Overcoming the rate-distance limit of device-independent quantum key distribution

TL;DR

This paper introduces a heralded DIQKD scheme using entangled coherent states that surpasses traditional key rate bounds, enabling long-distance secure quantum communication and advancing quantum internet development.

Contribution

The authors propose a novel heralded DIQKD protocol based on entangled coherent states that outperforms existing schemes and exceeds the secret key capacity limit.

Findings

Secret key rate surpasses traditional capacity bounds

Long-distance entanglement achieved via single-photon interference

Potential for quantum internet applications

Abstract

Device-independent quantum key distribution (DIQKD) exploits the violation of a Bell inequality to extract secure key even if the users' devices are untrusted. Currently, all DIQKD protocols suffer from the secret key capacity bound, i.e., the secret key rate scales linearly with the transmittance of two users. Here we propose a heralded DIQKD scheme based on entangled coherent states to improve entangling rates whereby long-distance entanglement is created by single-photon-type interference. The secret key rate of our scheme can significantly outperform the traditional two-photon-type Bell-state measurement scheme and, importantly, surpass the above capacity bound. Our protocol therefore is an important step towards a realization of DIQKD and can be a promising candidate scheme for entanglement swapping in future quantum internet.