Interaction-induced dynamics of collective atomic excitations

The dephasing dynamics of collective Rydberg excitations are investigated for atoms confined in a state-insensitive optical lattice. By measuring the second-order correlation function, g⁽²⁾, as a function of storage time, we observe a characteristic decrease of g⁽²⁾ that is found to be in agreement with a model based on the dephasing of multiple excitations resulting from van der Waals interactions.