Statistical properties of twin beams generated in spontaneous parametric downconversion

TL;DR

This paper analyzes the photon-number statistics of twin beams generated by spontaneous parametric downconversion, accounting for detection inefficiencies and noise, revealing strong correlations and nonclassical properties of the generated light.

Contribution

It presents a comprehensive model and experimental analysis of photon-number statistics in twin beams, including the joint distribution and nonclassical features, using an intensified CCD camera.

Findings

Photon pairs exhibit Poissonian statistics.

Strong correlations (80%) between signal and idler photon numbers.

Evidence of nonclassical light through negative distribution regions.

Abstract

Measurement of photon-number statistics of fields composed of photon pairs generated in spontaneous parametric downcoversion pumped by strong ultrashort pulses is described. Final detection quantum efficiencies, noises as well as possible loss of one or both photons from a pair are taken into account. Measured data provided by an intensified single-photon CCD camera are analyzed along the developed model. The joint signal-idler photon-number distribution is obtained using the expectation maximization algorithm. Covariance of the signal and idler photon-numbers equals 80 %. Statistics of the generated photon pairs are identified to be Poissonian in our case. Distribution of the integrated intensities of the signal and idler fields shows strong correlations between the fields. Negative values of this distribution occurring in some regions clearly demonstrate a nonclassical character of the light composed of photon pairs.