title: Cooperative excitation and many-body interactions in a cold Rydberg gas.
abstract: The dipole blockade of Rydberg excitations is a hallmark of the strong interactions between atoms in these high-lying quantum states [M. Saffman, T. G. Walker, and K. Mølmer, Rev. Mod. Phys. 82, 2313 (2010); D. Comparat and P. Pillet, J. Opt. Soc. Am. B 27, A208 (2010)]. One of the consequences of the dipole blockade is the suppression of fluctuations in the counting statistics of Rydberg excitations, of which some evidence has been found in previous experiments. Here we present experimental results on the dynamics and the counting statistics of Rydberg excitations of ultracold rubidium atoms both on and off resonance, which exhibit sub- and super-Poissonian counting statistics, respectively. We compare our results with numerical simulations using a novel theoretical model based on Dicke states of Rydberg atoms including dipole-dipole interactions, finding good agreement between experiment and theory.
authors.affiliation: INO-CNR, Pisa, Italy.
authors.forename: Matthieu
authors.initials: M
authors.lastname: Viteau
authors.forename: Paul
authors.initials: P
authors.lastname: Huillery
authors.forename: Mark G
authors.initials: MG
authors.lastname: Bason
authors.forename: Nicola
authors.initials: N
authors.lastname: Malossi
authors.forename: Donatella
authors.initials: D
authors.lastname: Ciampini
authors.forename: Oliver
authors.initials: O
authors.lastname: Morsch
authors.forename: Ennio
authors.initials: E
authors.lastname: Arimondo
authors.forename: Daniel
authors.initials: D
authors.lastname: Comparat
authors.forename: Pierre
authors.initials: P
authors.lastname: Pillet