2-GHz clock quantum key distribution over 260 km of standard telecom fiber

TL;DR

This paper demonstrates a 2-GHz clock quantum key distribution over 260 km of standard telecom fiber with low error rates, utilizing optimized interferometers and superconducting detectors to achieve secure communication over long distances.

Contribution

The study presents the first implementation of high-speed QKD over 260 km of telecom fiber with optimized interferometers and advanced superconducting detectors.

Findings

QKD over 260 km fiber with 52.9 dB loss achieved low error rates.

Quantum bit error rate below 2% at 205 km, 3.45% at 260 km.

High key rate enabled by improved superconducting detector efficiency.

Abstract

We report a demonstration of quantum key distribution (QKD) over a standard telecom fiber exceeding 50 dB in loss and 250 km in length. The differential phase shift QKD protocol was chosen and implemented with 2 GHz system clock rate. By careful optimization of the 1-bit delayed Faraday-Michelson interferometer and the use of the super-conducting single photon detector (SSPD), we achieved a quantum bit error rate below 2% when the fiber length was no more than 205 km, and of 3.45% for the 260 km length fiber with 52.9 dB loss. We also improved the quantum efficiency of SSPD to obtain high key rate for 50 km length.