Experimental Study On Quantum Self-testing And Quantum State Certification

The rapid development of quantum technology has new applications in the field-s of communication,simulation,sensing and computation.For example,the proposed quantum internet infrastructure enables unconditionally secure transmission and manip-ulation of information;carefully engineered quantum devices allow for the simulation of complex states of matter,etc.These application prospects put forward challenging requirements for the precision of quantum devices.Due to the defects of the device structure and the noise in the environment during the experiment,the actual output of quantum device is unknown state.Therefore,the certification of quantum states is particularly important in quantum information theory,especially the realization of the identification of quantum states in the case of device independence,that is,the unknown quantum states and measurement methods are determined only from the measurement results without considering the internal structure of the device.However,if the quan-tum protocol is implemented in device-independent scenarios,there are more and more experimental obstacles.Therefore,semi-device-independent approach without entan-glement is gradually formed.As a basic assumption of quantum mechanics,quantum measurement plays an irreplaceable role in quantum information.Quantum measure-ment is generally divided into projective measurement(von Neumann measurement)and generalized quantum measurement(Positive Operator Valued Measure).Since pro-jective measurement can only identify orthogonal states,Positive Operator Valued Mea-sure is more practical in some research tasks,such as quantum cryptography,random number generation,quantum computing,quantum state tomography and certification of non-orthogonal states.In this thesis,we discuss the problem of describing an unknown quantum measur-ing device in the semi-device-independent scenario and the new framework of prepare-and-measure(PAM).Firstly,we introduce the research background and significance of quantum information and certification of quantum states,and then we elaborate some theoretical basic knowledge of quantum states and basic devices related to quantum optical experiments.In order to realize the certification of quantum states and mea-surement methods,we theoretically studied the semi-device-independent certification of quantum states in the PAM scenario.Single photon source and two-photon entangle-ment source are prepared based on the spontaneous parametric down-conversion pro-cess of PPKTP crystal in the experiment.For the single photon source,when the pump beam power is 2.67m W,the total number of coincidence photons collected by the sin-gle photon detector in one second is about 3×10~4.For the two-photon entanglement source,the final entangled state is a Bell state with a fidelity of 98%by adjusting the initial optical path.On this basis,we also completed three works:(1)Experimentally verified the gen-uine three-outcome Positive Operator Valued Measure(POVM)for the first time under the hypothesis of finite overlap between initial quantum states;(2)Based on the discrete time quantum walk network,in the presence of noise,the final experimental results not only clearly verify the genuine three-outcome POVM,but also show that the greater the overlap of quantum states,the stronger the ability to tolerate noise;(3)It is experimen-tally verified that the optimal POVM can be self-tested when unambiguous quantum state discrimination is carried out.