Research Of Hidden Non-locality And Preparation Of Two-photon Tunable State Based On BD Interferometer

Quantum entanglement plays an important role in fundamental physics.It is the core resource of quantum information processing,and has been widely developed and applied in now.In the concept system of quantum entanglement,it is that the non-locality highlights the fundamental difference between the quantum world and the classic world,Non-locality has been widely concerned and applied in quantum teleportation,quantum entanglement exchange,quantum dense coding,quantum computing and so on.This paper mainly discusses the concept and the background of quantum nonlocality,and how to make use of local filters to extract hidden non-locality.We first introduce the research background and significance of quantum entanglement and important progress in the study of non-locality at home and abroad.Subsequently,this article introduces some basic theoretical knowledge of entangled light sources and a series of experimental operations based on entangled light sources.In the preparation of entangled light sources,this article mainly introduces the preparation scheme of two-photon entangled states.We use spontaneous parametric down-conversion to prepare a twophoton entangled source to obtain a maximum entangled state light source with a fidelity of 99.3%.On the basis of obtaining high-fidelity entangled light sources,on the one hand,in our experiment,we successfully establish a simple and adjustable parameter local state preparation scheme.The scheme includes a two-photon entangled light source based on spontaneous parameter downconversion and an adjustable parameter decoherence channel composed of a Sagnac ring and a decoherence channel.After obtaining the local state with adjustable parameters,we used the POVM composed of BD interference rings to form a local filter,and after performing the filtering operation on the obtained local state,quantum state tomography measurement was performed on the filtered state.After that,the Bell inequality value corresponding to the final quantum state is analyzed,and whether the local state has hidden non-locality is judged by their value of Bell inequality.On the other hand,by comparing the advantages and disadvantages of the BD interference ring and the Sagnac ring,we found that the BD interference ring has good stability and modular cascading operability.So we proposed to use the BD interference ring as a module basis to build adjustable parameters Theoretical experimental scheme of two-photon arbitrary state.