Sub-Gbps key rate four-state continuous-variable quantum key distribution within metropolitan area

TL;DR

This paper demonstrates a four-state continuous-variable quantum key distribution system achieving sub-Gbps secret key rates over metropolitan distances, significantly surpassing previous records and enabling practical high-speed quantum-secure communication.

Contribution

The authors experimentally realize a four-state CVQKD system with sub-Gbps key rates, overcoming previous rate limitations and paving the way for high-speed quantum networks in metropolitan areas.

Findings

Achieved secret key rates up to 233.87 Mbps over 5 km.

Demonstrated sub-Gbps key rates over 25 km transmission distance.

Surpassed previous CVQKD secret key rate records by an order of magnitude.

Abstract

Continuous-variable quantum key distribution (CVQKD) has potential advantages of high secret key rate, which is very suitable for high-speed metropolitan network application. However, the reported highest secret key rates of the CVQKD systems up to now are limited in a few Mbps. Here, we address the fundamental experimental problems and demonstrate a single-carrier four-state CVQKD with sub-Gbps key rate within metropolitan area. In the demonstrated four-state CVQKD using local local oscillator, an ultra-low level of excess noise is obtained and a high efficient post-processing setup is designed for practically extracting the final secure keys. Thus, the achieved secure key rates are 190.54 Mbps and 137.76 Mbps and 52.48 Mbps using linear channel assuming security analysis method and 233.87 Mbps, 133.6 Mbps and 21.53 Mbps using semidefinite programming security analysis method over transmission distances of 5 km, 10 km and 25 km, respectively. This record-breaking result increases the previous secret key rate record by an order of magnitude, which is sufficient to achieve the one-time pad cryptographic task. Our work shows the road for future high-rate and large-scale CVQKD deployment in secure broadband metropolitan and access networks.