Quantum dynamics in spatially resolved two-atom cavity QED

When two single emitters are placed in a high-finesse optical cavity, they become indistinguishable with respect to emission into the single light mode of the cavity. In this case, interference leads to collective effects in the dynamics of light-matter interaction. We realize the described setup with a pair of rubidium atoms in a deep two-dimensional optical lattice within a Fabry-Perot cavity. A spatial displacement of the atoms introduces a difference in the phase with which the atoms couple to the cavity and an external driving laser field. This appears as a new experimental degree of freedom that is not present in single-atom experiments. A high-numerical aperture objective is used to image the atoms and identify their position with single-site resolution, enabling us to deduce the phase from the images. As a function of this phase, we record the photons emitted from the cavity with high temporal resolution. Evaluation of the photon statistics reveals effects that are reminiscent of superradiant phenomena in dense atomic media in free space. Our system opens up new avenues for fundamental studies and applications in quantum information processing.