Noiseless Linear Amplification and Quantum Channels

TL;DR

This paper provides a general mathematical framework for analyzing noiseless linear amplifiers (NLAs) in quantum channels, applicable to both Gaussian and non-Gaussian states, and demonstrates their use in loss compensation and phase noise reduction.

Contribution

It introduces a unified effective channel description for noisy, lossy Gaussian channels combined with NLAs, extending analysis beyond fixed input state frameworks.

Findings

Effective channel description simplifies analysis of quantum amplification.

The framework applies to mixed Gaussian and non-Gaussian states.

Demonstrated potential in loss compensation and phase noise reduction.

Abstract

The employ of a noiseless linear amplifier (NLA) has been proven as a useful tool for mitigating imperfections in quantum channels. Its analysis is usually conducted within specific frameworks, for which the set of input states for a given protocol is fixed. Here we obtain a more general description by showing that a noisy and lossy Gaussian channel followed by a NLA has a general description in terms of effective channels. This has the advantage of offering a simpler mathematical description, best suitable for mixed states, both Gaussian and non-Gaussian. We investigate the main properties of this effective system, and illustrate its potential by applying it to loss compensation and reduction of phase uncertainty.