Discrete-modulation continuous-variable quantum key distribution with probabilistic amplitude shaping over a linear quantum channel

TL;DR

This paper explores a practical discrete-modulation continuous-variable quantum key distribution protocol using probabilistic amplitude shaping, achieving near-GG02 performance with current telecom technologies while maintaining unconditional security.

Contribution

It introduces a discrete-modulation CV-QKD protocol with probabilistic shaping, compatible with existing telecom hardware, and analyzes its security and performance over linear quantum channels.

Findings

Achieves secure key rates close to GG02 benchmark.

Demonstrates robustness over various distances and noise levels.

Compatible with current telecom modulation formats.

Abstract

The practical implementation difficulties arising from the Gaussian modulation of the GG02 protocol lead us to investigate the possibilities offered by the combination of probabilistic amplitude shaping technique and quadrature amplitude modulation formats in the context of continuous variable quantum key distribution systems. Our interest comes from the fact that quadrature amplitude modulation and probabilistic shaping can be implemented with current technologies and are widely used in classical telecom equipment. In this treatment, we assume to work in the scenario of a linear quantum channel and we analyze maximum achievable secure key rates, maximum reachable distances and the resilience to noise of our discrete-modulation based protocol with respect to GG02, which is taken as a benchmark. In particular, we deal with the infinite key size regime, consider a homodyne detection scheme, and analyze what happens for different cardinalities of the input alphabet at different distances, in the case of collective attacks and in the reverse reconciliation picture. We find that our protocol, beyond being easily reproducible in the laboratory, provides a way to closely approach the theoretical performance offered by GG02 and, at the same time, preserves the ability to assure an unconditional security level.