Abstract: | We demonstrate strong nonlinear interaction between individual light quanta propagating slowly in an atomic medium. These interactions are made possible by utilizing electromagnetically induced transparency (EIT) in combination with atomic excitation into the Rydberg states. The strong interactions of highly-excited Rydberg atoms result in efficient, long-range interactions between single photons. The cloud of properly excited cold atoms strongly suppresses the propagation of photon pairs, resulting in sub-Poissonian photon statistics, with photon-photon separations much larger than the Rydberg interaction range. |