Fully automated entanglement-based quantum cryptography system for telecom fiber networks

TL;DR

This paper introduces a fully automated, portable entanglement-based quantum cryptography system suitable for telecom fiber networks, demonstrating stable, long-term secure key exchange over real-world fiber links with high entanglement quality.

Contribution

The work presents a compact, automated QKD system with stable operation over deployed fibers, advancing practical quantum cryptography deployment in telecom infrastructure.

Findings

Demonstrated secure key exchange up to 50 km in laboratory conditions.

Achieved over two weeks of automatic key generation at 2000 bit/s in deployed fiber.

Maintained an average entanglement visibility of 93% during long-term operation.

Abstract

We present a quantum key distribution (QKD) system based on polarisation entanglement for use in telecom fibers. A QKD exchange up to 50km was demonstrated in the laboratory with a secure key rate of 550 bit/s. The system is compact, portable with a fully automated start-up and stabilisation modules for polarisation, synchronisation and photon coupling allow a hands-off operation. Stable and reliable key exchange in a deployed optical fiber of 16km length was demonstrated. In this fiber network we achieved over two weeks an automatic key generation with an average key rate of 2000 bit/s without manual intervention. During this period, the system had an average entanglement visibility of 93%, highlighting the technical level and stability achieved for entanglement-based quantum cryptography.