Photon-pair generation from a chip-scale Cs atomic vapor cell

The realization of a narrowband photonic quantum source based on an atomic device is considered essential in the practical development of photonic quantum information science and technology. In this study, we present the first step toward the development of a photon-pair source based on a microfabricated Cs atomic vapor cell. Time-correlated photon pairs from the millimeter-scale Cs vapor cell are emitted via the spontaneous four-wave mixing process of the cascade-type 6S_1/2-6P_3/2-8S_1/2 transition of ¹³³Cs. The maximum normalized cross-correlation value between the signal and idler photons is measured as 622(8) under a weak pump power of 10 µ;W. Our photon source violates the Cauchy-Schwartz inequality by a factor of >10⁵. We believe that our approach has very important applications in the context of realizing practical scalable quantum networks based on atom-photon interactions.