Practical long-distance quantum key distribution system using decoy levels

TL;DR

This paper demonstrates a practical, automated long-distance quantum key distribution system achieving secure key exchange over 144.3 km using advanced detectors and decoy states, marking a significant step toward real-world quantum communication.

Contribution

The authors present a fully automated QKD system with decoy levels and superconducting detectors, achieving a record long-distance secure key distribution of 144.3 km.

Findings

Secure key over 144.3 km of fiber

Record distance for practical QKD

System operates automatically and robustly

Abstract

Quantum key distribution (QKD) has the potential for widespread real-world applications. To date no secure long-distance experiment has demonstrated the truly practical operation needed to move QKD from the laboratory to the real world due largely to limitations in synchronization and poor detector performance. Here we report results obtained using a fully automated, robust QKD system based on the Bennett Brassard 1984 protocol (BB84) with low-noise superconducting nanowire single-photon detectors (SNSPDs) and decoy levels. Secret key is produced with unconditional security over a record 144.3 km of optical fibre, an increase of more than a factor of five compared to the previous record for unconditionally secure key generation in a practical QKD system.