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

2026-03-03

AI Summary

This work proposes a discrete-modulation-based continuous-variable quantum key distribution (CV-QKD) protocol to address the experimental challenges associated with Gaussian modulation in the GG02 protocol. By integrating probabilistic amplitude shaping with quadrature amplitude modulation for the first time, and employing homodyne detection together with reverse reconciliation, the scheme is proven unconditionally secure against collective attacks. Theoretical analysis demonstrates that, in the asymptotic limit of infinite key length, the protocol achieves performance closely approaching the GG02 benchmark in terms of maximum secret key rate, transmission distance, and noise tolerance, while substantially enhancing practical feasibility for real-world implementation.

Technology Category

• Computer Vision: Multi-modal Vision
• Machine Learning: Quantum Machine Learning
• Search and Optimization: Mixed Discrete/Continuous Search

Application Category

• Security and Privacy: Large-scale security measurements
• Economics, Online Markets and Human Computation: LLM based quality controls for crowd work
• User Modeling, Personalization and Recommendation: Attacks and countermeasures in recommendation systems

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.

Problem

• continuous-variable quantum key distribution
• discrete modulation
• probabilistic amplitude shaping
• GG02 protocol
• practical implementation

Innovation

• probabilistic amplitude shaping
• discrete modulation
• continuous-variable quantum key distribution
• quadrature amplitude modulation
• unconditional security