A Coherent Receiver Based on SIM for Quantum Communication

In this letter, we propose theoretically a coherent receiver based on solid-state impact-ionization multiplier (SIM) for quantum communication. In the newly proposed coherent receiver, the balanced photodetector (BPD) is used as a current source connected to the SIM. The signal from the BPD is fed into the SIM, where it is amplified through a desirable avalanche process, which is similar to the avalanche photodiodes, and can then be fed into a transimpedance amplifier for voltage readout. Compared with the conventional coherent receiver with only coherent gain, the signal gain of the proposed coherent receiver consists of two parts, the coherent gain produced by the local oscillator (LO) and the avalanche gain produced by the SIM, so the LO power can be decreased to avoid the saturation of the BPD without sacrificing the signal gain. What is more, the proposed receiver can operate at a higher bandwidth by optimizing the structure of the coherent receiving end and redesigning the geometry of the SIM.