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Laser Physics Letters

Quantum correlation swapping between two X states

Chuanmei Xie, Senbo Tian, Zhanjun Zhang, Jinhua Yu, Jianlan Chen, Xiaofeng Yin

Published Jul 1, 2025• 1 citation
Publisher

Abstract

Abstract In this paper, the quantum correlation (QC) swapping between two X states is studied. According to different parameter distributions in X states, three types of X states for QC swapping are respectively analysed. Two QC quantifiers, quantum discord and entanglement, are utilized. Moreover, in order to compare, classical correlation is also concerned. The characteristics and thresholds in all the concerned correlations appearing in the swapping process are revealed and explained. It is found that, corresponding to some types of X states, the varing features and size ordering among the concerned correlations before and after swapping process are invariant. In particular, with two special parameter-distribution X states as initial states, the swapping process cannot change the size ordering relationships among the concerned correlations.

DOI
10.1088/1612-202x/adf046

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Abstract In this study, the qubit quantum correlation swapping (QCS) is generalized to the qutrit case. To be concrete, two qutrit Werner states are taken as the research objects and the complete set of qutrit Bell states are utilized as the intermediate two-qutrit measure to implement QCS. The popular quantum correlation measure, i.e. quantum discord (Ollivier and Zurek 2001 Phys. Rev. Lett. 88 017901), is employed to characterize and quantify quantum correlations in the concerned states. The properties of the variance and threshold of quantum correlations occurring in the swapping process are revealed, and two distinct QCS phenomena are thus observed. Moreover, it is found that the maximal amount of quantum correlations in the final state can not exceed the minimal one of these in the initial states.
Abstract Werner derivatives are a special kind of mixing states that originate from the Werner state due to unitary evolutions. In this paper, quantum correlation (QC) swapping between two Werner derivatives is studied. Quantum discord (Ollivier and Zurek 2001 Phys. Rev. Lett. 88 017901) is employed as the QC quantifier to characterize and quantify all QCs inhabited in the states which emerge during the swapping process. All concerned QCs are analytically or numerically worked out and their behaviors and properties such as monotony features and thresholds are concretely analyzed. Particularly, the QC properties of the four different final states corresponding to four different Bell states are revealed, compared and discussed. More importantly, it is found that, long-distance shared QCs can be generated from two short-distance ones via Bell-state measures in the middle nodes of a quantum network.
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.
We derive explicit expressions for quantum discord and classical correlation for an X structure density matrix. Based on the characteristics of the expressions, the quantum discord and the classical correlation are easily obtained and compared under different initial conditions using a novel analytical method. We explain the relationships among quantum discord, classical correlation, and entanglement, and further find that the quantum discord is not always larger than the entanglement measured by concurrence in a general two-qubit X state. The new method, which is different from previous approaches, has certain guiding significance for analysing quantum discord and classical correlation of a two-qubit X state, such as a mixed state.
In this paper, quantum correlation (QC) swapping between two Werner-like states, which are transformed from Werner states undergoing local and nonlocal unitary operations, are studied. Bell states measures are performed in the middle node to realize the QC swapping and correspondingly final correlated sates are obtained. Two different QC quantifiers, i.e., measurement-induced disturbance (MID) and ameliorated MID, are employed to characterize and quantify all the concerned QCs in the swapping process. All QCs in the concerned states are evaluated analytically and numerically. Correspondingly, their characteristics and properties are exposed in detail. It is exposed that, through the QC swapping process, one can obtain the long-distance QC indeed. Moreover, the similarities of monotony features of MID and AMID between the initial states and final states are exposed and analyzed.