Quantum Lunch: Gaussian optimizers in quantum information

Speaker: Giacomo De Palma, NEST and CNR-NANO.

Giacomo will be here in Copenhagen for a week, arriving tuesday January, 26th and leaving the next thursday.

Abstract:
Quantum Gaussian channels provide a faithful model for almost all communication schemes exploiting the electromagnetic field, such as optical fibers, metal wires and radio communication. Determining the maximum rate at which information can be transmitted along such channels is a fundamental issue. I will first review the proof of the optimality of coherent-state encodings for the transmission of classical information through gauge-covariant quantum Gaussian channels, and the consequent determination of their classical capacity.
The classical capacity region of the Gaussian broadcast channel, where a sender wants to communicate classical information to multiple parties, is instead still undetermined. I will show how the so-called quantum Entropy Power Inequality provides nearly optimal bounds for this region, and present some recent results pointing towards the exact solution.