A chip-scale atomic beam for nonclassical light.

Nonclassical light is a critical resource for a broad range of quantum technologies and fundamental science. However, leading platforms such as laser-cooled atoms and solid-state systems both present substantial challenges to scalability due to complexity and spectral drift. Here, we demonstrate a hybrid approach using a chip-scale rubidium beam coupled to a high-finesse cavity-quantum electrodynamics (QED) system. Specifically, we generate nonclassical light and observe optical nonlinearities at the few photon level. This is achieved without degradation of the cavity-QED system. By demonstrating the compatibility of these two technologies, we open a path for distributed sources of nonclassical light and set the stage for using cavity-QED to enhance the performance of chip-scale magnetometers and atomic clocks.