One-sided DI-QKD secure against coherent attacks over long distances

TL;DR

This paper introduces a one-sided device-independent quantum key distribution protocol that is secure against coherent attacks over long distances with realistic detection efficiencies, advancing secure quantum communication.

Contribution

It demonstrates a nearly optimal one-sided DI QKD protocol secure against coherent attacks with detection efficiencies above 50.1%, suitable for long-distance implementation.

Findings

Secure against coherent attacks with >50.1% detection efficiency

Effective over distances comparable to standard QKD

Almost reaches the theoretical limit for protocols with two untrusted measurements

Abstract

Quantum Key Distribution (QKD) is a technique enabling provable secure communication but faces challenges in device characterization, posing potential security risks. Device-Independent (DI) QKD protocols overcome this issue by making minimal device assumptions but are limited in distance because they require high detection efficiencies, which refer to the ability of the experimental setup to detect quantum states. It is thus desirable to find quantum key distribution protocols that are based on realistic assumptions on the devices as well as implementable over long distances. In this work, we consider a one-sided DI QKD scheme with two measurements per party and show that it is secure against coherent attacks up to detection efficiencies greater than 50.1% specifically on the untrusted side. This is almost the theoretical limit achievable for protocols with two untrusted measurements. Interestingly, we also show that, by placing the source of states close to the untrusted side, our protocol is secure over distances comparable to standard QKD protocols.