Quantum decoherence of two qubits

Helm, Julius; Strunz, Walter T.

doi:10.1103/physreva.80.042108

Cited by 64 publications

(80 citation statements)

References 37 publications

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“…This behavior explains the observed buildup of the quasi-equilibrium in liquid crystals. The results of this work, together with the conclusions obtained in references 11,13 , can contribute to elucidate the underlying quantum mechanisms for decoherence of open quantum systems of interacting spins, for instance the role played by quantum correlations between the observed system and the environment in the damping of the spin coherences 25,26 . Certainly, these works showed that in liquid crystals it is essential to assume the quantum character of the spin-environment coupling to explain the observed irreversible decoherence.…”

Section: Discussionmentioning

confidence: 60%

“…Also, understanding the nature of the decoherence mechanism can contribute to the set up of a quantum spin-lattice relaxation theory beyond the Markovian limit, providing insight into the interplay of the quantum correlations developed in the microscopic irreversible dynamics and the dissipative macroscopic evolution. Finally, the analysis carried out in this work may contribute to the current discussion about the role of system-environment entanglement as basic mechanism of quantum decoherence of interacting particle systems 1,[25][26][27] .…”

Section: Introductionmentioning

confidence: 90%

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Quantum irreversible decoherence behaviour in open quantum systems with few degrees of freedom: Application to 1H NMR reversion experiments in nematic liquid crystals

Segnorile

Zamar²

2013

The Journal of Chemical Physics

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An experimental study of NMR spin decoherence in nematic liquid crystals is presented. Decoherence dynamics can be put in evidence by means of refocusing experiments of the dipolar interactions. The experimental technique used in this work is based on the MREV8 pulse sequence. The aim of the work is to detect the main features of the irreversible quantum decoherence in liquid crystals, on the basis of the theory presented by the authors recently. The focus is laid on experimentally probing the eigen-selection process in the intermediate time scale, between quantum interference of a closed system and thermalization, as a signature of the quantum spin decoherence of the open quantum system, as well as on quantifying the effects of non-idealities as possible sources of signal decays which could mask the intrinsic decoherence. In order to contrast experiment and theory, the theory was adapted to obtain the decoherence function corresponding to the MREV8 reversion experiments. Non-idealities of the experimental setting, like external field inhomogeneity, pulse misadjustments and the presence of non-reverted spin interaction terms are analysed in detail within this framework, and their effects on the observed signal decay are numerically estimated. It is found that, though all these non-idealities could in principle affect the evolution of the spin dynamics, their influence can be mitigated and they do not present the characteristic behaviour of the irreversible spin decoherence. As unique characteristic of decoherence, the experimental results clearly show the occurrence of eigen-selectivity in the intermediate timescale, in complete agreement with the theoretical predictions. We conclude that the eigen-selection effect is the fingerprint of decoherence associated with a quantum open spin system in liquid crystals. Besides, these features of the results account for the quasi-equilibrium states of the spin system, which were observed previously in these mesophases, and lead to conclude that the quasi-equilibrium is a definite stage of the spin dynamics during its evolution towards equilibrium.

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Section: Discussionmentioning

confidence: 60%

Section: Introductionmentioning

confidence: 90%

Quantum irreversible decoherence behaviour in open quantum systems with few degrees of freedom: Application to 1H NMR reversion experiments in nematic liquid crystals

Segnorile

Zamar²

2013

The Journal of Chemical Physics

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“…The reduced dynamics can be obtained from a local Schrödinger equation driven by a random Hermitian Hamiltonian. By contrast, genuine quantum decoherence may be found in two-qubit systems [28]. It is also worth noting that random unitary dynamics emerging from an open quantum system with environmental initial pure state can always be "undone"(quantum error correction) [41,42].…”

Section: Random Unitary Representationsmentioning

confidence: 99%

“…So even for larger Hilbert space dimension than two -on a local level -pure dephasing based on a quantum oscillator model like (1) cannot be distinguished from random unitary dynamics. For genuine quantum decoherence, one needs "more quantum mechanical" environments [28].…”

Section: Random Unitary Representationsmentioning

confidence: 99%

System–environment correlations and non-Markovian dynamics

Pernice

Helm

Strunz

2012

J. Phys. B: At. Mol. Opt. Phys.

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We determine the total state dynamics of a dephasing open quantum system using the standard environment of harmonic oscillators. Of particular interest are random unitary approaches to the same reduced dynamics and system-environment correlations in the full model. Concentrating on a model with an at times negative dephasing rate, the issue of "non-Markovianity" will also be addressed. Crucially, given the quantum environment, the appearance of non-Markovian dynamics turns out to be accompanied by a loss of system-environment correlations. Depending on the initial purity of the qubit state, these system-environment correlations may be purely classical over the whole relevant time scale, or there may be intervals of genuine system-environment entanglement. In the latter case, we see no obvious relation between the build-up or decay of these quantum correlations and "Non-Markovianity".

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“…In these situations, classical stochastic modeling of the environment represents a valid and reliable alternative. In fact, it has been shown that for certain system-environment interactions a classical description can be found that is completely equivalent to the quantum description [63][64][65][66][67][68]. In addition, there is experimental evidence that many quantum systems of interest interact with classical forms of noise, typically Gaussian noise [69][70][71].…”

Section: Introductionmentioning

confidence: 99%

Collapse and revival of quantum coherence for a harmonic oscillator interacting with a classical fluctuating environment

et al. 2015

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We address the dynamics of nonclassicality for a quantum system interacting with a noisy fluctuating environment described by a classical stochastic field. As a paradigmatic example, we consider a harmonic oscillator initially prepared in a maximally nonclassical state, e.g., a Fock number state or a Schrödinger-cat-like state, and then coupled to either a resonant or a nonresonant external field. Stochastic modeling allows us to describe the decoherence dynamics without resorting to approximated quantum master equations and to introduce non-Markovian effects in a controlled way. A detailed comparison among different nonclassicality criteria and a thorough analysis of the decoherence time reveal a rich phenomenology whose main features may be summarized as follows: (i) Classical memory effects increase the survival time of quantum coherence and (ii) a detuning between the natural frequency of the system and the central frequency of the classical field induces revivals of quantum coherence.

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Quantum decoherence of two qubits

Cited by 64 publications

References 37 publications

Quantum irreversible decoherence behaviour in open quantum systems with few degrees of freedom: Application to 1H NMR reversion experiments in nematic liquid crystals

Quantum irreversible decoherence behaviour in open quantum systems with few degrees of freedom: Application to 1H NMR reversion experiments in nematic liquid crystals

System–environment correlations and non-Markovian dynamics

Collapse and revival of quantum coherence for a harmonic oscillator interacting with a classical fluctuating environment

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