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f3c8e5c0df23cab35c94a23e3da2eee5c785083e340af30d6de47196a9278a84
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2026-01-13T00:00:00-05:00
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Graphene-assisted resonant transmission and enhanced Goos-H\"{a}nchen shift in a frustrated total internal reflection configuration
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arXiv:2601.07010v1 Announce Type: new Abstract: Graphene-assisted resonant transmission and enhanced Goos-H\"{a}nchen shift are investigated in a two-prism frustrated-total-internal-reflection configuration. Due to the excitation of surface plasmons induced by graphene in low terahertz frequency range, there exist the resonant transmission and anomalous Goos-H\"{a}nchen shifts in such optical tunneling configuration. As compared to the case of quantum well, graphene sheet with unique optical properties can enhance the resonant transmission with relatively low loss, and modulate the large negative and positive Goos-H\"{a}nchen shifts by adjusting chemical potential or electron relaxation time. These intriguing phenomena may lead to some potential applications in graphene-based electro-optic devices.
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https://arxiv.org/abs/2601.07010
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Academic Papers
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fc7d2a683f63a7b0d8dac2c5ed149bf3c555fcc5bdf0455c0bad83084c8793f2
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2026-01-13T00:00:00-05:00
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Irreversibility of decorrelating processes: an experimental assessment in cavity QED
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arXiv:2601.07011v1 Announce Type: new Abstract: Entropy production quantifies the amount of irreversibility of a physical process, leading to fundamental bounds for thermodynamic quantities. Particularly in the quantum realm, considerable research has been carried out in the last decades extending entropy production to nonequilibrium processes. We experimentally investigate the entropy production of forward-backward cycles containing different decorrelating processes realized to erase different types of correlations between two interacting systems, from obliterating solely quantum coherence to completely decorrelating local states. We apply these processes to the entanglement of a two-level atom, realized with a circular Rydberg atom, and a light field of a high-quality microwave cavity. The entropy production is computed from the full quantum-state tomography of the system performed at different stages of the interaction-decorrelation sequence. Due to the quantum nature of the atom-cavity system, we find that, although standard, the maximum likelihood estimation method for the density matrix leads to spurious divergences of the entropy production. We propose and implement an alternative estimator that remedies such divergences. Our work experimentally assesses irreversibility of non-thermal processes and addresses the care that must be taken in handling experimental data to estimate the entropy production.
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https://arxiv.org/abs/2601.07011
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Academic Papers
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94b48a7a4559f3da385f828f3fa66b461d7676cf291bfd59a254349380405d88
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2026-01-13T00:00:00-05:00
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Stochastic phase-space simulation of multimode cat states via the positive-P representation
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arXiv:2601.07049v1 Announce Type: new Abstract: We present a comprehensive study of the transient dynamics of multimode Schr\"odinger cat states in dissipatively coupled resonator arrays using the positive-P phase-space method. By employing the positive-P representation, we derive the exact stochastic differential equations governing the system's dynamics, enabling the simulation of system sizes significantly larger than those accessible via direct master equation simulation. We demonstrate the utility of this method by simulating transient dynamics for networks up to N=21 sites. Furthermore, we critically examine the method's usefulness and limitations, specifically highlighting the computational instability encountered when estimating the state parity in the systems. Our results provide a pathway for scalable simulations of non-Gaussian states in large open quantum systems.
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https://arxiv.org/abs/2601.07049
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Academic Papers
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c2dbe1b6683b0ac6a9d9b89ce1a1b2f5f34076380d631c88a5060bf8a02a64ac
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2026-01-13T00:00:00-05:00
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Nonadiabatic theory for subcycle ionic dynamics in multielectron tunneling ionization
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arXiv:2601.07050v1 Announce Type: new Abstract: Multielectron tunneling ionization creates ionic coherence crucial for lasing and driving electron motion in molecules. While tunneling is well understood as a single active electron process, less emphasis has been placed on theoretical descriptions of bound electrons during tunneling. This work systematically investigates multielectron tunneling ionization based on the strong field approximation, establishing a theoretical foundation and demonstrating the equivalence of wave function and density matrix approaches for subcycle ionic dynamics. An accurate subcycle nonadiabatic ionization rate is also derived and incorporated into the theory to improve its quantitative accuracy. Applying the theory to N$_{2}$ and CO$_{2}$, this work showcases how an intense laser field can induce ionic coherence in molecules as observed in previous experiments. These findings encourage future investigations into multielectron tunneling ionization and its applications in lasing and in controlling chemical reactions.
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https://arxiv.org/abs/2601.07050
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Academic Papers
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7d273e1867ac2a8000d63c3370574475e0b757cfc29a5fad1f63ab842dedb4e0
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2026-01-13T00:00:00-05:00
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Composable Verification in the Circuit-Model via Magic-Blindness
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arXiv:2601.07111v1 Announce Type: new Abstract: As quantum computing machines move towards the utility regime, it is essential that users are able to verify their delegated quantum computations with security guarantees that are (i) robust to noise, (ii) composable with other secure protocols, and (iii) exponentially stronger as the number of resources dedicated to security increases. Previous works that achieve these guarantees and provide modularity necessary to optimization of protocols to real-world hardware are most often expressed in the Measurement-Based Quantum Computation (MBQC) model. This leaves architectures based on the circuit model -- in particular those using the Magic State Injection (MSI) -- with fewer options to verify their computations or with the need to compile their circuits in MBQC leading to overheads. This paper introduces a family of noise robust, composable and efficient verification protocols for Clifford + MSI circuits that are secure against arbitrary malicious behavior. This family contains the verification protocol of Broadbent (ToC, 2018), extends its security guarantees while also bridging the modularity gap between MBQC and circuit-based protocols, and reducing quantum communication costs. As a result, it opens the prospect of rapid implementation for near-term quantum devices. Our technique is based on a refined notion of blindness, called magic-blindness, which hides only the injected magic states -- the sole source of non-Clifford computational power. This enables verification by randomly interleaving computation rounds with classically simulable, magic-free test rounds, leading to a trap-based framework for verification. As a result, circuit-based quantum verification attains the same level of security and robustness previously known only in MBQC. It also optimizes the quantum communication cost as transmitted qubits are required only at the locations of state injection.
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https://arxiv.org/abs/2601.07111
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Academic Papers
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a677608bec8318b44cb2b59460cced8e1b556c1be15101c3c8071af5a6e5480f
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2026-01-13T00:00:00-05:00
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Strong coupling of virtual negative states in the Kapitza-Dirac effect
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arXiv:2601.07157v1 Announce Type: new Abstract: Negative states are an intrinsic property of relativistic quantum theory and related to anti-particles in the context of the Dirac sea concept. We show that negative states can dominantly contribute to the diffraction amplitude in the quantum dynamics of the two-photon Kapitza-Dirac effect. We draw our conclusion by investigating solutions from time-dependent perturbation theory, where the perturbative solutions are in match with numeric solutions of the relativistic quantum system and also with the numeric and analytic solutions from the relativistic equations of motion of a classical point-like electron in an external standing wave light field. While our numeric solutions assume a strong laser field, the analytic solutions indicate that negative state coupling remains dominant for arbitrary low field amplitudes, where in the single-photon case (Compton scattering) negative state coupling can be mathematically associated with the interaction of a virtual electron-positron pair in the context of a quantized theory in old-fashioned perturbation theory.
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https://arxiv.org/abs/2601.07157
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c4726e250ff1ed32d98f574660d4e427b85469266d45ec026b32547ccb524a61
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2026-01-13T00:00:00-05:00
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Direct temperature readout in nonequilibrium quantum thermometry
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arXiv:2601.07198v1 Announce Type: new 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.
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https://arxiv.org/abs/2601.07198
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Academic Papers
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9cf417c4733c953558f595e6ab53ec6314df8fce5d51dc9477cfe5876ae3bc43
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2026-01-13T00:00:00-05:00
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Quantum-Compatible Dictionary Learning via Doubly Sparse Models
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arXiv:2601.07210v1 Announce Type: new Abstract: Dictionary learning (DL) is a core tool in signal processing and machine learning for discovering sparse representations of data. In contrast with classical successes, there is currently no practical quantum dictionary learning algorithm. We argue that this absence stems from structural mismatches between classical DL formulations and the operational constraints of quantum computing. We identify the fundamental bottlenecks that prevent efficient quantum realization of classical DL and show how a structurally restricted model, doubly sparse dictionary learning (DSDL), naturally avoids these problems. We present a simple, hybrid quantum-classical algorithm based on projection-based randomized Kaczmarz iterations with Qiskit-compatible quantum inner products. We outline practical considerations and share an open-source implementation at https://github.com/AngshulMajumdar/quantum-dsdl-kaczmarz. The goal is not to claim exponential speedups, but to realign dictionary learning with the realities of near-term quantum devices.
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https://arxiv.org/abs/2601.07210
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Academic Papers
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14c91c387c7e543f6eb4ad2678d38b700458121c259fef38acdbc4eac069762f
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2026-01-13T00:00:00-05:00
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Quantum Error Correction and Detection for Quantum Machine Learning
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arXiv:2601.07223v1 Announce Type: new Abstract: At the intersection of quantum computing and machine learning, quantum machine learning (QML) is poised to revolutionize artificial intelligence. However, the vulnerability of the current generation of quantum computers to noise and computational error poses a significant barrier to this vision. Whilst quantum error correction (QEC) offers a promising solution for almost any type of hardware noise, its application requires millions of qubits to encode even a simple logical algorithm, rendering it impractical in the near term. In this chapter, we examine strategies for integrating QEC and quantum error detection (QED) into QML under realistic resource constraints. We first quantify the resource demands of fully error-corrected QML and propose a partial QEC approach that reduces overhead while enabling error correction. We then demonstrate the application of a simple QED method, evaluating its impact on QML performance and highlighting challenges we have yet to overcome before we achieve fully fault-tolerant QML.
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https://arxiv.org/abs/2601.07223
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ee7f1c731124132493b1de905a29341becdfb1f15c8568030bf64e2bfdf3c8fa
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2026-01-13T00:00:00-05:00
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Reply to Comment on "Properties and dynamics of generalized squeezed states"
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arXiv:2601.07227v1 Announce Type: new Abstract: In our paper [1], our numerical simulations showed that, unlike displacement and conventional squeezing, higher-order squeezing exhibits oscillatory dynamics. Subsequently, Gordillo and Puebla pointed out that simulation results depend on whether the state space in the simulations is even or odd [2]. Using additional derivations, they argued that the oscillatory dynamics is unphysical and that the photon number must increase monotonically as a function of the squeezing parameter $r$. We agree with the observation of an even-odd parity dependence in the simulations. We independently noticed the same feature in our simulations after the publication of Ref. [1]. This observation led us to perform a more detailed investigation of the numerical simulation and mathematical aspects of the generalized squeezing problem. Our new findings were reported in Ref. [3]. Further analysis was reported in Ref. [4]. Our conclusion is that the generalized squeezing operator is physically not well defined but can be made well defined when combined with additional information about the physical system under study. We demonstrated this point in the case where we include an additional nonlinear interaction term in the Hamiltonian. We disagree with the claim that the photon number must be a monotonically increasing function of $r$. This claim contradicts the mathematically rigorous results of Ref. [4]. Furthermore, we show that the oscillatory behaviour persists in two closely related, well-behaved models.
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https://arxiv.org/abs/2601.07227
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ad43786876b4fed36cc22fddf658a43ee8365783a8afcb6cdafcd18d8e364add
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2026-01-13T00:00:00-05:00
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Fault-tolerant modular quantum computing with surface codes using single-shot emission-based hardware
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arXiv:2601.07241v1 Announce Type: new Abstract: Fault-tolerant modular quantum computing requires stabilizer measurements across the modules in a quantum network. For this, entangled states of high quality and rate must be distributed. Currently, two main types of entanglement distribution protocols exist, namely emission-based and scattering-based, each with its own advantages and drawbacks. On the one hand, scattering-based protocols with cavities or waveguides are fast but demand stringent hardware such as high-efficiency integrated circulators or strong waveguide coupling. On the other hand, emission-based platforms are experimentally feasible but so far rely on Bell-pair fusion with extensive use of slow two-qubit memory gates, limiting thresholds to $\approx 0.16\%$. Here, we consider a fully distributed surface code using emission-based entanglement schemes that generate GHZ states in a single shot, i.e., without the need for Bell-pair fusions. We show that our optical setup produces Bell pairs, W states, and GHZ states, enabling both memory-based and optical protocols for distilling high-fidelity GHZ states with significantly improved success rates. Furthermore, we introduce protocols that completely eliminate the need for memory-based two-qubit gates, achieving thresholds of $\approx 0.19\%$ with modest hardware enhancements, increasing to above $\approx 0.24\%$ with photon-number-resolving detectors. These results show the feasibility of emission-based architectures for scalable fault-tolerant operation.
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https://arxiv.org/abs/2601.07241
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Academic Papers
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d8a246efdb92cf2fbf84b3319e83e07d0d925b39fc91121b9a814f0053106c78
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2026-01-13T00:00:00-05:00
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Impact of Boundary Conditions on the Double-Kicked Quantum Rotor
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arXiv:2601.07339v1 Announce Type: new Abstract: We study the on-resonance Spin-1/2 Double Kicked Rotor, a periodically driven quantum system that hosts topological phases. Motivated by experimental constraints, we analyze the effects of open and periodic boundary conditions in contrast to the idealized case of infinite momentum space. As a bulk probe for topological invariants, we focus on the Mean Chiral Displacement (MCD) and show that it exhibits a pronounced sensitivity to boundary conditions, which can be traced to the dynamics in momentum space. Under open boundaries, states that would otherwise extend freely become localized at the edges of the finite momentum space, forming quasienergy edge states. While the bulk response measured by the MCD is strongly affected once the evolving wave packet reaches the boundaries, the persistence of these edge states still reflects the bulk-edge correspondence and provides reliable signatures of topological transitions.
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https://arxiv.org/abs/2601.07339
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7b5437ebb603b07dff4fd05bf673fe1f92070086cac902b293c7613f4418289a
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2026-01-13T00:00:00-05:00
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Scalable Certification of Entanglement in Quantum Networks
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arXiv:2601.07427v1 Announce Type: new Abstract: Quantum networks form the backbone of long-distance quantum information processing. Genuine multipartite entanglement (GME) serves as a key indicator of network performance and overall state quality. However, the widely used methods for certifying GME suffer from a major drawback that they either detect only a limited range of states or are applicable only to systems with a small number of parties. To overcome these limitations, we propose a family of sub-symmetric witnesses (SSWs), which are tractable both theoretically and experimentally. Analytically, we establish a connection between SSWs and the cut space of graph theory, enabling several powerful detection criteria tailored to practical quantum networks. Numerically, we show that the optimal detection can be formulated as a linear program, offering a significant efficiency advantage over the semidefinite programs commonly employed in quantum certification. Experimentally, SSWs can be evaluated via local measurements, with resource requirements independent of the local dimension in general, and even independent of the overall network size in many practical networks.
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https://arxiv.org/abs/2601.07427
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Academic Papers
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dffff77e88e23b0e5ffea0737c141a902375017724d890cc1284d837c57982a0
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2026-01-13T00:00:00-05:00
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Einstein's Worries and Actual Physics: Beyond Pilot Waves
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arXiv:2601.07441v1 Announce Type: new Abstract: Tim Maudlin has argued that the standard formulation of quantum mechanics fails to provide a clear ontology and dynamics and that the de Broglie--Bohm pilot-wave theory offers a better completion of the formalism, more in line with Einstein's concerns. I suggest that while Bohmian mechanics improves on textbook quantum theory, it does not go far enough. In particular, it relies on the ``quantum equilibrium hypothesis'' and accepts explicit nonlocality as fundamental. A deeper completion is available in stochastic mechanics, where the wavefunction and the Born rule emerge from an underlying diffusion process, and in a contextual, category-theoretic semantics in which measurement and EPR--Bell correlations are reinterpreted as features of contextual truth rather than of mysterious dynamics. In this framework, the measurement problem and ``spooky action-at-a-distance'' are dissolved rather than solved. Finally, a dynamics based on Rosen's ``classical Schr\"odinger equation'' provides a continuous passage between quantum and classical regimes, eliminating any sharp Heisenberg cut.
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https://arxiv.org/abs/2601.07441
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Academic Papers
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d3406eabf9e56d542e7141939f21054c2504fcc7ec90dc28926481b4cff827ce
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2026-01-13T00:00:00-05:00
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Thermodynamic Recycling in Quantum Computing: Demonstration Using the Harrow-Hassidim-Lloyd Algorithm and Information Erasure
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arXiv:2601.07522v1 Announce Type: new Abstract: Branch selection, including postselection, is a standard method for implementing nonunitary transformations in quantum algorithms. Conventionally, states associated with unsuccessful branches are discarded and treated as useless. Here we propose a generic framework that reuses these failure branches as thermodynamic resources. The central element is an athermal bath that is naturally generated during the reset of a failure branch. By coupling this bath to a target system prior to relaxation, useful thermodynamic tasks can be performed, enabling performance beyond conventional thermodynamic limits. As an application, we analyze information erasure and derive the resulting gain analytically. We further demonstrate the framework by implementing the Harrow-Hassidim-Lloyd algorithm on IBM's superconducting quantum processor. Despite substantial noise and errors in current hardware, our method achieves erasure with heat dissipation below the Landauer limit. These results establish a practical connection between quantum computing and quantum thermodynamics and suggest a route toward reducing thermodynamic costs in future large-scale quantum computers.
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https://arxiv.org/abs/2601.07522
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Academic Papers
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27d654184ccd2661ecf963d1ec61317d7c3d4d62b755ba7bba7e3d0b7b3bf9bf
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2026-01-13T00:00:00-05:00
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Hardware-Economic Manipulation of Dual-Type ${}^{171}$Yb$^+$ Qubits
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arXiv:2601.07529v1 Announce Type: new Abstract: The dual-type qubit scheme is an emerging method to suppress crosstalk errors in scalable trapped-ion quantum computation and quantum network. Here we report a hardware-economic way to control dual-type $^{171}\mathrm{Yb}^+$ qubits using a single $355\,$nm mode-locked pulsed laser. Utilizing its broad frequency comb structure, we drive the Raman transitions of both qubit types encoded in the $S_{1/2}$ and the $F_{7/2}$ hyperfine levels, and probe their carrier transitions and the motional sidebands. We further demonstrate a direct entangling gate between the two qubit types. Our work can simplify the manipulation of the $^{171}\mathrm{Yb}^+$ qubits both at the hardware and the software level.
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https://arxiv.org/abs/2601.07529
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Academic Papers
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e246339bda2c8423dba6216eb3c199c715aa8eff1ab749abd308429795cbdb89
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2026-01-13T00:00:00-05:00
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Quasi-optimal quantum Markov chain spectral gap estimation
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arXiv:2601.07601v1 Announce Type: new Abstract: This paper proposes a quantum algorithm for Markov chain spectral gap estimation that is quasi-optimal (i.e., optimal up to a polylogarithmic factor) in the number of vertices for all parameters, and additionally quasi-optimal in the reciprocal of the spectral gap itself, if the permitted relative error is above some critical value. In particular, these results constitute an almost quadratic advantage over the best-possible classical algorithm. Our algorithm also improves on the quantum state of the art, and we contend that this is not just theoretically interesting but also potentially practically impactful in real-world applications: knowing a Markov chain's spectral gap can speed-up sampling in Markov chain Monte Carlo. Our approach uses the quantum singular value transformation, and as a result we also develop some theory around block-encoding Markov chain transition matrices, which is potentially of independent interest. In particular, we introduce explicit block-encoding methods for the transition matrices of two algebraically-defined classes of Markov chains.
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https://arxiv.org/abs/2601.07601
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2a594dc61ade5b3acb9ae5942302462ced7764bbeaa8a9fe70c0a85f3ea4e57c
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2026-01-13T00:00:00-05:00
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On the Lifshitz formula of dispersion interaction
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arXiv:2601.07661v1 Announce Type: new Abstract: The Lifshitz formula and methods of its preparation in the literature are considered. It is shown that in Lifshitz's work itself, this formula is given without a consistent conclusion. Moreover, the approach to the conclusion proposed in this work does not allow us to obtain it. The most general conclusion of this formula can be the method proposed by Levin and Rytov, the variation method of Schwinger and the method proposed by Van Kampen and co-authors. The Levin and Rytov approach is applicable in principle to bodies of arbitrary shape if the diffraction loss fields for electric and magnetic dipoles are determined, while the Van Kampen approach is applicable to any plane-layered structure and is quite simple. It is enough to write down the dispersion equations of the plasmon-polaritone structure. The specific dispersion force for a number of structures is calculated based on the Van Kampen method. It is shown that at small gaps, the force (pressure) density changes the inverse fourth-degree dependence on the distance and practically ceases to depend on it at distances less than 1 nm. For thin identical plates, this density is proportional to the square of their thickness at such distances, but the dependence quickly becomes saturated and already at thicknesses of the order of 10 nm practically ceases to depend on it.
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https://arxiv.org/abs/2601.07661
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Academic Papers
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00ddd72ecc087a4c3f645ef3ac82ae441d9380899a1b9a9e6d671b204ecbcf51
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2026-01-13T00:00:00-05:00
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Bright Source of High-Dimensional Temporal Entanglement
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arXiv:2601.07678v1 Announce Type: new Abstract: High-dimensional entanglement is considered to hold great potential for quantum key distribution (QKD) in high-loss and -noise scenarios. To harness its robustness, we construct a source for high-dimensional time-bin entangled photons optimized for high brightness, low complexity, and long-term stability. We certify the generated high-dimensional entanglement with a new witness employing nested Franson interferometry. Finally, we obtain key rates using a novel, noise-resilient QKD protocol. Our flexible evaluation method, centered around discretizations of the time stream, enables the same dataset to be processed while varying parameters such as state dimensionality and time bin length, allowing optimization of performance under given environmental conditions. Our results indicate regions within the accessible parameter space where high key rates per time are achievable for dimensionalities larger than two.
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https://arxiv.org/abs/2601.07678
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41aa40642e08ced222a398f4e0ac29ecbed9d222288d6e8f1ff7c9045e3e3517
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2026-01-13T00:00:00-05:00
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A unified framework for Bell inequalities from continuous-variable contextuality
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arXiv:2601.07686v1 Announce Type: new Abstract: Although the original EPR paradox was formulated in terms of position and momentum, most studies of these phenomena have focused on measurement scenarios with only a discrete number of possible measurement outcomes. Here, we present a framework for studying non-locality that is agnostic to the dimension of the physical systems involved, allowing us to probe purely continuous-variable, discrete-variable, or hybrid non-locality. Our approach allows us to find the optimal Bell inequality for any given measurement scenario and quantifies the amount of non-locality that is present in measurement statistics. This formalism unifies the existing literature on continuous-variable non-locality and allows us to identify new states in which Bell non-locality can be probed through homodyne detection. Notably, we find the first example of continuous-variable non-locality that cannot be mapped to a CHSH Bell inequality. Moreover, we provide several examples of simple hybrid DV-CV entangled states that could lead to near-term violation of Bell inequalities.
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https://arxiv.org/abs/2601.07686
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c9cc98dbb4c5203ebbbae7b76bc6665c57b16c24f95b44acfdf192c4a287288d
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2026-01-13T00:00:00-05:00
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Non Markovian Corrections to Tegmark's Decoherence Bound in Biological Media
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arXiv:2601.07689v1 Announce Type: new Abstract: Tegmark's widely cited bound on decoherence times in biological systems is derived under the assumption of a delta correlated, memoryless environment. In this work we show that any finite environmental memory universally induces quadratic short time decoherence, in validating the exponential decay law at early times. For an Ornstein Uhlenbeck environment we derive a closed non markovian expression for the coherence dynamics and obtain a de-coherence time that scales as the square root of the bath correlation time. In the singular limit of vanishing bath memory our result reduces exactly to Tegmark's bound. Numerical simulations based on an exact pseudomode mapping confirm the predicted scaling. These findings demonstrate that Tegmark's result applies only in the Markovian limit and does not rule out mesoscopic quantum coherence in structured biological media.
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https://arxiv.org/abs/2601.07689
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f93b603ed87d2475c5732cad9b51bff45b53800ed88cbf3fc7928dcd7cb03269
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2026-01-13T00:00:00-05:00
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TrackHHL: The 1-Bit Quantum Filter for particle trajectory reconstruction
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arXiv:2601.07766v1 Announce Type: new Abstract: The transition to the High-Luminosity Large Hadron Collider (HL-LHC) presents a computational challenge where particle reconstruction complexity may outpace classical computing resources. While quantum computing offers potential speedups, standard algorithms like Harrow-Hassidim-Lloyd (HHL) require prohibitive circuit depths for near-term hardware. Here, we introduce the 1-Bit Quantum Filter, a domain-specific adaptation of HHL that reformulates tracking from matrix inversion to binary ground-state filtering. By replacing high-precision phase estimation with a single-ancilla spectral threshold and exploiting the Hamiltonian's sparsity, we achieve an asymptotic gate complexity of $O(\sqrt{N} \log N)$, given Hamiltonian dimension $N$. We validate this approach by simulating LHCb Vertex Locator events with a toy model, and benchmark performance using the noise models of Quantinuum H2 trapped-ion and IBM Heron superconducting processors. This work establishes a resource-efficient track reconstruction method capable of solving realistic event topologies on noise-free simulators and smaller tracking scenarios within the current constraints of the Noisy Intermediate Scale Quantum (NISQ) era.
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https://arxiv.org/abs/2601.07766
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f27d8a9f8cec1022587c527d800df1ddde798edfc3a369a29f0f1d5e187a65b4
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2026-01-13T00:00:00-05:00
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Disorder enhanced transport as a general feature of long-range hopping models
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arXiv:2601.07787v1 Announce Type: new Abstract: We analyze the interplay of disorder and long-range hopping in a paradigmatic one dimensional model of quantum transport. While typically the current is expected to decrease as the disorder strength increases due to localization effects, in systems with infinite range hopping it was shown in Chavez et al, Phys. Rev. Lett. 126, 153201 (2021), that the current can increase with disorder in the Disorder-Enhanced-Transport (DET) regime. Here, by analyzing models with variable hopping range decaying as $1/r^{\alpha}$ with the distance $r$ among the sites, we show that the DET regime is a general feature of long-range hopping systems and it occurs, not only in the strong long-range limit $\alpha<1$ but even for weak long-range $1 \le \alpha \le 3$. Specifically, we show that, after an initial decrease, the current grows with the disorder strength until it reaches a local maximum. Both disorder thresholds at which the DET regime starts and ends are determined. Our results open the path to understand the effect of disorder on transport in many realistic systems where long range hopping is present.
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https://arxiv.org/abs/2601.07787
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5f837d2206e9cb8b0a6d4b8dad7c2b2a0ac85d7140bdee49646b25b1642ca1b0
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2026-01-13T00:00:00-05:00
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Computing quantum magic of state vectors
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arXiv:2601.07824v1 Announce Type: new Abstract: Non-stabilizerness, also known as ``magic,'' quantifies how far a quantum state departs from the stabilizer set. It is a central resource behind quantum advantage and a useful probe of the complexity of many-body quantum states. Yet standard magic quantifiers, such as the stabilizer R\'enyi entropy (SRE) for qubits and the mana for qutrits, are costly to evaluate numerically, with the computational complexity growing rapidly with the number $N$ of qudits. Here we introduce efficient, numerically exact algorithms that exploit the fast Hadamard transform to compute the SRE for qubits ($d=2$) and the mana for qutrits ($d=3$) for pure states given as state vectors. Our methods reduce the runtime to $O(N d^{2N})$, an exponential improvement over the naive $O(d^{3N})$ scaling, while exposing substantial parallelism and enabling GPU acceleration. We further show how to combine the fast Hadamard transform with Monte Carlo sampling to estimate the SRE of state vectors, and we extend the approach to compute the mana of mixed states. All algorithms are implemented in the open-source Julia package HadaMAG.jl, which provides a high-performance, GPU-enabled toolbox for computing SRE and mana. The package, together with the methods developed in this work, offers a practical route to large-scale numerical studies of magic in quantum many-body systems.
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https://arxiv.org/abs/2601.07824
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ac86f11c7b2a2825b216a38bda311b1762425bc8e9628945367425646106cde4
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2026-01-13T00:00:00-05:00
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Mechanical Resonator-based Quantum Computing
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arXiv:2601.07825v1 Announce Type: new Abstract: Hybrid quantum systems combine the unique advantages of different physical platforms with the goal of realizing more powerful and practical quantum information processing devices. Mechanical systems, such as bulk acoustic wave resonators, feature a large number of highly coherent harmonic modes in a compact footprint, which complements the strong nonlinearities and fast operation times of superconducting quantum circuits. Here, we demonstrate an architecture for mechanical resonator-based quantum computing, in which a superconducting qubit is used to perform quantum gates on a collection of mechanical modes. We show the implementation of a universal gate set, composed of single-qubit gates and controlled arbitrary-phase gates, and showcase their use in the quantum Fourier transform and quantum period finding algorithms. These results pave the way toward using mechanical systems to build crucial components for future quantum technologies, such as quantum random-access memories.
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https://arxiv.org/abs/2601.07825
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59e1e192a81dad9f5981ff121c9df7dd4e3d43bd03e1bb86e4cc8b6a58fbb625
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2026-01-13T00:00:00-05:00
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The resource theory of causal influence and knowledge of causal influence
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arXiv:2512.11209v2 Announce Type: cross Abstract: Understanding and quantifying causal relationships between variables is essential for reasoning about the physical world. In this work, we develop a resource-theoretic framework to do so. Here, we focus on the simplest nontrivial setting -- two variables that are causally ordered, meaning that the first has the potential to influence the second, without hidden confounding. First, we introduce the resource theory that directly quantifies causal influence of a functional dependence in this setting and show that the problem of deciding convertibility of resources and identifying a complete set of monotones has a relatively straightforward solution. Following this, we introduce the resource theory that arises naturally when one has uncertainty about the functional dependence. We describe a linear program for deciding the question of whether one resource (i.e., state of knowledge about the functional dependence) can be converted to another. Then, we focus on the case where the variables are binary. In this case, we identify a triple of monotones that are complete in the sense that they capture the partial order over the set of all resources, and we provide an interpretation of each.
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https://arxiv.org/abs/2512.11209
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d9a7f1c2692d6e1885303116f16c73aa1916ed69774e8efc39940e66e5a5153c
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2026-01-13T00:00:00-05:00
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Emission of time-ordered photon pairs from a single polaritonic Bogoliubov mode
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arXiv:2601.06468v1 Announce Type: cross Abstract: In many-body quantum systems, interactions drive the emergence of correlations that are at the heart of the most intriguing states of matter. A remarkable example is the case of weakly interacting bosonic systems, whose ground state is a squeezed vacuum state, and whose elementary excitations have a collective nature. In this work, we report on the direct observation of the peculiar microscopic quantum structure of these elementary excitations. We perform time- and frequency-resolved two-photon correlation measurements on the fluctuations of weakly interacting polaritons in a resonantly-driven microcavity, and observe that upon decreasing the average number of fluctuation quanta below unity, large pair correlations build up together with strong time-ordering of the emitted photons. This behavior is a direct signature of the particle-hole quantum superposition which is at the heart of Bogoliubov excitations.
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https://arxiv.org/abs/2601.06468
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e6ecb1bc3b38df5ff29f32c6cae84076d74a6e4ef2def91baa2cbb226fa855d9
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2026-01-13T00:00:00-05:00
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Anisotropic anomalous Hall effect in distorted kagome GdTi3Bi4
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arXiv:2601.07578v1 Announce Type: cross Abstract: Topological kagome magnets offer a rich landscape for exploring the intricate interplay of quantum interactions among geometry, topology, spin, and correlation. GdTi3Bi4 crystallizes in layered Ti based kagome nets intertwined with zigzag Gd chains along the a axis and orders antiferromagnetically below 15 K. Here, we present the temperature and field dependent electrical transport of GdTi3Bi4 in different directions. The material exhibits anomalous Hall conductivity (AHC) of 410 S cm-1 at 2 K for B parallel c and it is completely absent for B parallel a, despite the similar magnetization observed in both orientations. This behavior is quite contradictory, as anomalous Hall effect (AHE) typically scales with the magnetization. Through first principles calculations, it is demonstrated that in the presence of time reversal symmetry broken by the Gd 4f sublattice and spin orbit coupling, the magnetization direction controls the orbital mixing in the Ti t2g bands, relocating Berry curvature hot spots and producing the observed orientation selective AHC. The results establish GdTi3Bi4 as platform for investigating new avenues of AHE, such as directional AHE, and thus shed new light on the intricate coupling between magnetic and electronic structures, paving the way for exploring novel quantum phenomena.
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https://arxiv.org/abs/2601.07578
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79743dbb2644f53879c36a7fc6900f5c048ff59d7bbd8a93bb3ee082d9b34cca
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2026-01-13T00:00:00-05:00
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From coherent to fermionized microwave photons in a superconducting transmission line
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arXiv:2601.07659v1 Announce Type: cross Abstract: We investigate superconducting transmission lines as a novel platform for realizing a quantum fluid of microwave photons in a propagating geometry. We predict that the strong photon-photon interactions provided by the intrinsic nonlinearity of Josephson junctions are sufficient to enter a regime of strongly interacting photons for realistic parameters. A suitable tapering of the transmission line parameters allows for the adiabatic conversion of an incident coherent field into a Tonks-Girardeau gas of fermionized photons close to its ground state. Signatures of the strong correlations are anticipated in the correlation properties of the transmitted light.
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https://arxiv.org/abs/2601.07659
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e265bf3b5e53ea27a4e916518997ce9815061da2d2578b2d7f9f3b08eee95f2f
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2026-01-13T00:00:00-05:00
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Phase transition, phase separation and mode softening of a two-component Bose-Einstein condensate in an optical cavity
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arXiv:2601.07772v1 Announce Type: cross Abstract: We investigate the superradiant phase transition in a two-component Bose-Einstein condensate with distinct atomic detunings, confined in an optical cavity and driven by a transverse pump laser. By combining perturbation theory and numerical simulations, we demonstrate that the phase transition is dominated by the red-detuned component, resulting in a phase diagram completely different from that of a single-component case under blue-detuned condition. The system exhibits spontaneous phase separation between the two components, manifested as alternating stripe patterns in the normal phase and distinct Bragg gratings in the superradiant phase. Furthermore, the Bogoliubov excitation spectrum reveals roton-type mode softening, indicating that the phase transition also corresponds to the superfluid-to-lattice supersolid transition. Our findings provide insights into the interplay between atomic detunings and collective quantum many-body phenomena, offering potential applications in quantum simulation and optical switching technologies.
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https://arxiv.org/abs/2601.07772
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1cdd06086c961cce5ba5f26423d9f5ab8f4fc9c1784048ddf7e3d626a2a528b5
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2026-01-13T00:00:00-05:00
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Theory-independent randomness generation from spatial symmetries
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arXiv:2210.14811v4 Announce Type: replace Abstract: We demonstrate a fundamental relation between the structures of physical space and of quantum theory: the set of quantum correlations in a rotational prepare-and-measure scenario can be derived from covariance alone, without assuming quantum physics. To show this, we consider a semi-device-independent randomness generation scheme where one of two spatial rotations is performed on an otherwise uncharacterized preparation device, and one of two possible measurement outcomes is subsequently obtained. An upper bound on a theory-independent notion of spin is assumed for the transmitted physical system. It turns out that this determines the set of quantum correlations and the amount of certifiable randomness in this setup exactly. Interestingly, this yields the basis of a theory-independent protocol for the secure generation of random numbers. Our results support the conjecture that the symmetries of space and time determine at least part of the probabilistic structure of quantum theory.
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https://arxiv.org/abs/2210.14811
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3b529a5606b36dbf14aade5e664a122e1a274c685b91bc303db3a838dbec7afa
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2026-01-13T00:00:00-05:00
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Efficient Lattice Hamiltonian Encoding for the Shortest Vector Problem
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arXiv:2307.12047v2 Announce Type: replace Abstract: The advent of quantum computing necessitates the transition of worldwide cryptosystems to post-quantum cryptography (PQC), which is founded upon the problem of finding short vectors in high-dimensional structured lattices. It is assumed that the structure of these lattices cannot be exploited by quantum or classical algorithms attempting to find short vectors. In this work, we focus on the structure of the lattices used in PQC protocols - nega-cyclic (and cyclic)lattices - and provide a quantum algorithmic framework that efficiently encodes the structured lattices into Hamiltonians by exploiting their underlying symmetries. The efficient encoding substantially reduces the dimension of the corresponding Hilbert space by limiting it to a relevant subspace where short vectors are likely to be found - leading to significant savings in quantum resources (e.g. qubit count and circuit depth) required to implement a quantum algorithm for finding short vectors. We analytically prove the efficient encoding procedure and benchmark the proposed framework using the variational quantum eigensolver, demonstrating improved results with reduced quantum resources.
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https://arxiv.org/abs/2307.12047
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010b3a9e3edb83982f43c02fb5c8f20c9c81bc72270c61f53e33417409d98ece
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2026-01-13T00:00:00-05:00
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Informed Dynamic Scheduling for QLDPC Codes
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arXiv:2410.01197v2 Announce Type: replace Abstract: Recent research has shown that syndrome-based belief propagation using layered scheduling (sLBP) can not only accelerate the convergence rate but also improve the error rate performance by breaking the quantum trapping sets for quantum low-density parity-check (QLDPC) codes, showcasing a result distinct from classical error correction codes. In this paper, we consider edge-wise informed dynamic scheduling (IDS) for QLDPC codes based on syndrome-based residual belief propagation (sRBP). However, the construction of QLDPC codes and the identical prior intrinsic information assignment will result in an equal residual in many edges, causing a performance limitation for sRBP. Two heuristic strategies, including edge pool design and error pre-correction, are introduced to tackle this obstacle and quantum trapping sets. Then, a novel sRBP equipped with a predict-and-reduce-error mechanism (PRE-sRBP) is proposed, which can provide over one order of performance gain on the considered bicycle codes and symmetric hypergraph (HP) code under similar iterations compared to sLBP.
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https://arxiv.org/abs/2410.01197
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f491cbd11324d0e862dbc51e161ef0c5d32afb882891da2d480c09dc57cb06ae
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2026-01-13T00:00:00-05:00
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Superradiant Quantum Phase Transition in Open Systems: System-Bath Interaction at the Critical Point
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arXiv:2411.16514v4 Announce Type: replace Abstract: The occurrence of a second-order quantum phase transition in the Dicke model is a well-established feature. On the contrary, a comprehensive understanding of the corresponding open system, particularly in the proximity of the critical point, remains elusive. When approaching the critical point, the system inevitably enters first the system-bath ultrastrong coupling regime and finally the deepstrong coupling regime, causing the failure of usual approximations adopted to describe open quantum systems. We study the interaction of the Dicke model with bosonic bath fields in the absence of additional approximations, which usually relies on the weakness of the system-bath coupling. We find that the critical point is not affected by the interaction with the environment. Moreover, the interaction with the environment is not able to affect the system ground-state condensates in the superradiant phase, whereas the bath fields are infected by the system and acquire macroscopic occupations. The obtained reflection spectra display lineshapes which become increasingly asymmetric, both in the normal and superradiant phases, when approaching the critical point.
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https://arxiv.org/abs/2411.16514
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a6a23f3eb0e3fb8cbc62cf3044d8e6c0cced60df23b46833608cd3b6e6969400
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2026-01-13T00:00:00-05:00
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Surveying optically addressable spin qubits for quantum information and sensing technology
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arXiv:2412.11232v4 Announce Type: replace Abstract: Quantum technologies offer ways to solve certain tasks more quickly, efficiently, and with greater precision than their classical counterparts. Yet substantial challenges remain in the construction of sufficiently error-free and scalable quantum platforms needed to unlock any real benefits to society. Acknowledging that this hardware can take vastly different forms, our review here focuses on so-called spintronic (\textit{i.e.}~spin-electronic) materials that use electronic or nuclear spins to embody qubits. Towards helping the reader to spot trends and pick winners, we have surveyed the various families of optically addressable spin qubits and attempted to benchmark and identify the most promising ones in each. We go on to reveal further trends that demonstrate how qubit lifetimes depend on the material's synthesis, the concentration/distribution of its embedded qubits, and the experimental conditions.
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https://arxiv.org/abs/2412.11232
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f437346071cd7792e670cb65a8772e4586dfaeb27a0f7330cf89fec2f7e230e7
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2026-01-13T00:00:00-05:00
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Evaluation of quantum entanglement state between photoelectron spin and emitted photon polarization in spin and polarization resolved XEPECS of $\rm Ti_{2}O_{3}$
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arXiv:2502.18818v2 Announce Type: replace Abstract: We theoretically investigated the mechanism of quantum entanglement between the spin of photoelectrons and linear polarization of emitted X-ray photons in the 3$d\rightarrow\ $2$p$ XEPECS process for $\rm Ti_{2}O_{3}$. In the calculation, we used a realistic $\rm TiO_{6}$-type cluster model with the full multiplet structure of the Ti ion and the charge-transfer effect between the Ti 3$d$ and ligand O 2$p$ orbitals. We found that quantum entanglement occurs between the spin of photoelectrons and linear polarization of emitted X-ray photons and that it depends on the angular geometry in the XEPECS process. In addition, we found that the degree of spin and polarization entanglement decreases as the Ti 3$d\ $- O 2$p$ hybridization becomes stronger and as the crystal field modifies the electronic states in terms of the tangle, an index for the degree of entanglement. These results highlight the crucial role of the charge transfer and crystal field effects in determining entanglement properties in real material systems.
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https://arxiv.org/abs/2502.18818
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355ed945f27160c8a4220e2ac0e60fa1b8202e69efb73075ddfeaa540d3961ad
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2026-01-13T00:00:00-05:00
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Low-loss Nb on Si superconducting resonators from a dual-use spintronics deposition chamber and with acid-free post-processing
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arXiv:2503.13285v2 Announce Type: replace Abstract: Magnetic impurities are known to degrade superconductivity. For this reason, physical vapor deposition chambers that have previously been used for magnetic materials have generally been avoided for making high-quality superconducting resonator devices. In this article, we show by example that such chambers can be used for this purpose; with Nb films sputtered in a chamber that continues to be used for magnetic materials, we demonstrate compact (\SI{3}{\micro\meter} gap) coplanar waveguide resonators with low-power internal quality factors near one million. We achieve this using a resist strip bath with no post-fabrication acid treatment, which results in performance comparable to previous strip baths with acid treatments. We also find evidence that this improved resist strip bath provides a better surface chemical template for post-fabrication hydrogen fluoride processing. These results are consistent across three Si substrate preparation methods, including a \SI{700}{\celsius} anneal. These results will inform nanofabrication for other superconducting materials and the integration of magnetic materials for hybrid systems.
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https://arxiv.org/abs/2503.13285
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8d6c77805b0361d438fd01cb28a8b879f84fd1ff41dfc919fd0ffa0d7c280bf8
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2026-01-13T00:00:00-05:00
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Quantum Dynamics Simulation of the Advection-Diffusion Equation
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arXiv:2503.13729v2 Announce Type: replace Abstract: The advection-diffusion equation is simulated on a superconducting quantum computer via several quantum algorithms. Three formulations are considered: (1) Trotterization, (2) variational quantum time evolution (VarQTE), and (3) adaptive variational quantum dynamics simulation (AVQDS). These schemes were originally developed for the Hamiltonian simulation of many-body quantum systems. The finite-difference discretized operator of the transport equation is formulated as a Hamiltonian and solved without the need for ancillary qubits. Computations are conducted on a quantum simulator (IBM Qiskit Aer) and an actual quantum hardware (IBM Fez). The former emulates the latter without the noise. The predicted results are compared with direct numerical simulation (DNS) data with infidelities of the order $10^{-5}$. In the quantum simulator, Trotterization is observed to have the lowest infidelity and is suitable for fault-tolerant computation. The AVQDS algorithm requires the lowest gate count and the lowest circuit depth. The VarQTE algorithm is the next best in terms of gate counts, but the number of its optimization variables is directly proportional to the number of qubits. Due to current hardware limitations, Trotterization cannot be implemented, as it has an overwhelming large number of operations. Meanwhile, AVQDS and VarQTE can be executed, but suffer from large errors due to significant hardware noise. These algorithms present a new paradigm for computational transport phenomena on quantum computers.
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https://arxiv.org/abs/2503.13729
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53b6bcb3a00facb46cd5e2f968b7a4004a7f8bc4afc30eb80e4b4c382893d64e
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2026-01-13T00:00:00-05:00
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Inductive Graph Representation Learning with Quantum Graph Neural Networks
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arXiv:2503.24111v3 Announce Type: replace Abstract: Quantum Graph Neural Networks (QGNNs) offer a promising approach to combining quantum computing with graph-structured data processing. While classical Graph Neural Networks (GNNs) are scalable and robust, existing QGNNs often lack flexibility due to graph-specific quantum circuit designs, limiting their applicability to diverse real-world problems. To address this, we propose a versatile QGNN framework inspired by GraphSAGE, using quantum models as aggregators. We integrate inductive representation learning techniques with parameterized quantum convolutional and pooling layers, bridging classical and quantum paradigms. The convolutional layer is flexible, allowing tailored designs for specific tasks. Benchmarked on a node regression task with the QM9 dataset, our framework, using a single minimal circuit for all aggregation steps, handles molecules with varying numbers of atoms without changing qubits or circuit architecture. While classical GNNs achieve higher training performance, our quantum approach remains competitive and often shows stronger generalization as molecular complexity increases. We also observe faster learning in early training epochs. To mitigate trainability limitations of a single-circuit setup, we extend the framework with multiple quantum aggregators on QM9. Assigning distinct circuits to each hop substantially improves training performance across all cases. Additionally, we numerically demonstrate the absence of barren plateaus as qubit numbers increase, suggesting that the proposed model can scale to larger, more complex graph-based problems.
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https://arxiv.org/abs/2503.24111
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b217bfb55a9ced67996c37b30a410a9d7e9105f47d55725f1505c8b1f09b943b
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2026-01-13T00:00:00-05:00
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Generalized cross-resonance scheme for maximally-entangling two-qutrit gates
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arXiv:2504.15265v4 Announce Type: replace Abstract: To utilize higher-dimensional quantum systems, in this Letter, we derive a generalized cross-resonance (GCR) scheme for realizing maximally entangling two-qutrit gates on fixed-frequency transmons beyond the 0-1 subspace. Our two-qutrit gates, namely, $U_{CR}^{01}$ and $U_{CR}^{12}$, acting on the $0{\text -}1$ and $1{\text -}2$ energy transitions of transmons, respectively, directly allow for entanglement on the $1{\text -}2$ levels. Unlike the known works, our gate is parametric in nature, enabling us to construct multiple entangling gates of interest. By performing simulations in Qiskit, we demonstrate two-qutrit generalized controlled-$X$ ($U_{CX}^{01}$ and $U_{CX}^{12}$) and controlled-$H$ ($U_{CH}^{01}$ and $U_{CH}^{12}$) gates, which are instances of the proposed $U_{CR}$ gates, with reported gate fidelities of $86.14\%~(99.73\%),~84.6\%~(97.88\%),~92.35\%~(99.39\%)$, and $91.99\%~(98.99\%)$, respectively with (and without) noise. We also reveal a two-qutrit Bell state with a fidelity of $99.06 \pm 0.01\%$, with a complete Bell state preparation in a $\sim514$ ns pulse sequence, which is less than the gate time of the known scheme by cross-Kerr-based entangling gates.
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https://arxiv.org/abs/2504.15265
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5bdaf3356ad098582c6b73d466f74636ee2d40270c51aa9f2dbd6a0bead10ca4
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2026-01-13T00:00:00-05:00
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Experimental Certification of Quantum Measurements with Maximally Mixed States
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arXiv:2504.16484v2 Announce Type: replace Abstract: So far, certifying quantum devices from their input-output statistics, under minimal assumptions, required the preparation of specific pure quantum states. Recently, Xu et al. [Phys. Rev. Lett. 132, 140201 (2024)] have demonstrated that certain sets of quantum observables can be certified using any state of full rank. However, their method is restricted to ideal conditions. Here, we address this problem and present an experimentally robust method that eliminates the need of preparing states with high fidelity with respect to specific pure states. We demonstrate the feasibility of the method by experimentally certifying photonic devices implementing Peres' set of 24 ququart observables [J. Phys. A 24, L175 (1991)] and Yu and Oh's set of 13 qutrit observables [Phys. Rev. Lett. 108, 030402 (2012)], using maximally mixed states as input. This approach offers a crucial advantage for certifying high-dimensional quantum systems, since it works with maximally mixed and thermal states.
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https://arxiv.org/abs/2504.16484
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c6642cfc389d849cdcd85044d2874e59214b51ce79727d9ab2d9edbd81f79f04
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2026-01-13T00:00:00-05:00
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Impossibility via W states and feasibility via W-like states for perfect quantum teleportation
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arXiv:2504.19747v2 Announce Type: replace Abstract: We examine the two-party perfect quantum teleportation of an unknown 1-qubit state in the case of sharing various 3-qubit entangled states between a sender and a receiver: GHZ state, W state and W-like state. We give an impossibility proof that the W state cannot be used as the sharing state to realize the perfect quantum teleportation for transmitting an arbitrary 1-qubit state, in sharp contrast with the GHZ state which is well known to realize the perfect quantum transportation. Moreover, we give a procedure of obtaining a modified entangled state which we call the W-like state to achieve the perfect quantum transportation under a prescribed measurement basis.
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https://arxiv.org/abs/2504.19747
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cd72123592821b3782c9c4be51f8e3390821f7baf514b71caf9eae9251b44c49
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2026-01-13T00:00:00-05:00
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Measurement-driven quantum advantages in shallow circuits
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arXiv:2505.04705v2 Announce Type: replace Abstract: Quantum advantage schemes probe the boundary between classically simulatable and classically intractable quantum dynamics. We explore the impact of mid-circuit measurements on the computational power of quantum circuits. To this effect, we focus on quantum sampling and introduce a constant-depth measurement-driven approach for efficiently sampling from a broad class of commuting diagonal quantum circuits and associated structured phase states, previously requiring polynomial-depth unitary circuits. By interleaving mid-circuit measurements with feed-forward in randomized "fan-out staircases", our dynamical circuits bypass Lieb-Robinson light-cone constraints, enabling global entanglement with flexible auxiliary qubit usage on bounded-degree lattices (e.g., two-dimensional grids). The generated phase states exhibit random-matrix statistics and anti-concentration comparable to fully random architectures. We further demonstrate measurement-driven feature maps that distinguish phases of an extended SSH model from random eigenstates in a quantum machine-learning benchmark (reservoir computing). Technologically, our results harness mid-circuit measurements to realize quantum advantages on bounded-degree hardware with a favorable topology. Conceptually, they provide complexity-theoretic support for quantum speedups by mid-circuit measurements.
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https://arxiv.org/abs/2505.04705
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e6b3f4b4bc9c2e9bb5e66c4954b37e51c7b4e2c9fdf4ec417c19580162d7c734
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2026-01-13T00:00:00-05:00
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A Thermodynamic Framework for Coherently Driven Systems
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arXiv:2505.08558v2 Announce Type: replace Abstract: The laws of thermodynamics are a cornerstone of physics. At the nanoscale, where fluctuations and quantum effects matter, there is no unique thermodynamic framework because thermodynamic quantities such as heat and work depend on the accessibility of the degrees of freedom. We derive a thermodynamic framework for coherently driven systems, where the output light is assumed to be accessible. The resulting second law of thermodynamics is strictly tighter than the conventional one and it demands the output light to be more noisy than the input light. We illustrate our framework across several well-established models and we show how the three-level maser can be understood as an engine that reduces the noise of a coherent drive. Our framework opens a new avenue for investigating the noise properties of driven-dissipative quantum systems.
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https://arxiv.org/abs/2505.08558
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5a305966c2ee6c6b9ab0b36c7109477b6bb3da5810d8394cf3437282ea40abd1
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2026-01-13T00:00:00-05:00
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Quantum feedback cooling of a trapped nanoparticle by using a low-pass filter
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arXiv:2505.10157v2 Announce Type: replace Abstract: We propose a low-pass-filter (LPF) feedback control for cooling a trapped particle with a low-pass filter, which utilizes a shift of the potential caused by the feedback operation. By incorporating this shift in the energy cost function, we show that the LPF control can achieve the minimum phonon occupation number that is lower than cold damping with a band-pass filter, that with delayed feedback, and linear--quadratic--Gaussian (LQG) control, the last two of which are the standard methods of ground-state cooling of a levitated nanoparticle. For the detection efficiency of $90\%$, the achievable phonon occupation number with the LPF control is about one third, two fifths and one half of that of cold damping with a band-pass filter, that with delayed feedback, and LQG control, respectively. Thus our method has a decisive advantage to reach the absolute ground state.
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https://arxiv.org/abs/2505.10157
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4ec4d3187ba45552002d10c2ff10aa42565c4c685d58a64885b71a55ccdf7d98
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2026-01-13T00:00:00-05:00
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Unbiased observable estimation with approximate channels in fault-tolerant quantum computation
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arXiv:2505.11486v2 Announce Type: replace Abstract: Unitary errors, such as those arising from fault-tolerant compilation of quantum algorithms, systematically bias observable estimates. Correcting this bias typically requires additional resources, such as an increased number of non-Clifford gates. In this work, we present an alternative method for correcting bias in the expectation values of observables. The method leverages a decomposition of the ideal quantum channel into a probabilistic mixture of noisy quantum channels. Using this decomposition, we construct unbiased estimators as weighted sums of expectation values obtained from the noisy channels. We provide a detailed analysis of the method, identify the conditions under which it is effective, and validate its performance through numerical simulations. In particular, we demonstrate unbiased observable estimation in the presence of unitary errors by simulating the time dynamics of the Ising Hamiltonian. Our strategy offers a resource-efficient way to reduce the impact of unitary errors, improving methods for estimating observables in noisy near-term quantum devices and fault-tolerant implementation of quantum algorithms.
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https://arxiv.org/abs/2505.11486
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e435595372981cb72bb029ee6b2eed6d5c1d3c077a8898f792871a65a77adac8
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2026-01-13T00:00:00-05:00
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State change via one-dimensional scattering in quantum mechanics
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arXiv:2506.24090v3 Announce Type: replace Abstract: This study aims to address the nature of state change, measurement, and probabilistic outcomes in non-relativistic quantum mechanics. We consider a pair of particles that interact in a one-dimensional setting via a delta-function potential. One of the particles is confined to a one-dimensional box, and the other particle is free. The free particle is incident from the left with specified energy, and it may cause changes in state of the confined particle before flying away to the left or to the right. We present a formulation and computational scheme that avoids the use of perturbation theory and determines the probability of any such outcome as a function of the initial state of the confined particle and the energy of the incident particle. As demonstrated by a direct comparison, this presented method holds multiple advantages over a standard perturbative method. The problem formulation and corresponding computational scheme may have applications in physical settings which admit one-dimensional scattering, e.g., in the study of quantum wires or quantum dots.
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https://arxiv.org/abs/2506.24090
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2026-01-13T00:00:00-05:00
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Analog Circuit-QED Simulator of Quantum Spin Dynamics Through the Extended Bose-Hubbard Model
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arXiv:2507.03587v2 Announce Type: replace Abstract: We propose and validate a framework for analog simulation of the Heisenberg spin model using a circuit quantum electrodynamics (circuit-QED) platform. Our method involves the Dyson-Maleev transformation, for which we develop a procedure to circumvent its inherent non-Hermiticity, yielding the extended Bose-Hubbard (EBH) Hamiltonian. We demonstrate the equivalence of this approach to the Holstein-Primakoff encoding for spin-1/2 systems. For the experimental realization of this EBH model, we design a scalable circuit-QED architecture based on an engineered Josephson junction array. Numerical simulations confirm that the microwave photon dynamics in this simulator accurately reproduces the original spin dynamics. Our work establishes an experimentally accessible method for investigating complex quantum spin dynamics in a highly controllable bosonic setting.
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https://arxiv.org/abs/2507.03587
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212b8167e1fc660eed4e3bcfb2cf87c96fb2893fb780d283d4e92fa5f331339f
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2026-01-13T00:00:00-05:00
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Do mixed states exhibit deep thermalisation?
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arXiv:2507.14135v2 Announce Type: replace Abstract: Deep thermalisation -- where ensembles of pure states on a local subsystem, conditioned on measurement outcomes on its complement, approach universal maximum-entropy ensembles -- represents a stronger form of ergodicity than conventional thermalisation. We show that this framework fails dramatically for mixed initial states, evolved unitarily, even with infinitesimal initial mixedness. To address this, we introduce a new paradigm of deep thermalisation for mixed states, fundamentally distinct from that for pure-state ensembles. In our formulation, the deep thermal ensemble arises by tracing out auxiliary degrees of freedom from a maximum-entropy ensemble defined on an augmented system, with the ensemble structure depending explicitly on the entropy of the initial state. We demonstrate that such ensembles emerge dynamically in generic, locally interacting chaotic systems. For the self-dual kicked Ising chain, which we show to be exactly solvable for a class of mixed initial states, we find exact emergence of the so-defined mixed-state deep thermal ensemble at finite times. Our results therefore lead to fundamental insights into how maximum entropy principles and deep thermalisation manifest themselves in unitary dynamics of states with finite entropy.
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https://arxiv.org/abs/2507.14135
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e7ef35c55261766d8d3ab2cb7411cc5651b8586cbc4f69ef30389bf847052eb3
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2026-01-13T00:00:00-05:00
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The spatiotemporal Born rule is quasiprobabilistic
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arXiv:2507.16919v2 Announce Type: replace Abstract: Contrary to general relativity, quantum theory treats space and time in fundamentally different ways. In particular, while joint probabilities associated with spacelike separated measurements are defined in terms of the Born rule, joint probabilities associated with measurements performed in sequence are defined in terms of the state-update rule. In this work, we show that one obtains a more unified perspective of space and time in quantum theory by embracing a quasiprobabilistic description of sequential measurements. More precisely, we show that there exists a unique \emph{pseudo}-density operator encoding canonical quasiprobabilities associated with sequential measurements in precisely the same manner that a density operator encodes joint probabilities associated with spacelike separated measurements, thus providing a natural extension of the Born rule into the temporal domain. As an application, we show how such a spatiotemporal Born rule combined in conjunction with a quantum Bayes' rule yields an operational notion of time-reversal symmetry for sequential measurements on an \emph{open} quantum system.
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https://arxiv.org/abs/2507.16919
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74b58e1163109d3b58bb30b3fee6a65ad7465ba8a0370231e60be31019e91942
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2026-01-13T00:00:00-05:00
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Complexity in multi-qubit and many-body systems
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arXiv:2507.22246v3 Announce Type: replace Abstract: Characterizing complexity and criticality in quantum systems requires diagnostics that are both computationally tractable and physically insightful. We apply a measure of quantum state complexity for n-qubit systems, defined as the divergence between the Shannon or von Neumann entropy of the computational basis distribution and the second-order Renyi entropy. This quantity has already been used earlier termed as structural entropy and it is particularly powerful as the Renyi entropy is directly related to state purity, linear entropy, and the inverse participation ratio, providing a clear physical grounding. While other Renyi orders could be used, the second order offers a deep and established connection to these key physical quantities. We first validate the measure in canonical noise channels, showing it peaks at the boundary between quantum and classical regimes. We then demonstrate its power in many-body physics. For systems exhibiting a many-body localization transition - including deformed random matrix ensembles and a disordered Heisenberg spin chain - the complexity measure reliably signals the crossover from integrable/localized to quantum-chaotic/ergodic phases. Crucially, the maximum complexity occurs in the non-ergodic yet extended states at the transition, precisely capturing the critical region where the system is neither fully localized nor thermalized. Furthermore, within the chaotic phase, the measure correlates with the survival probability of local excitations, revealing a spectrum of thermalization properties. Our results establish that the entropic complexity is a simple, versatile, and effective probe for identifying nontrivial quantum regimes and transitions giving a new and alternative insight into such systems.
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https://arxiv.org/abs/2507.22246
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2026-01-13T00:00:00-05:00
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Entangling Power and Its Deviation: A Quantitative Analysis on Input-State Dependence and Variability in Entanglement Generation
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arXiv:2508.00301v2 Announce Type: replace Abstract: Quantifying the entangling capability of quantum operations is a fundamental task in quantum information science. Traditionally, this capability is measured by the entangling power (EP), defined as the average entanglement generated when a quantum operation acts uniformly on all possible product states. However, EP alone cannot capture the intricate input-state-dependent nature of entanglement generation. To address this, we define a complementary metric -- entangling power deviation (EPD) -- as the standard deviation of entanglement generated over all product input states, thereby capturing the multifaceted nature of entangling behavior. We develop a general group-theoretical framework that yields closed-form expressions for both EP and EPD. Our analysis shows that any nontrivial entangling operation necessarily exhibits input-state dependence: nonzero EP implies a nonzero EPD. By analyzing representative two-qubit gates, we show that the gates with identical EP can exhibit markedly different EPD values, illustrating that the nature of entanglement generation can significantly differ depending on the gate functionality. Extending our framework to a class of generalized controlled-unitary operations acting on bipartite Hilbert spaces of arbitrary dimensions, we further analyze the interplay between the entangling strength and uniformity, as quantified by EP and EPD. Moreover, we uncover a subtle dimension-parity-dependent behavior in entanglement generation, which EP alone fails to detect. These findings highlight EPD as an indispensable diagnostic tool -- one that, alongside EP, provides a deeper and more complete characterization of the entangling structure.
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https://arxiv.org/abs/2508.00301
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aa949a6871e572cb42b4eacc85ea4640a4259e19c754dabe9a41dda43d8289d4
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2026-01-13T00:00:00-05:00
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Steady state of periodically driven quantum systems
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arXiv:2508.07674v2 Announce Type: replace Abstract: Periodic driving is used to steer physical systems to unique stationary states or nonequilibrium steady states (NESS), producing enhanced properties inaccessible to non-driven systems. For open quantum systems, characterizing the NESS is challenging and existing results are generally limited to specific types of driving and the Born-Markov approximation. Here we go beyond these limits by studying a generic periodically driven $ N$-level quantum system interacting with a low-density thermal gas. Exploiting the framework of Floquet scattering theory, we establish general Floquet thermalization conditions constraining the nature of the NESS and the transition rates. Moreover, we examine theoretically the structure of the NESS in the high temperature limit, and find out that the NESS complies, rather surprisingly, with an uniform probability distribution (predicted by the Boltzmann law) for any driving. Numerical calculations illustrate our theoretical elaborations for a simple toy model.
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https://arxiv.org/abs/2508.07674
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ebfeafe2dcb1b625c60ff838ba3032e1e19df9f31f80d2b2c368603aa502005b
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2026-01-13T00:00:00-05:00
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Attaining Quantum Sensing Enhancement from Monitored Dissipative Time Crystals
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arXiv:2508.15448v2 Announce Type: replace Abstract: This study investigates quantum-enhanced parameter estimation through continuous monitoring in open quantum systems that exhibit a dissipative time crystal phase. We first analytically derive the global quantum Fisher information (QFI) rate for boundary time crystals (BTCs), demonstrating that within the time-crystal phase, the ultimate precision exhibits a cubic scaling with the system size, $f_{\mathrm{global}}\sim N^3$. We then generalize this finding to a broader class of dynamics, including the transverse collective dephasing (TCD) model, which achieves a time-crystal phase through a closing Liouvillian gap without requiring a dissipative phase transition. We proceed to numerically demonstrate that this maximal global QFI rate is experimentally attainable for both the BTC and TCD models, even at finite system sizes, via continuous homodyne and photodetection. Moving towards practical implementations, we analyze the precision limits under inefficient detection, revealing a critical difference: for BTC dynamics, inefficiencies asymptotically restore a classical scaling, and only a constant-factor quantum advantage remains possible. In contrast, for TCD dynamics, a super-classical scaling is still in principle observable, and our numerical simulations confirm its presence, even under inefficient measurement conditions, establishing the TCD model as a highly robust platform for quantum metrology.
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https://arxiv.org/abs/2508.15448
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Beyond Traditional Quantum Routing
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arXiv:2508.18023v2 Announce Type: replace Abstract: Existing quantum routing implicitly mimics classical routing principles, with finding the ``best'' path (aka pathfinding), according to a selected routing metric, as a core mechanism for establishing end-to-end entanglement. However, optimal pathfinding is computationally intensive, particularly in complex topologies. In this paper, we propose a novel approach to quantum routing, which avoids the inherent overhead of conventional quantum pathfinding, by establishing directly entanglement between remote nodes. Our approach exploits graph complement strategies. It allows to improve the flexibility and efficiency of quantum networks, by paving the way for more practical quantum communication infrastructures.
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https://arxiv.org/abs/2508.18023
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2026-01-13T00:00:00-05:00
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Polynomial-time Extraction of Entanglement Resources
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arXiv:2508.18024v2 Announce Type: replace Abstract: The extraction of EPR pairs and n-qubits GHZ states among remote nodes in quantum networks constitutes the resource primitives for end-to-end and on-demand communications. However, the Bell-VM problem, which determines whether a given graph state can be transformed into a set of Bell pairs on specific vertices (not necessarily remote), is known to be NP-complete. In this paper, we extend this problem, not only by focusing on nodes remote within generic graph states, but also by determining the number of extractable n-qubit remote GHZ states -- beside the number of remote EPR pairs. The rationale for tackling the extraction of GHZ states among remote nodes, rather than solely remote EPR pairs, is that a GHZ state enables the dynamic extraction of an EPR pair between any pair of nodes sharing the state. This, in turn, implies the ability of accommodating the traffic requests on-the-fly. Specially, we propose a polynomial-time algorithm for solving the aforementioned NP-complete problem. Our results demonstrate that the proposed algorithm is able to effectively adapt to generic graph states for extracting entanglement resources across remote nodes.
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https://arxiv.org/abs/2508.18024
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f5f00fa97d04d909aca38e3658c1aa3aea728525de555014256e2124bc703ca1
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2026-01-13T00:00:00-05:00
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Quantum Paths: a Quantum Walk approach
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arXiv:2508.18077v2 Announce Type: replace Abstract: The quantum switch, a process enabling a coherent superposition of different orders of quantum channels, has garnered significant attention due to its ability to enable noiseless communications through noisy channels, such as entanglement-breaking channels. However, its practical implementation and scalability remain challenging. In contrast, the spatial superposition of quantum channels is more accessible experimentally and has been shown to enhance channel capacity, although it does not match the performance of the quantum switch. In this work, we present preliminary theoretical results demonstrating that, by applying tools of the quantum random walk framework to the spatial superposition of channels, it is possible to replicate the output of a quantum switch. These findings suggest a promising and more feasible route to emulate the quantum switch, offering both practical advantages and interpretative clarity.
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https://arxiv.org/abs/2508.18077
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2026-01-13T00:00:00-05:00
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Quantum Neural Ordinary and Partial Differential Equations
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arXiv:2508.18326v2 Announce Type: replace Abstract: We introduce a unified framework -- Quantum Neural Ordinary and Partial Differential Equations (QNODEs and QNPDEs) -- which extends the continuous-time formalism of classical neural ordinary and partial differential equations into quantum machine learning and quantum control. QNODEs denote the evolution of finite-dimensional quantum systems, whereas QNPDEs denote their infinite-dimensional (continuous-variable) counterparts; both are governed by generalised Schr\"odinger-type Hamiltonian dynamics, coupled with a corresponding loss function. This formalism permits gradient estimation via an adjoint-state method, facilitating efficient learning of quantum dynamics, and other dynamics that can be mapped (relatively easily) to quantum dynamics. Using this method, we present quantum algorithms for computing gradients with and without time discretisation, achieving efficient gradient computation that would otherwise be intractable on classical devices. We provide detailed resource estimates for these algorithms and investigate the local energy landscape for training. The formalism subsumes a wide array of applications, including quantum state preparation, Hamiltonian learning, learning dynamics in open systems, and the learning of both autonomous and non-autonomous classical ODEs and PDEs. In many cases of interest, the Hamiltonian is composed of a relatively small number of local operators, yet the corresponding classical simulation remains inefficient, making quantum approaches advantageous for gradient estimation. This continuous-time perspective can also serve as a blueprint for designing novel quantum neural network architectures, generalising discrete-layered models into continuous-depth models.
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https://arxiv.org/abs/2508.18326
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2026-01-13T00:00:00-05:00
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Quantum deliberating machines
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arXiv:2509.07940v3 Announce Type: replace Abstract: Within the familiar circuit-based quantum computational setting, we introduce and analyze a toy model of a quantum physical device capable of internal, self-referential deliberation. The key idea is to represent ``deliberation'' as a coherent iterative branching process, in which competing branch-dependent system evolutions are maintained in superposition, with additional control and memory registers recording branch histories, and the policy register adaptively biasing subsequent development. We provide explicit quantum circuit realizations and carry out detailed step-by-step derivations of the entangled control--memory--system--policy dynamics. We carefully distinguish between internally adaptive and internally reinforced deliberations, proposing the architectures for both, and briefly discuss categorical and controlled--Stinespring reformulations, as well as their conceptual implications. The primary construction models a memory-driven deliberation where the policy update depends on which actions were taken, not on their results. We also present a simple extension that allows for minimalistic, outcome-driven policy updates, implementing a coherent feedback loop that steers the system toward a target state regardless of initial branch-dependent evolution. This loop can be interpreted as a quantum autopilot or search-and-rescue mechanism, illustrating how a device can autonomously correct and optimize its internal strategy in superposition. Finally, we briefly consider various implementations of a dialogue that may take place between two deliberating machines. Taken together, this frames the proposed model as a plausible setting for exploring how such devices may maintain multiple alternatives in parallel, while performing an internal decision-making process through coherent branching, entanglement, adaptive policy updates, and policy-driven self-modifying unitary dynamics.
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https://arxiv.org/abs/2509.07940
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2026-01-13T00:00:00-05:00
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SQuaD: Smart Quantum Detection for Photon Recognition and Dark Count Elimination
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arXiv:2509.24383v4 Announce Type: replace Abstract: Quantum detectors of single photons are an essential component for quantum information processing across computing, communication and networking. Today's quantum detection system, which consists of single photon detectors, timing electronics, control and data processing software, is primarily used for counting the number of single photon detection events. However, it is largely incapable of extracting other rich physical characteristics of the detected photons, such as their wavelengths, polarization states, photon numbers, or temporal waveforms. This work, for the first time, demonstrates a smart quantum detection system, SQuaD, which integrates a field programmable gate array (FPGA) with a neural network model, and is designed to recognize the features of photons and to eliminate detector dark-count. The SQuaD is a fully integrated quantum system with high timing-resolution data acquisition, onboard multi-scale data analysis, intelligent feature recognition and extraction, and feedback-driven system control. Our \name experimentally demonstrates 1) reliable photon counting on par with the state-of-the art commercial systems; 2) high-throughput data processing for each individual detection events; 3) efficient dark count recognition and elimination; 4) up to 100\% accurate feature recognition of photon wavelength and polarization. Additionally, we deploy the SQuaD to an atomic (erbium ion) photon emitter source to realize noise-free control and readout of a spin qubit in the telecom band, enabling critical advances in quantum networks and distributed quantum information processing.
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https://arxiv.org/abs/2509.24383
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2026-01-13T00:00:00-05:00
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PhotonIDs: ML-Powered Photon Identification System for Dark Count Elimination
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arXiv:2509.26315v4 Announce Type: replace Abstract: Reliable single photon detection is the foundation for practical quantum communication and networking. However, today's superconducting nanowire single photon detector(SNSPD) inherently fails to distinguish between genuine photon events and dark counts, leading to degraded fidelity in long-distance quantum communication. In this work, we introduce PhotonIDs, a machine learning-powered photon identification system that is the first end-to-end solution for real-time discrimination between photons and dark count based on full SNSPD readout signal waveform analysis. PhotonIDs ~demonstrates: 1) an FPGA-based high-speed data acquisition platform that selectively captures the full waveform of signal only while filtering out the background data in real time; 2) an efficient signal preprocessing pipeline, and a novel pseudo-position metric that is derived from the physical temporal-spatial features of each detected event; 3) a hybrid machine learning model with near 98% accuracy achieved on photon/dark count classification. Additionally, proposed PhotonIDs ~ is evaluated on the dark count elimination performance with two real-world case studies: (1) 20 km quantum link, and (2) Erbium ion-based photon emission system. Our result demonstrates that PhotonIDs ~could improve more than 31.2 times of signal-noise-ratio~(SNR) on dark count elimination. PhotonIDs ~ marks a step forward in noise-resilient quantum communication infrastructure.
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https://arxiv.org/abs/2509.26315
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Block-Encoding Tensor Networks and QUBO Embeddings
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arXiv:2510.00935v2 Announce Type: replace Abstract: We give an algorithm that converts any tensor network (TN) into a sequence of local unitaries whose composition block-encodes the network contraction, suitable for Quantum Eigenvalue / Singular Value Transformation (QET/QSVT). The construction embeds each TN as a local isometry and dilates it to a unitary. Performing this step for every site of the tensor, allows the full network to be block-encoded. The theory is agnostic to virtual-bond sizes; for qubit resource counts and examples we assume global power-of-two padding. Further, we present a deterministic sweep that maps Quadratic Unconstrained Binary Optimization (QUBO) / Ising Hamiltonians into Matrix Product Operators (MPOs) and general TN. We provide formal statements, pseudo-code, resource formulae, and a discussion of the use for state preparation and learning of general quantum operators.
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https://arxiv.org/abs/2510.00935
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Velocity effects slightly mitigating the quantumness degradation of an Unruh-DeWitt detector
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arXiv:2510.01280v2 Announce Type: replace Abstract: In this work, we investigate the velocity effects on information degradation due to the Unruh effect in accelerated quantum systems (with finite interaction time). We consider a detector moving along a spatial trajectory within a two-dimensional plane. The quantum systems studied were: accelerated single-qubit, quantum interferometric circuit, and which-path distinguishability circuit. Thus, for non-relativistic velocity regime, we obtained analytical expressions such as transition rates, quantum coherence, visibility, distinguishability, and the complementarity relation. On the other hand, for the ultra-relativistic velocity regime, we saw that the Unruh effect is suppressed and therefore the detector does not respond in this case. Our findings revealed that velocity effects imply mitigation of information degradation, this interesting behaviors happen because of the composite effect of both velocity and acceleration. The results obtained show that the addition of the non-relativistic, transverse and constant motion of an accelerated detector can play a protective role in quantumness in systems at high accelerations, although the effects are very small.
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https://arxiv.org/abs/2510.01280
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068844b9918377f64fd8a28d46226135260f2711f10cdc730a187991a904ca16
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2026-01-13T00:00:00-05:00
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Simple Quantum Algorithm for Approximate $k$-Mismatch Problem
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arXiv:2510.02399v2 Announce Type: replace Abstract: In the $k$-mismatch problem, given a pattern and a text of length $n$ and $m$ respectively, we have to find if the text has a sub-string with a Hamming distance of at most $k$ from the pattern. This has been studied in the classical setting since 1982 and recently in the quantum computational setting by Jin and Nogler and Kociumaka, Nogler, and Wellnitz. We provide a simple quantum algorithm that solves the problem in an approximate manner, given a parameter $\epsilon \in (0, 1]$. It returns an occurrence as a match only if it is a $\left(1+\epsilon\right)k$-mismatch. If it does not return any occurrence, then there is no $k$-mismatch. This algorithm has a time (size) complexity of $\tilde{O}\left( \epsilon^{-1} \sqrt{\frac{mn}{k}} \right)$.
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https://arxiv.org/abs/2510.02399
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2026-01-13T00:00:00-05:00
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A quantum state transfer protocol with Ising Hamiltonians
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arXiv:2510.07481v2 Announce Type: replace Abstract: Quantum state transfer is a fundamental requirement for scalable quantum computation, where fast and reliable communication between distant subsystems is essential. In this work, we present a protocol for quantum state transfer in linear Ising chains. Starting from a perfect state transfer scheme via a Heisenberg Hamiltonian with inhomogeneous couplings, we adapt it for architectures implementing the transverse-field Ising model by encoding the information in domain walls. The resulting linear Ising chain makes quantum transport experiments accessible to many platforms for analog quantum simulation. We test the protocol for 1-, 2-, and 3- spin states, obtaining high transfer fidelities of up to 0.99 and study the accuracy dependence on the domain wall approximation. These results are the first step in paving the way for an experimental implementation of the protocol.
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https://arxiv.org/abs/2510.07481
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2c5289572438e8d1d81d7409f2010c4c82aec57d8d0ce03888e005bd00296b11
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2026-01-13T00:00:00-05:00
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Learning T-conjugated stabilizers: The multiple-squares dihedral StateHSP
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arXiv:2510.07872v2 Announce Type: replace Abstract: The state hidden subgroup problem (StateHSP) is a recent generalization of the hidden subgroup problem. We present an algorithm that solves the non-abelian StateHSP over $N$ copies of the dihedral group of order $8$ (the symmetries of a square). This algorithm is of interest for learning non-Pauli stabilizers, as well as related symmetries relevant for the problem of Hamiltonian spectroscopy. Our algorithm is polynomial in the number of samples and computational time, and requires only constant depth circuits. This result extends previous work on the abelian StateHSP and, as a special case, provides a solution for the ordinary hidden subgroup problem on this specific non-abelian group.
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https://arxiv.org/abs/2510.07872
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85fa7e81108b82bb8ba8ff4e5184310586c381c1f42ee9a36709b9c412892700
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2026-01-13T00:00:00-05:00
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An Information-Minimal Geometry for Qubit-Efficient Optimization
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arXiv:2511.08362v2 Announce Type: replace Abstract: Qubit-efficient optimization studies how large combinatorial problems can be addressed with quantum circuits whose width is far smaller than the number of logical variables. In quadratic unconstrained binary optimization (QUBO), objective values depend only on one- and two-body statistics, yet standard variational algorithms explore exponentially large Hilbert spaces. We recast qubit-efficient optimization as a geometric question: what is the minimal representation the objective itself requires? Focusing on QUBO problems, we show that enforcing mutual consistency among pairwise statistics defines a convex body -- the level-2 Sherali-Adams polytope -- that captures the information on which quadratic objectives depend. We operationalize this geometry in a minimal variational pipeline that separates representation, consistency, and decoding: a logarithmic-width circuit produces pairwise moments, a differentiable information projection enforces local feasibility, and a maximum-entropy ensemble provides a principled global decoder. This information-minimal construction achieves near-optimal approximation ratios on large unweighted Max-Cut instances (up to N=2000) at shallow depth, indicating that pairwise polyhedral geometry already captures the relevant structure in this regime. By making the information-minimal geometry explicit, this work establishes a clean baseline for qubit-efficient optimization and sharpens the question of where genuinely quantum structure becomes necessary.
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https://arxiv.org/abs/2511.08362
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2026-01-13T00:00:00-05:00
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Lazy Quantum Walks with Native Multiqubit Gates
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arXiv:2511.21608v2 Announce Type: replace Abstract: Quantum walks, the quantum analogue to the classical random walk, have been shown to model fluid dynamics. Neutral atom hardware is a promising choice of platform for implementing quantum walks due to its ability to implement native multiqubit ($\geq\!3$-qubit) gates and to dynamically re-arrange qubits. Using error modelling for multiqubit Rydberg gates via two-photon adiabatic rapid passage, we present the gate sequences and predicted final state fidelities for some toy quantum walks, including `lazy' quantum walks. These `lazy' quantum walks include a rest state and therefore provide an integral step towards quantum walks for fluid simulation.
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https://arxiv.org/abs/2511.21608
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ecab722a51326f66ccfd33a279eb4c474429b5853cc0ce1a55c994711a28f385
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2026-01-13T00:00:00-05:00
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Sum rule for non-adiabatic geometric phases
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arXiv:2511.22437v2 Announce Type: replace Abstract: Berry monopoles always cancel when summing over a complete set of energy eigenstates. We demonstrate that analogous sum rules exist for geometric phases and their underlying 2-forms in non-adiabatic evolution. Our result has implications for qudit computation as it limits the types of gates that can be implemented by purely geometric means.
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https://arxiv.org/abs/2511.22437
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7bddef4c7508b880cf6670045629430b1ee354fc69c0a6584c7c45de302b00c2
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2026-01-13T00:00:00-05:00
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Automated Compilation Including Dropouts: Tolerating Defective Components in Stabiliser Codes
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arXiv:2512.01943v2 Announce Type: replace Abstract: Utility-scale solid-state quantum devices will need to fabricate quantum devices at scale using imperfect processes. By introducing tolerance to fabrication defects into the design of the quantum devices, we can improve the yield of usable quantum chips and lower the cost of useful systems. Automated Compilation Including Dropouts (ACID) is a framework that works in the ancilla-free (or `middle-out') paradigm, to generate syndrome extraction circuits for general stabiliser codes in the presence of defective couplers or qubits. In the ancilla-free paradigm, we do not designate particular qubits as measurement ancillas, instead measuring stabilisers using any of the data qubits in their support. This approach leads to a great deal of flexibility in how syndrome extraction circuits can be implemented. ACID works by constructing and solving an optimisation problem within the ancilla-free paradigm to find a short syndrome extraction circuit. Applied to the surface code, ACID produces syndrome-extraction circuits of depth between $1\times$ (no overhead) and $1.5\times$ relative to the depth of defect-free circuits. The LUCI algorithm, the best prior art, yielded a $2 \times$ overhead, so ACID offers a significant time saving. The yield of surface code chips with a logical error rate at most $10\times$ the dropout-free baseline is up to $3\times$ higher using ACID than using LUCI. I demonstrate the broad applicability of ACID by compiling syndrome extraction circuits for bivariate bicycle codes and the colour code. For these circuits, we incur a circuit-depth overhead of between $1\times$ (no overhead) and $2.5\times$ relative to defect-free circuits. I believe this work is the first to simulate both of these families of codes in the presence of fabrication defects.
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https://arxiv.org/abs/2512.01943
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Academic Papers
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ef9f36b5810fbf5e074dd6b49531188803846f19dd6e0c1a470869493aca22d4
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2026-01-13T00:00:00-05:00
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Leveraging Symmetry Merging in Pauli Propagation
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arXiv:2512.12094v2 Announce Type: replace Abstract: We introduce a symmetry-adapted framework for simulating quantum dynamics based on Pauli propagation. When a quantum circuit possesses a symmetry, many Pauli strings evolve redundantly under actions of the symmetry group. We exploit this by merging Pauli strings related through symmetry transformations. This procedure, formalized as the symmetry-merging Pauli propagation algorithm, propagates only a minimal set of orbit representatives. Analytically, we show that symmetry merging reduces space complexity by a factor set by orbit sizes, with explicit gains for translation and permutation symmetries. Numerical benchmarks of all-to-all Heisenberg dynamics confirm improved stability, particularly under truncation and noise. Our results establish a group-theoretic framework for enhancing Pauli propagation, supported by open-source code demonstrating its practical relevance for classical quantum-dynamics simulations.
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https://arxiv.org/abs/2512.12094
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Academic Papers
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9fb3ca1b471ac96f3f261dbd33be6fd9b8592a8ff5fc1915b7b7a1952e6c61ee
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2026-01-13T00:00:00-05:00
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Error mitigation for logical circuits using decoder confidence
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arXiv:2512.15689v2 Announce Type: replace Abstract: Fault-tolerant quantum computers use decoders to monitor for errors and find a plausible correction. A decoder may provide a decoder confidence score (DCS) to gauge its success. We adopt a swim distance DCS, computed from the shortest path between syndrome clusters. By contracting tensor networks, we compare its performance to the well-known complementary gap and find that both reliably estimate the logical error probability (LEP) in a decoding window. We explore ways to use this to mitigate the LEP in entire circuits. For shallow circuits, we just abort if any decoding window produces an exceptionally low DCS: for a distance-13 surface code, rejecting a mere 0.1% of possible DCS values improves the entire circuit's LEP by more than 5 orders of magnitude. For larger algorithms comprising up to trillions of windows, DCS-based rejection remains effective for enhancing observable estimation. Moreover, one can use DCS to assign each circuit's output a unique LEP, and use it as a basis for maximum likelihood inference. This can reduce the effects of noise by an order of magnitude at no quantum cost; methods can be combined for further improvements.
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https://arxiv.org/abs/2512.15689
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Academic Papers
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a6f75a4719c168e8c91efbc4a3030e73ecd64fe5393d58078200f1842448fc58
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2026-01-13T00:00:00-05:00
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Systematic Construction of Time-Dependent Hamiltonians for Microwave-Driven Josephson Circuits
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arXiv:2512.20743v2 Announce Type: replace Abstract: Time-dependent electromagnetic drives are fundamental for controlling complex quantum systems, including superconducting Josephson circuits. In these devices, accurate time-dependent Hamiltonian models are imperative for predicting their dynamics and designing high-fidelity quantum operations. Existing numerical methods, such as black-box quantization (BBQ) and energy-participation ratio (EPR), excel at modeling the static Hamiltonians of Josephson circuits. However, these techniques do not fully capture the behavior of driven circuits stimulated by external microwave drives, nor do they include a generalized approach to account for the inevitable noise and dissipation that enter through microwave ports. Here, we introduce novel numerical techniques that leverage classical microwave simulations that can be efficiently executed in finite element solvers, to obtain the time-dependent Hamiltonian of a microwave-driven superconducting circuit with arbitrary geometries. Importantly, our techniques do not rely on a lumped-element description of the superconducting circuit, in contrast to previous approaches to tackling this problem. We demonstrate the versatility of our approach by characterizing the driven properties of realistic circuit devices in complex electromagnetic environments, including coherent dynamics due to charge and flux modulation, as well as drive-induced relaxation and dephasing. Our techniques offer a powerful toolbox for optimizing circuit designs and advancing practical applications in superconducting quantum computing.
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https://arxiv.org/abs/2512.20743
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Academic Papers
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a7a5401f3402e095ce92bdef87db7a30a452ed574d5380fbdc22ebc54bfa8d4b
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2026-01-13T00:00:00-05:00
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Probabilistic Entanglement Distillation: Error Exponents via Postselected Quantum Hypothesis Testing Against Separable States
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arXiv:2601.00383v2 Announce Type: replace Abstract: Entanglement distillation and entanglement cost are fundamental tasks in quantum entanglement theory. This work studies both in the probabilistic setting and focuses on the asymptotic error exponent of probabilistic entanglement distillation when the operational model is $\delta$-approximately nonentangling or $\delta$-approximately dually nonentangling quantum instruments. While recent progress has clarified limitations of probabilistic transformations in general resource theories, an analytic formula for the error exponent of probabilistic entanglement distillation under approximately (dually) nonentangling operations has remained unavailable. Building on the framework of postselected quantum hypothesis testing, we establish a direct connection between probabilistic distillation and postselected hypothesis testing against the set of separable states. In particular, we derive an analytical characterization of the distillation error exponent under $\delta$-approximately nonentangling quantum instruments. Besides, we relate the exponent to postselected hypothesis testing with measurements restricted to be separable. We further investigate probabilistic entanglement dilution and establish a relation between probabilistic entanglement costs under approximately nonentangling and approximately dually nonentangling instruments, together with a bound on the probabilistic entanglement cost under nonentangling instruments.
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https://arxiv.org/abs/2601.00383
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Academic Papers
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537003a55320dc2c122216b99136af99f10ab77192457bb0f7f5e0883019aba9
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2026-01-13T00:00:00-05:00
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Benchmarking Quantum Data Center Architectures: A Performance and Scalability Perspective
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arXiv:2601.01353v2 Announce Type: replace Abstract: Scalable distributed quantum computing (DQC) has motivated the design of multiple quantum data-center (QDC) architectures that overcome the limitations of single quantum processors through modular interconnection. While these architectures adopt fundamentally different design philosophies, their relative performance under realistic quantum hardware constraints remains poorly understood. In this paper, we present a systematic benchmarking study of four representative QDC architectures-QFly, BCube, Clos, and Fat-Tree-quantifying their impact on distributed quantum circuit execution latency, resource contention, and scalability. Focusing on quantum-specific effects absent from classical data-center evaluations, we analyze how optical-loss-induced Einstein-Podolsky-Rosen (EPR) pair generation delays, coherence-limited entanglement retry windows, and contention from teleportation-based non-local gates shape end-to-end execution performance. Across diverse circuit workloads, we evaluate how architectural properties such as path diversity and path length, and shared BSM (Bell State Measurement) resources interact with optical-switch insertion loss and reconfiguration delay. Our results show that distributed quantum performance is jointly shaped by topology, scheduling policies, and physical-layer parameters, and that these factors interact in nontrivial ways. Together, these insights provide quantitative guidance for the design of scalable and high-performance quantum data-center architectures for DQC.
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https://arxiv.org/abs/2601.01353
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Academic Papers
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debba0d3fdf31c4a337244a89e2bafee50cebd58183109ff46f427d22eb2a5f5
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2026-01-13T00:00:00-05:00
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Developments in superconducting erasure qubits for hardware-efficient quantum error correction
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arXiv:2601.02183v2 Announce Type: replace Abstract: Quantum computers are inherently noisy, and a crucial challenge for achieving large-scale, fault-tolerant quantum computing is to implement quantum error correction. A promising direction that has made rapid recent progress is to design hardware that has a specific noise profile, leading to a significantly higher threshold for noise with certain quantum error correcting codes. This Perspective focuses on erasure qubits, which enable hardware-efficient quantum error correction, by concatenating an inner code built-in to the hardware with an outer code. We focus on implementations of dual-rail encoded erasure qubits using superconducting qubits, giving an overview of recent developments in theory and simulation, and hardware demonstrators. We also discuss the differences between implementations; near-term applications using quantum error detection; and the open problems for developing this approach towards early fault-tolerant quantum computers.
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https://arxiv.org/abs/2601.02183
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Academic Papers
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638a554276a8b3f84edbade6d20593c7fcfa27193ed1fb5e9eb3baf627d5c6ea
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2026-01-13T00:00:00-05:00
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Open system dynamics in interacting quantum field theories
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arXiv:2403.18907v2 Announce Type: replace-cross Abstract: A quantum system that interacts with an environment generally undergoes nonunitary evolution described by a non-Markovian or Markovian master equation. In this paper, we construct the non-Markovian Redfield master equation for a quantum scalar field that interacts with a second field through a bilinear or nonlinear interaction on a Minkowski background. We use the resulting master equation to set up coupled differential equations that can be solved to obtain the equal-time two-point function of the system field. We show how the equations simplify under various approximations including the Markovian limit and argue that the Redfield equation-based solution provides a perturbative resummation to the standard second-order Dyson series result. For the bilinear interaction, we explicitly show that the Redfield solution is closer to the exact solution compared to the perturbation theory-based one. Further, the environment correlation function is oscillatory and nondecaying in this case, making the Markovian master equation a poor approximation. For the nonlinear interaction, on the other hand, the environment correlation function is sharply peaked and the Redfield solution matches that obtained using a Markovian master equation in the late-time limit.
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https://arxiv.org/abs/2403.18907
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Academic Papers
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2026-01-13T00:00:00-05:00
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Frustration-free free fermions and beyond
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arXiv:2503.12879v2 Announce Type: replace-cross Abstract: Frustration-free Hamiltonians provide pivotal models for understanding quantum many-body systems. In this paper, we establish a general framework for frustration-free fermionic systems. First, we derive a necessary and sufficient condition for a free fermion model to be frustration-free. In the case of translation-invariant, noninteracting systems, we show that any band touching between the valence and conduction bands is at least quadratic. Furthermore, by extending the Gosset-Huang inequality to fermionic systems, we demonstrate that even in interacting and non-translation-invariant cases, the finite-size gap of gapless excitations scales as $O((\log L)^2/L^2)$, provided the ground-state correlation function exhibits a power-law decay. Our results provide a foundation for studying frustration-free fermionic systems, including flat-band ferromagnetism and $\eta$-pairing states.
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https://arxiv.org/abs/2503.12879
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Academic Papers
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b690ba8a6a9dd2632cec248a9b7309e77f10e72bf287021e4e8fa71a98936201
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2026-01-13T00:00:00-05:00
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Frustration-free free fermions
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arXiv:2503.14312v2 Announce Type: replace-cross Abstract: We develop a general theory of frustration-free free-fermion systems and derive the necessary and sufficient conditions for such Hamiltonians. Assuming locality and translation invariance, we find that any band touching between the valence and the conduction bands is always quadratic or softer, which rules out the possibility of describing Dirac and Weyl semimetals using frustration-free local Hamiltonians. We further construct a frustration-free free-fermion model on the honeycomb lattice and show that its density fluctuations acquire an anomalous gap originating from the diverging quantum metric associated with the quadratic band-touching points. Nevertheless, an $O(1/L^2)$ finite-size scaling of the charge-neutral excitation gap can be verified even in the presence of interactions, consistent with the more general results we derive in an accompanying work [arXiv:2503.12879].
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https://arxiv.org/abs/2503.14312
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Academic Papers
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85fd35e20d722ea93cc08c5cd1bada821e8e4062df8fb01e94c6b7fcd9b31aaf
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2026-01-13T00:00:00-05:00
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Inferring charge-noise source locations from correlations in spin qubits
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arXiv:2505.05875v2 Announce Type: replace-cross Abstract: We investigate low-frequency noise in a spin-qubit device made in isotopically purified Si/Si-Ge. Observing sizable cross-correlations among energy fluctuations of different qubits, we conclude that these fluctuations are dominated by charge noise. At low frequencies, the noise spectra are not well described by a power law; instead, they reveal the presence of a few individual two-level fluctuators (TLFs). We demonstrate that the noise cross-correlations allow one to get information on the spatial location of such individual TLFs.
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https://arxiv.org/abs/2505.05875
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Academic Papers
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b77e1b20481ee697613913b2bcdd23e51b151057c37b0f97ec616aec652b3cc3
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2026-01-13T00:00:00-05:00
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Observe novel tricritical phenomena in self-organized Fermi gas induced by higher order Fermi surface nesting
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arXiv:2508.05273v2 Announce Type: replace-cross Abstract: Cold atom systems in optical lattices have long been recognized as an ideal platform for bridging condense matter physics and quantum optics. Here, we investigate the 1D fermionic superradiance in an optical lattice, and observe novel tricritical phenomena and multistability in finite-temperature cases. As a starting point, which can be analytically calculated, we compare the 1D and 2D Fermi gases in zero-temperature limit. It turns out that the tricritical point originates from the higher-order Fermi surface nesting (FSN), and the infrared divergence in 1D systems is absent in 2D cases. When extending to finite-temperature cases, our numerical results reveal that both quantum- and classical-type trcritical phenomena can be observed simultaneously. Moreover, there exists an optimal temperature for observing superradiance. This work provides a new approach to understanding the relation between quantum and classical phase transitions.
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https://arxiv.org/abs/2508.05273
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Academic Papers
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64eb532766732112655abbad9b7ff0590c607a9a1afa02bae3f220f65087f9e5
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2026-01-13T00:00:00-05:00
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Spin ladder quantum simulators from spin-orbit-coupled quantum dot spin qubits
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arXiv:2508.08358v2 Announce Type: replace-cross Abstract: Motivated by the recent Ge hole spin qubit experiments, we construct and study a two-leg spin ladder from a quantum dot array with spin-orbit couplings (SOCs), aiming to uncover the many-body phase diagrams and provide concrete guidance for the Ge hole spin qubit experiments. The spin ladder is described by an unprecedented, complex spin Hamiltonian, which contains antiferromagnetic Heisenberg exchange, Dzyaloshinskii-Moriya (DM), and anisotropic exchange interactions. We analyze the spin ladder Hamiltonian in two complementary situations, the strong rung coupling limit and the weak rung coupling limit. In the strong rung coupling limit, we systematically construct effective spin-1/2 chain models, connecting the well-studied one-dimensional spin models and providing a recipe for Hamiltonian engineering. It is worth emphasizing that effective DM interactions can be completely turned off while the microscopic DM interactions are generically inevitable. Moreover, the staggered DM interactions, which are not possible in the microscopic spin model, can also be realized in the effective spin-1/2 model. In the weak rung coupling limit, we employ Abelian bosonization and Luther-Emery fermionization, uncovering a multitude of phases. Several commensurate-incommensurate transitions are driven by both the longitudinal magnetic field and the DM interactions in the legs (chains). Remarkably, the low-energy phase diagrams show strong dependence in the DM interaction, providing a concrete way to identify the strength of SOC in the experiments. Our work bridges quantum many-body theory and spin qubit device physics, establishing spin ladders made of spin-orbit-coupled quantum dots as a promising platform for engineering exotic spin models, constructing quantum many-body states, and enabling programmable quantum computations.
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https://arxiv.org/abs/2508.08358
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Academic Papers
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967f29d16d8121ba60f62ecee8c77893464c5dfd172a4a7e08f4ae6733c0c09e
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2026-01-13T00:00:00-05:00
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Julia Set in Quantum Evolution: The case of Dynamical Quantum Phase Transitions
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arXiv:2509.14923v2 Announce Type: replace-cross Abstract: Dynamical quantum phase transitions (DQPTs) are a class of non-equilibrium phase transitions that occur in many-body quantum systems during real-time evolution, rather than through parameter tuning as in conventional phase transitions. This paper presents an exact analytical approach to studying DQPTs by combining complex dynamics with the real-space renormalization group (RG). RG transformations are interpreted as iterated maps on the complex plane, establishing a connection between DQPTs and the Julia set, the boundary separating the basins of attraction of the stable fixed points. This framework is applied to a quantum quench in the one-dimensional transverse field Ising model, where we examine the sensitivity of DQPTs to variations in boundary conditions. We show that altering the topology of the spin chain can suppress DQPTs and provide a qualitative explanation based on quantum speed limits.
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https://arxiv.org/abs/2509.14923
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Academic Papers
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1c56f6d75054bcd7a09d40e87929c2c0bb598c79bbf672952440dca166b50812
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2026-01-13T00:00:00-05:00
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Subsystem fidelity in two-dimensional conformal field theories
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arXiv:2510.17208v2 Announce Type: replace-cross Abstract: We investigate the short-interval expansion of the subsystem fidelity in two-dimensional conformal field theories (2D CFTs) using the operator product expansion (OPE) of twist operators. We obtain universal contributions from general quasiprimary operators valid for arbitrary 2D CFTs, along with specific results in free massless boson and fermion theories. The analytical predictions demonstrate excellent agreement with established analytical results in field theories and numerical calculations in integrable models. Furthermore, we extend the method to holographic CFTs, where subsystem fidelity serves to analyze the distinguishability of black hole microstates through the AdS/CFT correspondence. This work establishes a unified framework for quantifying quantum state distinguishability across various 2D CFTs, bridging quantum information techniques with applications in quantum gravity.
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https://arxiv.org/abs/2510.17208
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Academic Papers
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37a7f0a3ff047d4b1a020a9380082a7982a4f96a2ddb1c08b231a61560c6a797
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2026-01-13T00:00:00-05:00
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Asymptotic-freedom and massive glueballs in a qubit-regularized SU(2) gauge theory
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arXiv:2512.11068v2 Announce Type: replace-cross Abstract: We argue that a simple qubit-regularized $\mathrm{SU}(2)$ lattice gauge theory on a plaquette chain serves as a pseudo-one-dimensional toy model for Yang-Mills theory in three spatial dimensions. We map the chain Hamiltonian to the Transverse Field Ising Model in a uniform magnetic field and demonstrate that it can be tuned to a continuum limit in which the short-distance physics is governed by the asymptotically free Ising conformal field theory describing free Majorana fermions, while the long-distance regime contains massive excitations of the $E_8$ quantum field theory that can be interpreted as one-dimensional analogues of glueballs. Furthermore, we find $\sqrt{\sigma}/m_1 = 0.249(1)$ where $\sigma$ is the string tension between two static quarks and $m_1$ is the mass of the lightest glueball.
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https://arxiv.org/abs/2512.11068
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a2eae8ac6a3bd90cf1243ef983cc3b05f10b932ae5b23b4081bbea1540241f66
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2026-01-13T00:00:00-05:00
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Symmetry and Topology in the Non-Hermitian Kitaev chain
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arXiv:2601.00951v2 Announce Type: replace-cross Abstract: We investigate the non-Hermitian Kitaev chain with non-reciprocal hopping amplitudes and asymmetric superconducting pairing. We work out the symmetry structure of the model and show that particle-hole symmetry (PHS) is preserved throughout the entire parameter regime. As a consequence of PHS, the topological phase transition point of a finite open chain coincides with that of the periodic (infinite) system. By explicitly constructing the zero-energy wave functions (Majorana modes), we show that Majorana modes necessarily occur as reciprocal localization pairs accumulating on opposite boundaries, whose combined probability density exhibits an exact cancellation of the non-Hermitian skin effect for the zero energy modes. Excited states, by contrast, generically display skin-effect localization, with particle and hole components accumulating at opposite ends of the system. At the level of bulk topology, we further construct a $\mathbb{Z}_2$ topological invariant in restricted parameter regimes that correctly distinguishes the topological and trivial phases. Finally, we present the topological phase diagram of the non-Hermitian Kitaev chain across a broad range of complex parameters and delineate the associated phase boundaries.
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https://arxiv.org/abs/2601.00951
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Academic Papers
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aea999f7655168e6b27ed84680e4e47726ba198f9947f69119ae8d31b86d50f5
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2026-01-13T05:00:28+00:00
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UBS boss Sergio Ermotti plans to step down in April 2027
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Race for coveted role comes as bank fights Swiss government over threat of more stringent capital buffers
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https://www.ft.com/content/0b6e4687-0804-448c-a7c4-155bc6005136
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Business & Finance
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852c04dbd81f75484222e5e412b8e610623be12b92861f5608b1e836e46bd070
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2026-01-12T23:33:45+00:00
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Top Republicans denounce justice department’s criminal probe into Fed chair
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Backlash builds as Trump administration’s prosecutors target head of US central bank
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https://www.ft.com/content/0af6d453-84dc-46bc-90b6-711242adde73
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Business & Finance
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58ddaf3de7f523f4b335811135ca983e66da7fd5cf16a9d2febe42d12c5345b6
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2026-01-13T05:00:28+00:00
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California’s billionaire tax plan will backfire
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Over the past 50 years the state has become overly reliant on a few deep pockets that it cannot afford to lose
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https://www.ft.com/content/122f71b9-bf0f-47c3-a46d-827740d4ce73
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Business & Finance
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f649b505ed1d26074a3d63339361589fdbdc6f82a777d9fd452f52ec7e4835e1
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2026-01-13T05:00:28+00:00
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When robots meet commercial reality
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Implementing automation systems requires a lot of planning, time and money
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https://www.ft.com/content/ed4e523e-923c-493d-b402-98a03f0cf7dd
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Business & Finance
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c081499ee6f3269369dbde7f169f370af7be7cc2c3e1fc870b1665947eee3171
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2026-01-12T22:07:49+00:00
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Trump announces 25% tariff on countries ‘doing business’ with Iran
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Levies to be applied immediately by US could affect nations such as China and India
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https://www.ft.com/content/c266f78d-1b53-4aa5-99ff-1726a5126a23
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Business & Finance
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3e80442972e90c6c8b7f064727559ad41dd8e0d077f6d6f8a78b22f9279ccfbd
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2026-01-13T05:00:28+00:00
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Trade between EU member states is slowing, data shows
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Findings reinforce warnings from policymakers such as Christine Lagarde that internal market has ‘stood still’
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https://www.ft.com/content/fbc7a2e8-0adb-494b-9a1e-267d06ebd446
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Business & Finance
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9c8208db5cd993d71fe77df3e1f58efde9160042ad7a04087dcf085e59bae1c9
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2026-01-13T04:34:47+00:00
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Japan fuels talk of yen intervention as ‘Takaichi trade’ roars back
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Finance minister Satsuki Katayama says US Treasury secretary shares Tokyo’s concerns about currency’s weakness
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https://www.ft.com/content/54a3eca2-33cf-474c-ba87-098489a8eee2
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Business & Finance
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8736288928f7dce160564b296726fbac0d4e204b879fcddda74fe8af9e30344e
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2026-01-13T05:00:19+00:00
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Microsoft warns that China is winning AI race outside the west
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DeepSeek’s technology is being rapidly adopted across Africa and beyond, tech group’s research shows
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https://www.ft.com/content/f7a5b184-1fef-4f02-b957-4c2b07adf91f
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Business & Finance
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884b999a677100dd92e0b5217130f002e11c303be75c5989d7b831519b322f71
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2026-01-12T21:25:11+00:00
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Alphabet hits $4tn valuation on AI hopes
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Deal with Apple fuels investor optimism over Big Tech group’s competitiveness with OpenAI’s ChatGPT
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https://www.ft.com/content/02d44794-815f-40dc-9b49-0e10432147a9
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Business & Finance
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8b16eeb5d7805d4db27f38eddc918c06938b1d21110a592aec802a1a74d02291
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2026-01-13T01:41:00+00:00
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‘I still have a mortgage’: I’m no longer confident that my costs will actually fall in retirement. What can I do?
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“I think my withdrawals from my 401(k) and IRA may need to be larger than my current take-home pay.”
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https://www.marketwatch.com/story/i-still-have-a-mortgage-im-no-longer-confident-that-my-costs-will-actually-fall-in-retirement-what-can-i-do-ff9164a5?mod=mw_rss_topstories
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Business & Finance
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aab4ccd0611ac6ef710ad9c8887a2dceef0d38dfa5902147bac29a20f8f249f5
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2026-01-13T00:48:00+00:00
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Why oil prices could rise as U.S.-Iran tensions swell
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The Strait of Hormuz, a critical chokepoint for global oil markets, is back in focus for oil traders
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https://www.marketwatch.com/story/why-oil-prices-could-rise-as-u-s-iran-tensions-swell-ee893694?mod=mw_rss_topstories
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Business & Finance
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2026-01-13T00:40:00+00:00
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BlackRock’s Rieder repeats his view that Fed needs to bring interest rates down to 3%
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“The Fed has got to get the rate down to 3% — I think that is closer to equilibrium,” BlackRock’s chief investment officer of global fixed income said.
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https://www.marketwatch.com/story/blackrocks-rieder-repeats-his-view-that-fed-needs-to-bring-interest-rates-down-to-3-0c1a61d3?mod=mw_rss_topstories
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Business & Finance
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https://images.mktw.net/im-87756370
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de35cb9f0de80c01fd13dbb67f27e989ce9ae370e568777bdd3a3f73a1d49a41
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2026-01-12T23:36:00+00:00
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Show us the math: Paramount sues Warner Bros. over how it determined Netflix’s bid is better
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Paramount says it is suing Warner Bros. Discovery and filing a competing slate of directors in an effort to get the Warner board to take its offer to acquire the company seriously.
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https://www.marketwatch.com/story/show-us-the-math-paramount-sues-warner-bros-over-how-it-determined-netflixs-bid-is-better-a023e3d5?mod=mw_rss_topstories
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Business & Finance
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https://images.mktw.net/im-17795657
|
2bf641ff4307d3f1df22461fb19a4de67d09052b9e0905fcd157d27c59582a41
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2026-01-12T23:33:00+00:00
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Could Apple’s Gemini deal be the catalyst the stock needs?
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The iPhone maker reportedly sealed a long-rumored partnership with Google Gemini, sparking hope that Apple is taking AI more seriously.
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https://www.marketwatch.com/story/could-apples-gemini-deal-be-the-catalyst-the-stock-needs-b3cbc2af?mod=mw_rss_topstories
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Business & Finance
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https://images.mktw.net/im-13513792
|
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