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A new inequality for the von Neumann entropy

Noah Linden·Andreas Winter
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Abstract

Strong subadditivity of von Neumann entropy, proved in 1973 by Lieb and Ruskai, is a cornerstone of quantum coding theory. All other known inequalities for entropies of quantum systems may be derived from it. Here we prove a new inequality for the von Neumann entropy which we prove is independent of strong subadditivity: it is an inequality which is true for any four party quantum state, provided that it satisfies three linear relations (constraints) on the entropies of certain reduced states.

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Noah Linden, Andreas Winter. 2004-06-22. A new inequality for the von Neumann entropy. https://doi.org/10.1007/s00220-005-1361-2

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