High-rate subgigahertz-linewidth bichromatic entanglement source for quantum networking

The generation of entangled photon pairs, which are compatible with quantum devices and standard telecommunication channels are critical for the development of long-range fiber quantum networks. Aside from wavelength, bandwidth matching, and high fidelity of produced pairs are necessary for high interfacing efficiency. High-rate, robust entanglement sources that satisfy all these conditions remain an outstanding experimental challenge. In this work, we study an entanglement source based on four-wave mixing in a diamond configuration in a warm rubidium vapor. We theoretically and experimentally investigate an alternative operating regime and demonstrate an entanglement source, which produces highly nondegenerate 795- and 1324-nm photon pairs. With this source we are able to achieve in-fiber pair-generation rates greater than 10⁷/s, orders of magnitude higher than previously reported atomic entanglement sources. Additionally, given our source's native compatibility with telecom infrastructure and atomic systems, it is a step towards scalable quantum networks.