Secure quantum key distribution over 421 km of optical fiber

TL;DR

This paper demonstrates a quantum key distribution system capable of securely transmitting keys over 421 km of optical fiber with high repetition rate and low error rates, advancing long-distance quantum communication.

Contribution

The authors develop a high-speed, long-distance QKD system using a three-state time-bin protocol with decoy states and superconducting detectors, achieving record distances and key rates.

Findings

Secure key distribution over 421 km fiber

Secret key rate of 6.5 bps at 405 km

Utilization of superconducting detectors and ultra low-loss fiber

Abstract

We present a quantum key distribution system with a 2.5 GHz repetition rate using a three-state time-bin protocol combined with a one-decoy approach. Taking advantage of superconducting single-photon detectors optimized for quantum key distribution and ultra low-loss fiber, we can distribute secret keys at a maximum distance of 421 km and obtain secret key rates of 6.5 bps over 405 km.