Quantum Discord and Logarithmic Negativity in the Generalized n-qubit Werner State

Abstract We study the dimensionless time evolution of the logarithmic negativity and geometric quantum discord of a qubit-qutrit XXX spin model under the both Markovian and non-Markovian noise channels. We find that at a special temperature interval the quantum entanglement based on the logarithmic negativity reveals entanglement sudden deaths together with revivals. The revival phenomenon is due to the non-Markovianity resulting from the feedback effect of the environment. At high temperatures, the scenario of death and revival disappears. The geometric quantum discord evolves alternatively versus time elapsing with damped amplitudes until the system reaches steady state. It is demonstrated that the dynamics of entanglement negativity undergoes substantial changes by varying temperature, and it is much more fragile against the temperature rather than the geometric quantum discord. The real complex heterodinuclear [Ni(dpt (H2O)Cu(pba)]·2H2O [with pba =1,3-propylenebis(oxamato) and dpt = bis-(3-aminopropyl)amine] is an experimental representative of our considered bipartite qubit-qutrit system that may show remarkable entanglement deaths and revivals at relatively high temperatures and high magnetic field that is comparable with the strength of the exchange interaction J between Cu+2 and Ni+2 ions, i.e., kBT ≈ J and μBB ≈ J.

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QUANTUM CORRELATIONS IN THE "q-DEFORMED" WERNER STATE

International Journal of Quantum Information ◽

10.1142/s0219749913500184 ◽

2013 ◽

Vol 11 (02) ◽

pp. 1350018 ◽

Cited By ~ 2

Author(s):

BO LIU ◽

KANG XUE ◽

GANGCHENG WANG ◽

CHUNFANG SUN ◽

LIDAN GOU ◽

...

Keyword(s):

Quantum Discord ◽

Singlet State ◽

Great Influence ◽

Quantum Correlations ◽

Werner State ◽

Single Loop ◽

Geometric Measure ◽

Topological Parameter ◽

Spin Singlet ◽

Two Parameters

We investigate quantum discord of the "q-deformed" Werner state via Yang–Baxterization approach. There are two parameters q and u in this "q-deformed" Werner state. The parameter u, which plays an important role in some typical models, is related to the probability of the "q-deformed" two-qubit spin singlet state in this study. The "q-deformed" parameter q is related to the single loop through d = q + q-1. When topological parameter d approaches 2 (i.e. q → 1), the "q-deformed" Werner state degenerates into the well-known Werner state. The results show that topological parameter d has great influence on quantum correlations of the "q-deformed" Werner state. When we fix the parameter u, the quantum correlations decrease with increasing the single loop d. When d approaches +∞ (i.e. q → 0+ or +∞), quantum discord, geometric measure of quantum discord and entanglement all tend to 0. While d approaches 2 (i.e. q → 1), all of them just have the same results with the Werner state.

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Quantum Correlation Dynamics in Controlled Two-Coupled-Qubit Systems

Entropy ◽

10.3390/e22070785 ◽

2020 ◽

Vol 22 (7) ◽

pp. 785 ◽

Cited By ~ 1

Author(s):

Iulia Ghiu ◽

Roberto Grimaudo ◽

Tatiana Mihaescu ◽

Aurelian Isar ◽

Antonino Messina

Keyword(s):

Time Evolution ◽

Quantum Correlation ◽

Quantum Dynamics ◽

Quantum Discord ◽

Quantum Correlations ◽

Initial State ◽

Analytical Treatment ◽

Werner State ◽

Driven System ◽

Physical Reasons

We study and compare the time evolutions of concurrence and quantum discord in a driven system of two interacting qubits prepared in a generic Werner state. The corresponding quantum dynamics is exactly treated and manifests the appearance and disappearance of entanglement. Our analytical treatment transparently unveils the physical reasons for the occurrence of such a phenomenon, relating it to the dynamical invariance of the X structure of the initial state. The quantum correlations which asymptotically emerge in the system are investigated in detail in terms of the time evolution of the fidelity of the initial Werner state.

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Analytic Expression of Quantum Discords in Werner States under LQCC

Entropy ◽

10.3390/e22020147 ◽

2020 ◽

Vol 22 (2) ◽

pp. 147

Author(s):

Chuanmei Xie ◽

Zhanjun Zhang ◽

Jianlan Chen ◽

Xiaofeng Yin

Keyword(s):

Quantum Discord ◽

Special Kind ◽

Classical Communication ◽

Werner State ◽

Quantum Operations ◽

Local Quantum ◽

Before And After ◽

Projective Measures ◽

Analytic Expression ◽

Werner States

In this paper, quantum discords in a special kind of states, i.e., Werner states by local quantum operations and classical communication (LQCC) protocols (WLQCC states), are studied. Nineteen parameters to quantify the quantum discords are reduced to four parameters in terms of properties of Werner states and quantum discord. In the case of orthogonal projective measures, analytic expression of quantum discords in WLQCC states is analytically worked out. Some properties of the quantum discord in the WLQCC states are obtained, especially the variation relations between the quantum discords and the parameters characterizing the WLQCC states. By virtue of numerical computations, quantum discords in a Werner state before and after LQCC protocols are compared. It is found that quantum discord in any WLQCC state cannot exceed that in the original Werner state.

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Quantum discord of the Werner state in noninertial frames

Physica Scripta ◽

10.1088/1402-4896/abbf72 ◽

2020 ◽

Vol 95 (11) ◽

pp. 115102

Author(s):

M A Mercado Sanchez ◽

Guo-Hua Sun ◽

Shi-Hai Dong

Keyword(s):

Quantum Discord ◽

Werner State

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Local, nonlocal quantumness and information theoretic measures

International Journal of Quantum Information ◽

10.1142/s0219749916400347 ◽

2016 ◽

Vol 14 (06) ◽

pp. 1640034 ◽

Cited By ~ 2

Author(s):

Pankaj Agrawal ◽

Sk Sazim ◽

Indranil Chakrabarty ◽

Arun K. Pati

Keyword(s):

Quantum Discord ◽

Quantum Correlations ◽

Information Theoretic ◽

Werner State ◽

Information Theoretic Measures

It has been suggested that there may exist quantum correlations that go beyond entanglement. The existence of such correlations can be revealed by information theoretic quantities such as quantum discord, but not by the conventional measures of entanglement. We argue that a state displays quantumness, that can be of local and nonlocal origin. Information theoretic measures not only characterize the nonlocal quantumness, but also the local quantumness, such as the “local superposition”. This can be a reason, why such measures are nonzero, when there is no entanglement. We consider a generalized version of the Werner state to demonstrate the interplay of local quantumness, nonlocal quantumness and classical mixedness of a state.

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