Enhancing Long-distance Continuous-variable Quantum-key-distribution with an Error-correcting Relay

TL;DR

This paper combines noiseless linear amplifiers and unitary averaging to mitigate thermal-loss and phase noise, enabling long-distance continuous-variable quantum key distribution that exceeds the fundamental repeaterless bound.

Contribution

It introduces a novel protocol integrating NLAs and unitary averaging to improve long-distance CV QKD performance beyond existing limits.

Findings

Achieves long-distance CV QKD surpassing the repeaterless bound.

Demonstrates effective mitigation of thermal-loss and phase noise.

Provides a new approach for scalable quantum communication.

Abstract

Noiseless linear amplifiers (NLAs) serve as an effective means to enable long-distance continuous-variable (CV) quantum key distribution (QKD), even under realistic conditions with non-unit reconciliation efficiency. Separately, unitary averaging has been suggested to mitigate some stochastic noise, including phase noise in continuous-variable states. In this work, we combine these two protocols to simultaneously compensate for thermal-loss effects and suppress phase noise, thereby enabling long-distance CV QKD that surpasses the repeaterless bound, the fundamental rate-distance limit, for repeaterless quantum communication systems.