Quantum and classical correlations for a two-qubit X structure density matrix

doi:10.1088/1674-1056/20/10/100302

Abstract 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.

Keywords: quantum and classical mutual information X structure density matrix quantum discord classical correlation entanglement

Received: 08 May 2011
Revised: 13 June 2011
Accepted manuscript online:

PACS:	03.65.Yz	(Decoherence; open systems; quantum statistical methods)
	03.65.Ta	(Foundations of quantum mechanics; measurement theory)
	03.67.-a	(Quantum information)

Fund: Project supported by the Natural Science Foundation of Hunan Province of China (Grant No. 09JJ6011) and the Natural Science Foundation of Education Department of Hunan Province, China (Grant Nos. 08A055 and 07C528).

Cite this article:

Ding Bang-Fu(丁邦福), Wang Xiao-Yun(王小云), and Zhao He-Ping(赵鹤平) Quantum and classical correlations for a two-qubit X structure density matrix 2011 Chin. Phys. B 20 100302

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