Source monitoring for continuous-variable quantum key distribution

TL;DR

This paper proposes two practical schemes to monitor source noise in continuous-variable quantum key distribution, enabling better estimation of eavesdropper's knowledge and improving security bounds.

Contribution

It introduces active and passive source monitoring schemes for CVQKD and compares their security performance, highlighting the superiority of the passive approach.

Findings

Passive scheme outperforms active scheme in security bounds

Both schemes effectively estimate Eve's knowledge

Security bounds derived for collective attacks

Abstract

The noise in optical source needs to be characterized for the security of continuous-variable quantum key distribution (CVQKD). Two feasible schemes, based on either active optical switch or passive beamsplitter are proposed to monitor the variance of source noise, through which, Eve's knowledge can be properly estimated. We derive the security bounds for both schemes against collective attacks in the asymptotic case, and find that the passive scheme performs better.