Research On Quantum Correlation Under Positive Operator Vauled Measurement

Compareing with classical world,the quantum world is a completely different system.Quantum nonlocality,is one of the most important properties in quantum information science,it plays an immeasurable role in the development of this field.The paper first reviews some developments and research background in the quantum field,summarizing the definition and important concepts of Bell nonlocality,EPR steering,and entanglement.Furthermore,the paper introduces situations that multiple observers can measure one particle in a two-particle system,which is derived from the scene that two observers separately measure their particle in early stage.Subsequently,the paper has a discussion about nonlocality,then reproducing one of them by simulation.Basing on these theories and protocols,the article proposes a new idea: Under the premise that both parties have multiple observers,whether the system can satisfy the characteristics of quantum correlation? if using symmetric or asymmetric weak measurements in observers of both sides,Could the system satisfies the EPR steering? It will elaborate on both points in the following section.In addition to the theoretical proof,the article also gives full thought to the error under the optical system,and then analysis the feasibility of experimental analysis.The paper also introduces the experimental work which has been done during the postgraduate period.It describes the properties of the commonly used optical equipment and introducing the principle of the spontaneous parametric down-conversion process,which is the most mature technique for the experimental preparation of entanglement sources.With the entanglement source whose fidelity is 98.3%,the experiment of the randomness verification of measurement shows that,if use symmetric information completed positive operator value measurement,elegant Bell inequality,and an entangled photon pair,it can successfully verify that the randomness of more than1 bit in each round.Besides,Based on the 2+2 EPR steering system and actual error proposed in the third chapter,the experiment can be designed in detail.