Finite-key security for quantum key distribution systems utilizing weak coherent states

TL;DR

This paper provides a finite-key security analysis for quantum key distribution using weak coherent states, extending previous proofs to include intercept-resend attacks and demonstrating the impact on secret key length.

Contribution

It introduces a finite-key security proof for phase-coded weak coherent state QKD, considering intercept-resend attacks and the Holevo bound's role in mutual information analysis.

Findings

Holevo bound determines maximum mutual information between Alice and Eve.

Finite-key effects significantly influence secret key length.

Analysis applied to subcarrier wave QKD protocol.

Abstract

In this paper we present finite-key security analysis for quantum key distribution protocol based on weak coherent (in particular phase-coded) states using a fully quantum asymptotic equipartition property technique. This work is the extension of the proof for non-orthogonal states on the coherent states. Below we consider two types of attacks each of them maximizes either Alice-Eve or Eve-Bob mutual information. The cornerstone of this paper is that we do assume the possibility of crucial intercept-resend attack based on errorless unambiguous state discrimination measurement. We demonstrate that Holevo bound always gives the highest mutual information between Alice and Eve regardless particular kind of isometry. As the main result we present the dependence of the extracted secret key length. As the example we implement the proposed analysis to the subcarrier wave quantum key distribution protocol.