Integrated Photonics and Electronics for High‐Speed Quantum Key Distribution

Abstract Quantum key distribution (QKD) has made significant advancements over the past few decades and is gradually transitioning from laboratory to industrial domain. This transformation process poses urgent demands for integrated, cost‐effective, and mass‐producible QKD devices. Here, by interfacing a laser diode, a QKD encoding photonics chip, and their associated electronics driver chips, the QKD transmitter has been condensed from several bulky discrete components to integrated modules with dimensions of a few centimeters, while the modulation rate of the transmitter has been enhanced to 3.33 GHz. Based on this transmitter, QKD is demonstrated over a 100 km standard fiber channel, capable of generating secure keys at a record high key rate of 2.82 Mbps over this distance. This work demonstrates the feasibility of high‐speed integrated QKD transmitters, thereby further propelling the research on QKD in practical applications.