Analytic Expression of Quantum Discords in Werner States under LQCC.

Chuanmei Xie,Jianlan Chen,Zhanjun Zhang,Xiaofeng Yin

doi:10.3390/e22020147

Chuanmei Xie, Jianlan Chen + Show 2 more

Open Access

https://doi.org/10.3390/e22020147

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Journal: Entropy	Publication Date: Jan 26, 2020
Citations: 4	License type: CC BY 4.0

Affiliation: Anhui University, Zhejiang Gongshang University

Abstract

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.

Highlights

In quantum information processing, in the theoretical and experimental investigation of quantum correlations, the local quantum operations, and classical communication (LQCC) protocols play an essential role
The form of quantum correlation related to LQCC operations is focused on quantum entanglement
We will study whether quantum discord (QD) involved in two-qubit Werner states can be increased by the single-state LQCC protocol or not

Summary

Introduction

In the theoretical and experimental investigation of quantum correlations, the local quantum operations, and classical communication (LQCC) protocols play an essential role. The first kind of QCDE, namely quantum discord (QD), was first revealed by Ollivier and Zurek [18] in 2001 It exists even in some separable states, where quantum entanglement does not emerge obviously. We will study whether QDs involved in two-qubit Werner states can be increased by the single-state LQCC protocol or not As for this specific topic, our main motivations are fourfold: (1) study the QD in the concerned states through LQCC operations quantitatively; (2) discover whether LQCC can increase QD or not similar to the quantum entanglement case; (3) if yes or no, seek out the similarities and differences among them qualitatively; (4) try to expose the quantitative features of QDs in the LQCC process.

WLQCC State

Quantum Discord in the WLQCC State

Analyses and Discussions

Summary