Hierarchy of efficiently computable and faithful lower bounds to quantum discord
arXiv:1501.06855 · doi:10.1103/PhysRevLett.117.080401
Abstract
Quantum discord expresses a fundamental non-classicality of correlations more general than quantum entanglement. We combine the no-local-broadcasting theorem, semidefinite-programming characterizations of quantum fidelity and quantum separability, and a recent breakthrough result of Fawzi and Renner about quantum Markov chains to provide a hierarchy of computationally efficient lower bounds to quantum discord. Such a hierarchy converges to the surprisal of measurement recoverability introduced by Seshadreesan and Wilde, and provides a faithful lower bound to quantum discord already at the lowest non-trivial level. Furthermore, the latter constitutes by itself a valid discord-like measure of the quantumness of correlations.
7 pages, 2 figures; comments -- also about "extendable" Vs "extendible" -- welcome
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