Erlangen 2018 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 34: Quantum Information (Quantum Communication)

Q 34.1: Talk

Tuesday, March 6, 2018, 14:00–14:15, K 1.020

Coherent state coding approaches the capacity of non-Gaussian bosonic channels — •Stefan Huber and Robert König — Institute for Advanced Study & Zentrum Mathematik, Technische Universität München, 85748 Garching, Deutschland

The additivity problem asks if the use of entanglement can boost the information-carrying capacity of a given channel beyond what is achievable by coding with simple product states only. This has recently been shown not to be the case for phase-insensitive one-mode Gaussian channels, but remains unresolved in general. Here we consider two general classes of bosonic noise channels, which include phase-insensitive Gaussian channels as special cases: these are beamsplitters with general, potentially non-Gaussian environment states and classical noise channels with general probabilistic noise. We show that additivity violations, if existent, are rather minor for all these channels: the maximal gain in classical capacity is bounded by a constant independent of the input energy. Our proof shows that coding by simple classical modulation of coherent states is close to optimal.