Wenda Shi

Twin-field quantum key distribution (TF-QKD) promises long-distance quantum networks, but practical deployment demands compact and phase-stable hardware--requirements well matched by thin-film lithium niobate (TFLN) electro-optic photonics. Here, we propose and demonstrate a coherent dual-band TFLN chip to enable system miniaturization and an open-channel architecture. EO-comb generation and quantum signal encoding are monolithically integrated on a single chip. Coherent on-chip comb lines serve as channel references for fast and robust phase stabilization. Using this integrated platform, we demonstrate TF-QKD over a 508 km fiber link, achieving a quantum bit error rate below 0.5% and a secure key rate that surpasses the linear rate limit by a factor of 2.67. These results establish integrated TFLN photonics as a scalable and robust solution for practical, long-distance quantum communication.