Twin-field quantum key distribution with fully discrete phase randomization

TL;DR

This paper introduces a secure twin-field quantum key distribution protocol that uses fully discrete phase randomization, addressing practical implementation issues and achieving higher secret-key rates than protocols with continuous phase randomization.

Contribution

It proposes and proves the security of a TF-QKD variant based solely on discrete phase randomization, improving practical security and performance.

Findings

Secure TF-QKD with discrete phase randomization demonstrated.

Higher secret-key rates achieved compared to continuous phase protocols.

Addresses practical implementation loopholes in quantum communication.

Abstract

Twin-field (TF) quantum key distribution (QKD) can overcome fundamental secret-key-rate bounds on point-to-point QKD links, allowing us to reach longer distances than ever before. Since its introduction, several TF-QKD variants have been proposed, and some of them have already been implemented experimentally. Most of them assume that the users can emit weak coherent pulses with a continuous random phase. In practice, this assumption is often not satisfied, which could open up security loopholes in their implementations. To close this loophole, we propose and prove the security of a TF-QKD variant that relies exclusively on discrete phase randomisation. Remarkably, our results show that it can also provide higher secret-key rates than counterpart protocols that rely on continuous phase randomisation.