Quantum and classical correlations for a two-qubit X structure density matrix |
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Authors: | Ding Bang-Fu Wang Xiao-Yun Zhao He-Ping |
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Affiliation: | College of Physical Science and Information Engineering, Jishou University, Jishou 416000, China;College of Physical Science and Information Engineering, Jishou University, Jishou 416000, China;College of Physical Science and Information Engineering, Jishou University, Jishou 416000, China |
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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. |
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Keywords: | quantum and classical mutual information X structure density matrix quantum discord classical correlation entanglement |
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