Light-by-light control at quantum level mediated by flying atoms

Quantum interface between photons is a long- standing goal of fundamental significance, and also serves as powerful tools for quantum technologies. Remarkable advances in quantum optics have recently developed in several platforms to demonstrate the generation of optical nonlinearities at the level of individual photons, which enable a number of unique applications such as light-by-light control at quantum level. Here, we present two examples in the realm of continuous variables based on the platform of flying atoms where thermal motion of atoms with long-lived coherence of ground state mediate the coupling between the spatially separated optical channels.