Curator's Take
This breakthrough demonstrates a major leap forward for practical quantum cryptography by achieving an unprecedented 10.34 Mbps secret key rate over free-space channels - roughly 10 times faster than previous continuous-variable quantum key distribution systems. The researchers solved a critical engineering challenge by developing a self-referenced local oscillator scheme that dramatically reduces noise and improves stability, making quantum-secured communication viable even in turbulent atmospheric conditions with high signal loss. This work bridges the gap between laboratory demonstrations and real-world deployment of quantum cryptography, potentially enabling secure quantum communications for applications ranging from satellite links to urban quantum networks where fiber optic cables aren't feasible.
— Mark Eatherly
Summary
Continuous-variable quantum key distribution (CVQKD) using passive state preparation (PSP) offers low-cost, high-rate secure communication. However, the existing PSP-CVQKD scheme with a transmitted local oscillator has high photon leakage noise and poor stability, making it unsuitable for high-loss transmission. In this work, for the first time, we propose and implement a local local oscillator (LLO) CVQKD system using a self-referenced (SR) PSP scheme, and give a theoretical proof of the equivalence of the PSP and GMCS protocol using temporal-mode theory. By employing the novel self-referenced pilot scheme to achieve high-precision time-varying frequency and phase compensation algorithms, we significantly improve the system' s signal-to-noise ratio and stability. The system achieves a record-high asymptotic secret key rate of 10.34 Mbps over a free-space channel with up to 23.5 dB loss, while maintaining low excess noise and robust performance under turbulent conditions. This work establishes the feasibility of SR-LLO CVQKD, providing a practical pathway toward secure, high-rate quantum communication in realistic environments.