Investigation On Photon Statistics Of PDC Quantum Optical Field

Parametric down-conversion(PDC)is the dominant approach for generating nonclassical photon sources,which are attracting increasing interest recently in field of quantum communication,quantum computation,high-resolution quantum measurement,and quantum-information processing.The measurement of the photon number statistical distribution in the parametric down conversion quantum light field is of great significance to the quality evaluation and optimization of the parametric down conversion quantum light source.In this paper,a direct measurement scheme based on PMT is proposed,which can reliably resolve more than 7 photons.We study the effect of pump power on the PDC photon number and the photon number statistics of photon by pumping the barium metaborate(BBO)crystal with different pumping power.The main work of this paper is as follows:(1)According to the phase matching theory,the BBO crystal's type?and type?parametric down-conversion phase-matching angle between pump and optical axis,noncollinear angle between the PDC light and pump,the wavelength of the PDC light are calculated.We also draw the relationship graph among the phase-matching angle,noncollinear angle and wavelength of PDC light,which provides theoretical support for the experiment.(2)The characteristics of the quantum light source are systematically and comprehensively analyzed,focusing on the non-classical characteristics of the singlephoton source and entangled light source.The characteristics and distinguishing methods of photon number distribution of different types such as Poisson distribution,Sub-Poisson distribution,Super-Poisson analysis and thermal distribution are analyzed in detail,laying a foundation for determining the photon number distribution of PDC light field.(3)The optical path of preparation and detection of BBO crystal PDC optical field was established,and the photon counting rate of BBO crystal PDC optical field under different pump powers was measured with a single-photon detector.The experiment found that,with the increase of pump power,the number of photons in the PDC optical field increased exponentially(4)The PMT based photon number resolving detection system was improved to accurately measure the photon number distribution of PDC quantum light field generated by the BBO crystal under different pump power ranging from 0.01 m W to 100 m W,and the statistical analysis was carried out.The experiment verified the theoretical result that the average photon number of PDC quantum light field changes with the pump light power.(5)Poisson distribution,thermal distribution and multi-mode thermal distribution are used to fit the measured photon statistic.After deeply analyzing the correlation coefficient and the Mandle's Q parameter,we demonstrate that the PDC photons generated in the experiment obey the sub multi-thermal distribution,which is a new kind of super Poisson distribution.