The Research And Application Of Single Photon Coincidence Detection

Coincidence measurement can select the time-related events in the output pulse of different detectors by using electronic methods.Single photon detector can detect single photon which carries the quantum information,and converted to electrical signal output,and then extract the quantum information carried by a single photon through the measurement,counting and other means.Single photon coincidence detection has an important application in single photon source,quantum operation,multiphoton interference entangled photon pairs detection,single photon interference research,all-optical quantum computing,quantum communication and information fields.So we can know that coincidence measurement plays a very important role in the detection of single photon.The electronic system used to measure coincidence event is called the conformity technology system.A simple coincidence counting can be achieved by the combination of discrete components and multiplier,which may bring additional delay to the signal.In recent years,with the rapid development of field programmable gate array(FPGA),it has more gate circuit,smaller size,lower cost,and convenient to modify the design to meet the requirements of the experiment.More and more people design the counting system based on FPGA,but all of them have the same problem: the inconsistency of delay brings the error of coincidence counting when the two channel signal arrives at the path introduced by the FPGA.In order to solve this problem,we designed a pulse edge triggered single photon detector in the laboratory against the single photon detector with external trigger and verified the rationality.The main content is as following:Firstly,I introduced the basic principle of coincidence measurement and various single photon detectors,and compared the range of the use of these single photon detectors.In terms of the single photon detector,I designed a dual channel coincidence counting system which can be divided into three parts.It consists of plastic surgery,delay coincidence,and coincidence counting.The first part is the most difficult among them,which is the innovation of this paper.It successfully solves the error caused by the path delay.We verified the correctness of the system through the experiment that we used Quartus II to stimulate the Model Sim-Altera to simulate.Secondly,I introduced the two order autocorrelation function of the single photon source.In the experiment,I used a single photon source based on Er doped fiber for the first time,and the two order autocorrelation function is the most important index to evaluate the single photon source.We measured the function through the coincidence measurement in order to evaluate the single photon source.Compared with the previous system,the design of the system has higher accuracy,which can better satisfy the single photon detection experiment.