On the transitional behavior of quantum Gaussian memory channels

TL;DR

This paper investigates when entangled input states are optimal for quantum Gaussian memory channels, linking their optimality to symmetry properties, and discusses various channel models within this framework.

Contribution

It establishes a criterion connecting entangled input optimality to channel symmetry in a class of Gaussian memory channels.

Findings

Entangled inputs are optimal under specific symmetry conditions.

The criterion applies to several channel models.

Symmetry properties determine input state optimality.

Abstract

We address the question of optimality of entangled input states in quantum Gaussian memory channels. For a class of such channels, that can be traced back to the memoryless setting, we state a criterion which relate the optimality of entangled inputs to the symmetry properties of the channels' action. Several examples of channel models belonging to this class are discussed.