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Universal recovery maps and approximate sufficiency of quantum relative entropy

, , , , and . (2015)cite arxiv:1509.07127Comment: v3: 24 pages, 1 figure, final version published in Annales Henri Poincaré.
DOI: 10.1007/s00023-018-0716-0

Abstract

The data processing inequality states that the quantum relative entropy between two states $\rho$ and $\sigma$ can never increase by applying the same quantum channel $N$ to both states. This inequality can be strengthened with a remainder term in the form of a distance between $\rho$ and the closest recovered state $(R N)(\rho)$, where $R$ is a recovery map with the property that $= (R N)(\sigma)$. We show the existence of an explicit recovery map that is universal in the sense that it depends only on $\sigma$ and the quantum channel $N$ to be reversed. This result gives an alternate, information-theoretic characterization of the conditions for approximate quantum error correction.

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Universal recovery maps and approximate sufficiency of quantum relative entropy

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