Study On Preparation And Application Of High Brightness Entangled Photon Source

In recent years,the research of quantum computing and quantum information and other fields has developed rapidly.As one of the essential bases for the development of these fields,the quality of quantum entangled photon source is a major factor affecting applications in many fields.The study of high-brightness entangled photon source is of great significance for the development of quantum information and other fields.The fabrication methods of quantum Parametric Down-Conversion are mainly introduced as follows: Spontaneous parametric down-conversion(SPDC)process and four-wave mixing process.SPDC process is a widely used scheme for the preparation of entangled photon source due to its mature technology,high photon correlation degree and convenient detection.When propagating in optical fiber,1310 nm photon has the characteristics of low attenuation and low dispersion.In this paper,the preparation of entangled photon source based on SPDC technology is studied,and the preparation scheme based on BBO and PPLN crystals is designed.The high brightness signal photon of 1310 nm wavelength is obtained and applied in the efficiency calibration of photon detector.The main work can be divided into the following two parts:Part Ⅰ: The preparation scheme of pump photon with wavelength of 248 nm and355nm is designed,the phase matching curve of the angle tuned BBO crystal is calculated,and the optimal matching mode of signal photon with wavelength of 1310 nm is selected to build the photon source path based on BBO crystal.After optimizing pump photon power and other parameters,the average value of photon counting is improved effectively.The prepared photon pairs of 487 nm and 1310 nm wavelength were used to measure the quantum efficiency of the detector,and the results were consistent with the factory data.Part Ⅱ: After comparing several kinds of periodic polarized crystals,the preparation scheme of PPLN crystals doped with 5% magnesium oxide and pumped photon with wavelength of 532 nm was designed.The polarization period,pump wavelength,temperature and angle tuning curves of PPLN crystals were calculated,and the relationship between the output wavelength and polarization period at different temperatures was further analyzed.The optimum polarization period of 1310 nm signal photon crystal is 6.85μm and the optimum operating temperature is 451 K.The optical path based on PPLN crystal was built,and the quantum efficiency measurement experiment of the detector was completed by using the conversion photons at wavelength895 nm and 1310 nm.After optimizing the output power and other parameters of the pump photon,the measurement result was 11.69%,which was 0.31% different from the factory data.In summary,this paper designed and built a photon source system using BBO crystal and PPLN crystal to prepare 1310 nm signal photon,and completed the measurement of the quantum efficiency of the detector at this wavelength.The feasibility and accuracy of the proposed scheme are verified,which can lay a foundation for expanding the application of high brightness entangled photon source.