FPGA-based High-precision Coincidence Counter Design

Coincidence measurement is an important technique in quantum optic. With thedevelopment of quantum information science, coincidence counter is widely used in a variety ofquantum optical experiments. At present, the existed coincidence measurement system is lessprecise, which is affected by dark counts and spatial light noise. To solve this problem, this thesiswill develop a FPGA-based high-precision coincidence counter. It can select the pulse width inaccordance with experimental requirements, and eliminate interference factors to a certainextent.Coincidence resolution time is an important parameter to meet the accuracy of thecoincidence counter. First, the thesis presents two coincidence counting unit design schemesafter introducing the coincidence counter’s physical significance and implementing method. Thedetail design concept and the specific digital circuit implementation are given for the twoschemes, respectively, and simulations are performed to prove the correctness of two schemes.The simulation results show that both schemes improve the coincidence measurement accuracyand reduce the resolution time.Then, the thesis studies the implementation of the digital delay unit, which is used toimplement the delay modules of coincidence counting units. Based on the counting and memorymethod, the digital delay units are designed and tested. The results show that the designs areachiveable and feasible.Finally, the thesis presents a high-precision coincidence counter with the secondcoincidence counting unit design scheme on the DE2-115development board. The coincidencecounter can support pulse inputs on four channels, select pulse width and measurement channelsaccording to experimental requirements, and realize real-time interaction with the user host viaRS232serial port. In addition, the device eliminates the need for data acquisition card of theexisting system to save costs. By testing, the results show that the coincidence counter caneffectively improve the measurement precision to ensure the results accuracy in quantum opticsexperiments.