Robert Koenig: The quantum entropy power inequality and the classical capacity of thermal noise channels

Abstract:

We present new upper bounds on the classical capacity of bosonic thermal noise channels, the quantum analogues of the additive white Gaussian noise channel. Our main technical tool is a quantum entropy power inequality that controls the entropy production as two quantum signals combine at a beam splitter. Its proof involves a new connection between entropy production rates and a quantum Fisher information, and uses a quantum thermalization process that smooths arbitrary states towards Gaussians.

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