Classical capacities of memoryless but not identical quantum channels

TL;DR

This paper investigates the classical capacities of a sequence of memoryless quantum channels that are not identical, providing new coding theorems and analyzing specific cases like lossy bosonic channels.

Contribution

It introduces coding theorems for classical capacities of non-identical quantum channels and applies the theory to lossy bosonic channels, revealing contrasting behaviors.

Findings

Capacities can or cannot be derived from the lossy parameter's limiting behavior.

Derived coding theorems for entanglement-assisted and unassisted capacities.

Specialized results for lossy bosonic quantum channels.

Abstract

We study quantum channels that vary on time in a deterministic way, that is, they change in an independent but not identical way from one to another use. We derive coding theorems for the classical entanglement assisted and unassisted capacities. We then specialize the theory to lossy bosonic quantum channels and show the existence of contrasting examples where capacities can or cannot be drawn from the limiting behavior of the lossy parameter.