Field test of a continuous-variable quantum key distribution prototype

TL;DR

This paper reports the design, implementation, and field testing of a continuous-variable quantum key distribution prototype that achieves secure key exchange over optical fibers, demonstrating its potential for high-speed metropolitan network security.

Contribution

The paper presents the first field test of a continuous-variable QKD system with real-world performance data over optical fibers, including security against coherent attacks.

Findings

Achieved an average secret key rate of 8 kbit/s over 3 dB loss fiber

Operated stably and automatically for 57 hours in a network environment

Validated security against general coherent eavesdropping attacks

Abstract

We have designed and realized a prototype that implements a continuous-variable quantum key distribution protocol based on coherent states and reverse reconciliation. The system uses time and polarization multiplexing for optimal transmission and detection of the signal and phase reference, and employs sophisticated error-correction codes for reconciliation. The security of the system is guaranteed against general coherent eavesdropping attacks. The performance of the prototype was tested over preinstalled optical fibres as part of a quantum cryptography network combining different quantum key distribution technologies. The stable and automatic operation of the prototype over 57 hours yielded an average secret key distribution rate of 8 kbit/s over a 3 dB loss optical fibre, including the key extraction process and all quantum and classical communication. This system is therefore ideal for securing communications in metropolitan size networks with high speed requirements.