Chip-Based Measurement-Device-Independent Quantum Key Distribution Using Integrated Silicon Photonic Systems

Measurement-device-independent (MDI) quantum key distribution (QKD) employs an untrusted relay to prevent the receiver from side-channel attacks commonly encountered in earlier QKD protocols. Con-ventional MDI QKD systems rely entirely on bulky and expensive optical setups that present great challenges for system scaling and integration. In this work, an all-chip-based MDI QKD system including two transmitter chips and one server chip is demonstrated using integrated silicon photonic technology. The system is capable of generating polarization-encoded weak coherent states with polarization extinc-tion ratios of over 20 dB, sufficient for low-error MDI QKD. In the proof-of-concept experiment, the chip-based MDI QKD system generates a key rate per pulse of 2.923 x 10(-6) over a distance correspond-ing to a 50-km standard fiber with 25% detection efficiency and a predicted distance of 120 km with 85% detection efficiency. Our proof-of-concept prototype makes a giant step forward towards fully chip-based MDI QKD systems and highly integrated quantum communication networks in the near future with its high scalability and cost effectiveness.