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arXiv:quant-ph/0301171 · Physical Review A

Entropy inequalities and Bell inequalities for two-qubit systems

Emilio Santos

Published Feb 17, 2004• 11 citations
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Abstract

Sufficient conditions for the nonviolation of the Bell-Clauser-Horne-Shimony-Holt inequalities in a mixed state of a two-qubit system are: (1) the linear entropy of the state is not smaller than 0.457; (2) the sum of the conditional linear entropies is not smaller than -0.086; (3) the von Neumann entropy is not smaller than 0.833; and (4) the sum of the conditional von Neumann entropies is not smaller than 0.280.

DOI
10.1103/physreva.69.022305

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Sufficient conditions for the nonviolation of the Bell-Clauser-Horne-Shimony-Holt inequalities in a mixed state of a two-qubit system are: (1) the linear entropy of the state is not smaller than 0.457; (2) the sum of the conditional linear entropies is not smaller than -0.086; (3) the von Neumann entropy is not smaller than 0.833; and (4) the sum of the conditional von Neumann entropies is not smaller than 0.280.
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We investigate the nonlocality of Schmidt-correlated (SC) states, and present analytical expressions of the maximum violation value of Bell inequalities. It is shown that the violation of Clauser—Horne—Shimony—Holt (CHSH) inequality is necessary and sufficient for the nonlocality of two-qubit SC states, whereas the violation of the Svetlichny inequality is only a sufficient condition for the genuine nonlocality of three-qubit SC states. Furthermore, the relations among the maximum violation values, concurrence, and relative entropy entanglement are discussed.
We investigate the nonlocality of Schmidt-correlated (SC) states, and present analytical expressions of the maximum violation value of Bell inequalities. It is shown that the violation of Clauser—Horne—Shimony—Holt (CHSH) inequality is necessary and sufficient for the nonlocality of two-qubit SC states, whereas the violation of the Svetlichny inequality is only a sufficient condition for the genuine nonlocality of three-qubit SC states. Furthermore, the relations among the maximum violation values, concurrence, and relative entropy entanglement are discussed.