Universal scaling in a strongly interacting Rydberg gas

We study a gas of ultracold atoms resonantly driven into a strongly interacting Rydberg state. The long distance behavior of the spatially frozen effective pseudospin system is determined by a set of dimensionless parameters, and we find that the experimental data exhibits algebraic scaling laws for the excitation dynamics and the saturation of Rydberg excitation. Mean field calculations as well as numerical simulations provide an excellent agreement with the experimental finding, and are evidence for universality in a strongly interacting frozen Rydberg gas.