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quantum discord and its dynamics for multipartite systems

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Chinese Physics B 2024年第6期33卷 168-175页

作者：罗嘉欣郭琼 College of Sciences Shanghai Institute of TechnologyShanghai 201418China

quantum discord, one of the famous quantum correlations, has been recently generalized to multipartite systems by Radhakrishnan et al. Here we give analytical solutions of the quantum discord for a family of N-qubit quantum states. For the bipartite system, we derive a zero quantum discord which will remain unchanged under the phase damping channel. For multiparitite systems, it is found that the quantum discord can be classified into three categories and the quantum discord for odd-partite systems can exhibit freezing under the phase damping channel, while the freezing does not exist in the even-partite systems.

关键词： quantum discord multipartite systems decoherence channels frozen discord

quantum discord in the three-spin XXZ chain with Dzyaloshinskii-Moriya interaction

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Science China(Physics,Mechanics & Astronomy) 2012年第11期55卷 2081-2087页

作者： ZHU YinYan ZHANG Yong School of Science Beijing University of Posts and TelecommunicationsBeijing 100876China

The quantum discord(QD) of a three-qubit Heisenberg XXZ system with the Dzyaloshinskii-Moriya(DM) interaction parameter is investigated,and the three-qubit QD under Ornstein-Uhlenbeck noise is *** find that both DM interaction parameter D z and anisotropic parameter J z can increase QD and entanglement but D z is a more efficient parameter in the antiferromagnetic *** observe a complex range of QD with the change of D z and a sudden change of QD with the variation of J z in the ferromagnetic *** show that the decrease durations of both QD and entanglement can be prolonged by increasing DM interaction and reducing noise bandwidth in the evolutionary process.

关键词： quantum discord XXZ-spin chain DM interaction Ornstein-Uhlenbeck noise

quantum discord of Non-X State

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Communications in Theoretical Physics 2013年第6期59卷 693-699页

作者：姚晶莹董裕力朱士群 School of Physical Science and Technology Soochow University

The level surfaces of quantum discord for a class of two-qubit states are investigated when the Bloch vectors T and S are perpendicularly oriented. The geometric objects of tetrahedron T and octahedron 0 are deformed. The level surfaces of constant discord are formed by three interaction ＂tubes＂ along three orthogonal directions. They shrink to the center when the B1oeh vectors are increased and are expanded and cut off by the state tetrahedron T when the quantum discord is increased, in the phase damping channel, the quantum discord keeps approximately a constant when the time increases.

关键词： quantum discord classical correlation phase damping

quantum discord in any Mixture of Two Bi-Qubit Arbitrary Product States

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Communications in Theoretical Physics 2013年第12期60卷 667-672页

作者：王胜房刘益民李国锋刘先松张战军 Engineering Technology Research Center of Magnetic Materials Anhui Province School of Physics & Materials ScienceAnhui University Department of Physics Shaoguan University

quantum discord in any mixture of two bi-qubit arbitrary product states is studied with two different approaches. In the first approach the maximM classicM correlations are obtained via numerical computations, while in the second approach they are analytically derived. quantum correlations captured with both approaches completely coincide, as is in accord with the conclusion of Cen et al. [Phys. Rev. A 83 （2011） 054101]. The symmetry reduction of the concerned states concerning quantum correlations is accomplished. The captured discords are amply analyzed so that some inherent distinct properties are revealed.

关键词： quantum discord numerical computation approach analytic expression any mixture two bi-qubit arbitrary product states

quantum discord of thermal states of a spin chain with Calogero-Moser type interaction

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Science China(Physics,Mechanics & Astronomy) 2013年第3期56卷 600-605页

作者： MA XiaoSan QIAO Ying ZHAO GuangXing WANG AnMin School of Electric Engineering and Information Anhui University of Technology Department of Modern Physics University of Science and Technology of China

In this paper,we have investigated the effect of Calogero-Moser type interaction on the quantum discord of thermal states of a spin *** results imply that the quantum discord depends on the relative distance between the spins,the external magnetic field,and the *** a comparison between the quantum discord and the entanglement of formation,the quantum discord is more robust than the entanglement of formation in the sense that the latter takes a zero value in a large range of the parameters,while the former takes a nonzero value.

关键词： quantum discord entanglement of formation Calogero-Moser interactions

quantum discord Dynamics of Three Qubits in Non-Markovian Environments

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Communications in Theoretical Physics 2014年第6期61卷 691-698页

作者：张燕刘金明李艳杰 State Key Laboratory of Precision Spectroscopy East China Normal University

We investigate the dynamics of palrwise quantum discord （QD） for a mixed three-qubit W-type state in three independent non-Markovian reservoirs at zero temperature, each of which is modeled by a leaky cavity with Lorentzian spectral density. The influence of the environment＇s amount of non-Markovianity, the detuning between the qubit frequency and the cavity centre frequency, and the purity of the initial state on the QD dynamics are analyzed in detail. It is found that in the non-Maxkovian regime the system-reservoir interactions induce QD revivals and oscillations no matter whether the detuning is zero or not. Moreover, QD can be preserved for a long time if the non-Markovian condition and the detuning condition are satisfied simultaneously.

关键词： quantum discord non-Markovian environment W-type state detuning

quantum discord in three-spin XXZ chain with three-spin interaction

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Science China(Physics,Mechanics & Astronomy) 2012年第9期55卷 1641-1645页

作者： YUE HaiDi ZHANG Yong GONG Jian School of Physical Science and Technology Inner Mongolia University Hohhot 010021 China Department of Physics Beijing University of Posts and Telecommunications Beijing 100876 China

quantum discord, as a kind of measurement of quantum correlation, has received much attention since it was introduced. This paper focuses on studying quantum discord in three-spin XXZ chain with three-spin interaction. The effects of all kinds of pa- rameters on quantum discord in the ferromagnetic region J=-I are studied. The three-spin interaction may increase the value of quantum discord between two spins, while the anisotropy may decrease the value. In addition, the regrowth of quantum discord with temperature is found in the model. For zero temperature, quantum phase transition is existent.

关键词： quantum discord three-spin interaction XXZ-spin chain

quantum discord in Two-Qubit System Constructed from the Yang-Baxter Equation

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Communications in Theoretical Physics 2014年第3期61卷 349-353页

作者： GOU Li-Dan WANG Xiao-Qian XU Yu-Mei SUN Yuan-Yuan Department of Physics Changchun University of Science and Technology Changchun 130022 China Department of Admissions Weifang Nursing Vocational College Weifang 262500 China Combat Command Department Aviation University of Air Force Changchun 130022 China

quantum correlations among parts of a composite quantum system are a fundamental resource for several applications in quantum information. In general, quantum discord can measure quantum correlations. In that way,we investigate the quantum discord of the two-qubit system constructed from the Yang–Baxter Equation. The density matrix of this system is generated through the unitary Yang–Baxter matrix R. The analytical expression and numerical result of quantum discord and geometric measure of quantum discord are obtained for the Yang–Baxter system. These results show that quantum discord and geometric measure of quantum discord are only connect with the parameter θ,which is the important spectral parameter in Yang–Baxter equation.

关键词： quantum correlations quantum discord Yang-Baxter equation

Robustness of quantum discord to sudden death in nuclear magnetic resonance

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Chinese Physics B 2012年第4期21卷 60-66页

作者：胥建卫陈起辉 Key Laboratory for Radiation Physics and Technology Institute of Nuclear Science and TechnologySichuan UniversityChengdu 610065China Physics Department Sichuan UniversityChengdu 610065China

We investigate the dynamics of the entanglement and quantum discord of two qubits in liquid state homonuclear nuclear magnetic resonance. Applying a phenomenological description for nuclear magnetic resonance under a relaxation process, and taking a group of typical parameters of nuclear magnetic resonance, we show that when a zero initial state experiences a relaxation process, its entanglement disappears completely after a sequence of so-called sudden deaths and revivals, while the quantum discord retains remarkable values after a sequence of oscillations. That is to say, the quantum discord is more robust than entanglement.

关键词： quantum discord nuclear magnetic resonance concurrence sudden death