An experimental setup to generate narrowband bi-photons via four-wave mixing in cold atoms

Abstract

We present our recently-built experimental setup designed to generate near-infrared and narrow-band correlated photon pairs by inducing four-wave mixing in a cold gas of 87Rb atoms confined in a magneto-optical trap. The experimental setup and its automation and control approach are described in detail. A characterization of the optical density of the atomic ensemble as well as the basic statistical measurements of the generated light are reported. The non-classical nature of the photon pairs is confirmed by observing a violation of Cauchy-Schwarz inequality by a factor of 5.6 × 105 in a Hanbury Brown – Twiss interferometer. A 1/e coherence time for the heralded, idler photons of 4. 4 ± 0. 1 ns is estimated from our observations. We are able to achieve a value of 104 s− 1 pair-detection-rate, which results in a spectral brightness of 280 (MHz s)− 1. The combination of high brightness and narrow-band spectrum makes this photon-pair source a viable tool in fundamental studies of quantum states and opens the door to use them in quantum technologies.