Coexistence of continuous-variable quantum key distribution and classical data over 120-km fiber

TL;DR

This paper demonstrates the longest-distance continuous-variable quantum key distribution over 120 km fiber, coexisting with classical data, showing its potential for scalable, cost-effective quantum-secured communication in existing networks.

Contribution

It presents the longest-distance CV-QKD over 120 km fiber coexisting with classical data, using natural mode filtering and phase noise mitigation, advancing practical quantum communication.

Findings

Longest-distance CV-QKD achieved over 120 km fiber

Successful coexistence with classical data over same fiber

Benchmarking confirms CV-QKD's feasibility for real-world networks

Abstract

Integrating quantum key distribution (QKD) with classical data transmission over the same fiber is crucial for scalable quantum-secured communication. However, noise from classical channels limits QKD distance. We demonstrate the longest-distance continuous-variable QKD (CV-QKD) over 120 km (20 dB loss) in the asymptotic regime, and over 100 km (17 dB loss) in the finite-size regime, both coexisting with a fully populated coarse wavelength division multiplexing system. Natural mode filtering of the local oscillator and phase noise mitigation enabled this without additional filtering or wavelength reallocation. Benchmarking against a commercial discrete-variable QKD system and considering finite-size effects confirms the feasibility of CV-QKD as a plug-and-play solution for typical 80-100 km long-haul optical networks. Our results set a record fiber distance for CV-QKD, showing its potential for cost-effective, large-scale deployment in existing network infrastructure.