Simple security proof of twin-field type quantum key distribution protocol

TL;DR

This paper presents a simpler twin-field quantum key distribution protocol that uses local phase randomization, making security analysis easier and achieving a square-root rate improvement over traditional point-to-point QKD.

Contribution

It introduces a conceptually simpler TF-QKD protocol based on local phase randomization, with a rigorous security proof and improved key rate.

Findings

Secure key rate has a square-root improvement over point-to-point capacity.

Simplifies security analysis by using local phase randomization.

Experimental demands are reduced due to the simplified protocol.

Abstract

Twin-field (TF) quantum key distribution (QKD) was conjectured to beat the private capacity of a point-to-point QKD link by using single-photon interference in a central measuring station. This remarkable conjecture has recently triggered an intense research activity to prove its security. Here, we introduce a TF-type QKD protocol which is conceptually simpler than the original proposal. It relies on local phase randomization, instead of global phase randomization, which significantly simplifies its security analysis and is arguably less demanding experimentally. We demonstrate that the secure key rate of our protocol has a square-root improvement over the point-to-point private capacity, as conjectured by the original TF-QKD scheme.