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36dcbefe794f22df19929b3247da6ad433522331 | raskar joined mit media lab in 2008. raskar, | raskar joined mit media lab in 2008. raskar, together with others developed a computational display technology that allows observers with refractive errors, cataracts and some other eye disorders to perceive a focused image on a screen without wearing refraction-corrective spectacles. the technology uses a light field ... | wikipedia |
b0efafebe85a4fdb19075a420941cada88d8315d | raskar joined mitsubishi electric research laboratories in 2002. | raskar joined mitsubishi electric research laboratories in 2002. his significant contribution in computer vision and imaging domain led him to win 'tr 100' in 2004, 'the global indus technovator award' in 2004 respectively. | wikipedia |
23a332039ab4c855e130b09d51bf3c9692aee70f | in february 2020, raskar and his team launched | in february 2020, raskar and his team launched private kit: safepaths, a public health tool for contact tracing for covid-19 pandemic. he is also the founder and chief scientist of pathcheck. he is a co-founder of akasha.im which was acquired by alphabet spin-off company intrinsic. | wikipedia |
6477cadfa05b805f03257cf9674491d6ebc85e25 | ramesh raskar is a massachusetts institute of technology | ramesh raskar is a massachusetts institute of technology associate professor and head of the mit media lab's camera culture research group. previously he worked as a senior research scientist at mitsubishi electric research laboratories (merl) during 2002 to 2008. he holds 132 patents in computer vision, computational ... | wikipedia |
71903dda4306d7b5930989054a887de8c7efb272 | dan stroup is a coach for the washington | dan stroup is a coach for the washington stealth of the national lacrosse league. prior to his retirement, stroup played for several teams over a 13-season career which included winning the champion's cup four times: three with the toronto rock, and one (2006) with the colorado mammoth. | wikipedia |
ee69cf68080c7c32c4f24d555e4868ce423103ea | gp – games played; g – goals; a | gp – games played; g – goals; a – assists; pts – points; lb – loose balls; pim – penalty minutes; pts/gp – points per games played; lb/gp – loose balls per games played; pim/gp – penalty minutes per games played. | wikipedia |
d09dafc15fa3169b1bd10c305c52637f3cefe7d4 | dan stroup (born december 18, 1968, in vancouver, | dan stroup (born december 18, 1968, in vancouver, british columbia) is a coach for the washington stealth of the national lacrosse league. prior to his retirement, stroup played for several teams over a 13-season career which included winning the champion's cup four times: three (1999, 2000, and 2002) with the toronto ... | wikipedia |
ae7133a15791139b9023eb7d4fbf002a5ff13a50 | john bohannon is an american science journalist and | john bohannon is an american science journalist and scientist who is director of science at primer, an artificial intelligence company headquartered in san francisco, california. he is known for his career prior to primer as a science journalist and harvard university biologist, most notably with his "gonzo scientist" ... | wikipedia |
b5401e338cbc8e5afc0859f4d68dca8938d85f5f | showing how uncritical mass media can become victims | showing how uncritical mass media can become victims of claims made in fake scientific papers (2015) bohannon is involved in the effective altruism movement. in july 2015 he became a member of giving what we can, an organization whose members pledge to give at least 10% of their income to effective charities. | wikipedia |
5a5817796f95b9ee8a5bbfeab57917e1650d1be1 | in 2015, bohannon appeared on the "adam ruins | in 2015, bohannon appeared on the "adam ruins nutrition" episode of the adam ruins everything trutv series. in 2016, he joined adam ruins everything host adam conover on episode 5 of adam's adam ruins everything podcast series, "science journalism with john bohannon", where he spoke about the fake chocolate study descr... | wikipedia |
050e7451bc79cd6a5ecabf7c60999ace67e4f543 | bohannon performed with the black label movement dance | bohannon performed with the black label movement dance troupe at tedx brussels in november 2011, where he satirized jonathan swift 's a modest proposal by modestly proposing that powerpoint software be replaced by live dancers. bohannon then went on to perform with black label movement at ted 2012 in march in long beac... | wikipedia |
afe8b2ac7ca3cd8def7913d6daa176981b281159 | many gonzo scientist columns were devoted to advertising | many gonzo scientist columns were devoted to advertising the dance your phd competition, which bohannon created in early 2008. the annual competition encourages scientists from all around the world to interpret their doctoral dissertations in dance form. slate magazine ran a profile on bohannon and the competition in 2... | wikipedia |
3794df2708d7767bc394c333d0a94a192c820655 | bohannon's science journalism extended to his on-line "gonzo | bohannon's science journalism extended to his on-line "gonzo scientist" series at science magazine, where he adopted the " gonzo scientist" persona. as the gonzo scientist, bohannon took "a look at the intersections among science, culture, and art – and, in true gonzo style, shrink from making himself a part of the sto... | wikipedia |
6a6f2422fa4bc88216a43a84a7da0a98f3553506 | the only problem with the diet science beat | the only problem with the diet science beat is that it's science. you have to know how to read a scientific paper – and actually bother to do it. for far too long, the people who cover this beat have treated it like gossip, echoing whatever they find in press releases. hopefully our little experiment will make reporter... | wikipedia |
1073798e97eefba371a6d2fc642bd8918057ed55 | the few journalists who contacted bohannon (acting as | the few journalists who contacted bohannon (acting as johannes) asked puff piece questions, and no reporter published how many subjects were tested or quoted independent researchers. most outlets sought to maximize page views by including "vaguely pornographic images of women eating chocolate." bohannon says: | wikipedia |
55b0f44b1f9cd150edb935bfbdec88580b2aa943 | bohannon submitted the manuscript to 20 open-access publishers | bohannon submitted the manuscript to 20 open-access publishers well known for their predatory journals and ended up being published in the international archives of medicine. he invented a fake institute, "the institute of diet and health", to go along with his fake name, "johannes bohannon", and fabricated a press rel... | wikipedia |
1a5ca936767328120f7a995f5c0b4a089984103b | bohannon's bogus study had a tiny sample size | bohannon's bogus study had a tiny sample size of 15 and measured 18 variables, almost guaranteeing an erroneously statistically significant result (false positive) due to random fluctuations in participant outcomes. he told a statistician to deliberately massage the data using overfitting and p-hacking. the study had o... | wikipedia |
7d09c7661ec94a97be9d6955ccdfcaa826c1309d | under the pseudonym johannes bohannon, john bohannon wrote | under the pseudonym johannes bohannon, john bohannon wrote a paper – "chocolate with high cocoa content as a weight-loss accelerator" – detailing a deliberately bad study that he had designed and run to see how the media would pick up the "meaningless" findings. he worked with film-maker peter onneken, who was making a... | wikipedia |
6dee7d44c5b8668239e676689d667f8287cc60d0 | in september 2013, bohannon submitted a fake and | in september 2013, bohannon submitted a fake and very flawed scientific article to a large number of fee-charging open-access publishers, revealing that less than 40% were living up to their promise of rigorously peer-reviewing what is published. the spoof paper was accepted by 157 of the 255 open-access journals (61.6... | wikipedia |
abc5b8099ba8982fa1e9a7c5d76147f6ffde7d27 | bohannon has frequently reported on the intersections of | bohannon has frequently reported on the intersections of science and war. he received a reuters environmental journalism award in 2006 for his reporting on the water crisis in gaza. in that year he also critiqued the lancet surveys of iraq war casualties. after embedding in southern afghanistan in 2010, he was the firs... | wikipedia |
11ea8e9733a338ba0a0bde617a5af1e71d631453 | bohannon is director of science at primer, a | bohannon is director of science at primer, a san francisco, california, company that develops and sells artificial intelligence technology, started by his friend sean gourley. before joining primer, bohannon was a contributing correspondent for science magazine and also wrote for discover magazine, wired, the guardian,... | wikipedia |
2addb2699475d9add9ab6ce27c85510bd6bb6c64 | bohannon completed his doctor of philosophy degree in | bohannon completed his doctor of philosophy degree in molecular biology at the university of oxford in 2002, supervised by paul rainey. his doctoral thesis investigated the role of an operon in the adaptive evolution of populations of the bacterium pseudomonas fluorescens and was supervised by paul rainey. | wikipedia |
0e91ab1a23e2ab9c5a5a2de728a354dd9779e65c | john bohannon is an american science journalist and | john bohannon is an american science journalist and scientist who is director of science at primer, an artificial intelligence company headquartered in san francisco, california. he is known for his career prior to primer as a science journalist and harvard university biologist, most notably with his "gonzo scientist" ... | wikipedia |
a5c0176fc8bd80e832afbd2c6b65bcf14a618a5b | non-ionizing radiation refers to any type of electromagnetic | non-ionizing radiation refers to any type of electromagnetic radiation that does not carry enough energy per quantum to ionize atoms or molecules—that is, to completely remove an electron from an atom or molecule. instead of producing charged ions when passing through matter, non-ionizing electromagnetic radiation has ... | wikipedia |
66697533f8c749fe1e3e9421a5441d585a926576 | black-body radiation is radiation from an idealized radiator | black-body radiation is radiation from an idealized radiator that emits at any temperature the maximum possible amount of radiation at any given wavelength. a black body will also absorb the maximum possible incident radiation at any given wavelength. the radiation emitted covers the entire electromagnetic spectrum and... | wikipedia |
389fae3c9e775fbc5da67c965ead8d89a26a39c4 | as noted above, even low-frequency thermal radiation may | as noted above, even low-frequency thermal radiation may cause temperature-ionization whenever it deposits sufficient thermal energy to raises temperatures to a high enough level. common examples of this are the ionization (plasma) seen in common flames, and the molecular changes caused by the " browning " in food-cook... | wikipedia |
4c7185d3338d0846dd8b2d96546a06eda38e09ee | parts of the electromagnetic spectrum of thermal radiation | parts of the electromagnetic spectrum of thermal radiation may be ionizing, if the object emitting the radiation is hot enough (has a high enough temperature). a common example of such radiation is sunlight, which is thermal radiation from the sun's photosphere and which contains enough ultraviolet light to cause ioniz... | wikipedia |
ea19b18f835add4788c936d4f41f8baad6e2e42a | thermal radiation, a common synonym for infrared when | thermal radiation, a common synonym for infrared when it occurs at temperatures commonly encountered on earth, is the process by which the surface of an object radiates its thermal energy in the form of electromagnetic waves. infrared radiation that one can feel emanating from a household heater, infra-red heat lamp, o... | wikipedia |
177424de8c27e3f871e1dab56c3c41b724f1741e | extremely low frequency (elf) is the range of | extremely low frequency (elf) is the range of radiation frequencies from 300 hz to 3 khz. in atmosphere science, an alternative definition is usually given, from 3 hz to 3 khz. in the related magnetosphere science, the lower frequency electromagnetic oscillations (pulsations occurring below ~3 hz) are considered to be ... | wikipedia |
58efcdf9afba8cc15ec035bbbf5c37c312ef4f40 | very low frequency or vlf is the range | very low frequency or vlf is the range of rf of 3 to 30 khz. since there is not much bandwidth in this band of the radio spectrum, only the very simplest signals are used, such as for radio navigation. also known as the myriametre band or myriametre wave as the wavelengths range from ten to one myriametre (an obsolete ... | wikipedia |
7d4424b389fc085497e3fcd09eb7ab9e8a42f442 | radio waves are a type of electromagnetic radiation | radio waves are a type of electromagnetic radiation with wavelengths in the electromagnetic spectrum longer than infrared light. like all other electromagnetic waves, they travel at the speed of light. naturally occurring radio waves are made by lightning, or by astronomical objects. artificially generated radio waves ... | wikipedia |
e3da172f766bc4c900a6c7f873a267ac662382b8 | microwaves are electromagnetic waves with wavelengths ranging from | microwaves are electromagnetic waves with wavelengths ranging from as long as one meter to as short as one millimeter, or equivalently, with frequencies between 300 mhz (0.3 ghz) and 300 ghz. this broad definition includes both uhf and ehf (millimeter waves), and various sources use different boundaries. in all cases, ... | wikipedia |
9b74d87a9bf028a1fd96f08c2e39aeee98e7e71a | infrared (ir) light is electromagnetic radiation with a | infrared (ir) light is electromagnetic radiation with a wavelength between 0.7 and 300 micrometers, which equates to a frequency range between approximately 1 and 430 thz. ir wavelengths are longer than that of visible light, but shorter than that of terahertz radiation microwaves. bright sunlight provides an irradianc... | wikipedia |
7439a3edd7de65c9f850b9b2cead221d03cf55d9 | light, or visible light, is the very narrow | light, or visible light, is the very narrow range of electromagnetic radiation that is visible to the human eye (about 400–700 nm), or up to 380–750 nm. more broadly, physicists refer to light as electromagnetic radiation of all wavelengths, whether visible or not. | wikipedia |
c5ff115c14f36325d5b2a1672669e11e4bab72b6 | for example, ultraviolet light, even in the non-ionizing | for example, ultraviolet light, even in the non-ionizing range, can produce free radicals that induce cellular damage, and can be carcinogenic. photochemistry such as pyrimidine dimer formation in dna can happen through most of the uv band, including much of the band that is formally non-ionizing. ultraviolet light ind... | wikipedia |
b4dbea94e188610c80fa4fd7828bac068c50d91d | ultraviolet light can cause burns to skin and | ultraviolet light can cause burns to skin and cataracts to the eyes. ultraviolet is classified into near, medium and far uv according to energy, where near and medium ultraviolet are technically non-ionizing, but where all uv wavelengths can cause photochemical reactions that to some extent mimic ionization (including ... | wikipedia |
3a6eda99b6051bd3df44eab27fda68bdf656d5c5 | the international agency for research on cancer recently | the international agency for research on cancer recently stated that there could be some risk from non-ionizing radiation to humans. but a subsequent study reported that the basis of the iarc evaluation was not consistent with observed incidence trends. this and other reports suggest that there is virtually no way that... | wikipedia |
1649d8da305166c9b5a4f56809444465526a3bdf | in addition to the well-known effect of non-ionizing | in addition to the well-known effect of non-ionizing ultraviolet light causing skin cancer, non-ionizing radiation can produce non-mutagenic effects such as inciting thermal energy in biological tissue that can lead to burns. in 2011, the international agency for research on cancer (iarc) from the world health organiza... | wikipedia |
539fafc456a395685c27aaeb33e8c8555a11a3a9 | exposure to non-ionizing ultraviolet light is a risk | exposure to non-ionizing ultraviolet light is a risk factor for developing skin cancer (especially non-melanoma skin cancers), sunburn, premature aging of skin, and other effects.despite the possible hazards it is beneficial to humans in the right dosage, since vitamin d is produced due to the biochemical effects of ul... | wikipedia |
c0eca39e96585108bea09686c4ed648e79e7aa18 | different biological effects are observed for different types | different biological effects are observed for different types of non-ionizing radiation. the upper frequencies(lower energy ultraviolet) of non-ionizing radiation are capable of non-thermal biological damage, similar to ionizing radiation. it is still to be proven that non-thermal effects of radiation of much lower fre... | wikipedia |
655245f503fef273842154504b5fa069089a6de0 | the energy of non-ionizing radiation is low, and | the energy of non-ionizing radiation is low, and instead of producing charged ions when passing through matter, it has only sufficient energy to change the rotational, vibrational or electronic valence configurations of molecules and atoms. this produces thermal effects. the possible non-thermal effects of non-ionizing... | wikipedia |
26b28ff10c9e97e205b2249308c12d02dfbca84c | the occurrence of ionization depends on the energy | the occurrence of ionization depends on the energy of the individual particles or waves, and not on their number. an intense flood of particles or waves will not cause ionization if these particles or waves do not carry enough energy to be ionizing, unless they raise the temperature of a body to a point high enough to ... | wikipedia |
8789e3cd4f14b26466d251ae7664dcab82a2fab0 | near ultraviolet, visible light, infrared, microwave, radio waves, | near ultraviolet, visible light, infrared, microwave, radio waves, and low-frequency radio frequency (very low frequency, extremely low frequency) are all examples of non-ionizing radiation. by contrast, far ultraviolet light, x-rays, gamma-rays, and all particle radiation from radioactive decay are ionizing. visible a... | wikipedia |
471a6363d94b400d349ab962e08f1691a5056f7a | the region at which radiation is considered "ionizing" | the region at which radiation is considered "ionizing" is not well defined, since different molecules and atoms ionize at different energies. the usual definitions have suggested that radiation with particle or photon energies less than 10 electronvolts (ev) be considered non-ionizing. another suggested threshold is 33... | wikipedia |
b58ade8eaffe312aa51f8de710da3320ed217d43 | non-ionizing (or non-ionising) radiation refers to any type | non-ionizing (or non-ionising) radiation refers to any type of electromagnetic radiation that does not carry enough energy per quantum (photon energy) to ionize atoms or molecules—that is, to completely remove an electron from an atom or molecule. instead of producing charged ions when passing through matter, non-ioniz... | wikipedia |
82d3a04091dc0b7f720ce4ddf36ed2d04cd71d18 | the station consists of one ground-level side platform | the station consists of one ground-level side platform and one island platform. the station building is located adjacent to platform 1 of the side platform, and to platforms 2 and 3 on the island platform are connected by a footbridge. most trains use platforms 1 and 3, and platform 2 is used only for return trains bet... | wikipedia |
e98a9368283a8c4d7c8f73385cffec3ac51d8d0c | yoshinaga station (吉永駅, yoshinaga-eki) is a passenger railway | yoshinaga station (吉永駅, yoshinaga-eki) is a passenger railway station located in the yoshinaga neighborhood of the city of bizen, okayama prefecture, japan, operated by the west japan railway company (jr west). | wikipedia |
c5d6d720fbfbc540d84ef4f736bf558a835ea915 | quantum decoherence is the loss of quantum coherence. | quantum decoherence is the loss of quantum coherence. quantum decoherence has been studied to understand how quantum systems convert to systems which can be explained by classical mechanics. beginning out of attempts to extend the understanding of quantum mechanics, the theory has developed in several directions and ex... | wikipedia |
6616be7d707f15c7fbeecb7715d3cb753739173c | in august 2020 scientists reported that ionizing radiation | in august 2020 scientists reported that ionizing radiation from environmental radioactive materials and cosmic rays may substantially limit the coherence times of qubits if they aren't shielded adequately which may be critical for realizing fault-tolerant superconducting quantum computers in the future. | wikipedia |
ee64c2c1aa2a059833dc17ae8f0d074202ac513b | decoherence is a challenge for the practical realization | decoherence is a challenge for the practical realization of quantum computers, since such machines are expected to rely heavily on the undisturbed evolution of quantum coherences. they require that the coherence of states be preserved and that decoherence be managed, in order to actually perform quantum computation. th... | wikipedia |
2c5817df3ba2cc8adab87ddd326f444061f90622 | in july 2011, researchers from university of british | in july 2011, researchers from university of british columbia and university of california, santa barbara showed that applying high magnetic fields to single molecule magnets suppressed two of three known sources of decoherence. they were able to measure the dependence of decoherence on temperature and magnetic field s... | wikipedia |
09230967c3d394825798e0ad38c66c328268c3f0 | the process of a quantum superposition gradually obliterated | the process of a quantum superposition gradually obliterated by decoherence was quantitatively measured for the first time by serge haroche and his co-workers at the École normale supérieure in paris in 1996. their approach involved sending individual rubidium atoms, each in a superposition of two states, through a mic... | wikipedia |
a7366e36482f82d383957eb952296e33c6633032 | that is, we have a diagonal mixed state, | that is, we have a diagonal mixed state, there is no constructive or destructive interference, and the "probabilities" add up classically. the time it takes for u (t) (the unitary operator as a function of time) to display the decoherence property is called the decoherence time. | wikipedia |
bb51848771b45a384eef74126789a0c1a23e1117 | this often turns out to be true (as | this often turns out to be true (as a reasonable conjecture) in the position basis because how a interacts with the environment would often depend critically upon the position of the objects in a. then, if we take the partial trace over the environment, we would find the density state is approximately described by | wikipedia |
c701bcef3563e9985caa0dcc81f27918f55f56e7 | respectively. one thing to realize is that the | respectively. one thing to realize is that the environment contains a huge number of degrees of freedom, a good number of them interacting with each other all the time. this makes the following assumption reasonable in a handwaving way, which can be shown to be true in some simple toy models. assume that there exists a... | wikipedia |
98a9b3766494cd8e3a5a4afa0bb74ed7e1518420 | where | ψ 1 ⟩ {\displaystyle |\psi _{1}\rangle | where | ψ 1 ⟩ {\displaystyle |\psi _{1}\rangle } and | ψ 2 ⟩ {\displaystyle |\psi _{2}\rangle } are orthogonal, and there is no entanglement initially. also, choose an orthonormal basis { | e i ⟩ } i {\displaystyle \{|e_{i}\rangle \}_{i}} for h a {\displaystyle {\mathcal {h}}_{a}}. (this could be a "continuously indexe... | wikipedia |
7336e41f34cd6d9e4b2077a27b4283fb9ae4adb5 | this is a reasonably good approximation in the | this is a reasonably good approximation in the case where a and ϵ {\displaystyle \epsilon } are relatively independent (e.g. there is nothing like parts of a mixing with parts of ϵ {\displaystyle \epsilon } or conversely). the point is, the interaction with the environment is for all practical purposes unavoidable (e.g... | wikipedia |
cf2bb3c0793e1de9b04d9e27558be4cdff9c482e | assume for the moment that the system in | assume for the moment that the system in question consists of a subsystem a being studied and the "environment" ϵ {\displaystyle \epsilon }, and the total hilbert space is the tensor product of a hilbert space h a {\displaystyle {\mathcal {h}}_{a}} describing a and a hilbert space h ϵ {\displaystyle {\mathcal {h}}_{\ep... | wikipedia |
3da7efe9d065b07d89d4573b9005f02560a33d44 | decoherence represents an extremely fast process for macroscopic | decoherence represents an extremely fast process for macroscopic objects, since these are interacting with many microscopic objects, with an enormous number of degrees of freedom in their natural environment. the process is needed if we are to understand why we tend not to observe quantum behavior in everyday macroscop... | wikipedia |
0dd74729102b80914c2ab844bb7be518a0768355 | dissipation is a decohering process by which the | dissipation is a decohering process by which the populations of quantum states are changed due to entanglement with a bath. an example of this would be a quantum system that can exchange its energy with a bath through the interaction hamiltonian. if the system is not in its ground state and the bath is at a temperature... | wikipedia |
04af12f49844ec540566600bde4cd72d0e1a143b | depolarizing is a non-unitary transformation on a quantum | depolarizing is a non-unitary transformation on a quantum system which maps pure states to mixed states. this is a non-unitary process because any transformation that reverses this process will map states out of their respective hilbert space thus not preserving positivity (i.e. the original probabilities are mapped to... | wikipedia |
c801e40ae3383d58df98b9d42e7ee7d0eac6202d | observe that the off-diagonal elements—the coherence terms—decay as | observe that the off-diagonal elements—the coherence terms—decay as the spread of the random phase, σ {\displaystyle \sigma }, increases over time (which is a realistic expectation). thus the density matrices for each qubit of the system become indistinguishable over time. this means that no measurement can distinguish... | wikipedia |
d96a9110e86ce02aa05a3fc0e8c68a9ffce9451e | where p (⋅) {\displaystyle p(\cdot)} is a probability | where p (⋅) {\displaystyle p(\cdot)} is a probability measure of the random phase, ϕ {\displaystyle \phi }. although not entirely necessary, let us assume for simplicity that this is given by the gaussian distribution, i.e. p (d ϕ) = 1 2 π σ e − 1 2 (ϕ σ) 2 d ϕ {\displaystyle p({\text{d}}\phi)={\frac {1}{{\sqrt {2\pi }... | wikipedia |
62506797254127e61eaa23da22568193fc5ff77e | this state will decohere, since it is not | this state will decohere, since it is not ‘encoded’ with (dependent upon) the dephasing factor e i ϕ {\displaystyle e^{i\phi }}. this can be seen by examining the density matrix averaged over the random phase ϕ {\displaystyle \phi }: | wikipedia |
cfcf1a99143b6d345a2b07aba9d99068ef84c7fa | since any qubit in this space can be | since any qubit in this space can be expressed in terms of the basis qubits, then all such qubits will be transformed under this rotation. consider the j {\displaystyle j} th qubit in a pure state | ψ j ⟩ ⟨ ψ j | {\displaystyle \vert \psi _{j}\rangle \langle \psi _{j}\vert } where | ψ j ⟩ = a | 0 ⟩ + b | 1 ⟩ {\displays... | wikipedia |
c1af794c9e4808e6ad3d8ae38d1c782278db16a5 | consider a system of n qubits that is | consider a system of n qubits that is coupled to a bath symmetrically. suppose this system of n qubits undergoes a rotation around the | ↑ ⟩ ⟨ ↑ |, | ↓ ⟩ ⟨ ↓ | {\displaystyle |{\uparrow }\rangle \langle {\uparrow }|,|{\downarrow }\rangle \langle {\downarrow }|} (| 0 ⟩ ⟨ 0 |, | 1 ⟩ ⟨ 1 |) {\displaystyle {\big (}|0\rangl... | wikipedia |
eae32b29d0eb746f73c30c528eee81e411e38aa8 | decoherence can be modelled as a non- unitary | decoherence can be modelled as a non- unitary process by which a system couples with its environment (although the combined system plus environment evolves in a unitary fashion). thus the dynamics of the system alone, treated in isolation, are non-unitary and, as such, are represented by irreversible transformations ac... | wikipedia |
412f8b4eb0bc488450a0f286c3f5c0253aabfc6e | the { f α } α = 1 | the { f α } α = 1 m {\displaystyle \{\mathbf {f} _{\alpha }\}_{\alpha =1}^{m}} are basis operators for the m -dimensional space of bounded operators that act on the system hilbert space h s {\displaystyle {\mathcal {h}}_{s}} and are the error generators. the matrix elements b α β {\displaystyle b_{\alpha \beta }} repre... | wikipedia |
e196b4a3bdc3a6720fed8d120274f8c31921f493 | where h ~ s = h s + | where h ~ s = h s + Δ {\displaystyle {\tilde {h}}_{s}=h_{s}+\delta } is the system hamiltonian h s {\displaystyle h_{s}} along with a (possible) unitary contribution Δ {\displaystyle \delta } from the bath, and l d {\displaystyle l_{d}} is the lindblad decohering term. the lindblad decohering term is represented as | wikipedia |
4ef897cb5e60fa45c5731be533fa505b38361951 | a more general consideration for the existence of | a more general consideration for the existence of decoherence in a quantum system is given by the master equation, which determines how the density matrix of the system alone evolves in time (see also the belavkin equation for the evolution under continuous measurement). this uses the schrödinger picture, where evoluti... | wikipedia |
b281997e17febc58c13f7045cdc6dce19e53924a | this restriction determines whether decoherence will occur or | this restriction determines whether decoherence will occur or not in the osr. in particular, when there is more than one term present in the sum for ρ s (t) {\displaystyle \rho _{s}(t)}, then the dynamics of the system will be non-unitary, and hence decoherence will take place. | wikipedia |
56f120b5800b84c24937b2e505d692cd5a2d0b09 | where a ^ l, a ^ l † | where a ^ l, a ^ l † {\displaystyle {\hat {a}}_{l},{\hat {a}}_{l}^{\dagger }} are defined as the kraus operators and are represented as (the index l {\displaystyle l} combines indices k {\displaystyle k} and j {\displaystyle j}): | wikipedia |
4f3c73f59f0090f852e713f83703c4b0fe521be3 | ρ s (t) {\displaystyle \rho _{s}(t)} is called | ρ s (t) {\displaystyle \rho _{s}(t)} is called the reduced density matrix and gives information about the system only. if the bath is written in terms of its set of orthogonal basis kets, that is, if it has been initially diagonalized, then ρ b (0) = ∑ j a j | j ⟩ ⟨ j | {\displaystyle \textstyle \rho _{b}(0)=\sum _{j}a... | wikipedia |
26793ac941a104afd5c79c179d1d5207e45840f3 | where s ^ i ⊗ b ^ i | where s ^ i ⊗ b ^ i {\displaystyle {\hat {s}}_{i}\otimes {\hat {b}}_{i}} is the operator acting on the combined system–bath hilbert space, and s ^ i, b ^ i {\displaystyle {\hat {s}}_{i},{\hat {b}}_{i}} are the operators that act on the system and bath respectively. this coupling of the system and bath is the cause of d... | wikipedia |
a984d65c9e1183338c389d8854497b2edc46b6f2 | where the unitary operator is u ^ = | where the unitary operator is u ^ = e − i h ^ t / ℏ {\displaystyle {\hat {u}}=e^{-i{\hat {h}}t/\hbar }}. if the system and bath are not entangled initially, then we can write ρ s b = ρ s ⊗ ρ b {\displaystyle \rho _{sb}=\rho _{s}\otimes \rho _{b}}. therefore, the evolution of the system becomes | wikipedia |
5129c7de789f3ea4ebd627c085d567195250779f | where h ^ s, h ^ b {\displaystyle | where h ^ s, h ^ b {\displaystyle {\hat {h}}_{s},{\hat {h}}_{b}} are the system and bath hamiltonians respectively, h ^ i {\displaystyle {\hat {h}}_{i}} is the interaction hamiltonian between the system and bath, and i ^ s, i ^ b {\displaystyle {\hat {i}}_{s},{\hat {i}}_{b}} are the identity operators on the system and... | wikipedia |
88450575833eeff9d1f820ae3674fdd0420be9ab | consider a system s and environment (bath) b, | consider a system s and environment (bath) b, which are closed and can be treated quantum-mechanically. let h s {\displaystyle {\mathcal {h}}_{s}} and h b {\displaystyle {\mathcal {h}}_{b}} be the system's and bath's hilbert spaces respectively. then the hamiltonian for the combined system is | wikipedia |
f60165e4b316836cf750548affad5dcc246eb0c2 | to get the reduced density matrix of the | to get the reduced density matrix of the system, we trace out the environment and employ the decoherence/ einselection condition and see that the off-diagonal terms vanish (a result obtained by erich joos and h. d. zeh in 1985): | wikipedia |
cb61c61590728f35cf0d39867637ca4b42e97558 | where ψ i = ⟨ i | ψ | where ψ i = ⟨ i | ψ ⟩ {\displaystyle \psi _{i}=\langle i|\psi \rangle }, ψ i ∗ = ⟨ ψ | i ⟩ {\displaystyle \psi _{i}^{*}=\langle \psi |i\rangle }, and ϕ i = ⟨ i | ϕ ⟩ {\displaystyle \phi _{i}=\langle i|\phi \rangle } etc. | wikipedia |
20cee15d3b4f920117960a3dfea55f6648aa49b1 | where | ϵ ⟩ {\displaystyle |\epsilon \rangle } | where | ϵ ⟩ {\displaystyle |\epsilon \rangle } is the state of the environment.then if the transition happens before any interaction takes place between the system and the environment, the environment subsystem has no part and can be traced out, leaving the reduced density matrix for the system: | wikipedia |
d03b4dd7a393a998b2c7f3def0b81d4a22bc9f2e | the effect of decoherence on density matrices is | the effect of decoherence on density matrices is essentially the decay or rapid vanishing of the off-diagonal elements of the partial trace of the joint system's density matrix, i.e. the trace, with respect to any environmental basis, of the density matrix of the combined system and its environment. the decoherence irr... | wikipedia |
823de600770116158c39030863fec2b723abdde3 | have vanished from the transition-probability calculation. the decoherence | have vanished from the transition-probability calculation. the decoherence has irreversibly converted quantum behaviour (additive probability amplitudes) to classical behaviour (additive probabilities). however, ballentine shows that the significant impact of decoherence to reduce interference need not have significanc... | wikipedia |
7d3ff65658aba2211f31d239ab771e8854e7b054 | if we compare this with the formula we | if we compare this with the formula we derived before the environment introduced decoherence, we can see that the effect of decoherence has been to move the summation sign ∑ i {\displaystyle \textstyle \sum _{i}} from inside of the modulus sign to outside. as a result, all the cross- or quantum interference -terms | wikipedia |
5d5f0e5036e63ca1508bcc6b784121268c29789b | the internal summation vanishes when we apply the | the internal summation vanishes when we apply the decoherence/ einselection condition ⟨ ϵ i | ϵ j ⟩ ≈ δ i j {\displaystyle \langle \epsilon _{i}|\epsilon _{j}\rangle \approx \delta _{ij}}, and the formula simplifies to | wikipedia |
cc3f864f3e492908b04884c5e9a1b1b1d5b8fa8d | to calculate the probability of observing the system | to calculate the probability of observing the system making a quantum leap from ψ {\displaystyle \psi } to ϕ {\displaystyle \phi } after ψ {\displaystyle \psi } has interacted with its environment, then application of the born probability rule states that we must sum over all the relevant possible states | ϵ i ⟩ {\disp... | wikipedia |
65d01d026bcf46ecbcccf107071bf3d02cc4d5e0 | the above expansion of the transition probability has | the above expansion of the transition probability has terms that involve i ≠ j {\displaystyle i\neq j}; these can be thought of as representing interference between the different basis elements or quantum alternatives. this is a purely quantum effect and represents the non-additivity of the probabilities of quantum alt... | wikipedia |
cb61c61590728f35cf0d39867637ca4b42e97558 | where ψ i = ⟨ i | ψ | where ψ i = ⟨ i | ψ ⟩ {\displaystyle \psi _{i}=\langle i|\psi \rangle }, ψ i ∗ = ⟨ ψ | i ⟩ {\displaystyle \psi _{i}^{*}=\langle \psi |i\rangle }, and ϕ i = ⟨ i | ϕ ⟩ {\displaystyle \phi _{i}=\langle i|\phi \rangle } etc. | wikipedia |
5137118cdec4503eacbf5a3128d9e4af4e933dbc | the utility of decoherence lies in its application | the utility of decoherence lies in its application to the analysis of probabilities, before and after environmental interaction, and in particular to the vanishing of quantum interference terms after decoherence has occurred. if we ask what is the probability of observing the system making a transition from ψ {\display... | wikipedia |
ebd862fa9fd67fb5e30372dd936a159bed8f6d69 | note that if the system basis | i | note that if the system basis | i ⟩ {\displaystyle |i\rangle } were not an einselected basis, then the last condition is trivial, since the disturbed environment is not a function of i {\displaystyle i}, and we have the trivial disturbed environment basis | ϵ j ⟩ = | ϵ ′ ⟩ {\displaystyle |\epsilon _{j}\rangle =|\epsilo... | wikipedia |
3c186d791047c9f4f0eeb736770f68cf934b9fdc | where ⟨ ϵ i | ϵ i ⟩ | where ⟨ ϵ i | ϵ i ⟩ = 1 {\displaystyle \langle \epsilon _{i}|\epsilon _{i}\rangle =1} was used. additionally, decoherence requires, by virtue of the large number of hidden degrees of freedom in the environment, that | wikipedia |
e3efbc66bf169b0f3b0eb0e333644188a17d2d83 | the unitarity of time evolution demands that the | the unitarity of time evolution demands that the total state basis remains orthonormal, i.e. the scalar or inner products of the basis vectors must vanish, since ⟨ i | j ⟩ = δ i j {\displaystyle \langle i|j\rangle =\delta _{ij}}: | wikipedia |
c98f9877969d204761fc34b148833c5eb8cc29c4 | where | i ⟩ | ϵ ⟩ {\displaystyle | where | i ⟩ | ϵ ⟩ {\displaystyle |i\rangle |\epsilon \rangle } is shorthand for the tensor product | i ⟩ ⊗ | ϵ ⟩ {\displaystyle |i\rangle \otimes |\epsilon \rangle }. there are two extremes in the way the system can interact with its environment: either (1) the system loses its distinct identity and merges with the env... | wikipedia |
0ba04a9c80e287e5be86939c9c48717456064766 | where the | i ⟩ {\displaystyle |i\rangle } | where the | i ⟩ {\displaystyle |i\rangle } s form an einselected basis (environmentally induced selected eigenbasis), and let the environment initially be in the state | ϵ ⟩ {\displaystyle |\epsilon \rangle }. the vector basis of the combination of the system and the environment consists of the tensor products of the b... | wikipedia |
6aa92bbe1b3f68f2bf2b8d6f39103dd8ee646f60 | as a consequence, the system behaves as a | as a consequence, the system behaves as a classical statistical ensemble of the different elements rather than as a single coherent quantum superposition of them. from the perspective of each ensemble member's measuring device, the system appears to have irreversibly collapsed onto a state with a precise value for the ... | wikipedia |
7b3c353807dd59f1c7fd6e7f67fc17769cea135b | any measuring device or apparatus acts as an | any measuring device or apparatus acts as an environment, since at some stage along the measuring chain, it has to be large enough to be read by humans. it must possess a very large number of hidden degrees of freedom. in effect, the interactions may be considered to be quantum measurements. as a result of an interacti... | wikipedia |
3de6eb58e72aa0d3a01b5ed8965773e887fce356 | the original system's wave function can be expanded | the original system's wave function can be expanded in many different ways as a sum of elements in a quantum superposition. each expansion corresponds to a projection of the wave vector onto a basis. the basis can be chosen at will. choosing an expansion where the resulting basis elements interact with the environment ... | wikipedia |
361eb0b44cdfd7bf4f0b57400dfa3dfe2b4a1596 | different previously isolated, non-interacting systems occupy different phase | different previously isolated, non-interacting systems occupy different phase spaces. alternatively we can say that they occupy different lower-dimensional subspaces in the phase space of the joint system. the effective dimensionality of a system's phase space is the number of degrees of freedom present, which—in non-r... | wikipedia |
e8d68d459537452697f9da798bf356a7ea14d422 | an n -particle system can be represented in | an n -particle system can be represented in non-relativistic quantum mechanics by a wave function ψ (x 1, x 2, …, x n) {\displaystyle \psi (x_{1},x_{2},\dots,x_{n})}, where each x is a point in 3-dimensional space. this has analogies with the classical phase space. a classical phase space contains a real-valued functio... | wikipedia |
6fad8171c7a7e2309859cce76d455ef37f2d1492 | to examine how decoherence operates, an "intuitive" model | to examine how decoherence operates, an "intuitive" model is presented below. the model requires some familiarity with quantum theory basics. analogies are made between visualizable classical phase spaces and hilbert spaces. a more rigorous derivation in dirac notation shows how decoherence destroys interference effect... | wikipedia |
2c0d4a1e8c79835494c9fd396ef366cabdacab7f | decoherence does not claim to provide a mechanism | decoherence does not claim to provide a mechanism for some actual wave-function collapse; rather it puts forth a reasonable framework for the appearance of wave-function collapse. the quantum nature of the system is simply "leaked" into the environment so that a total superposition of the wave function still exists, bu... | wikipedia |
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