Strongly-interacting photons mediated by Rydberg interactions

Photons usually do not interact with each other. Strong photon-photon interactions have been a long-standing goal in quantum optics, and are crucial to deterministic all-optical quantum logic, single-photon transistors, as well as exploration of optical many-body phenomena. I will show our experimental demonstration of strong interactions between individual photons, by coupling to strongly-interacting Rydberg atoms in free space. I will discuss our on-going efforts to harness these interactions for applications in quantum information processing and quantum networks. Photons propagating through a cloud of ultracold Rb-87, under ladder-scheme electromagnetically induced transparency, will acquire a nonlinear phase if detuned from the intermediate state. We aim to extend such nonlinear phase for non-destructive detection of optical photons. To get around the fundamental dissipation problem associated with these Rydberg-mediated photon-photon interactions, we will explore collective optical responses of sub-wavelength-spaced atomic arrays, for creation of multi-photon entangled states and high-fidelity all-optical devices.