Research On Quantum State Analysis Based On Two-photon Interference

Estimating the unknown state of a quantum system is of great importance in the field of quantum information processing and quantum computing.As a method of analyzing the state of the system,quantum state tomography can infer the state of the system according to the output of the quantum system.This paper mainly discusses the concept of quantum state tomography and how to carry out quantum state tomography via Hong-Ou-Mandel(HOM)interference under the semi-device-independent framework.We first introduce the background and significance of quantum state tomography and the important progress of quantum state tomography at home and abroad.Subsequently,this article introduces the basic theory of spontaneous parametric down-conversion process(SPDC),the operation of photonic system,the commonly used experimental devices and the basic theory of state tomography.In the preparation of parametric light source,we use ?-type barium metaborate(BBO)crystal to realize SPDC,and obtain rate photon pairs with high coincidence.On the basis of high coincidence rate parametric light source,we construct a semi-device-independent quantum state tomography scheme using HOM interference.The scheme mainly uses HOM interference to construct joint measurement operator to realize the joint measurement of two photons,which are composed of trusted auxiliary state and unknown state.As the two inputs of HOM interference,auxiliary state and unknown state are prepared by photon pairs generated by SPDC process,In order to reconstruct the unknown state,the auxiliary state set must be tomographic complete.Therefore,we propose a scheme to reconstruct the unknown state with only one measurement operator and a set of auxiliary states with complete information.Compared with the state tomography scheme which needs a set of complete measurement operator,this scheme only needs one measurement operator,and the completeness of the operator is replaced by the completeness of the state,which greatly reduces the requirement of the measurement equipment.