Hierarchy of efficiently computable and faithful lower bounds to quantum discord

Piani, Marco (2016) Hierarchy of efficiently computable and faithful lower bounds to quantum discord. Physical Review Letters, 117 (8). 080401. ISSN 0031-9007

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    Abstract

    Quantum discord expresses a fundamental non-classicality of correlations that is more general than entanglement, but that, in its standard definition, is not easily evaluated. We derive a hierarchy of computationally efficient lower bounds to the standard quantum discord. Every non-trivial element of the hierarchy constitutes by itself a valid discord-like measure, based on a fundamental feature of quantum correlations: their lack of shareability. Our approach emphasizes how the difference between entanglement and discord depends on whether shareability is intended as a static property or as a dynamical process.