Simple and Rigorous Proof Method for the Security of Practical Quantum Key Distribution in the Single-Qubit Regime Using Mismatched Basis Measurements

TL;DR

This paper introduces a simple, rigorous method for calculating secure key rates in practical quantum key distribution systems, ensuring unconditional security even with device imperfections in the single-qubit regime.

Contribution

It provides a new, straightforward proof technique for the security of practical QKD implementations, applicable to various protocols including measurement-device-independent QKD.

Findings

Method rigorously proves unconditional security against all attacks.

Applicable to practical, imperfect QKD devices in the single-qubit regime.

Aims to become a standard tool for QKD security analysis.

Abstract

Quantum key distribution (QKD) protocols aim at allowing two parties to generate a secret shared key. While many QKD protocols have been proven unconditionally secure in theory, practical security analyses of experimental QKD implementations typically do not take into account all possible loopholes, and practical devices are still not fully characterized for obtaining tight and realistic key rates. We present a simple method of computing secure key rates for any practical implementation of discrete-variable QKD (which can also apply to measurement-device-independent QKD), initially in the single-qubit lossless regime, and we rigorously prove its unconditional security against any possible attack. We hope our method becomes one of the standard tools used for analysing, benchmarking, and standardizing all practical realizations of QKD.