Enhanced Quantum Communication via Optical Refocusing

TL;DR

This paper analyzes how optical refocusing systems, modeled as thin lenses with finite pupils, can significantly improve quantum communication capacity despite potential information loss.

Contribution

It introduces a general method for calculating the capacity of linear optical refocusing systems, demonstrating their advantage over free-space communication.

Findings

Refocusing can enhance reliable communication rates.

Finite pupils may cause some information loss.

Refocusing systems outperform free-space propagation in capacity.

Abstract

We consider the problem of quantum communication mediated by an optical refocusing system, which is schematized as a thin lens with a finite pupil. This model captures the basic features of all those situations in which a signal is either refocused by a repeater for long distance communication, or it is focused on a detector prior to the information decoding process. Introducing a general method for linear optical systems, we compute the communication capacity of the refocusing apparatus. Although the finite extension of the pupil may cause loss of information, we show that the presence of the refocusing system can substantially enhance the rate of reliable communication with respect to the free-space propagation.