A mixed light field generated from a two-level atomic ensemble can be used for two-photon interference. In this mixed light field, correlated paired photons generated from a four-wave mixing process provide a signal of two-photon interference, while Rayleigh scattered photons of the pump laser provide a stable reference to calibrate the normalized second-order correlation function. We demonstrate two-photon interference using the Hong–Ou–Mandel and Hanbury Brown–Twiss interferometers. A direct quantitative comparison between theoretical predictions and experimental data is performed under perturbed experimental conditions, which reveal this kind of light source has potential application for quantum metrology.

A Fourier optics approach can be a concise and powerful tool to solve problems in atom optics. In this report, we adopt it to investigate the kinetic behavior of cold atoms passing through a far red-detuned Gaussian beam. We demonstrate that the aberration has significant influence on the evolution of the atomic cloud, which is rooted in the deviation of the Gaussian profile from the quadratic form. In particular, we observe an intriguing effect analogous to Fresnel’s double prism with cold atoms. The experimental results are in good agreement with the numerical simulation.