title: Atom counting statistics in ensembles of interacting Rydberg atoms.
abstract: We show that the probability distributions for the number of Rydberg excitations in small ensembles of cold atoms, excited using short (100 ns) laser pulses, can be highly sub-Poissonian. The phenomenon occurs if the atom density and the principal quantum number of the excited Rydberg level are sufficiently high. Our observations are attributed to a blockade of the Rydberg atom excitation.
authors.affiliation: FOCUS Center and Michigan Center for Theoretical Physics, Department of Physics, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors.forename: T Cubel
authors.initials: TC
authors.lastname: Liebisch
authors.forename: A
authors.initials: A
authors.lastname: Reinhard
authors.forename: P R
authors.initials: PR
authors.lastname: Berman
authors.forename: G
authors.initials: G
authors.lastname: Raithel