Quantum nonlinear optics using cold Rydberg atoms

Abstract

Although photons do no a ect each other in vacuum, interactions between individual photons could enable a wide variety of scienti c and engineering applications. Here we report on the creation of a quantum nonlinear medium with large photon-photon interactions at the single photon level. Our approach relies on Electromagnetically Induced Transparency (EIT) techniques, in which individual photons are coherently mapped onto strongly interacting Rydberg atoms. Under EIT conditions, photons traveling in the medium are best described as part-matter part-light quantum particles, called polaritons, which experience long-range interactions through the Rydberg blockade. In particular, we demonstrate coherent photon-photon interactions, akin to those associated with conventional massive particles, paving the way for novel photonics states and quantum simulation with light.