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

Robert Koenig, Institute for Quantum Computing (IQC)

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.