High-rate continuous-variable measurement device-independent quantum key distribution with finite-size security

TL;DR

This paper demonstrates a high-rate, secure, continuous-variable measurement-device-independent quantum key distribution system over 10 km, achieving a record secret key rate and paving the way for scalable quantum networks.

Contribution

First experimental validation of a finite-size CV MDI-QKD system with high secret key rate over 10 km fiber, using innovative system design and real-time phase locking.

Findings

Achieved a secure key rate of 2.6 Mbit/s over 10 km fiber.

Implemented a real-time phase locking system and digital signal processing pipeline.

Set a new benchmark for secure key exchange in CV MDI-QKD.

Abstract

Building scalable and secure quantum networks requires advanced quantum key distribution (QKD) protocols that support multi-user connectivity. Continuous-variable (CV) measurement-device-independent (MDI) QKD, which eliminates all detector side-channel attacks, is a promising candidate for creating various quantum network topologies-such as quantum access networks and star-type topologies-using standard technology and providing high secure key rates. However, its security has so far only been experimentally demonstrated in asymptotic regimes with limited secret key rates and complex experimental setups, limiting its practical applications. Here, we report the first experimental validation of a CV MDI-QKD system, achieving a secure key rate of 2.6 Mbit/s against collective attacks in the finite-size regime over a 10 km fiber link. This is achieved using a new system design, incorporating a locally generated local oscillator, a new relay structure, a real-time phase locking system, and a well-designed digital-signal-processing pipeline for quantum state preparation and CV Bell measurements at a symbol rate of 20 MBaud. Our results set a new benchmark for secure key exchange and open the possibility of establishing high-performance CV MDI-QKD networks, paving the way toward a scalable quantum network.