Tight finite-key security for twin-field quantum key distribution

TL;DR

This paper extends the security analysis of a variant of twin-field quantum key distribution to the finite-key regime, demonstrating it can achieve higher key rates over practical distances with around 10 billion signals.

Contribution

It provides the first finite-key security proof for this TF-QKD variant, surpassing fundamental bounds and applicable techniques to other protocols.

Findings

Achieves secure key distribution with ~10^10 signals.

Offers higher key rates than alternative variants in relevant distance regimes.

Develops techniques applicable to other QKD protocols.

Abstract

Quantum key distribution (QKD) offers a reliable solution to communication problems that require long-term data security. For its widespread use, however, the rate and reach of QKD systems must be improved. Twin-field (TF) QKD is a step forward toward this direction, with early demonstrations suggesting it can beat the current rate-versus-distance records. A recently introduced variant of TF-QKD is particularly suited for experimental implementation, and has been shown to offer a higher key rate than other variants in the asymptotic regime where users exchange an infinite number of signals. Here, we extend the security of this protocol to the finite-key regime, showing that it can overcome the fundamental bounds on point-to-point QKD with around $10^{10}$ transmitted signals. Within distance regimes of interest, our analysis offers higher key rates than those of alternative variants. Moreover, some of the techniques we develop are applicable to the finite-key analysis of other QKD protocols.