Quantum key distribution overcoming practical correlated intensity fluctuations

TL;DR

This paper introduces and experimentally validates a new quantum key distribution protocol that is tolerant to intensity correlations, significantly improving security and performance over previous methods by mitigating a common security loophole.

Contribution

The authors develop and demonstrate the first practical QKD protocol that overcomes security vulnerabilities caused by intensity correlations, enhancing robustness and transmission distances.

Findings

Enhanced maximum transmission distances

Increased secret key rates

Validated practical implementation

Abstract

Intensity correlations between neighboring pulses open a prevalent yet often overlooked security loophole in decoy-state quantum key distribution (QKD). As a solution, we present and experimentally demonstrate an intensity-correlation-tolerant QKD protocol that mitigates the negative effect that this phenomenon has on the secret key rate according to existing security analyses. Compared to previous approaches, our method significantly enhances the robustness against correlations, notably improving both the maximum transmission distances and the achievable secret key rates across different scenarios. By relaxing constraints on correlation parameters, our protocol enables practical devices to counter intensity correlations. We experimentally demonstrate this first practical solution that directly overcomes this security vulnerability, establish the feasibility and efficacy of our proposal, taking a major step towards loophole-free and high-performance QKD.