An ASIC for Discriminating Single Photon Detector Signal of High-Speed Quantum Key Distribution System

An ASIC is presented in this paper for discriminating signal from single photon detector (SPD) of high-speed quantum key distribution (QKD) system. The circuit is designed in 130 nm CMOS process. It receives and discriminates a small voltage pulse from a SPD, coinciding with a trigger signal and outputs the effective signal to next stage of QKD system. The pulse width of the voltage signal from SPD is less than 400 ps. The circuit mainly consists of bandgap reference, high speed comparator, delay chain and current mode logic (CML) driver. It should operate at a speed of 1.25 GHz. This work integrate all the front-end electronics for SPD into a chip. The area, stray capacitance and power consumption of the whole circuit are reduced. And then the whole receiver of QKD system can be integrated into a chip to improve performance.