arXiv:quant-ph/0307170

Quantum Stein's lemma revisited, inequalities for quantum entropies, and a concavity theorem of Lieb

Igor Bjelaković, Rainer Siegmund‐Schultze

Published Jul 24, 2003• 14 citations

Abstract

We derive the monotonicity of the quantum relative entropy by an elementary operational argument based on Stein's lemma in quantum hypothesis testing. For the latter we present an elementary and short proof that requires the law of large numbers only. Joint convexity of the quantum relative entropy is proven too, resulting in a self-contained elementary version of Tropp's approach to Lieb's concavity theorem, according to which the map tr(exp(h+log a)) is concave in a on positive operators for self-adjoint h.

DOI: 10.48550/arxiv.quant-ph/0307170

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