Continuous-variable quantum key distribution over 50.4 km fiber using integrated silicon photonic transmitter and receiver

TL;DR

This paper demonstrates a high-speed, integrated silicon photonic continuous-variable quantum key distribution system capable of secure communication over 50.4 km fiber, advancing practical quantum networks.

Contribution

It introduces a fully integrated silicon photonic CV-QKD system with high symbol rate and long-distance transmission, addressing cost and size challenges of traditional setups.

Findings

Achieved a symbol rate of 1.5625 GBaud.

Secure key rates of 31.05 Mbps over 25.8 km.

Secure key rates of 5.05 Mbps over 50.4 km.

Abstract

Quantum key distribution (QKD) is the fastest-growing and relatively mature technology in the field of quantum information, enabling information-theoretically secure key distribution between two remote users. Although QKD based on off-the-shelf telecom components has been validated in both laboratory and field tests, its high cost and large volume remain major obstacles to large-scale deployment. Photonic integration, featured by its compact size and low cost, offers an effective approach to addressing the above challenges faced by QKD. Here, we implement a high-performance, integrated local local oscillator continuous-variable (CV) QKD system based on an integrated silicon photonic transmitter and receiver. By employing a high-speed silicon photonic integrated in-phase and quadrature modulator, a low-noise and high bandwidth silicon photonic integrated heterodyne detector, and digital signal processing, our CV-QKD system achieves a symbol rate of up to 1.5625 GBaud. Furthermore, the system achieves asymptotic secret key rates of 31.05 and 5.05 Mbps over 25.8 and 50.4 km standard single-mode fiber, respectively, using an 8-phase-shift keying discrete modulation. Our integrated CV-QKD system with high symbol rate and long transmission distance pays the way for the quantum secure communication network at metropolitan area.