Improved postselection security analysis of phase error estimation in quantum key distribution

TL;DR

This paper introduces an improved security analysis method for phase error estimation in quantum key distribution, enhancing performance over traditional postselection techniques by correlating failure probabilities and applying entropy uncertainty relations.

Contribution

It proposes a novel approach linking failure probabilities of phase error estimation under collective and coherent attacks, enabling better key rate calculations in QKD protocols.

Findings

Enhanced key rate estimation for QKD protocols.

Finite-key analysis shows improved performance.

Applicable to various secure QKD schemes.

Abstract

Quantum key distribution (QKD) enables the generation of secure keys between two distant users. Security proof of QKD against general coherent attacks is challenging, while the one against collective attacks is much easier. As an effective and general solution, the postselection method tries to extend security analyses of collective attacks to be against coherent attacks. However, it gives a bad performance. To overcome this drawback, instead of directly calculating key rate by postselection method, we propose a method correlating the failure probabilities of phase error estimation against collective and coherent attacks, enabling the use of the independent and identically distributed assumption in parameter estimation against coherent attacks. Then the key rate can be obtained by uncertainty relation of entropy. Our method can be applied to various QKD protocols, providing better performance compared with the traditional postselection method. For instance, we give the finite-key analyses of the side-channel-secure (SCS) QKD and the no-phase-postselection (NPP) twin-field (TF) QKD to show their performance improvements with the proposed method.