-based error descriptions to address uncertainty or time-dependence in the errors. Our results give rise to guidelines for robust algorithm design and compilation by optimizing our theoretical robustness measure. We demonstrate the practicality of the framework with numerical results on algorithm analysis and robust optimization, including the robustness analysis of a 50-qubit modular adder circuit. - oai:arXiv.org:2509.08481v2 - quant-ph - cs.SY - eess.SY - math.OC - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Julian Berberich, Tobias Fellner, Robert L. Kosut, Christian Holm - - - Cost-aware Photonic Graph State Generation: A Graphical Framework - https://arxiv.org/abs/2509.22777 - arXiv:2509.22777v2 Announce Type: replace -Abstract: Photonic graph states are essential resources for quantum computation and communication. Deterministic emitter-based generation of graph states overcomes the scalability issues of probabilistic approaches; nonetheless, their experimental realization is constrained by technological demands, often expressed by the number of two-qubit gates and the depth and/or width of the quantum circuits used to model the generation process. Here, we introduce a cost-aware framework for the generation of photonic graph states of arbitrary size and shape, built on a complete set of necessary and sufficient conditions and a universal set of elementary graph operations that govern the evolution of the state toward the target. Within this framework, we develop Graph Builder, a deterministic generation algorithm that achieves substantial reductions (up to an order of magnitude) in two-qubit gate usage for both random and structured graphs, compared with alternative approaches. Furthermore, we show that this framework enables the identification of elementary building blocks in specific cases, such as encoded 6-ring states. The algorithm uses the minimum number of emitters possible for a fixed emission sequence, while also supporting the use of extra emitters for controlled trade-offs between emitter count and other cost metrics. Moreover, by systematically identifying the degrees of freedom at each stage of the generation process, this framework fully characterizes the optimization landscape, enabling analytic, heuristic, or exhaustive strategies for further cost reductions. Our approach provides a general and versatile tool for designing and optimizing emitter-based photonic graph state generation protocols, essential for scalable and resource-efficient photonic quantum information processing. - oai:arXiv.org:2509.22777v2 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Sobhan Ghanbari, Hoi-Kwong Lo - - - Approximate Quantum State Preparation with Tree-Based Bayesian Optimization Surrogates - https://arxiv.org/abs/2510.00145 - arXiv:2510.00145v3 Announce Type: replace -Abstract: We study the problem of approximate state preparation on near-term quantum computers, where the goal is to construct a parameterized circuit that reproduces the output distribution of a target quantum state while minimizing resource overhead. This task is especially relevant for near-term algorithms where distributional matching suffices, but it is challenging due to stochastic outputs, limited circuit depth, and a high-dimensional, non-smooth parameter space. We propose CircuitTree, a surrogate-guided optimization framework based on Bayesian Optimization with tree-based models, which avoids the scalability and smoothness assumptions of Gaussian Process surrogates. Our framework introduces a structured layerwise decomposition strategy that partitions parameters into blocks aligned with variational circuit architecture, enabling distributed and sample-efficient optimization with theoretical convergence guarantees. Empirical evaluations on synthetic benchmarks and variational tasks validate our theoretical insights, showing that CircuitTree achieves low total variation distance and high fidelity while requiring significantly shallower circuits than existing approaches. - oai:arXiv.org:2510.00145v3 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by/4.0/ - Nicholas S. DiBrita, Jason Han, Younghyun Cho, Hengrui Luo, Tirthak Patel - - - Angular--Momentum--Resolved Aharonov--Bohm Coupling Energy - https://arxiv.org/abs/2510.06016 - arXiv:2510.06016v2 Announce Type: replace -Abstract: We present an angular--momentum--resolved energetic formulation of the Aharonov--Bohm (AB) response for a confined Dirac electron based on two gauge--invariant interaction functionals: a magnetization--field functional and a current--potential functional. Using exact Dirac eigenmodes in a cylindrical cavity threaded by a solenoidal flux, we show that the magnetization--field functional yields a core--localized interaction energy restricted to the $l=0$ channel, with all higher angular--momentum contributions suppressed and vanishing entirely in the limit $a\!\to\!0$. The current--potential functional, by contrast, produces a finite, mode--dependent energy shift for $l\!\ge\!1$ in the same limit, arising from a local interaction between the solenoidal vector potential and the spatially distributed Dirac current, and explicitly encoding the geometric and topological structure of the coupling energy. - oai:arXiv.org:2510.06016v2 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by/4.0/ - Ju Gao, Fang Shen - - - Exact WKB method for radial Schr\"odinger equation - https://arxiv.org/abs/2510.11766 - arXiv:2510.11766v3 Announce Type: replace -Abstract: We revisit exact WKB quantization for radial Schr\"odinger problems from the modern resurgence perspective, with emphasis on how ``physically meaningful'' quantization paths should be chosen and interpreted. Using connection formulae at simple turning points and at regular singular points, we show that the nontrivial-cycle data give the spectrum. In particular, for the $3$-dimensional harmonic oscillator and the $3$-dimensional Coulomb potential, we explicitly compute a closed contour which starts at $+\infty$, bulges into the $r<0$ sector to encircle the origin, and returns to $+\infty$. Also we propose that the appropriate slice of the closed path provides a physical local basis at $r=0$, which is used by an origin-to-$\infty$ open path. Via the change of variables $r=e^x$ ($x\in(-\infty,\infty)$), the origin data are pushed to the boundary condition of convergence at $x\to-\infty$, which renders the equivalence between open-connection and closed-cycle quantization transparent. The Maslov contribution from the regular singularity is incorporated either as a small-circle monodromy which is justified in terms of renormalization group, or, equivalently, as a boundary phase; we also develop an optimized/variational perturbation theory on exact WKB. Our analysis clarifies, in radial settings, how mathematical monodromy data and physical boundary conditions dovetail, thereby addressing recent debates on path choices in resurgence-based quantization. - oai:arXiv.org:2510.11766v3 - quant-ph - nucl-th - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Okuto Morikawa, Shoya Ogawa - - - Quantum State Designs via Magic Teleportation - https://arxiv.org/abs/2510.13950 - arXiv:2510.13950v2 Announce Type: replace -Abstract: We investigate how non-stabilizer resources enable the emergence of quantum state designs within the projected ensemble. Starting from initial states with finite magic and applying resource-free Clifford circuits to scramble them, we analyze the ensemble generated by performing projective Pauli measurements on a subsystem of the final state. Using both analytical arguments and large-scale numerics, we show that the projected ensemble converges towards a state $k$-design with an error that decays exponentially with the $k$-th Stabilizer R\'enyi Entropy of the pre-measurement state, via a Magic-Induced Design Ansatz (MIDA) that we introduce. We identify a universal scaling form, valid across different classes of magic initial states, and corroborate it through numerical simulations and analytical calculations of the frame potential. For finite-depth Clifford unitaries, we show that the timescales at which state designs emerge are controlled by the transport of magic. We identify a ``magic teleportation'' mechanism whereby non-Clifford resources injected locally spread through Clifford scrambling and measurements across distances beyond the lightcone. Our results demonstrate how a small and controlled amount of magic suffices to generate highly random states, providing a systematic route toward generating quantum state designs in early fault-tolerant devices. - oai:arXiv.org:2510.13950v2 - quant-ph - cond-mat.stat-mech - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by/4.0/ - Hugo L\'oio, Guglielmo Lami, Lorenzo Leone, Max McGinley, Xhek Turkeshi, Jacopo De Nardis - - - Macroscopic quantum phenomena and quantum computing - https://arxiv.org/abs/2510.19846 - arXiv:2510.19846v2 Announce Type: replace -Abstract: This News & Views article provides a perspective on the 2025 Nobel Prize in Physics, including the groundbreaking discovery of macroscopic quantum tunneling and energy quantization in superconducting circuits, the history and causes giving rise to this breakthrough, and its impact on subsequent progress in quantum computing. - oai:arXiv.org:2510.19846v2 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by/4.0/ - 10.1016/j.scib.2025.11.018 - Science Bulletin 71, 1 (2026) - J. Q. You - - - Measurement-only circuit of perturbed toric code on triangular lattice: Topological entanglement, 1-form symmetry and logical qubits - https://arxiv.org/abs/2510.23162 - arXiv:2510.23162v3 Announce Type: replace -Abstract: Measurement-only (quantum) circuit (MoC) gives possibility to realize the states with rich entanglements, topological orders and quantum memories. This work studies the MoC, in which the projective-measurement operators consist of stabilizers of the toric code and competitive local Pauli operators. The former correspond to terms of the toric code on a triangular lattice and the later to external magnetic and electric fields. We employ efficient numerical stabilizer algorithm to trace evolving states undergoing phase transitions. We elucidate the phase diagram of the MoC system with the observables such as, topological entanglement entropy (TEE), disorder parameters of 1-form symmetries and emergent logical operators. We clarify the locations of the phase transitions through the observation of the above quantities and obtain precise critical exponents to examine if the observables exhibit the critical behavior simultaneously under the MoC and transitions belong to the same universality class. In contrast to the TC Hamiltonian system and toric code MoC on a square lattice, the system on the triangular lattice is not self-dual nor bipartite, and then, coincidence by symmetries, such as critical behaviors across the TC and Higgs/confined phase, does not takes place. Then, the toric code MoC on the triangular lattice provides us a suitable playground to clarify the mutual relationship between the TEE, spontaneous symmetry breaking of the 1-form symmetries, and emergence of logical operators. Obtained results indicate that toric code MoC on the triangular lattice exhibits a few distinct phase transitions with different location and critical exponents, and some of them are closely related with the two-dimensional percolation transition. - oai:arXiv.org:2510.23162v3 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by/4.0/ - 10.1103/l9d5-yndm - Phys. Rev. B 113, 024111 (2026) - Keisuke Kataoka, Yoshihito Kuno, Takahiro Orito, Ikuo Ichinose - - - Overcoming disorder in superconducting globally driven quantum computing - https://arxiv.org/abs/2510.25996 - arXiv:2510.25996v2 Announce Type: replace -Abstract: We study the impact of static disorder on a globally-controlled superconducting quantum computing architecture based on a quasi-two-dimensional ladder geometry [R. Menta et al., Phys. Rev. Research 7, L012065 (2025)]. Specifically, we examine how fabrication-induced inhomogeneities in qubit resonant frequencies and coupling strengths affect quantum state propagation and the fidelity of fundamental quantum operations. Using numerical simulations, we quantify the degradation in performance due to disorder and identify single-qubit rotations, two-qubit entangling gates, and quantum information transport as particularly susceptible. To address this challenge, we rely on pulse optimization schemes, and, in particular, on the GRAPE (Gradient Ascent Pulse Engineering) algorithm. Our results demonstrate that, even for realistic levels of disorder, optimized pulse sequences can achieve high-fidelity operations, exceeding 99.9% for the three quantum operations, restoring reliable universal quantum logic and robust information flow. These findings highlight pulse optimization as a powerful strategy to enhance the resilience to disorder of solid-state globally-driven quantum computing platforms. - oai:arXiv.org:2510.25996v2 - quant-ph - cond-mat.supr-con - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - 10.1103/zzzc-nqxd - Phys. Rev. A 113, 012616 (2026) - Riccardo Aiudi, Julien Despres, Roberto Menta, Ashkan Abedi, Guido Menichetti, Vittorio Giovannetti, Marco Polini, Francesco Caravelli - - - Optimizing quantum violation for multipartite facet Bell inequalities - https://arxiv.org/abs/2511.07523 - arXiv:2511.07523v2 Announce Type: replace -Abstract: Nonlocality shapes quantum correlations, revealed through the violation of Bell inequalities. The intersection of all valid Bell inequalities is the so-called local polytope. In multipartite systems, characterizing the local polytope quickly becomes an intractable task as the system size increases. Optimizing Bell inequalities to maximize the ratio between their quantum value and classical bound is key to understanding multipartite nonlocality. We propose a gradient-based method for this optimization. Numerical results indicate that local maxima of this ratio typically correspond to facet Bell inequalities of the local polytope. This enables an iterative search for tight and robust Bell inequalities. Applied to permutation-invariant scenarios, the method provides tight Bell inequalities with large quantum violations and facilitates experimental certification of Bell correlations without full knowledge of the local polytope. Moreover, analytical results of the maximum ratio are derived in the thermodynamic limit. - oai:arXiv.org:2511.07523v2 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Jin-Fu Chen, Mengyao Hu, Jordi Tura - - - Separating QMA from QCMA with a classical oracle - https://arxiv.org/abs/2511.09551 - arXiv:2511.09551v2 Announce Type: replace -Abstract: We construct a classical oracle proving that, in a relativized setting, the set of languages decidable by an efficient quantum verifier with a quantum witness (QMA) is strictly bigger than those decidable with access only to a classical witness (QCMA). The separating classical oracle we construct is for a decision problem we coin spectral Forrelation -- the oracle describes two subsets of the boolean hypercube, and the computational task is to decide if there exists a quantum state whose standard basis measurement distribution is well supported on one subset while its Fourier basis measurement distribution is well supported on the other subset. This is equivalent to estimating the spectral norm of a "Forrelation" matrix between two sets that are accessible through membership queries. - Our lower bound derives from a simple observation that a query algorithm with a classical witness can be run multiple times to generate many samples from a distribution, while a quantum witness is a "use once" object. This observation allows us to reduce proving a QCMA lower bound to proving a sampling hardness result which does not simultaneously prove a QMA lower bound. To prove said sampling hardness result for QCMA, we observe that quantum access to the oracle can be compressed by expressing the problem in terms of bosons -- a novel "second quantization" perspective on compressed oracle techniques, which may be of independent interest. Using this compressed perspective on the sampling problem, we prove the sampling hardness result, completing the proof. - oai:arXiv.org:2511.09551v2 - quant-ph - cs.CC - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - John Bostanci, Jonas Haferkamp, Chinmay Nirkhe, Mark Zhandry - - - High-Fidelity Universal Quantum Gate Compilation for Non-semisimple Ising Anyons via Genetic Algorithm-Optimized Solovay-Kitaev Decomposition - https://arxiv.org/abs/2511.13194 - arXiv:2511.13194v2 Announce Type: replace -Abstract: We present a systematic numerical construction of a universal quantum gate set for topological quantum computation based on the non-semisimple Ising anyons model. By employing a Genetic Algorithm-enhanced Solovay-Kitaev Algorithm (GA-enhanced SKA), we achieve high-fidelity approximations of standard single-qubit gates (Hadamard H-gate and phase T-gate) with a recursion level of just three, meeting the fidelity requirements for fault-tolerant quantum computation. Our numerical results demonstrate that for the critical parameter range {\alpha} \in [2.001, 2.022], a few braiding operations can approximate the local equivalence class [CNOT] with high precision. Specifically, at {\alpha} =2.012, 2.015, 2.020, and 2.022, we successfully construct a universal gate set {H, T, CNOT} with leakage errors of two-qubit gate below 0.07,0.08,0.09 and 0.10, respectively. This work establishes a new pathway towards universal quantum computation using non-semisimple Ising anyons, overcoming the limitations of traditional Ising models through optimized braiding sequences and Genetic Algorithm-driven compilation. - oai:arXiv.org:2511.13194v2 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Jiangwei Long, Zihui Liu, Yizhi Li, Jianxin Zhong, Lijun Meng - - - TRAM: A Transverse Relaxation Time-Aware Qubit Mapping Algorithm for NISQ Devices - https://arxiv.org/abs/2511.16051 - arXiv:2511.16051v2 Announce Type: replace -Abstract: Noisy intermediate-scale quantum (NISQ) devices impose dual challenges on quantum circuit execution: limited qubit connectivity requires extensive SWAP-gate routing, while time-dependent decoherence progressively degrades quantum information. Existing qubit mapping algorithms optimize for hardware topology and static calibration metrics but systematically neglect transverse relaxation dynamics (T2), creating a fundamental gap between compiler decisions and evolving noise characteristics. We present TRAM (Transverse Relaxation Time-Aware Qubit Mapping), a coherence-guided compilation framework that elevates decoherence mitigation to a primary optimization objective. TRAM integrates calibration-informed community detection to construct noise-resilient qubit partitions, generates time-weighted initial mappings that anticipate coherence decay, and dynamically schedules SWAP operations to minimize cumulative error accumulation. Evaluated on Qiskit-based simulators with realistic noise models, TRAM outperforms SABRE by 3.59% in fidelity, reduces gate count by 11.49%, and shortens circuit depth by 12.28%, establishing coherence-aware optimization as essential for practical quantum compilation in the NISQ era. - oai:arXiv.org:2511.16051v2 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Yifei Huang, Pascal Jahan Elahi, Ugo Varetto, Kan He, Jinchuan Hou, Shusen Liu - - - COMPAS: A Distributed Multi-Party SWAP Test for Parallel Quantum Algorithms - https://arxiv.org/abs/2511.23434 - arXiv:2511.23434v2 Announce Type: replace -Abstract: The limited number of qubits per chip remains a critical bottleneck in quantum computing, motivating the use of distributed architectures that interconnect multiple quantum processing units (QPUs). However, executing quantum algorithms across distributed systems requires careful co-design of algorithmic primitives and hardware architectures to manage circuit depth and entanglement overhead. We identify multivariate trace estimation as a key subroutine that is naturally suited for distribution, and broadly useful in tasks such as estimating R\'enyi entropies, virtual cooling and distillation, and certain applications of quantum signal processing. In this work, we introduce COMPAS, an architecture that realizes multivariate trace estimation across a multi-party network of interconnected modular and distributed QPUs by leveraging pre-shared entangled Bell pairs as resources. COMPAS adds only a constant depth overhead and consumes Bell pairs at a rate linear in circuit width, making it suitable for near-term hardware. Unlike other schemes, which must choose between asymptotic optimality in circuit depth or GHZ width, COMPAS achieves both at once. Additionally, we analyze network-level errors and simulate the effects of circuit-level noise on the architecture. - oai:arXiv.org:2511.23434v2 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by/4.0/ - 10.1145/3779212.3790143 - Brayden Goldstein-Gelb (Harry), Kun Liu (Harry), John M. Martyn (Harry), Hengyun (Harry), Zhou, Yongshan Ding, Yuan Liu - - - Folded optimal transport and its application to separable quantum optimal transport - https://arxiv.org/abs/2512.01722 - arXiv:2512.01722v3 Announce Type: replace -Abstract: We introduce folded optimal transport, as a method to extend a cost or distance defined on the extreme boundary of a convex to the whole convex, related to convex extension. This construction broadens the framework of standard optimal transport, found to be the particular case of the convex being a simplex. Relying on Choquet's theory and standard optimal transport, we introduce the folded Kantorovich cost and folded Wasserstein distances, and study their induced metric properties. We then apply the construction to the quantum setting, and obtain an actual separable quantum Wasserstein distance on the set of density matrices from a distance on the set of pure states, closely related to the semi-distance of Beatty and Stilck-Franca [4], and of which we obtain a variety of properties. We also find that the semiclassical Golse-Paul [16] cost writes as a folded Kantorovich cost. Folded optimal transport therefore provides a unified framework for classical, semiclassical and separable quantum optimal transport. - oai:arXiv.org:2512.01722v3 - quant-ph - math-ph - math.FA - math.MP - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by/4.0/ - Thomas Borsoni - - - Interplay between Standard Quantum Detailed Balance and Thermodynamically Consistent Entropy Production - https://arxiv.org/abs/2512.06707 - arXiv:2512.06707v2 Announce Type: replace -Abstract: We demonstrate that, for a quantum Markovian semigroup on a finite-dimensional Hilbert space, if it satisfies the standard quantum detailed balance condition, its generator admits a special representation that yields a vanishing entropy production rate. Conversely, if the generator admits a special representation adhering to the condition of thermodynamic consistency and leading to a vanishing entropy production rate, then the corresponding quantum Markovian semigroup must satisfy the standard quantum detailed balance condition. In this context, we adopt the definition of entropy production rate that is motivated by the physics literature and standard for thermodynamically consistent Lindbladians. - oai:arXiv.org:2512.06707v2 - quant-ph - cond-mat.stat-mech - math-ph - math.MP - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Xin-Hai Tong, Kohei Yoshimura, Tan Van Vu, Naruo Ohga - - - Physics-Informed Generative Machine Learning for Accelerated Quantum-centric Supercomputing - https://arxiv.org/abs/2512.06858 - arXiv:2512.06858v3 Announce Type: replace -Abstract: Quantum centric supercomputing (QCSC) framework, such as sample-based quantum diagonalization (SQD) holds immense promise toward achieving practical quantum utility to solve challenging problems. QCSC leverages quantum computers to perform the classically intractable task of sampling the dominant fermionic configurations from the Hilbert space that have substantial support to a target state, followed by Hamiltonian diagonalization on a classical processor. However, noisy quantum hardware produces erroneous samples upon measurements, making robust and efficient configuration-recovery strategies essential for a scalable QCSC pipeline. Toward this, in this work, we introduce PIGen-SQD, an efficiently designed QCSC workflow that utilizes the capability of generative machine learning (ML) along with physics-informed configuration screening via implicit low-rank tensor decompositions for accurate fermionic state reconstruction. The physics-informed pruning is based on a class of efficient perturbative measures that, in conjunction with hardware samples, provide a substantial overlap with the target state. This distribution induces an anchoring effect on the generative ML models to stochastically explore only the dominant sector of the Hilbert space for effective identification of additional important configurations in a self-consistent manner. Our numerical experiments performed on IBM Heron R2 quantum processors demonstrate this synergistic workflow produces compact, high-fidelity subspaces that substantially reduce diagonalization cost while maintaining chemical accuracy under strong electronic correlations. By embedding classical many body intuitions directly into the generative ML model, PIGen-SQD advances the robustness and scalability of QCSC algorithms, offering a promising pathway toward chemically reliable quantum simulations on utility-scale quantum hardware. - oai:arXiv.org:2512.06858v3 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by/4.0/ - Chayan Patra, Dibyendu Mondal, Sonaldeep Halder, Dipanjali Halder, Mostafizur Rahaman Laskar, Richa Goel, Rahul Maitra - - - Information-efficient decoding of surface codes - https://arxiv.org/abs/2512.14255 - arXiv:2512.14255v2 Announce Type: replace -Abstract: Surface codes are a popular error-correction route to fault-tolerant quantum computation. The so-called exponential backlog problem that can arise when one has to do logical $T$-gates within the surface code demands real-time decoding of the syndrome information to diagnose the appropriate Pauli frame in which to do the gate. This in turn puts a minimum requirement on the communication rate between the quantum processing unit, where the syndrome information is collected, and the classical processor, where the decoding algorithm is run. This minimum communication rate can be difficult to achieve while preserving the quality of the quantum processor. Here, we present two decoders that make use of a reduced syndrome information volume, relying on a number of syndrome bits that scale only as the width -- and not the usual area -- of the surface-code patch. This eases the communication requirements necessary for real-time decoding. - oai:arXiv.org:2512.14255v2 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by/4.0/ - Long D. H. My, Shao-Hen Chiew, Jing Hao Chai, Hui Khoon Ng - - - Improved Lower Bounds for QAC0 - https://arxiv.org/abs/2512.14643 - arXiv:2512.14643v2 Announce Type: replace -Abstract: In this work, we prove the strongest known lower bounds for QAC$^0$, allowing polynomially many gates and ancillae. Our main results show that: - (1) Depth-3 QAC$^0$ circuits cannot compute PARITY, and require $\Omega(\exp(\sqrt{n}))$ gates to compute MAJORITY. - (2) Depth-2 circuits cannot approximate high-influence Boolean functions (e.g., PARITY) with non-negligible advantage, regardless of size. - We develop new classical simulation techniques for QAC$^0$ to obtain our depth-3 bounds. In these results, we relax the output requirement of the quantum circuit to a single bit, making our depth $2$ approximation bound stronger than the previous best bound of Rosenthal (2021). This also enables us to draw natural comparisons with classical AC$^0$ circuits, which can compute PARITY exactly in depth $2$ (exp size). Our techniques further suggest that, for boolean total functions, constant-depth quantum circuits do not necessarily provide more power than their classical counterparts. Our third result shows that depth $2$ QAC$^0$ circuits, regardless of size, cannot exactly synthesize an $n$-target nekomata state (a state whose synthesis is directly related to the computation of PARITY). This complements the depth $2$ exponential size upper bound of Rosenthal (2021) for approximating nekomatas (which is used as a sub-circuit in the only known constant depth PARITY upper bound). Finally, we argue that approximating PARITY in QAC0, with significantly better than 1/poly(n) advantage on average, is just as hard as computing it exactly. Thus, extending our techniques to higher depths would also rule out approximate circuits for PARITY and related problems - oai:arXiv.org:2512.14643v2 - quant-ph - cs.CC - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Malvika Raj Joshi, Avishay Tal, Francisca Vasconcelos, John Wright - - - Quadratic Stability of Entropy Minimizers under Block-Separable Convex Constraints - https://arxiv.org/abs/2512.16192 - arXiv:2512.16192v2 Announce Type: replace -Abstract: We investigate entropy minimization problems for quantum states subject to convex block-separable constraints. Our principal result is a quantitative stability theorem: under a natural confining (fixed-support) hypothesis, if a state has entropy within {\epsilon} of the minimum permitted by the constraint, then it must lie within O({\epsilon}^{1/2}) in trace norm of the set of entropy minimizers. We show that this rate is optimal and cannot be improved uniformly. - The analysis is entirely finite-dimensional and exploits the block-separable structure of the constraint set, which induces a natural decomposition of entropy into a marginal (classical) component and conditional (internal) components. Quadratic stability emerges from the curvature of Shannon entropy on the marginal polytope and of von Neumann entropy on the constrained block states, yielding explicit stability constants determined by the geometry of the constraint. - We further demonstrate that this stability phenomenon cannot be derived from Pinsker-type inequalities or standard entropy continuity bounds, since no reference state is fixed a priori and the entropy minimizer arises intrinsically from the constraint geometry. The framework is abstract and independent of any arithmetic input, and provides a general quadratic stability principle for entropy minimization under structured convex constraints. - oai:arXiv.org:2512.16192v2 - quant-ph - math.FA - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Hassan Nasreddine - - - Shuttling Compiler for Trapped-Ion Quantum Computers Based on Large Language Models - https://arxiv.org/abs/2512.18021 - arXiv:2512.18021v2 Announce Type: replace -Abstract: Trapped-ion quantum computers based on segmented traps rely on shuttling operations to establish long-range connectivity between sub-registers. Qubit routing dynamically reconfigures qubit positions so that all qubits involved in a gate operation are co-located within the same segment, a task whose complexity increases with system size. To address this challenge, we propose a layout-independent compilation strategy based on large language models (LLMs). Specifically, we fine-tune pretrained LLMs to generate the required shuttling operations. We evaluate this approach on linear and branched one-dimensional architectures using quantum circuits of up to $16$ qubits. Our results show that the fine-tuned LLMs generate valid shuttling schedules and, in some cases, outperform previous shuttling compilers by requiring approximately $15\,\%$ less shuttle overhead. However, results degrade as the algorithms increase in width and depth. In future, we plan to improve LLM-based shuttle compilation by enhancing our training pipeline using Direct Preference Optimization (DPO) and Gradient Regularized Policy Optimization (GRPO). - oai:arXiv.org:2512.18021v2 - quant-ph - cs.ET - cs.LG - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by/4.0/ - Fabian Kreppel, Reza Salkhordeh, Ferdinand Schmidt-Kaler, Andr\'e Brinkmann - - - EMU circulation planning for Silesian Railways: case study and a quantum approach - https://arxiv.org/abs/2512.19340 - arXiv:2512.19340v2 Announce Type: replace -Abstract: We study daily rolling stock circulation planning for electric multiple units (EMUs) on a regional passenger network, focusing on services where identical EMUs may be coupled in pairs on selected routes. Motivated by the operational needs of the regional operator Silesian Railways in Poland, we formulate an acyclic mixed-integer linear program on a one-day horizon that incorporates depot balance constraints, demand-driven seat and bicycle capacity limits (which is a new aspect requested by the regional operator and the local passenger community), and simple crew availability constraints. Using a graph-hypergraph representation of trips and single or coupled EMU movements, we first solve the problem with a classical ILP solver. We then derive a Quadratic Unconstrained Binary Optimization (QUBO) reformulation, which is frequently used as input for quantum optimization, and evaluate its solutions using quantum annealing on D-Wave Advantage systems and the classical quantum-inspired VeloxQ solver. Computational experiments on real-world instances from the Silesian network, with up to 404 train trips and 11 EMU types, show that the ILP approach can obtain high-quality daily circulation plans within at most about 40 minutes. In contrast, current quantum and quantum-inspired solvers are restricted to substantially smaller subinstances (up to 51 and 78 train trips, respectively) due to the large number of terms in the QUBO and, in the case of quantum hardware, embedding limitations. These results quantify the current frontier of QUBO-based methods for rolling stock circulation and point toward hybrid decision-support architectures in which quantum or quantum-inspired optimizers address only local subproblems within a broader classical planning framework. - oai:arXiv.org:2512.19340v2 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by/4.0/ - Ewa K\k{e}dziera, Wojciech Gamon, M\'aty\'as Koniorczyk, Zakaria Mzaouali, Andrea Galad\'ikov\'a, Krzysztof Domino - - - Real Matrix Representations of Quantum Operators: An Introduction to Quantum Index Algebra - https://arxiv.org/abs/2512.19977 - arXiv:2512.19977v2 Announce Type: replace -Abstract: We introduce Quantum Index Algebra (QIA) as a finite, index-based algebraic framework for representing and manipulating quantum operators on Hilbert spaces of dimension $2^m$. In QIA, operators are expressed as structured combinations of basis elements indexed by Boolean codes, allowing products, commutators, and conjugations to be computed through finite rules on discrete indices rather than through dense matrix arithmetic. This representation unifies combinatorial index structure, explicit matrix realization, and transformation properties under Walsh-Hadamard-type transforms within a single formalism. Using QIA and its associated block-matrix realization, we reformulate the Bernstein-Vazirani hidden-string problem in its phase-oracle form entirely within a real, finite-dimensional algebraic setting. We show that, under structured oracle access, the QIA procedure reproduces the Bernstein-Vazirani algorithm exactly and achieves the same asymptotic query complexity and circuit depth as the standard quantum algorithm. In particular, the hidden string is recovered by symbolic manipulation of a sparse algebraic representation of the oracle rather than by numerical simulation of quantum amplitudes. Our results demonstrate that the apparent quantum speed-up in this setting is a consequence of operator structure rather than Hilbert-space dimensionality alone. QIA thus provides a precise language for separating genuinely quantum resources from those arising from algebraic and combinatorial structures and offers a new perspective on the classical simulability of structured quantum circuits. - oai:arXiv.org:2512.19977v2 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - A. Yu. Volkov, G. A. Koroteev, Yu. S. Volkov - - - Efficient Calculation of the Maximal R\'{e}nyi Divergence for a Matrix Product State via Generalized Eigenvalue Density Matrix Renormalization Group - https://arxiv.org/abs/2601.02122 - arXiv:2601.02122v2 Announce Type: replace -Abstract: The study of quantum and classical correlations between subsystems is fundamental to understanding many-body physics. In quantum information theory, the quantum mutual information, $I(A;B)$, is a measure of correlation between the subsystems $A,B$ in a quantum state, and is defined by the means of the von Neumann entropy: $I\left(A;B\right)=S\left(\rho_{A}\right)+S\left(\rho_{B}\right)-S\left(\rho_{AB}\right)$. However, such a computation requires an exponential amount of resources. This is a defining feature of quantum systems, the infamous ``curse of dimensionality'' . Other measures, which are based on R\'{e}nyi divergences instead of von Neumann entropy, were suggested as alternatives in a recent paper showing them to possess important theoretical features, and making them leading candidates as mutual information measures. In this work, we concentrate on the maximal R\'{e}nyi divergence. This measure can be shown to be the solution of a generalized eigenvalue problem. To calculate it efficiently for a 1D state represented as a matrix product state, we develop a generalized eigenvalue version of the density matrix renormalization group algorithm. We benchmark our method for the paradigmatic XXZ chain, and show that the maximal R\'enyi divergence may exhibit different trends than the von Neumann mutual information. - oai:arXiv.org:2601.02122v2 - quant-ph - cond-mat.str-el - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Uri Levin, Noa Feldman, Moshe Goldstein - - - Local Scale Invariance in Quantum Theory: A Non-Hermitian Pilot-Wave Formulation - https://arxiv.org/abs/2601.03567 - arXiv:2601.03567v3 Announce Type: replace -Abstract: We show that Weyl's abandoned idea of local scale invariance has a natural realization at the quantum level in pilot-wave (deBroglie-Bohm) theory. We obtain the Weyl covariant derivative by complexifying the electromagnetic gauge coupling parameter. The resultant non-hermiticity has a natural interpretation in terms of local scale invariance in pilot-wave theory. The conserved current density is modified from $|\psi|^2$ to the local scale invariant, trajectory-dependent ratio $|\psi|^2/ \mathbf{1}^2[\mathcal{C}]$, where $\mathbf 1[\mathcal C]$ is a scale factor that depends on the pilot-wave trajectory $\mathcal C$ in configuration space. Our approach is general, and we implement it for the Schr\"odinger, Pauli, and Dirac equations coupled to an external electromagnetic field. We also implement it in quantum field theory for the case of a quantized axion field interacting with a quantized electromagnetic field. We discuss the equilibrium probability density and show that the corresponding trajectories are unique. - oai:arXiv.org:2601.03567v3 - quant-ph - gr-qc + cond-mat.stat-mech hep-th - physics.hist-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by/4.0/ - Indrajit Sen, Matthew Leifer - - - Improved Lower Bounds for Learning Quantum Channels in Diamond Distance - https://arxiv.org/abs/2601.04180 - arXiv:2601.04180v4 Announce Type: replace -Abstract: We prove that learning an unknown quantum channel with input dimension $d_A$, output dimension $d_B$, and Choi rank $r$ to diamond distance $\varepsilon$ requires $ \Omega\!\left( \frac{d_A d_B r}{\varepsilon \log(d_B r / \varepsilon)} \right)$ channel queries when $d_A= rd_B$, and $\Omega\!\left( \frac{d_A d_B r}{\varepsilon^2 \log(d_B r / \varepsilon)} \right)$ channel queries when $d_A\le rd_B/2$. These lower bounds improve upon the best previous $\Omega(d_A d_B r)$ bound by introducing explicit, near-optimal $\varepsilon$-dependence. Moreover, when $d_A\le rd_B/2$, the lower bound is optimal up to a logarithmic factor. The proof constructs ensembles of channels that are well separated in diamond norm yet admit Stinespring isometries that are close in operator norm. - oai:arXiv.org:2601.04180v4 - quant-ph math-ph math.MP - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Aadil Oufkir, Filippo Girardi - - - Holographic codes seen through ZX-calculus - https://arxiv.org/abs/2601.04467 - arXiv:2601.04467v2 Announce Type: replace -Abstract: We re-visit the pentagon holographic quantum error correcting code from a ZX-calculus perspective. By expressing the underlying tensors as ZX-diagrams, we study the stabiliser structure of the code via Pauli webs. In addition, we obtain a diagrammatic understanding of its logical operators, encoding isometries, R\'enyi entropy and toy models of black holes/wormholes. Then, motivated by the pentagon holographic code's ZX-diagram, we introduce a family of codes constructed from ZX-diagrams on its dual hyperbolic tessellations and study their logical error rates using belief propagation decoders. - oai:arXiv.org:2601.04467v2 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by/4.0/ - Kwok Ho Wan, H. C. W. Price, Qing Yao - - - Maximal Entanglement and Frozen Information: A Unified Framework for Dynamical Quantum Phase Transitions - https://arxiv.org/abs/2601.04535 - arXiv:2601.04535v2 Announce Type: replace -Abstract: Dynamical quantum phase transitions (DQPTs) are temporal singularities marked by zeros of the Loschmidt echo, yet their underlying quantum-information structure remains elusive. Here, we introduce a momentum-resolved entanglement entropy as a direct probe of DQPTs in translation-invariant free systems. We analytically establish that every critical momentum mode $k^{*}$ associated with a DQPT saturates its entanglement to the maximal value $\ln{2}$, coinciding with the vanishing of the Loschmidt echo. Crucially, we demonstrate that this maximal entanglement universally suppresses information scrambling: a momentum-resolved out-of-time-ordered correlator (OTOC) vanishes identically for all times at $k^{*}$. These three signatures -- Fisher zeros, maximal entanglement, and vanished OTOC -- are proved to be equivalent in both the transverse-field Ising and Su-Schrieffer-Heeger models, despite their distinct bipartitions (momentum-pair vs. sublattice). Our results establish a unified, information-theoretic framework for DQPTs, revealing them a points where quantum correlations saturate and information flow halts. This work elevates entanglement and scrambling to central dynamical order parameters, offering a universal perspective on nonequilibrium quantum critically. - oai:arXiv.org:2601.04535v2 - quant-ph - cond-mat.quant-gas - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by/4.0/ - Kaiyuan Cao, Mingzhi Li, Xiang-Ping Jiang, Shu Chen, Jian Wang - - - Restoring Locality: The Heisenberg Picture as a Separable Description of Quantum Theory - https://arxiv.org/abs/2601.06522 - arXiv:2601.06522v2 Announce Type: replace -Abstract: Local realism has been the subject of much discussion in modern physics, partly because our deepest theories of physics appear to contradict one another in regard to whether reality is local. According to general relativity, it is, as physical quantities (perceptible or not) in two spacelike separated regions cannot affect one another. Yet, in quantum theory, it has traditionally been thought that local realism cannot hold and that such effects do occur. This apparent discrepancy between the two theories is resolved by Everettian quantum theory, as first proven by Deutsch & Hayden (2000). In this paper, I will explain how local realism is respected in quantum theory and review the advances in our understanding of locality since Deutsch & Hayden's work, including the concept of local branching and the more general analysis by Raymond-Robichaud (2021) - oai:arXiv.org:2601.06522v2 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Sam Kuypers - - - Direct temperature readout in nonequilibrium quantum thermometry - https://arxiv.org/abs/2601.07198 - arXiv:2601.07198v2 Announce Type: replace -Abstract: Quantum thermometry aims to measure temperature in nanoscale quantum systems, paralleling classical thermometry. However, temperature is not a quantum observable, and most theoretical studies have therefore concentrated on analyzing fundamental precision limits set by the quantum Fisher information through the quantum Cramer-Rao bound. In contrast, whether a direct temperature readout can be achieved in quantum thermometry remains largely unexplored, particularly under the nonequilibrium conditions prevalent in real-world applications. To address this, we develop a direct temperature readout scheme based on a thermodynamic inference strategy. The scheme integrates two conceptual developments: (i) By applying the maximum entropy principle with the thermometer's mean energy as a constraint, we assign a reference temperature to the nonequilibrium thermometer. We demonstrate that this reference temperature outperforms a commonly used effective temperature defined through equilibrium analogy. (ii) We obtain positive semi-definite error functions that lower-bound the deviation of the reference temperature from the true temperature-in analogy to the quantum Cramer-Rao bound for the mean squared error-and vanish upon thermalization with the sample. Combining the reference temperature with these error functions, we introduce a notion of corrected dynamical temperature which furnishes a postprocessed temperature readout under nonequilibrium conditions. We validate the corrected dynamical temperature in a qubit-based thermometer under a range of nonequilibrium initial states, confirming its capability to estimate the true temperature. Importantly, we find that increasing quantum coherence can enhance the precision of this readout. - oai:arXiv.org:2601.07198v2 - quant-ph - cond-mat.stat-mech - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by-sa/4.0/ - Yan Xie, Junjie Liu - - - Breaking the Orthogonality Barrier in Quantum LDPC Codes - https://arxiv.org/abs/2601.08824 - arXiv:2601.08824v3 Announce Type: replace -Abstract: Classical low-density parity-check (LDPC) codes are a widely deployed and well-established technology, forming the backbone of modern communication and storage systems. It is well known that, in this classical setting, increasing the girth of the Tanner graph while maintaining regular degree distributions leads simultaneously to good belief-propagation (BP) decoding performance and large minimum distance. In the quantum setting, however, this principle does not directly apply because quantum LDPC codes must satisfy additional orthogonality constraints between their parity-check matrices. When one enforces both orthogonality and regularity in a straightforward manner, the girth is typically reduced and the minimum distance becomes structurally upper bounded. In this work, we overcome this limitation by using permutation matrices with controlled commutativity and by restricting the orthogonality constraints to only the active part of the construction, while preserving regular check-matrix structures. This design circumvents conventional structural distance limitations induced by parent-matrix orthogonality, and enables the construction of quantum LDPC codes with large girth while avoiding latent low-weight logical operators. As a concrete demonstration, we construct a girth-8, (3,12)-regular $[[9216,4612, \leq 48]]$ quantum LDPC code and show that, under BP decoding combined with a low-complexity post-processing algorithm, it achieves a frame error rate as low as $10^{-8}$ on the depolarizing channel with error probability $4 \%$. - oai:arXiv.org:2601.08824v3 - quant-ph - cs.IT - math.IT - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by/4.0/ - Kenta Kasai - - - Reservoir-Engineered Refrigeration of a Superconducting Cavity with Double-Quantum-Dot Spin Qubits - https://arxiv.org/abs/2601.09516 - arXiv:2601.09516v3 Announce Type: replace -Abstract: We present an analytically tractable theory of reservoir-engineered refrigeration of a superconducting microwave cavity and map it onto a realistic solid-state implementation based on gate-defined double-quantum-dot (DQD) spin qubits. Treating the DQD not as a spectroscopic element but as a tunable engineered reservoir, we show how gate control of populations, coherences, linewidths, and detuning defines an effective photon birth-death process with predictable detailed balance. This framework yields closed-form expressions for the cavity steady state, identifies cooling bounds and detuning-dependent refrigeration valleys, and clarifies when refrigeration can drive the cavity below both the bath temperature and the DQD setpoint. By distinguishing refreshed (collision-like) and persistent reservoir regimes, we show how memory effects, saturation, and dark-state formation constrain cooling in realistic devices, while collective bright-mode coupling in a two-dot configuration can enhance refrigeration subject to mismatch and dephasing, as confirmed by numerical Lindblad simulations demonstrating targeted millikelvin cavity cooling relevant for cryogenic circuit-QED architectures. - oai:arXiv.org:2601.09516v3 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by-nc-nd/4.0/ - Daryoosh Vashaee, Jahanfar Abouie - - - Classical simulation of a quantum circuit with noisy magic inputs - https://arxiv.org/abs/2601.10111 - arXiv:2601.10111v2 Announce Type: replace -Abstract: Magic states are essential for universal quantum computation and are widely viewed as a key source of quantum advantage, yet in realistic devices they are inevitably noisy. In this work, we characterize how noise on injected magic resources changes the classical simulability of quantum circuits and when it induces a transition from classically intractable behavior to efficient classical simulation. We adopt a resource-centric noise model in which only the injected magic components are noisy, while the baseline states, operations, and measurements belong to an efficiently simulable family. Within this setting, we develop an approximate classical sampling algorithm with controlled error and prove explicit noise-dependent conditions under which the algorithm runs in polynomial time. Our framework applies to both qubit circuits with Clifford baselines and fermionic circuits with matchgate baselines, covering representative noise channels such as dephasing and particle loss. We complement the analysis with numerical estimates of the simulation cost, providing concrete thresholds and runtime scaling across practically relevant parameter regimes. - oai:arXiv.org:2601.10111v2 - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 + Fri, 23 Jan 2026 00:00:00 -0500 replace http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Jiwon Heo, Sojeong Park, Changhun Oh + Himanshu Badhani, Dhanuja G. S., Siddhartha Das - Unifying Quantum and Classical Dynamics - https://arxiv.org/abs/2601.10423 - arXiv:2601.10423v2 Announce Type: replace -Abstract: Classical and quantum physics represent two distinct theories; however, quantum physics is regarded as the more fundamental of the two. It is posited that classical mechanics should arise from quantum mechanics under certain limiting conditions. Nevertheless, this remains a challenging objective. In this work, we explore the potential for unifying the dynamics of classical and quantum physics. This discussion does not suggest that classical behavior emerges from quantum mechanics; rather, it demonstrates the exact equivalence between the dynamics of quantum observables and their classical counterparts. It is shown that the Heisenberg equations of motion can be cast in a form that is identical to Newton's equations of motion, with $\hbar$ being absent from the formulation. In a generalized analysis, the Heisenberg equations are cast in a form that is identical to the classical Hamilton's equations of motion. This implies that both quantum and classical dynamics are governed by the same equations, with the Heisenberg operators substituting the classical observables. - oai:arXiv.org:2601.10423v2 + Quantum Energy Teleportation under Equilibrium and Nonequilibrium Environments + https://arxiv.org/abs/2511.01518 + arXiv:2511.01518v2 Announce Type: replace +Abstract: Quantum energy teleportation (QET), implemented via local operations and classical communication, enables carrier-free energy transfer by exploiting quantum resources. While QET has been extensively studied theoretically and validated experimentally in various quantum platforms, enhancing energy output for mixed initial states, as the system inevitably interacts with environments, remains a significant challenge. In this work, we study QET performance in a two-qubit system coupled to equilibrium or nonequilibrium reservoirs. We derive an analytical expression for the energy output in terms of the system Hamiltonian eigenstates, enabling analysis of energy output for mixed states. Using the Redfield master equation, we systematically examine the effects of qubit detuning, nonequilibrium temperature difference, and nonequilibrium chemical potential difference on the energy output. We find that the energy output for mixed states often follows that of the eigenstate with the highest population, and that nonequilibrium environments can enhance the energy output in certain parameter regimes. + oai:arXiv.org:2511.01518v2 quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 + Fri, 23 Jan 2026 00:00:00 -0500 replace http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Abdul Rahaman Shaikh, Tabish Qureshi + Xiaokun Yan, Kun Zhang, Jin Wang - Nonlinear quantum Kibble-Zurek ramps in open systems at finite temperature - https://arxiv.org/abs/2601.10465 - arXiv:2601.10465v2 Announce Type: replace -Abstract: We analyze quantum systems under a broad class of protocols in which the temperature and a Hamiltonian control parameter are ramped simultaneously and, in general, in a nonlinear fashion toward a quantum critical point. Using an open-system version of a Kitaev quantum wire as an example, we show that, unlike finite-temperature protocols at fixed temperature, these protocols allow us to probe, in an out-of-equilibrium situation and at finite temperature, the universality class (characterized by the critical exponents $\nu$ and $z$) of an equilibrium quantum phase transition at zero temperature. Key to this is the identification of ramps in which both coherent and incoherent parts of the open-system dynamics affect the excitation density in a non-negligible way. We also identify the specific ramps for which subleading corrections to the asymptotic scaling laws are suppressed, which serves as a guide to dynamically probing quantum critical exponents in experimentally realistic finite-temperature situations. - oai:arXiv.org:2601.10465v2 + Towards Quantum Software for Quantum Simulation + https://arxiv.org/abs/2511.13520 + arXiv:2511.13520v2 Announce Type: replace +Abstract: Quantum simulation is a leading candidate for demonstrating practical quantum advantage over classical computation, as it is believed to provide exponentially more compute power than any classical system. It offers new means of studying the behaviour of complex physical systems, for which conventionally software-intensive simulation codes based on numerical high-performance computing are used. Instead, quantum simulations map properties and characteristics of subject systems, for instance chemical molecules, onto quantum devices that then mimic the system under study. + Currently, the use of these techniques is largely limited to fundamental science, as the overall approach remains tailored for specific problems: We lack infrastructure and modelling abstractions that are provided by the software engineering community for other computational domains. + In this paper, we identify critical gaps in the quantum simulation software stack-particularly the absence of general-purpose frameworks for model specification, Hamiltonian construction, and hardware-aware mappings. We advocate for a modular model-driven engineering (MDE) approach that supports different types of quantum simulation (digital and analogue), and facilitates automation, performance evaluation, and reusability. Through an example from high-energy physics, we outline a vision for a quantum simulation framework capable of supporting scalable, cross-platform simulation workflows. + oai:arXiv.org:2511.13520v2 quant-ph - cond-mat.quant-gas - cond-mat.stat-mech - Wed, 21 Jan 2026 00:00:00 -0500 + cs.SE + Fri, 23 Jan 2026 00:00:00 -0500 replace http://creativecommons.org/licenses/by/4.0/ - Johannes N. Kriel, Emma C. King, Michael Kastner + 10.1145/3786150.3788611 + Proceedings of the 48th International Conference of Software Engineering 2026, Workshop on Quantum Software Engineering (Q-SE@ICSE'26) + Maja Franz, Lukas Schmidbauer, Joshua Ammermann, Ina Schaefer, Wolfgang Mauerer - Quantifying the properties of evolutionary quantum states of the XXZ spin model using quantum computing - https://arxiv.org/abs/2601.10650 - arXiv:2601.10650v2 Announce Type: replace -Abstract: The entanglement distance of evolutionary quantum states of a two-spin system with the XXZ model has been studied. The analysis has been conducted both analytically and using quantum computing. An analytical dependence of the entanglement distance on the values of the model coupling constants and the parameters of the initial states has been obtained. The speed of evolution of a two-spin system has been investigated. The analysis has been performed analytically and using quantum computing. An explicit dependence of the speed of evolution on the coupling constants and on the parameters of the initial state has been obtained. The results of quantum computations are in good agreement with the theoretical predictions. - oai:arXiv.org:2601.10650v2 + Precision Bounds for Characterising Quantum Measurements + https://arxiv.org/abs/2512.20091 + arXiv:2512.20091v2 Announce Type: replace +Abstract: Quantum measurements, alongside quantum states and processes, form a cornerstone of quantum information processing. However, unlike states and processes, their efficient characterisation remains relatively unexplored. We resolve this asymmetry by introducing a comprehensive framework for efficient detector estimation that reveals the fundamental limits to extractable parameter information and errors arising in detector analysis - the detector quantum Fisher information. Our development eliminates the need to optimise for the best probe state, while highlighting aspects of detector analysis that fundamentally differ from quantum state estimation. Through proofs, examples and experimental validation, we demonstrate the relevance and robustness of our proposal for current quantum detector technologies. By formalising a dual perspective to state estimation, our framework completes and connects the triad of efficient state, process, and detector tomography, advancing quantum information theory with broader implications for emerging technologies reliant on precisely calibrated measurements. + oai:arXiv.org:2512.20091v2 quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 + physics.ins-det + physics.optics + Fri, 23 Jan 2026 00:00:00 -0500 replace http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - M. P. Tonne, Kh. P. Gnatenko + 10.1038/s41467-026-68529-7 + Nat. Commun. (2026) + Aritra Das, Simon K. Yung, Lorcan O. Conlon, Ozlem Erkilic, Angus Walsh, Yong-Su Kim, Ping K. Lam, Syed M. Assad, Jie Zhao - Reversing quantum dynamics with near-optimal quantum and classical fidelity - https://arxiv.org/abs/quant-ph/0004088 - arXiv:quant-ph/0004088v2 Announce Type: replace -Abstract: We consider the problem of reversing quantum dynamics, with the goal of preserving an initial state's quantum entanglement or classical correlation with a reference system. We exhibit an approximate reversal operation, adapted to the initial density operator and the ``noise'' dynamics to be reversed. We show that its error in preserving either quantum or classical information is no more than twice that of the optimal reversal operation. Applications to quantum algorithms and information transmission are discussed. - oai:arXiv.org:quant-ph/0004088v2 + Entanglement Entropy for Screened Interactions via Dimensional Mapping to Harmonic Oscillators + https://arxiv.org/abs/2601.02877 + arXiv:2601.02877v2 Announce Type: replace +Abstract: We investigate interaction-induced corrections to entanglement entropy by mapping a screened Yukawa-type interaction to an effective harmonic oscillator system with controlled anharmonic perturbations. Starting from a one-dimensional interaction $V(x) = -g^2 e^{-\alpha m x}/x$, we reformulate the problem in terms of a four-dimensional radial oscillator, where the finite screening length generates a systematic hierarchy of polynomial interactions in the radial coordinate. This mapping enables a controlled Rayleigh-Schrodinger perturbative treatment of the ground-state wavefunction and an explicit spectral analysis of the reduced density matrix. Working in the weak-screening regime, we compute the leading non-Gaussian correction arising from the quartic interaction $\rho^4$, which appears at order $\alpha^2$ in the expansion of the Yukawa-like potential. We obtain closed analytic expressions for the resulting small eigenvalues of the reduced density matrix and evaluate their contribution to the von Neumann entanglement entropy. We show that the entropy receives analytic corrections at order $\alpha^2$, originating both from explicit anharmonic state-mixing effects and from the implicit $\alpha$ dependence of the Gaussian width parameter. Our results clarify the distinct roles of harmonic renormalization and genuinely non-Gaussian interactions in generating entanglement, establish a systematic power-counting and normalization scheme for higher-order $\rho^{2n}$ perturbations, and provide a transparent oscillator-based framework for computing entanglement entropy in weakly interacting low-dimensional and field-theoretic systems. + oai:arXiv.org:2601.02877v2 quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 + hep-th + Fri, 23 Jan 2026 00:00:00 -0500 replace http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - 10.1063/1.1459754 - Journal of Mathematical Physics 43 (2002) 2097-2106 - H. Barnum, E. Knill + Akshay Kulkarni, Rahul Nigam - Matrix-product-state-based band-Lanczos solver for quantum cluster approaches - https://arxiv.org/abs/2310.10799 - arXiv:2310.10799v2 Announce Type: replace-cross -Abstract: We present matrix-product state (MPS) based band Lanczos method as solver for quantum cluster methods such as the variational cluster approximation. While a na\"ive implementation of MPS as cluster solver would barely improve its range of applicability, we show that our approach makes it possible to treat cluster geometries well beyond the reach of exact diagonalization methods. The key modifications we introduce are a continuous energy truncation combined with a convergence criterion that is more robust against approximation errors introduced by the MPS representation and provides a bound to deviations in the resulting Green's function. The potential of the resulting cluster solver is demonstrated by computing the self-energy functional for the single-band Hubbard model at half filling in the strongly correlated regime, on different cluster geometries. Here, we find that only when treating large cluster sizes, observables can be extrapolated to the thermodynamic limit, which we demonstrate at the example of the staggered magnetization. Treating clusters sizes with up to $6\times 6$ sites we obtain significant improvement over the extrapolation accessible with exact diagonalization solvers when comparing to quantum Monte Carlo results. Finally, we illustrate the applicability of the MPS cluster solver to more complex models by calculating spectral properties as relevant for the electron-doped cuprate CaCuO$_2$. - oai:arXiv.org:2310.10799v2 - cond-mat.str-el - physics.comp-ph + Madelung hydrodynamics of spin-orbit coupling: action principles, currents, and correlations + https://arxiv.org/abs/2601.10698 + arXiv:2601.10698v2 Announce Type: replace +Abstract: We exploit the variational and Hamiltonian structures of quantum hydrodynamics with spin to unfold the correlation and torque mechanisms accompanying spin-orbit coupling (SOC) in electronic motion. Using Hamilton's action principle for the Pauli equation, we isolate SOC-induced quantum forces that act on the orbital Madelung--Bohm trajectories and complement the usual force terms known to appear in quantum hydrodynamics with spin. While the latter spin-hydrodynamic forces relate to the quantum geometric tensor (QGT), SOC-induced orbital forces originate from a particular current operator that contributes prominently to the spin current. This distinction between force terms reveals two fundamentally different mechanisms generating quantum spin-orbit correlations. Leveraging the Hamiltonian structure of the hydrodynamic system, we also elucidate spin transport features such as the correlation-induced quantum torques and the current shift in the spin Hall effect. This Hall shift leads to a new definition of the transport spin current thereby addressing an open question in spintronics. Finally, we illustrate the framework via the Madelung--Rashba equations for planar SOC configurations and propose a particle-based scheme for numerical implementation. + oai:arXiv.org:2601.10698v2 quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace-cross - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - 10.1103/tjnr-kqmk - Phys. Rev. B 112, 235108 (2025) - Sebastian Paeckel, Thomas K\"ohler, Salvatore R. Manmana, Benjamin Lenz - - - On Dirac equations on phase spaces - https://arxiv.org/abs/2402.06404 - arXiv:2402.06404v3 Announce Type: replace-cross -Abstract: We consider Dirac equations on relativistic phase spaces $T^*{\mathbb R}^{p-1,1}$, where ${\mathbb R}^{p-1,1}$ is Minkowski space with $p=2,4$. We use the geometric quantization approach in which the wave functions are polarized sections of a complex line bundle $L_{\sf{v}}$ over $T^*{\mathbb R}^{p-1,1}$. The covariant derivatives with connection $A_{\sf{vac}}$ in this bundle define canonical commutation relations. Fermions are charged with respect to the field $A_{\sf{vac}}$, so lifting the Dirac equations from space-time ${\mathbb R}^{p-1,1}$ to phase space $T^*{\mathbb R}^{p-1,1}$ results in their solutions being localized in the space ${\mathbb R}^{p-1}$ or in space-time ${\mathbb R}^{p-1,1}$. We describe the explicit form of these solutions. - oai:arXiv.org:2402.06404v3 - hep-th + cond-mat.mes-hall + cond-mat.other math-ph math.MP - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace-cross + Fri, 23 Jan 2026 00:00:00 -0500 + replace http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Alexander D. Popov + Cesare Tronci - Addressing general measurements in quantum Monte Carlo - https://arxiv.org/abs/2412.01384 - arXiv:2412.01384v4 Announce Type: replace-cross -Abstract: Quantum Monte Carlo is one of the most promising approaches for dealing with large-scale quantum many-body systems. It has played an extremely important role in understanding strongly correlated physics. However, two fundamental problems, namely the sign problem and general measurement issues, have seriously hampered its scope of application. We propose a universal scheme to tackle the problems of general measurement. The target observables are expressed as the ratio of two types of partition functions $\langle \mathrm{O} \rangle=\bar{Z}/Z$, where $\bar{Z}=\mathrm{tr} (\mathrm{Oe^{-\beta H}})$ and $Z=\mathrm{tr} (\mathrm{e^{-\beta H}})$. These two partition functions can be estimated separately within the reweight-annealing frame, and then be connected by an easily solvable reference point. We have successfully applied this scheme to XXZ model and transverse field Ising model, from 1D to 2D systems, from two-body to multi-body correlations and even non-local disorder operators, and from equal-time to imaginary-time correlations. The reweighting path is not limited to physical parameters, but also works for space and time. Essentially, this scheme solves the long-standing problem of calculating the overlap between different distribution functions in mathematical statistics, which can be widely used in statistical problems, such as quantum many-body computation, big data and machine learning. - oai:arXiv.org:2412.01384v4 - cond-mat.str-el - cond-mat.stat-mech - physics.comp-ph + Multiparameter estimation for the superresolution of two incoherent sources + https://arxiv.org/abs/2601.14876 + arXiv:2601.14876v2 Announce Type: replace +Abstract: We experimentally demonstrate the simultaneous estimation of the three parameters characterizing a pair of incoherent optical sources in the sub-Rayleigh regime, enabling super-resolved scene characterization. Using spatial-mode demultiplexing (SPADE) with two demultiplexers--one deliberately shifted--we determine separations well below the diffraction limit and achieve sensitive joint estimation of separation, centroid, and relative brightness over a broad range of scene configurations in a single experimental setting. We benchmark our performance using Fisher-information-based Cram\'er-Rao bounds, and discuss the corresponding quantum limits. We investigate two complementary scenarios: a realistic case with slightly non-identical sources, and an idealized case of indistinguishable sources. + oai:arXiv.org:2601.14876v2 quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace-cross + Fri, 23 Jan 2026 00:00:00 -0500 + replace http://creativecommons.org/licenses/by/4.0/ - 10.1038/s41467-025-67324-0 - Nature Communications (2026) - Zhiyan Wang, Zenan Liu, Bin-Bin Mao, Zhe Wang, Zheng Yan + Antonin Grateau, Alexander Boeschoten, Tanguy Favin-L\'ev\^eque, Isael Herrera, Nicolas Treps - A non-semisimple non-invertible symmetry - https://arxiv.org/abs/2412.19635 - arXiv:2412.19635v2 Announce Type: replace-cross -Abstract: We investigate the action of a non-invertible symmetry on spins chains whose topological lines are labelled by representations of the four-dimensional Taft algebra. The main peculiarity of this symmetry is the existence of junctions between distinct indecomposable lines. Sacrificing Hermiticity, we construct several symmetric, frustration-free, gapped Hamiltonians with real spectra and analyse their ground state subspaces. Our study reveals two intriguing phenomena. First, we identify a smooth path of gapped symmetric Hamiltonians whose ground states transform inequivalently under the symmetry. Second, we find a model where a product state and the so-called W state spontaneously break the symmetry, and propose an explanation for the indistinguishability of these two states in the infinite-volume limit in terms of the symmetry category. - oai:arXiv.org:2412.19635v2 + Duality between open systems and closed bilayer systems: Thermofield double states as quantum many-body scars + https://arxiv.org/abs/2304.03155 + arXiv:2304.03155v4 Announce Type: replace-cross +Abstract: We establish a duality between open many-body systems governed by the Gorini-Kossakowski-Sudarshan-Lindblad (GKSL) equation and satisfying the detailed balance condition on the one side, and closed bilayer systems with a self-adjoint Hamiltonian on the other side. Under this duality, the identity operator on the open system side maps to a quantum many-body scar of the dual Hamiltonian $\mathcal H$. This scar eigenstate has a form of a thermofield double state for a single-body conserved quantity entering the detailed balance conditions. A remarkable feature of this thermofield scar is a tunable single-layer entanglement entropy controlled by the reservoir temperature on the open system side. Further, we identify broad classes of many-body open systems with nontrivial explicit eigen operators $Q$ of the Lindbladian superoperator. The expectation values of the corresponding observables exhibit a simple exponential decay, $\langle Q\rangle_t=e^{-\Gamma t} \langle Q \rangle_0$, irrespectively of the initial state. Under the above duality, these eigen operators give rise to additional (towers of) scars. Finally, we point out that more general superoperators (not necessarily of the GKSL form) can be mapped to self-adjoint Hamiltonians of bilayer systems harbouring scars, and provide an example thereof. + oai:arXiv.org:2304.03155v4 + cond-mat.stat-mech cond-mat.str-el - hep-th - math-ph - math.MP quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace-cross - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - 10.1103/nbf9-ywmd - Clement Delcamp, Edmund Heng, Matthew Yu - - - Tensorization of neural networks for improved privacy and interpretability - https://arxiv.org/abs/2501.06300 - arXiv:2501.06300v3 Announce Type: replace-cross -Abstract: We present a tensorization algorithm for constructing tensor train/matrix product state (MPS) representations of functions, drawing on sketching and cross interpolation ideas. The method only requires black-box access to the target function and a small set of sample points defining the domain of interest. Thus, it is particularly well-suited for machine learning models, where the domain of interest is naturally defined by the training dataset. We show that this approach can be used to enhance the privacy and interpretability of neural network models. Specifically, we apply our decomposition to (i) obfuscate neural networks whose parameters encode patterns tied to the training data distribution, and (ii) estimate topological phases of matter that are easily accessible from the MPS representation. Additionally, we show that this tensorization can serve as an efficient initialization method for optimizing MPS in general settings, and that, for model compression, our algorithm achieves a superior trade-off between memory and time complexity compared to conventional tensorization methods of neural networks. - oai:arXiv.org:2501.06300v3 - math.NA - cs.LG - cs.NA - physics.comp-ph - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 + Fri, 23 Jan 2026 00:00:00 -0500 replace-cross http://creativecommons.org/licenses/by/4.0/ - 10.21468/SciPostPhysCore.8.4.095 - SciPost Phys. Core 8, 095 (2025) - Jos\'e Ram\'on Pareja Monturiol, Alejandro Pozas-Kerstjens, David P\'erez-Garc\'ia + 10.1103/PhysRevB.110.L241105 + Phys. Rev. B 110, L241105 (2024) + Alexander Teretenkov, Oleg Lychkovskiy - Valley Splitting Correlations Across a Silicon Quantum Well Containing Germanium - https://arxiv.org/abs/2504.12455 - arXiv:2504.12455v3 Announce Type: replace-cross -Abstract: Quantum dots in SiGe/Si/SiGe heterostructures host coherent electron spin qubits, which are promising for future quantum computers. The silicon quantum well hosts near-degenerate electron valley states, creating a low-lying excited state that is known to reduce spin qubit readout and control fidelity. The valley energy splitting is dominated by the microscopic disorder in the SiGe alloy and at the Si/SiGe interfaces, and while Si devices are compatible with large-scale semiconductor manufacturing, achieving a uniformly large valley splitting energy across a many-qubit device spanning mesoscopic distances is an outstanding challenge. In this work we study valley splitting variations in a 1D quantum dot array, formed in a Si$_{0.972}$Ge$_{0.028}$ quantum well, manufactured by Intel. We observe correlations in valley splitting, at both sub-100nm (single gate) and >1$\mu$m (device) lengthscales, that are consistent with alloy disorder-dominated theory and simulation. Our results develop the mesoscopic understanding of Si/SiGe heterostructures necessary for scalable device design. - oai:arXiv.org:2504.12455v3 + Vestigial Gapless Boson Density Wave Emerging between $\nu = 1/2$ Fractional Chern Insulator and Finite-Momentum Supersolid + https://arxiv.org/abs/2408.07111 + arXiv:2408.07111v2 Announce Type: replace-cross +Abstract: The roton-triggered charge-density-wave (CDW)is widely studied in fractional quantum Hall (FQH) and fractional Chern insulator (FCI) systems, and there also exist field theoretical and numerical realizations of continuous transition from FCI to superfluid (SF). However, the theory and numerical explorations of the transition between FCI and supersolid (SS) are still lacking. In this work, we study the topological flat-band lattice models with $\nu$ = 1/2 hard-core bosons, where the previous studies have discovered the existence of FCI states and possible direct FCI-SS transitions. While the FCI is robust, we find the direct FCI-SS transition is absent, and there exist more intriguing scenarios. In the case of checkerboard lattice, we find an intermediate gapless CDW state without SF, sandwiched between FCI and SS. This novel state is triggered by the roton instability in FCI and it further continuously brings about the intertwined finite-momentum SF fluctuation when the CDW order is strong enough, eventually transiting into an unconventional finite-momentum SS state. The intermediate gapless CDW state is a vestige from the SS state, since the increasing quantum fluctuation melts only the Larkin-Ovchinnikov-type SF order in SS but its (secondary) product -- the CDW order -- survives. On honeycomb lattice, we find no evidence of SS, but discover an interesting sequence of FCI-Solid I-Solid II transitions, with both solids incompressible. Moreover, in contrast to previous single-roton condensation, this sequence of FCI-Solid I-Solid II transitions is triggered by the softening of multi-roton modes in FCI. Considering the intertwined wave vectors of the CDW orders, Solid I is a vestige of Solid II. Our work provides new horizon not only for the quantum phase transitions in FCI but also for the intertwined orders and gapless states in bosonic systems, which will inspire future studies. + oai:arXiv.org:2408.07111v2 cond-mat.mes-hall + cond-mat.str-el quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace-cross - http://creativecommons.org/licenses/by/4.0/ - 10.1038/s41467-025-67325-z - Nat Commun 16, 11381 (2025) - Jonathan C. Marcks, Emily Eagen, Emma C. Brann, Merritt P. Losert, Talise Oh, J. Reily, Christopher S. Wang, Daniel Keith, Fahd A. Mohiyaddin, Florian Luthi, Matthew J. Curry, Jiefei Zhang, F. Joseph Heremans, Mark Friesen, M. A. Eriksson - - - Compton Form Factor Extraction using Quantum Deep Neural Networks - https://arxiv.org/abs/2504.15458 - arXiv:2504.15458v3 Announce Type: replace-cross -Abstract: We extract Compton form factors (CFFs) from deeply virtual Compton scattering measurements at the Thomas Jefferson National Accelerator Facility (JLab) using quantum-inspired deep neural networks (QDNNs). The analysis implements the twist-2 Belitsky-Kirchner-M\"uller formalism and employs a fitting strategy that emulates standard local fits. Using pseudodata, we benchmark QDNNs against classical deep neural networks (CDNNs) and find that QDNNs often deliver higher predictive accuracy and tighter uncertainties at comparable model complexity. Guided by these results, we introduce a quantitative selection metric that indicates when QDNNs or CDNNs are optimal for a given experimental fit. After obtaining local extractions from the JLab data, we perform a standard neural-network global CFF fit and compare with previous global analyses. The results support QDNNs as an efficient and complementary tool to CDNNs for CFF determination and for future multidimensional studies of parton distributions and hadronic structure. - oai:arXiv.org:2504.15458v3 - cs.LG - hep-ph - nucl-th - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 + Fri, 23 Jan 2026 00:00:00 -0500 replace-cross http://creativecommons.org/licenses/by/4.0/ - Brandon B. Le, Dustin Keller + 10.1103/1bhm-9pk4 + Phys. Rev. B 113, 035141 (2026) + Hongyu Lu, Han-Qing Wu, Bin-Bin Chen, Zi Yang Meng - Acoustic phonons, spin-phonon coupling and spin relaxation via the lattice reorientation mechanism in hexagonal germanium nanowires - https://arxiv.org/abs/2504.18198 - arXiv:2504.18198v3 Announce Type: replace-cross -Abstract: Spin relaxation via electron-phonon interaction is an important decoherence mechanism for spin qubits. In this work, we study spin relaxation in hexagonal (2H) germanium, a novel direct-gap semiconductor showing great potential to combine highly coherent spin qubits with optical functionality. Focusing on electrostatically defined quantum dots in hexagonal germanium nanowires, we (i) identify geometries where spin qubit experiments are feasible, (ii) compute the nanowire phonon modes, and (iii) describe spin relaxation of hole spin qubits due to phonon-induced lattice reorientation, a direct spin-phonon coupling mechanism that is absent in cubic semiconductors typically used for spin qubits (GaAs, cubic Si, cubic Ge). We obtain the spin relaxation time as a function of nanowire cross section, quantum dot confinement length, and magnetic field. For realistic parameters, we find relaxation times above 10 ms, and reveal that the magnetic field direction maximizing the relaxation time depends on the qubit Larmor frequency. Our results facilitate the design of nanowire quantum dot experiments with long qubit relaxation times. - oai:arXiv.org:2504.18198v3 + Electrical Interconnects for Silicon Spin Qubits + https://arxiv.org/abs/2411.01366 + arXiv:2411.01366v2 Announce Type: replace-cross +Abstract: Scalable spin qubit devices will likely require long-range qubit interconnects. We propose to create such an interconnect with a resistive topgate. The topgate is positively biased, to form a channel between the two dots; an end-to-end voltage difference across the nanowire results in an electric field that propels the electron from source dot to target dot. The electron is momentum-incoherent, but not necessarily spin-incoherent; we evaluate threats to spin coherence due to spin-orbit coupling, valley physics, and nuclear spin impurities. We find that spin-orbit coupling is the dominant threat, but momentum-space motional narrowing due to frequent scattering partially protects the electron, resulting in characteristic decoherence lengths ~15 mm for plausible parameters. + oai:arXiv.org:2411.01366v2 cond-mat.mes-hall quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 + Fri, 23 Jan 2026 00:00:00 -0500 replace-cross http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - 10.1103/gfk2-lm2j - Phys. Rev. B 112, 205409 (2025) - Baksa Kolok, Gy\"orgy Frank, Andr\'as P\'alyi + Christopher David White, Anthony Sigillito, Michael J. Gullans - $\mathcal{P}$, $\mathcal{T}$-violating axion-mediated interactions in RaOH molecule - https://arxiv.org/abs/2505.08667 - arXiv:2505.08667v3 Announce Type: replace-cross -Abstract: If axion simultaneously has the scalar couplings to the nucleons and pseudo-scalar couplings to the electrons, it may mediate a $\mathcal{P}$, $\mathcal{T}$-violating interaction between the electronic shell and nuclei in the molecules. The polyatomic molecule RaOH, which is considered as a promising platform for the $\mathcal{P}$, $\mathcal{T}$ violation searches, is studied for its sensitivity to such interactions. Due to the long-range nature (on molecular scales) of the axion-mediated interaction, it is important whether the enhancement parameter would be sensitive to the vibration of the molecule. Our results imply that the impact of the vibrations on the axion-mediated electron-nucleon interaction in the molecule is similar to the impact on the short-range electron-nucleon scalar-pseudoscalar interaction studied earlier. - oai:arXiv.org:2505.08667v3 - hep-ph + Light-induced, fictitious magnetic trapping of cold alkali atoms using an optical tweezers-nanofiber hybrid platform + https://arxiv.org/abs/2412.04809 + arXiv:2412.04809v4 Announce Type: replace-cross +Abstract: We present a magnetic trapping scheme for cold 87Rb atoms based on light-induced fictitious magnetic fields generated by the evanescent field of an optical nanofiber (ONF) integrated with an optical tweezers. We calculate and compare the trapping potentials for both Gaussian and Laguerre-Gaussian modes of the tweezers beam, combined with a quasi-linearly polarized ONF-guided field. Based on the optical powers in the tweezers and ONF modes, we analyze the trap depths and the positions of the potential minima from the nanofiber surface. We show that, by varying the optical powers in the two fields, the trap position can be tuned over several hundred nanometers, while simultaneously influencing the trap depth and trap frequencies. Such control over atom-surface position is essential for studying distance-dependent effects on atoms trapped near a dielectric surface and optimizing atom-photon interfaces for quantum technology applications. + oai:arXiv.org:2412.04809v4 physics.atom-ph + physics.optics quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace-cross - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Anna Zakharova - - - High-Order Hermite Optimization: Fast and Exact Gradient Computation in Open-Loop Quantum Optimal Control using a Discrete Adjoint Approach - https://arxiv.org/abs/2505.09857 - arXiv:2505.09857v3 Announce Type: replace-cross -Abstract: This work introduces the High-Order Hermite Optimization (HOHO) method, an open-loop discrete adjoint method for quantum optimal control. Our method is the first of its kind to efficiently compute exact (discrete) gradients when using continuous, parameterized control pulses while solving the forward equations (e.g. Schrodinger's equation or the Linblad master equation) with an arbitrarily high-order Hermite Runge-Kutta method. The HOHO method is implemented in QuantumGateDesign$.$jl (https://github.com/leespen1/QuantumGateDesign.jl), an open-source software package for the Julia programming language, which we use to perform numerical experiments comparing the method to Juqbox$.$jl (https://github.com/LLNL/Juqbox.jl). For realistic model problems we observe speedups up to 775x. - oai:arXiv.org:2505.09857v3 - math.NA - cs.NA - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace-cross - http://creativecommons.org/licenses/by/4.0/ - Spencer Lee, Daniel Appelo - - - Emergent Thermalization Thresholds in Unitary Dynamics of Inhomogeneously Disordered Quantum Systems - https://arxiv.org/abs/2505.11253 - arXiv:2505.11253v2 Announce Type: replace-cross -Abstract: Inspired by the avalanche scenario for many-body localization (MBL) instability, we reverse the conventional set-up and ask whether a large weakly-disordered chain can thermalize a smaller, strongly-disordered chain when the composite system evolves unitarily. Using transport as a dynamical probe, we identify three distinct thermalization regimes as a function of the disorder strength of the smaller chain: (i) complete thermalization with self-averaging at weak disorder, (ii) realization-dependent thermalization with strong sample-to-sample fluctuations at intermediate disorder, and (iii) absence of thermalization at strong disorder. We find that for a fixed length of the smaller chain, the non-self-averaging regime broadens with the size of the weakly-disordered chain, revealing a nuanced interplay between disorder and system size. These results highlight how inhomogeneous disorder can induce emergent thermalization thresholds in closed quantum systems, providing direct access to disorder regimes where thermalization or its absence can be reliably observed. - oai:arXiv.org:2505.11253v2 - cond-mat.stat-mech - cond-mat.dis-nn - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 + Fri, 23 Jan 2026 00:00:00 -0500 replace-cross - http://creativecommons.org/licenses/by/4.0/ - 10.1103/ycdx-sd5m - Physical Review E 113, 014205 (2026) - Soumya Kanti Pal, C L Sriram, Shamik Gupta + http://creativecommons.org/licenses/by-nc-nd/4.0/ + Alexey Vylegzhanin, Dylan J. Brown, Sergey Abdrakhmanov, Sile Nic Chormaic - Lattice models with subsystem/weak non-invertible symmetry-protected topological order - https://arxiv.org/abs/2505.11419 - arXiv:2505.11419v2 Announce Type: replace-cross -Abstract: We construct a family of lattice models which possess subsystem non-invertible symmetry-protected topological (SPT) order and analyze their interface modes protected by the symmetry, whose codimension turns out to be more than one. We also propose 2+1d lattice models which belong to two different weak SPT phases distinguished by a combination of translational symmetry and non-invertible symmetry. We show that the interface between them exhibits an exotic Lieb-Schultz-Mattis (LSM) anomaly associated with a modulated symmetry, which cannot be factorized into a direct product of internal and translational symmetries. - oai:arXiv.org:2505.11419v2 + Non-hermitian Green's function theory with $N$-body interactions: the coupled-cluster similarity transformation + https://arxiv.org/abs/2503.06586 + arXiv:2503.06586v3 Announce Type: replace-cross +Abstract: We present the diagrammatic theory of the irreducible self-energy and Bethe-Salpeter kernel that naturally arises within the Green's function formalism for a general $N$-body non-hermitian interaction. In this work, we focus specifically on the coupled-cluster self-energy generated by the similarity transformation of the electronic structure Hamiltonian. We develop the biorthogonal quantum theory to construct dynamical correlation functions where the time-dependence of operators is governed by a non-hermitian Hamiltonian. We extend the Gell-Mann and Low theorem to include non-hermitian interactions and to generate perturbative expansions of many-body Green's functions. We introduce the single-particle coupled-cluster Green's function and derive the perturbative diagrammatic expansion for the non-hermitian coupled-cluster self-energy in terms of the `non-interacting' reference Green's function, $\tilde{\Sigma}[G_0]$. From the exact equation-of-motion of the single-particle coupled-cluster Green's function, we derive the self-consistent renormalized coupled-cluster self-energy, $\tilde{\Sigma}[\tilde{G}]$, and demonstrate its relationship to the perturbative expansion of the self-energy, $\tilde{\Sigma}[G_0]$. Subsequently, we show that the usual electronic self-energy can be recovered from the coupled-cluster self-energy by neglecting the effects of the similarity transformation. We show how the coupled-cluster ground state energy can be obtained from the coupled-cluster self-energy and provide an overview of the relationship between approximations for the coupled-cluster self-energy, IP/EA-EOM-CC and the $G_0W_0$ approximation. As a result, we introduce the CC-$G_0W_0$ self-energy by leveraging the connections between Green's function and coupled-cluster theory. Finally, we derive the diagrammatic expansion of the coupled-cluster Bethe-Salpeter kernel. + oai:arXiv.org:2503.06586v3 cond-mat.str-el - hep-th - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace-cross - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Yuki Furukawa - - - Impact of the honeycomb spin-lattice on topological magnons and edge states in ferromagnetic 2D skyrmion crystals - https://arxiv.org/abs/2506.02192 - arXiv:2506.02192v4 Announce Type: replace-cross -Abstract: Magnons have been intensively studied in two-dimensional (2D) ferromagnetic (FM) skyrmion crystals (SkXs) stabilized on Bravais lattices, particularly triangular and square lattices. In these systems, topological edge states (TESs) have been reported in higher-energy magnon gaps, while the first magnon gap is found to be topologically trivial. In this context, antiferromagnetic (AFM) SkXs on the triangular spin lattice have been considered potentially more interesting for applications, since TESs emerge already in the first magnon gap. Meanwhile, the magnon topology of SkXs stabilized on non-Bravais spin lattices remains largely unexplored. In this work, we theoretically investigate the magnon band structure and TESs in 2D FM SkXs stabilized on the honeycomb spin lattice, including experimentally motivated parameter sets relevant to van der Waals magnets. We show that chiral TESs emerge in the first magnon gap over significant ranges of the Dzyaloshinskii-Moriya interaction and single-ion magnetic anisotropy. Magnetic-field-driven topological phase transitions modify the number of these TESs before eventually trivializing them. In addition, we find that TESs can coexist in the first and higher magnon gaps, which could enable frequency-multiplexed magnonic edge transport. These findings highlight the role of lattice geometry in shaping the magnon topology and edge transport in noncollinear spin textures. - oai:arXiv.org:2506.02192v4 - cond-mat.mes-hall cond-mat.mtrl-sci - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace-cross - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Doried Ghader, Bilal Jabakhanji - - - Tunable spin-phonon polarons in a chiral molecular qubit framework - https://arxiv.org/abs/2506.04885 - arXiv:2506.04885v2 Announce Type: replace-cross -Abstract: Chiral structures that produce asymmetric spin-phonon coupling can theoretically generate spin-phonon polarons -- quasiparticles exhibiting non-degenerate spin states with phonon displacements. These quasiparticles are speculated to be the origin of chirality-induced spin selectivity and presumably can display exotic dynamic behaviors. However, direct experimental evidence of spin-phonon polarons has been lacking. Using a chiral molecular qubit framework embedding stable semiquinone-like radicals, we report spin dynamic signatures that indicate the formation of spin-phonon polarons for the first time. Our non-adiabatic model reveals that these quasiparticles introduce an active spin relaxation channel when polaron reorganization energy approaches Zeeman splitting. This new channel manifests itself as anomalous, temperature-independent spin relaxation, which can be suppressed by high magnetic fields or pore-filling solvents (e.g. CH2Cl2, CS2). Such field- and guest-tunable relaxation is unattainable in conventional spin systems. Harnessing this mechanism could boost repetition rates in spin-based quantum information technologies without compromising coherence or quantum sensing performance. - oai:arXiv.org:2506.04885v2 - cond-mat.mes-hall + nucl-th physics.chem-ph quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 + Fri, 23 Jan 2026 00:00:00 -0500 replace-cross - http://creativecommons.org/licenses/by-nc-nd/4.0/ - Aimei Zhou, Ruihao Bi, Zhenghan Zhang, Luming Yang, Xudong Tian, Denan Li, Yingchao Wang, Mingshu Tan, Weibin Ni, Haozhou Sun, Jinkun Guo, Xiaohe Miao, Xinxing Zhao, Zhifu Shi, Wei Tong, Zhitao Zhang, Jiandong Feng, Jin-Hu Dou, Feng Jin, Shi Liu, Mircea Dinca, Tijana Rajh, Jian Li, Wenjie Dou, Lei Sun + http://creativecommons.org/licenses/by/4.0/ + Christopher J. N. Coveney, David P. Tew - Compression, simulation, and synthesis of turbulent flows with tensor trains - https://arxiv.org/abs/2506.05477 - arXiv:2506.05477v2 Announce Type: replace-cross -Abstract: Numerical simulations of turbulent fluids are paramount to real-life applications, from predicting and modeling flows to diagnostic purposes in engineering. However, they are also computationally challenging due to their intrinsically non-linear dynamics, which require a very high spatial resolution to accurately describe them. A promising idea is to represent flows on a discrete mesh using tensor trains (TTs), featuring a convenient scaling of the number of parameters with the mesh size. However, it is unclear how the compression power of TTs is affected by the complexity of the flows, as measured by the Reynolds number. In fact, no comprehensive analysis of how the TT representation affects the turbulent properties has yet been carried out. We fill this gap by analyzing TTs as an Ansatz to compress, simulate, and generate 3D snapshots with turbulent-like features. Specifically, we first investigate the effect of TT compression on key turbulence signatures, such as the energy spectrum, the PDF of velocity increments, and flatness. Second, we extend the 2D TT-solver introduced in [1] to a 3D cubic domain with periodic boundary conditions. We use it to simulate the incompressible Navier-Stokes dynamics at $Re_{\lambda}=315$ for a total of 9-10 Kolmogorov turnover times, showcasing the numerical stability of the TT-solver in fully developed turbulent regimes. Third, we develop a TT algorithm to synthesize artificial snapshots that exhibit turbulent-like features, with a logarithmic cost in the mesh size. Our analysis demonstrates the ability of the TT representation to capture the characteristic features of turbulence. This offers a powerful quantum-inspired toolkit for the computational treatment of turbulent flows. - oai:arXiv.org:2506.05477v2 - physics.flu-dyn - physics.comp-ph + Fusion Dynamics of Majorana Zero Modes + https://arxiv.org/abs/2503.09800 + arXiv:2503.09800v2 Announce Type: replace-cross +Abstract: Braiding and fusion of Majorana zero modes are key elements of any future topological Majorana-based quantum computer. Here, we investigate the fusion dynamics of Majorana zero modes in the spinless Kitaev model, as well as in a spinful model describing magnet-superconductor hybrid structures. We consider various scenarios allowing us to reproduce the fusion rules of the Ising anyon model. Particular emphasis is given to the charge of the fermion obtained after fusing two Majorana zero modes: as long as it remains on the superconductor, charge quantization is absent. When moving the fermion to a non-superconducting region, such as a quantum dot, nearly-quantized charge can be measured. Our findings confirm for both platforms that fusion dynamics of Majorana zero modes can indeed be used for the readout of Majorana qubits. + oai:arXiv.org:2503.09800v2 + cond-mat.mes-hall + cond-mat.supr-con quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 + Fri, 23 Jan 2026 00:00:00 -0500 replace-cross http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Stefano Pisoni, Raghavendra Dheeraj Peddinti, Egor Tiunov, Siddhartha E. Guzman, Leandro Aolita + 10.1103/2qxk-wbs6 + Phys. Rev. B 113, 035429 (2026) + Themba Hodge, Tuan Kieu, Jasmin Bedow, Eric Mascot, Dirk K. Morr, Stephan Rachel - Finite-temperature entanglement and coherence in asymmetric bosonic Josephson junctions - https://arxiv.org/abs/2506.06224 - arXiv:2506.06224v2 Announce Type: replace-cross -Abstract: We investigate the finite-temperature properties of a bosonic Josephson junction composed of N interacting atoms confined by a quasi-one-dimensional asymmetric double-well potential, modeled by the two-site Bose-Hubbard Hamiltonian. We compute numerically the spectral decomposition of the statistical ensemble of states, the thermodynamic and entanglement entropies, the population imbalance, the quantum Fisher information, and the coherence visibility. We analyze their dependence on the system parameters, showing in particular how finite temperature and on-site energy asymmetry affect the entanglement and coherence properties of the system. Moreover, starting from a quantum phase model which accurately describes the system over a wide range of interactions, we develop a reliable description of the strong tunneling regime, where thermal averages may be computed analytically using a modified Boltzmann weight involving an effective temperature. We discuss the possibility of applying this effective description to other models in suitable regimes. - oai:arXiv.org:2506.06224v2 + Bose-Einstein condensation in exotic lattice geometries + https://arxiv.org/abs/2505.16885 + arXiv:2505.16885v2 Announce Type: replace-cross +Abstract: Modern quantum engineering techniques allow for synthesizing quantum systems in exotic lattice geometries, from self-similar fractal networks to negatively curved hyperbolic graphs. We demonstrate that these structures profoundly reshape Bose-Einstein condensation. Fractal lattices dramatically lower the condensation temperature and enhance condensation fluctuations. In a Sierpi\'nski carpet, quasi-degeneracies in the tight-binding spectrum fragment the condensate. Hyperbolic lattices, on the other hand, exhibit condensation features similar to regular three-dimensional lattices, despite their embedding in only two dimensions: The critical temperature increases as the system grows, and the temperature-dependence of the condensate fraction follows the same power-law as for cubic lattices. We explain these similarities through the similarity of the densities of state at low energies. When strong repulsive interactions are included, the gas enters a Mott insulating state. Using a multi-site Gutzwiller approach as well as a simple strong-coupling expansion, for the Sierpi\'nski triangle we find a smooth interpolation between the characteristic insulating lobes of one-dimensional and two-dimensional systems. Our findings establish lattice geometry as a powerful tuning knob for quantum phase phenomena and pave the way for experimental exploration in photonic waveguide arrays and Rydberg-atom tweezer arrays. + oai:arXiv.org:2505.16885v2 cond-mat.quant-gas quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace-cross - http://creativecommons.org/licenses/by/4.0/ - 10.1103/v6xk-3xsh - Phys. Rev. A 111, 063310 (2025) - Cesare Vianello, Matteo Ferraretto, Luca Salasnich - - - Emergence of cosmic structure from Planckian discreteness - https://arxiv.org/abs/2506.15413 - arXiv:2506.15413v2 Announce Type: replace-cross -Abstract: In the standard inflationary paradigm the inhomogeneities observed in the CMB arise from quantum fluctuations of an initially homogeneous and isotropic vacuum state. This picture suffers from two well-known weaknesses. First, it assumes that quantum field theory remains valid at trans-Planckian scales, without modifications from quantum gravity. Second, it necessitates a quantum-to-classical transition in which fluctuations of a homogeneous quantum state become the classical inhomogeneities seen in the CMB. Recently, an alternative paradigm has been proposed in which such inhomogeneities are present from the very beginning, emerging from the assumed discreteness of spacetime at the Planck scale predicted by certain approaches to quantum gravity. Within this framework, scale-invariant scalar perturbations are generated naturally, without relying on trans-Planckian assumptions or invoking a quantum-to-classical transition. Specifically, inhomogeneities in the quantum state at the Planck scale propagate into semiclassical inhomogeneities on CMB scales. Here, we extend the aforementioned proposal to the most realistic case of a quasi-de Sitter expansion; in particular, we compute the scalar perturbation spectrum as a function of the slow-roll parameters, systematically encoded through the Hubble flow functions. - oai:arXiv.org:2506.15413v2 - gr-qc - hep-ph - hep-th - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 + Fri, 23 Jan 2026 00:00:00 -0500 replace-cross http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Gabriel R. Bengochea, Gabriel Leon, Alejandro Perez + 10.1103/dp1h-rfkg + Phys. Rev. A 113, 013320 (2026) + Kamil Dutkiewicz, Marcin P{\l}odzie\'n, Abel Rojo-Franc\`as, Bruno Juli\'a-D\'iaz, Maciej Lewenstein, Tobias Grass - Surrogate Modeling via Factorization Machine and Ising Model with Enhanced Higher-Order Interaction Learning - https://arxiv.org/abs/2507.01389 - arXiv:2507.01389v2 Announce Type: replace-cross -Abstract: Recently, a surrogate model was proposed that employs a factorization machine to approximate the underlying input-output mapping of the original system, with quantum annealing used to optimize the resulting surrogate function. Inspired by this approach, we propose an enhanced surrogate model that incorporates additional slack variables into both the factorization machine and its associated Ising representation thereby unifying what was by design a two-step process into a single, integrated step. During the training phase, the slack variables are iteratively updated, enabling the model to account for higher-order feature interactions. We apply the proposed method to the task of predicting drug combination effects. Experimental results indicate that the introduction of slack variables leads to a notable improvement of performance. Our algorithm offers a promising approach for building efficient surrogate models that exploit potential quantum advantages. - oai:arXiv.org:2507.01389v2 - cs.LG + Floquet Non-Bloch Formalism for a Non-Hermitian Ladder: From Theoretical Framework to Topolectrical Circuits + https://arxiv.org/abs/2507.23744 + arXiv:2507.23744v2 Announce Type: replace-cross +Abstract: Periodically driven systems intertwined with non-Hermiticity opens a rich arena for topological phases that transcend conventional Hermitian limits. The physical significance of these phases hinges on obtaining the topological invariants that restore the bulk-boundary correspondence, a task well explored for static non-Hermitian (NH) systems, while it remains elusive for the driven scenario. Here, we address this problem by constructing a generalized Floquet non-Bloch framework that analytically captures the spectral and topological properties of time-periodic NH systems. Employing a high-frequency Magnus expansion, we analytically derive an effective Floquet Hamiltonian and formulate the generalized Brillouin zone for a periodically driven quasi-one-dimensional system, namely, the Creutz ladder with a staggered complex potential. Our study demonstrates that the skin effect remains robust (despite the absence of non-reciprocal hopping) across a broad range of driving parameters, and is notably amplified in the low-frequency regime due to emergent longer-range couplings. We further employ a symmetric time frame approach that generates chiral-partner Hamiltonians, whose invariants, when appropriately combined, account for the full edge-state structure. To substantiate the theoretical framework, we propose a topolectrical circuit (TEC) that serves as a viable experimental setting. Apart from capturing the skin modes, the proposed TEC design faithfully reproduces the presence of distinct Floquet edge states, as revealed through the voltage and impedance profiles, respectively. Thus, our work not only offers a theoretical framework for exploring NH-driven systems, but also provides an experimentally feasible TEC architecture for realizing these phenomena stated above in a laboratory. + oai:arXiv.org:2507.23744v2 + cond-mat.mes-hall + cond-mat.other + physics.app-ph quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 + Fri, 23 Jan 2026 00:00:00 -0500 replace-cross http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - 10.1103/knt1-yd9s - Anbang Wang, Dunbo Cai, Yu Zhang, Yangqing Huang, Xiangyang Feng, Zhihong Zhang + 10.1103/s3b6-wz16 + Phys. Rev. Research 7, 043331 (2025) + Koustav Roy, Dipendu Halder, Koustabh Gogoi, B. Tanatar, Saurabh Basu Quantum Bootstrap Approach to a Non-Relativistic Potential for Quarkonium systems https://arxiv.org/abs/2508.02916 - arXiv:2508.02916v2 Announce Type: replace-cross + arXiv:2508.02916v3 Announce Type: replace-cross Abstract: The quantum bootstrap method is applied to determine the bound-state spectrum of Quarkonium systems using a non-relativistic potential approximation. The method translates the Schr\"odinger equation into a set of algebraic recursion relations for radial moments $\langle r^m \rangle$, which are constrained by the positive semidefiniteness of their corresponding Hankel matrices. The numerical implementation is first validated by calculating the $1S$ and $1P$ mass centroids for both charmonium ($c\bar{c}$) and bottomonium ($b\bar{b}$) systems, finding deviations of less than 0.5\% from experimental data from the Particle Data Group (PDG). This analysis is then extended to the hypothetical toponium ($t\bar{t}$) system, predicting a $1S$ ground state mass of $M \approx 344.3 \text{ GeV}$. This theoretical mass is in agreement with the energy of the recently observed resonance-like enhancement in the $t\bar{t}$ cross-section by the ATLAS and CMS collaborations. This result provides theoretical support for the interpretation of this experimental phenomenon as the formation of a quasi-bound toponium state and highlights the predictive power of the non-relativistic potential approach for systems of two massive quarks. - oai:arXiv.org:2508.02916v2 + oai:arXiv.org:2508.02916v3 hep-ph hep-lat hep-th quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 + Fri, 23 Jan 2026 00:00:00 -0500 replace-cross http://creativecommons.org/licenses/by/4.0/ Jairo Alexis Lopez, Carlos Sandoval - Floquet-engineered moire quasicrystal patterns of ultracold Bose gases in twisted bilayer optical lattices - https://arxiv.org/abs/2508.21093 - arXiv:2508.21093v5 Announce Type: replace-cross -Abstract: We investigate the formation of moire quasicrystal patterns in Bose gasses confined in twisted bilayer optical lattices via Floquet-engineered intralayer atomic interactions. Dynamical evolutions of the total density wave amplitude exhibit the stage for the emergence of moire quasicrystal patterns, where the pattern formation is closely associated with the momenta of collective modes excited by the weak periodic drive. Through analyzing the radial and angular density wave amplitude, we find that these new collective modes are only coupled radially and cannot be decoupled eventually. The symmetry of quasicrystal patterns can be easily manipulated by the modulation frequencies and amplitudes. Reducing the frequencies and increasing the amplitudes can both facilitate lattice symmetry breaking and the subsequent emergence of rotational symmetry. Notably, a twelve-fold quasicrystal pattern emerges under specific parameters, closely resembling the moire quasicrystal in twisted bilayer graphene. The momentum-space distributions also exhibit high rotational symmetry, which is consistent with the real-space patterns at specific evolution times. Our findings establish a new quantum platform for exploring quasicrystals and their symmetry properties in ultracold bosonic systems. - oai:arXiv.org:2508.21093v5 - cond-mat.quant-gas - physics.atom-ph - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace-cross - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Zhenze Fan, Juan Wang, Yan Li - - - There and Back Again: A Gauging Nexus between Topological and Fracton Phases - https://arxiv.org/abs/2509.19440 - arXiv:2509.19440v2 Announce Type: replace-cross -Abstract: Coupled layer constructions are a valuable tool for capturing the universal properties of certain interacting quantum phases of matter in terms of the simpler data that characterizes the underlying layers. In the study of fracton phases, the X-Cube model in 3+1D can be realized via such a construction by starting with a stack of 2+1D Toric Codes and turning on a coupling which condenses a composite "particle-string" object. In a recent work [Phys. Rev. B 112, 125124 (2025)], we have demonstrated that in fact, the particle-string can be viewed as a symmetry defect of a topological 1-form symmetry. In this paper, we study the result of gauging this symmetry in depth. We unveil a rich gauging web relating the X-Cube model to symmetry protected topological (SPT) phases protected by a mix of subsystem and higher-form symmetries, subsystem symmetry fractionalization in the 3+1D Toric Code, and non-trivial extensions of topological symmetries by subsystem symmetries. Our work emphasizes the importance of topological symmetries in non-topological, geometric phases of matter. - oai:arXiv.org:2509.19440v2 + Non-Abelian Statistics for Bosonic Symmetry-Protected Topological Phases + https://arxiv.org/abs/2508.12444 + arXiv:2508.12444v4 Announce Type: replace-cross +Abstract: Symmetry-protected non-Abelian (SPNA) statistics opens new frontiers in quantum statistics and enriches the schemes for topological quantum computing. In this work, we propose a new paradigm of SPNA statistics in one-dimensional correlated bosonic symmetry-protected topological (SPT) phases and uncover exotic universal features from a systematic investigation. In particular, we show that for generic bosonic SPT phases described by real Hamiltonians, the SPNA statistics of topological zero modes fall into two distinct classes. The first class exhibits conventional braiding of hard-core bosonic zero modes. Furthermore, we discover a second class of unconventional braiding statistics characterized by a nonlinear transformation, featuring a fractionalization of the first class and reminiscent of the non-Abelian statistics of symmetry-protected Majorana pairs. The two distinct classes of statistics have topological origin in classifying non-Abelian Berry phases for braiding processes of real-Hamiltonian systems, distinguished by whether the holonomy involves a reflection operation. To illustrate, we focus on a specific bosonic SPT phase with particle-hole symmetry, and demonstrate that both classes of braiding statistics can be feasibly realized in a tri-junction with and without the aid of a controlled defect, respectively. Analytic and numerical results are given. We demonstrate how to encode logical qubits and implement both single- and two-qubit gates using the two classes of SPNA statistics. Finally, we propose feasible experimental schemes to observe these predictions and identify the parameter regimes for the high-fidelity braiding, paving the way for the experimental observation of our results in the near future. + oai:arXiv.org:2508.12444v4 cond-mat.str-el - hep-th - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace-cross - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Pranay Gorantla, Abhinav Prem, Nathanan Tantivasadakarn, Dominic J. Williamson - - - Transfer tensor analysis of localization in the Anderson and Aubry-Andr\'e-Harper models - https://arxiv.org/abs/2509.21374 - arXiv:2509.21374v2 Announce Type: replace-cross -Abstract: We use the transfer tensor method to analyze localization and transport in simple disordered systems, specifically the Anderson and Aubry-Andr\'e-Harper models. Emphasis is placed on the memory effects that emerge when ensemble-averaging over disorder, even when individual trajectories are strictly Markovian. We find that transfer tensor memory effects arise to remove fictitious terms that would correspond to redrawing static disorder at each time step, which would create a temporally uncorrelated dynamic disorder. Our results show that while eternal memory is a necessary condition for localization, it is not sufficient. We determine that signatures of localization and transport can be found within the transfer tensors themselves by defining a metric called "outgoing-pseudoflux". This work establishes connections between theoretical research on dynamical maps and Markovianity and localization phenomena in physically realizable model systems. - oai:arXiv.org:2509.21374v2 - cond-mat.dis-nn - physics.chem-ph - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace-cross - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Michelle C. Anderson, Chern Chuang - - - Slow dynamics from a nested hierarchy of frozen states - https://arxiv.org/abs/2510.03159 - arXiv:2510.03159v3 Announce Type: replace-cross -Abstract: We identify the mechanism of slow heterogeneous relaxation in quantum kinetically constrained models (KCMs) in which the potential energy strength is controlled by a coupling parameter. The regime of slow relaxation includes the large-coupling limit. By expanding around that limit, we reveal a \emph{nested hierarchy} of states that remain frozen on time scales determined by powers of the coupling. The classification of such states, together with the evolution of their Krylov complexity, reveals that these time scales are related to the distance between the sites where facilitated dynamics is allowed by the kinetic constraint. While correlations within frozen states relax slowly and exhibit metastable plateaus that persist on time scales set by powers of the coupling parameter, the correlations in the rest of the states decay rapidly. We compute the plateau heights of correlations across all frozen states up to second-order corrections in the inverse coupling. Our results explain slow relaxation in quantum KCMs and elucidate dynamical heterogeneity by relating the relaxation times to the spatial separations between the active regions. - oai:arXiv.org:2510.03159v3 - cond-mat.stat-mech - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace-cross - http://creativecommons.org/licenses/by/4.0/ - Vanja Mari\'c, Luka Paljk, Lenart Zadnik - - - Log-majorizations between quasi-geometric type means for matrices - https://arxiv.org/abs/2510.04691 - arXiv:2510.04691v3 Announce Type: replace-cross -Abstract: In this paper, for $\alpha\in(0,\infty)\setminus\{1\}$, $p>0$ and positive semidefinite matrices $A$ and $B$, we consider the quasi-extension $\mathcal{M}_{\alpha,p}(A,B):=\mathcal{M}_\alpha(A^p,B^p)^{1/p}$ of several $\alpha$-weighted geometric type matrix means $\mathcal{M}_\alpha(A,B)$ such as the $\alpha$-weighted geometric mean in Kubo--Ando's sense, the R\'enyi mean, etc. The log-majorization $\mathcal{M}_{\alpha,p}(A,B)\prec_{\log}\mathcal{N}_{\alpha,q}(A,B)$ is examined for pairs $(\mathcal{M},\mathcal{N})$ of those $\alpha$-weighted geometric type means. The joint concavity/convexity of the trace functions $\mathrm{Tr}\,\mathcal{M}_{\alpha,p}$ is also discussed based on theory of quantum divergences. - oai:arXiv.org:2510.04691v3 - math.FA - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace-cross - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - 10.1016/j.laa.2026.01.003 - Linear Algebra and its Applications 735 (2026), 123--174 - Fumio Hiai - - - When Abstraction Breaks Physics: Rethinking Modular Design in Quantum Software - https://arxiv.org/abs/2510.18557 - arXiv:2510.18557v2 Announce Type: replace-cross -Abstract: Abstraction is a fundamental principle in classical software engineering, which enables modularity, reusability, and scalability. However, quantum programs adhere to fundamentally different semantics, such as unitarity, entanglement, the no-cloning theorem, and the destructive nature of measurement, which introduce challenges to the safe use of classical abstraction mechanisms. This paper identifies a fundamental conflict in quantum software engineering: abstraction practices that are syntactically valid may violate the physical constraints of quantum computation. We present three classes of failure cases where naive abstraction breaks quantum semantics and propose a set of design principles for physically sound abstraction mechanisms. We further propose research directions, including quantum-specific type systems, effect annotations, and contract-based module design. Our goal is to initiate a systematic rethinking of abstraction in quantum software engineering, based on quantum semantics and considering engineering scalability. - oai:arXiv.org:2510.18557v2 - cs.SE - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace-cross - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Jianjun Zhao - - - Cosmological Entanglement Entropy from the von Neumann Algebra of Double-Scaled SYK & Its Connection with Krylov Complexity - https://arxiv.org/abs/2511.03779 - arXiv:2511.03779v2 Announce Type: replace-cross -Abstract: We investigate entanglement entropy between the pair of type II$_1$ algebras of the double-scaled SYK (DSSYK) model given a chord state, its holographic interpretation as generalized horizon entropy; particularly in the (anti-)de Sitter ((A)dS) space limits of the bulk dual; and its connection with Krylov complexity. The density matrices in this formalism are operators in the algebras, which are specified by the choice of global state; and there exists a trace to evaluate their von Neumann entropy since the algebras are commutants of each other, which leads to a notion of algebraic entanglement entropy. We match it in triple-scaling limits to an area computed through a Ryu-Takayanagi formula in (A)dS$_2$ space with entangling surfaces at the asymptotic timelike or spacelike boundaries respectively; providing a first-principles example of holographic entanglement entropy for (A)dS$_2$ space. This result reproduces the Bekenstein-Hawking and Gibbons-Hawking entropy formulas for specific entangling regions points, while it decreases for others. This construction does not display some of the puzzling features in dS holography. The entanglement entropy remains real-valued since the theory is unitary, and it depends on the Krylov spread complexity of the Hartle-Hawking state. At last, we discuss higher dimensional extensions. - oai:arXiv.org:2511.03779v2 - hep-th - gr-qc - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace-cross - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Sergio E. Aguilar-Gutierrez - - - Empirical Quantum Advantage in Constrained Optimization from Encoded Unitary Designs - https://arxiv.org/abs/2511.14296 - arXiv:2511.14296v3 Announce Type: replace-cross -Abstract: We introduce the Constraint-Enhanced Quantum Approximate Optimization Algorithm (CE-QAOA), a shallow, constraint-aware ansatz that operates inside the one-hot product space [n]^m, where m is the number of blocks and each block is initialized in an n-qubit W_n state. We give an ancilla-free, depth-optimal encoder that prepares W_n using n-1 two-qubit rotations per block, and a two-local block-XY mixer that preserves the one-hot manifold and has a constant spectral gap on the one-excitation sector. At the level of expressivity, we establish per-block controllability, implying approximate universality per block. At the level of distributional behavior, we show that, after natural block and symbol permutation twirls, shallow CE-QAOA realizes an encoded unitary 1-design and supports approximate second-moment (2-design) behavior; combined with a Paley-Zygmund argument, this yields finite-shot anticoncentration guarantees. - Algorithmically, we wrap constant-depth sampling with a deterministic feasibility checker to obtain a polynomial-time hybrid quantum-classical solver (PHQC) that returns the best observed feasible solution in O(S n^2) time, where S is a polynomial shot budget. We obtain two advantages. First, when CE-QAOA fixes r >= 1 locations different from the start city, we achieve a Theta(n^r) reduction in shot complexity even against a classical sampler that draws uniformly from the feasible set. Second, against a classical baseline restricted to raw bitstring sampling, we show an exp(Theta(n^2)) minimax separation. In noiseless circuit simulations of traveling salesman problem instances with n in {4,...,10} locations from the QOPTLib benchmark library, we recover the global optimum at depth p = 1 using polynomial shot budgets and coarse parameter grids defined by the problem size. - oai:arXiv.org:2511.14296v3 - cs.ET - cs.DM - math-ph - math.MP - physics.app-ph - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace-cross - http://creativecommons.org/licenses/by/4.0/ - Chinonso Onah, Roman Firt, Kristel Michielsen - - - Collective cluster nucleation dynamics in quantum magnets - https://arxiv.org/abs/2512.04656 - arXiv:2512.04656v3 Announce Type: replace-cross -Abstract: Strongly interacting many-body systems exhibit collective properties that emerge from complex correlations among microscopic degrees of freedom. These cooperative phenomena govern the non-equilibrium response of quantum systems, with relevance ranging from condensed matter physics to quantum field theories describing fundamental aspects of our universe. Understanding such emergent dynamics from first principles remains one of the central challenges in quantum many-body physics. Here we report on the observation of collective cluster nucleation dynamics following quenches in 2D ferromagnetic quantum Ising systems implemented in an atomic Rydberg array. Our experiments reveal two distinct regimes: In the confined regime, we observe an energy-dependent cluster size, revealing large collective clusters exceeding ten spins. In contrast, the deconfined regime is characterized by kinetically constrained, avalanche-like nucleation dynamics involving the entire system. Our findings establish a new frontier for quantum simulations with Rydberg arrays, enabling controlled exploration of non-equilibrium phenomena previously out of reach. Beyond advancing experimental capabilities, they provide fundamental insights into highly correlated processes with implications that reach from quantum magnetism and glassy dynamics to cosmological models of the early universe. - oai:arXiv.org:2512.04656v3 - cond-mat.quant-gas quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 + Fri, 23 Jan 2026 00:00:00 -0500 replace-cross http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Philip Osterholz, Fabio Bensch, Shuanghong Tang, Silpa Baburaj Sheela, Bj\"orn Sbierski, Igor Lesanovsky, Christian Gro{\ss} - - - Robust, fast, and efficient formation of stable tetratomic molecules from ultracold atoms via generalized stimulated Raman exact passage - https://arxiv.org/abs/2512.04681 - arXiv:2512.04681v4 Announce Type: replace-cross -Abstract: The study of the conversion of ultracold atoms into molecules has long remained a hot topic in atomic, molecular, and optical physics. However, most prior research has focused on diatomic molecules, with relatively scarce exploration of polyatomic molecules. Here we propose a two-step strategy for the formation of stable ultracold tetratomic molecules. We first suggest a generalized nonlinear stimulated Raman exact passage (STIREP) technique for the coherent conversion of ultracold atoms to tetratomic molecules, which is subsequently followed by a chainwise-STIREP technique to transfer the resulting molecules into a sufficiently stable ground state. Through systematic numerical analysis, we demonstrate that the proposed two-step strategy holds great potential for the robust, fast, and efficient formation of stable ultracold tetratomic molecules. - oai:arXiv.org:2512.04681v4 - cond-mat.quant-gas - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace-cross - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Jia-Hui Zhang, Wen-Yuan Wang, Fu-Quan Dou - - - Affine Symmetry and the Group-Theoretic Basis of the Unruh Effect - https://arxiv.org/abs/2512.22648 - arXiv:2512.22648v2 Announce Type: replace-cross -Abstract: A massless scalar field in two spacetime dimensions splits into two independent sectors of left and right-moving modes on the light cone. At the quantum level, these two sectors carry a representation of the group of affine transformations of the real line, with translations corresponding to transformations generated by light-cone momenta and dilations given by light-cone Rindler momenta formed by a linear combination of generators of boosts and dilations. One-particle states for inertial observers are eigenvectors of translation generators belonging to irreducible representations of the affine group. Rindler one-particle states are related to eigenfunctions of the generator of dilations. We show that simple manipulations connecting these two representations involving the Mellin transform can be used to derive the thermal spectrum of Rindler particles observed by an accelerated observer. Beyond providing a representation-theoretic basis for vacuum thermal effects, our results suggest that analogous phenomena may arise in any quantum system admitting realizations of translation and dilation eigenstates. - oai:arXiv.org:2512.22648v2 - hep-th - gr-qc - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace-cross - http://creativecommons.org/licenses/by/4.0/ - Michele Arzano, Alessandra D'Alise, Simone del Rosso, Domenico Frattulillo - - - Les Houches Lecture Notes on Tensor Networks - https://arxiv.org/abs/2512.24390 - arXiv:2512.24390v2 Announce Type: replace-cross -Abstract: Tensor networks provide a powerful new framework for classifying and simulating correlated and topological phases of quantum matter. Their central premise is that strongly correlated matter can only be understood by studying the underlying entanglement structure and its associated (generalised) symmetries. In essence, tensor networks provide a compressed, holographic description of the complicated vacuum fluctuations in strongly correlated systems, and as such they break down the infamous many-body exponential wall. These lecture notes provide a concise overview of the most important conceptual, computational and mathematical aspects of this theory. - oai:arXiv.org:2512.24390v2 - cond-mat.str-el - hep-th - math-ph - math.MP - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace-cross - http://creativecommons.org/licenses/by/4.0/ - Bram Vancraeynest-De Cuiper, Weronika Wiesiolek, Frank Verstraete - - - Collective behaviors of an electron gas in the mean-field regime - https://arxiv.org/abs/2512.24666 - arXiv:2512.24666v3 Announce Type: replace-cross -Abstract: In this paper, we study the momentum distribution of an electron gas in a $3$-dimensional torus. The goal is to compute the occupation number of Fourier modes for some trial state obtained through random phase approximation. We obtain the mean-field analogue of momentum distribution formulas for electron gas in [Daniel and Voskov, Phys. Rev. \textbf{120}, (1960)] in high density limit and [Lam, Phys. Rev. \textbf{3}, (1971)] at metallic density. The analysis in the present paper is majorly based on the work [Christiansen, Hainzl, Nam, Comm. Math. Phys. \textbf{401}, (2023)]. Our findings are related to recent results obtained independently by Benedikter, Lill and Naidu, and the analysis applies to a general class of singular potentials rather than just the Coulomb case. - oai:arXiv.org:2512.24666v3 - math-ph - math.MP - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace-cross - http://creativecommons.org/licenses/by/4.0/ - Dong Hao Ou Yang - - - Magnetically Induced Transparency-Absorption and Normal-Anomalous Dispersion Characteristics of ${}^{87}\text{Rb}$ Medium or Any J-Type Configuration Atomic Vapors Subject to a Vector Magnetic Field and a Weak Resonant Pump - https://arxiv.org/abs/2601.02113 - arXiv:2601.02113v3 Announce Type: replace-cross -Abstract: We have developed an analytical framework for magnetically induced transparency-absorption (MITA) and normal-anomalous dispersion (MINAD) in a weakly driven ${}^{87}\text{Rb}$ vapor, or any J-type three-level system, under a vector magnetic field. By solving the Bloch equations in the stationary, quasi-stationary, and short-pulse regimes, we obtained closed-form expressions for the atomic populations and coherences and identified a bifurcation in the oscillatory dynamics at zero longitudinal Zeeman splitting. The Fourier-domain analysis reveals alternating transparency/absorption and normal/anomalous dispersion with frequency-dependent sign reversals, enabling spectrally selective filtering and group-delay effects. Slow oscillatory behavior in the radio-frequency range makes the system suitable for weak magnetic-field sensing, while fast oscillations at optical frequencies suggest applications in spectral filtering and frequency-comb-like signal shaping. The results provide a theoretical basis for experimental observation of MITA/MINAD and for optimizing atomic-vapor platforms for precision magnetometry and related photonic functionalities. - oai:arXiv.org:2601.02113v3 - physics.atom-ph - physics.optics - quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 - replace-cross - http://creativecommons.org/licenses/by/4.0/ - Hayk L. Gevorgyan + Hong-Yu Wang, Bao-Zong Wang, Jian-Song Hong, Xiong-Jun Liu - Construction of asymptotic quantum many-body scar states in the SU($N$) Hubbard model - https://arxiv.org/abs/2601.04640 - arXiv:2601.04640v2 Announce Type: replace-cross -Abstract: We construct asymptotic quantum many-body scars (AQMBS) in one-dimensional SU($N$) Hubbard chains ($N\geq 3$) by embedding the scar subspace into an auxiliary Hilbert subspace $\mathcal{H}_P$ and identifying a parent Hamiltonian within it, together with a corresponding extension of the restricted spectrum-generating algebra to the multi-ladder case. Unlike previous applications of the parent-Hamiltonian scheme, we show that the parent Hamiltonian becomes the SU($N$) ferromagnetic Heisenberg model rather than the spin-1/2 case, so that its gapless magnons realize explicit AQMBS of the original model. Working in the doublon-holon subspace, we derive this mapping, obtain the one-magnon dispersion for periodic and open boundaries, and prove (i) orthogonality to the tower of scar states, (ii) vanishing energy variance in the thermodynamic limit, and (iii) subvolume entanglement entropy with rigorous MPS/MPO bounds. Our results broaden the parent-Hamiltonian family for AQMBS beyond spin-1/2 and provide analytic, low-entanglement excitations in SU($N$)-symmetric systems. - oai:arXiv.org:2601.04640v2 - cond-mat.stat-mech - cond-mat.quant-gas + TeMFpy: a Python library for converting fermionic mean-field states into tensor networks + https://arxiv.org/abs/2510.05227 + arXiv:2510.05227v2 Announce Type: replace-cross +Abstract: We introduce TeMFpy, a Python library for converting fermionic mean-field states to finite or infinite matrix product state (MPS) form. TeMFpy includes new, efficient, and easy-to-understand algorithms for both Slater determinants and Pfaffian states. Together with Gutzwiller projection, these also allow the user to build variational wave functions for various strongly correlated electron systems, such as quantum spin liquids. We present all implemented algorithms in detail and describe how they can be accessed through TeMFpy, including full example workflows. TeMFpy is built on top of TeNPy and, therefore, integrates seamlessly with existing MPS-based algorithms. + oai:arXiv.org:2510.05227v2 cond-mat.str-el + cond-mat.mes-hall + cond-mat.supr-con + physics.comp-ph quant-ph - Wed, 21 Jan 2026 00:00:00 -0500 + Fri, 23 Jan 2026 00:00:00 -0500 replace-cross http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Daiki Hashimoto, Masaya Kunimi, Tetsuro Nikuni + Simon H. Hille, Attila Szab\'o