Tagging idea in continuous variable quantum key distribution and its application

TL;DR

This paper extends the tagging security proof method from discrete to continuous variable quantum key distribution, enabling rigorous security analysis of practical systems with multiple imperfections.

Contribution

It introduces a generic imperfection model and generalizes the tagging idea to CV-QKD, allowing for security proofs under realistic device imperfections.

Findings

Security can be guaranteed despite modulation flaws

Detection imperfections do not compromise security when properly modeled

The approach enables secure key generation in practical CV-QKD systems

Abstract

Despite tremendous theoretical and experimental progress in continuous variable (CV) quantum key distribution (QKD), its security has not been rigorously established for practical systems with multiple imperfections. The idea of tagging is widely used in security proofs of discrete variable quantum key distribution with imperfect devices. In this paper, we generalize the tagging idea from discrete variable to continuous variable. Based on untagged signals, we prove the security of the imperfect quantum key distribution system in the most conservative case. By introducing a generic imperfection model, we can evaluate and further incorporate multiple imperfections in the different stages such as modulation, channel and detection. Finally, with this generic model and tagging idea, we can prove the security of continuous variable key distribution system with multiple imperfections. Our case study shows our proofs are able to provide secure keys in the presence of both modulation and detection flaws.