Continuous-variable quantum key distribution over 28.6 km fiber with an integrated silicon photonic receiver chip

TL;DR

This paper demonstrates a silicon photonic receiver chip enabling continuous-variable quantum key distribution over 28.6 km fiber, achieving Mbps secret key rates and advancing scalable, integrated quantum communication networks.

Contribution

It introduces a high-performance integrated silicon photonic receiver chip for CV-QKD, overcoming previous limitations related to noise and bandwidth, and extends transmission distance significantly.

Findings

Achieved 28.6 km fiber transmission with integrated chip

Realized Mbps-level secret key generation rates

Demonstrated stable, high-bandwidth homodyne detection

Abstract

Quantum key distribution, which ensures information-theoretically secret key generation, is currently advancing through photonic integration to achieve high performance, cost reduction and compact size, thereby facilitating the large-scale deployment. Continuous-variable quantum key distribution is an attractive approach for photonic integrations due to its compatibility with off-the-shelf optical communication devices. However, its chip-based systems have encountered significant limitations primarily related to the shot-noise-limited receiver design, which demands low noise, wide bandwidth, high clearance and well stability. Here, we report the implementation of a real local oscillator continuous-variable quantum key distribution system with an integrated silicon photonic receiver chip. Thanks to the well-designed chip-based homodyne detectors with a bandwidth up to 1.5 GHz and a clearance up to 7.42 dB, the transmission distance of the system has been extended to 28.6 km, achieving a secret key generation rate of Mbps level. This technological advancement enables the quantum key distribution systems with photonic integrated receivers to achieve the coverage in both access network scenarios and short-distance metropolitan interconnections, paving the way for the development of the next-generation quantum key distribution networks on a large scale.