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Laser Physics

Quantum correlation swapping between Bell-diagonal states

Chuanmei Xie, Senbo Tian, Zekai Xie, Jinhua Yu, Zhanjun Zhang

Published Aug 20, 2024• 1 citation
Publisher

Abstract

Abstract Quantum correlation (QC) swapping is a generalization of quantum entanglement swapping, in which the concerned QCs can be quantum entanglement, QC beyond quantum entanglement, or both of them. In general, QC swapping is different from quantum entanglement swapping. Obviously, the study range of the former is beyond than the latter, and the former can give more interesting and significant applications in quantum information processings. So far, QC swapping has been studied explicitly only for a rather limited set of two-qubit quantum states as the initial states and cases for more general QC swapping with multi-parameter initial states are not known. In this article, we explore the QC swapping case with three-parameter Bell-diagonal (BD) states as the initial states. The familiar QC measure, quantum discord (Ollivier and Zurek 2001 Phys. Rev. Lett. 88 017901), is utilized to quantify all the QCs in the concerned states. It is found that a long-distance shared QC can be acquired through the BD-initial states case of QC swapping. Moreover, some distinct features and characteristics can be exposed.

DOI
10.1088/1555-6611/ad6d4e

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Quantum discord, a kind of quantum correlation, is defined as the difference between quantum mutual information and classical correlation in a bipartite system. In general, this correlation is different from entanglement, and quantum discord may be nonzero even for certain separable states. Even in the simple case of bipartite quantum systems, this different kind of quantum correlation has interesting and significant applications in quantum information processing. So far, quantum discord has been calculated explicitly only for a rather limited set of two-qubit quantum states and expressions for more general quantum states are not known. In this article, we derive explicit expressions for quantum discord for a larger class of two-qubit states, namely, a seven-parameter family of so called XXX states that have been of interest in a variety of contexts in the field. We also study the relation between quantum discord, classical correlation, and entanglement for a number of two-qubit states to demonstrate that they are independent measures of correlation with no simple relative ordering between them.
Abstract In this paper we study quantum correlation (QC) swapping between two different kinds of quantum-correlated states. To be concrete, one is the famous Werner state while another is a kind of separable state. We employ measurement-induced disturbance (Luo 2008 Phys. Rev. A 77 02230) as the quantifier to characterize and quantify QC. We work out QCs in all the concerned states and concretely analyze their behaviors and properties such monotony features and thresholds. We find that a long-distance shared QC can be generated from two short-distance ones via intermediate measure. Moreover, the amount of the long-distance shared QC cannot reach that in the Werner state but that in the separable state.