Excess Loss in Homodyne Detection Originating from Distributed Photocarrier Generation in Photodiodes

Optical homodyne (single-frequency) measurement is a key technology in optical quantum information processing and key distribution, since it can realize high-speed quantum measurement with a high signal-to-noise ratio. Researchers show that photodiodes have an intrinsic noise mechanism in the photodetection process, due to distributed photocarrier generation, and the excess noise cause an effective optical loss in homodyne detection at high frequencies. They evaluate this excess loss theoretically and experimentally, showing that it depends on the photodiode's material, and suggesting further requirements for high-efficiency, high-speed hardware.