Provably Secure and Practical Quantum Key Distribution over 307 km of Optical Fibre

TL;DR

This paper demonstrates a practical quantum key distribution system capable of securely transmitting keys over 307 km of optical fibre, significantly surpassing previous distance limitations by using advanced detectors and security analysis.

Contribution

The authors develop a compact, autonomous QKD system that achieves secure key distribution over 307 km using standard telecom components and low-noise detectors, with an innovative finite-key security approach.

Findings

Secure key distribution over 307 km of optical fibre achieved.

Utilizes low-noise semiconductor SPDs for enhanced performance.

Demonstrates feasibility of long-distance practical QKD with standard telecom components.

Abstract

Proposed in 1984, quantum key distribution (QKD) allows two users to exchange provably secure keys via a potentially insecure quantum channel. Since then, QKD has attracted much attention and significant progress has been made in both theory and practice. On the application front, however, the operating distance of practical fibre-based QKD systems is limited to about 150 km, which is mainly due to the high background noise produced by commonly used semiconductor single-photon detectors (SPDs) and the stringent demand on the minimum classical- post-processing (CPP) block size. Here, we present a compact and autonomous QKD system that is capable of distributing provably-secure cryptographic key over 307 km of ultra-low-loss optical fibre (51.9 dB loss). The system is based on a recently developed standard semiconductor (inGaAs) SPDs with record low background noise and a novel efficient finite-key security analysis for QKD. This demonstrates the feasibility of practical long-distance QKD based on standard fibre optic telecom components.