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Title: Quantum discord of two-qubit X states
Authors: Chen, Q. 
Zhang, C. 
Yu, S. 
Yi, X.X. 
Oh, C.H. 
Issue Date: 6-Oct-2011
Source: Chen, Q., Zhang, C., Yu, S., Yi, X.X., Oh, C.H. (2011-10-06). Quantum discord of two-qubit X states. Physical Review A - Atomic, Molecular, and Optical Physics 84 (4) : -. ScholarBank@NUS Repository.
Abstract: Quantum discord provides a measure for quantifying quantum correlations beyond entanglement and is very hard to compute even for two-qubit states because of the minimization over all possible measurements. Recently a simple algorithm to evaluate the quantum discord for two-qubit X states was proposed by Ali, Rau, and Alber with minimization taken over only a few cases. Here we shall at first identify a class of X states, whose quantum discord can be evaluated analytically without any minimization, for which their algorithm is valid, and also identify a family of X states for which their algorithm fails. And then we demonstrate that this special family of X states provides furthermore an explicit example for the inequivalence between the minimization over positive operator-valued measures and that over von Neumann measurements. © 2011 American Physical Society.
Source Title: Physical Review A - Atomic, Molecular, and Optical Physics
ISSN: 10502947
DOI: 10.1103/PhysRevA.84.042313
Appears in Collections:Staff Publications

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