Citations
Altmetric:
Alternative Title
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.
Keywords
Source Title
Physical Review A - Atomic, Molecular, and Optical Physics
Publisher
Series/Report No.
Collections
Rights
Date
2011-10-06
DOI
10.1103/PhysRevA.84.042313
Type
Article