Long-distance device-independent quantum key distribution using single-photon entanglement

TL;DR

This paper proposes a photonic implementation of device-independent quantum key distribution using single-photon entanglement, enabling secure long-distance communication by overcoming losses that hinder Bell tests.

Contribution

It introduces a novel single-photon entanglement scheme for DIQKD that maintains positive key rates over hundreds of kilometers, advancing practical long-distance quantum security.

Findings

Key rate scales with the square root of transmittance

Positive key rates achievable over hundreds of kilometers

Photonic realization enhances long-distance DIQKD feasibility

Abstract

Device-independent quantum key distribution (DIQKD) provides the strongest form of quantum security, as it allows two honest users to establish secure communication channels even when using fully uncharacterized quantum devices. The security proof of DIQKD is derived from the violation of a Bell inequality, mitigating side-channel attacks by asserting the presence of nonlocality. This enhanced security comes at the cost of a challenging implementation, especially over long distances, as losses make Bell tests difficult to conduct successfully. Here, we propose a photonic realization of DIQKD, utilizing a heralded preparation of a single-photon path entangled state between the honest users. Being based on single-photon interference effects, the obtained secret key rate scales with the square root of the quantum channel transmittance. This leads to positive key rates over distances of up to hundreds of kilometers, making the proposed setup a promising candidate for securing long-distance communication in quantum networks.