Capacity with energy constraint in coherent state channel

TL;DR

This paper investigates the capacity of coherent state channels under two different energy constraints, applying conventional and general capacity formulas to understand their effects on channel performance.

Contribution

It introduces a comprehensive analysis of coherent state channel capacity considering both total energy and code-specific energy constraints, extending existing formulas.

Findings

Capacity under total energy constraint is straightforward to compute.

Capacity under code-specific energy constraint requires the general classical-quantum capacity formula.

Provides insights into optimal encoding strategies under different energy limitations.

Abstract

We consider two kind of energy constraints when the output state is a coherent state. One is a constraint on the total energy during a fixed period; the other is a constraint on the total energy for a single code. The first setting can be easily dealt with by using the conventional capacity formula. The second setting requires the general capacity formula for a classical-quantum channel.