Effect of detector dead-times on the security evaluation of differential-phase-shift quantum key distribution against sequential attacks

TL;DR

This paper examines how detector dead-times affect the security of differential-phase-shift QKD against sequential attacks, providing upper bounds on the maximum secure distance in different device trust scenarios.

Contribution

It introduces a detailed analysis of detector dead-time effects on DPS QKD security, deriving upper bounds for secure communication distances under various attack models.

Findings

Dead-times limit the maximum secure distance of DPS QKD.

Upper bounds are established for trusted and untrusted device scenarios.

Sequential attacks based on unambiguous state discrimination are effectively analyzed.

Abstract

We investigate limitations imposed by detector dead-times on the performance of sequential attacks against a differential-phase-shift (DPS) quantum key distribution (QKD) protocol with weak coherent pulses. In particular, we analyze sequential attacks based on unambiguous state discrimination of the signal states emitted by the source and we obtain ultimate upper bounds on the maximal distance achievable by a DPS QKD scheme both in the so-called trusted and untrusted device scenarios, respectively.