Controllable single-photon scattering in a Rydberg-atom-waveguide system via van der Waals interactions

Abstract: We investigate single-photon scattering in a system comprising a waveguide coupled to a pair of Rydberg atoms, illuminated by a coherent field. By adjusting the interatomic distance, we can transition between the Rydberg blockade and Rydberg antiblockade regimes, as the van der Waals interaction strength varies with distance. These distinct regimes, manifesting themselves in single-photon scattering, allow flexible reflection control due to their analogy to those of a small- and giant-atom interactions with the waveguide. We also derive scattering criteria for Rydberg blockade and Rydberg antiblockade, corresponding to specific single-photon reflection spectrum. Based on these criteria, the blockade and antiblockade distances can be estimated.