High nonclassical correlations of large-bandwidth photon pairs generated in warm atomic vapor

TL;DR

This paper demonstrates the generation of high-bandwidth nonclassical photon pairs in warm atomic vapor with strong correlations, using a simple setup suitable for quantum communication applications.

Contribution

It introduces a novel, simple method for producing wide-bandwidth nonclassical photon pairs with high correlations in warm vapor, advancing quantum light source technology.

Findings

Spectral bandwidth of up to 560 MHz achieved.

Low two-photon noise levels observed.

Method is technologically simple and compatible with quantum memories.

Abstract

Generation of nonclassical light suitable for interaction with atoms corresponds to a crucial goal pursued across the broad quantum optics community. We present the generation of nonclassical photon pairs using the process of spontaneous four-wave mixing in warm atomic vapor with an unprecedentedly high degree of nonclassical photon correlations. We show how the unique combination of excitation of atoms in the proximity of the vapor cell viewport, single excitation laser beam, double-$\Lambda$ energy level scheme, auxiliary optical pumping, and particular optical filtering setups, allow for the spectral bandwidth of generated nonclassical light fields of up to $560 \pm 20$ MHz and low two-photon noise. We provide a quantitative analysis of particular noise mechanisms which set technological and fundamental limits on the observable photon correlations. The overall technological simplicity of the presented scheme together with the availability of spectrally matched quantum memories implementable with warm atomic vapors promises the feasibility of realization of GHz bandwidth on-demand nonclassical light sources and efficient quantum communication nodes.