Chip-based Long-distance Twin-field Quantum Key Distribution Networks

Authors

Abstract

We demonstrate a scalable integrated photonic network for twin-field quantum key distribution (TF-QKD). The architecture employs a star topology, utilizing a server-side Si3N4 optical microcomb and 20 monolithically integrated InP transmitter chips. Coherent comb lines are used to seed client lasers, enabling wavelength-division multiplexing and ensuring stable interference. Sequential pairwise TF-QKD is performed across ten channels among 20 users, with each channel surpassing the repeaterless secret-key-capacity bound at a distance of 370 km. This yields an overall networking capability of 3,700 km. Wafer-scale chip reproducibility confirms the platform’s practicability for building large-scale quantum communication networks. Furthermore, we demonstrate a design utilizing a broadly tunable on-chip laser, which is expected to cover the entire telecommunication C-band. This approach enables dozens of wavelength channels to operate in parallel, thereby scaling the network capacity up to hundred-user-level.