title: Echo experiments in a strongly interacting Rydberg gas.
abstract: When ground state atoms are excited to a Rydberg state, van der Waals interactions among them can lead to a strong suppression of the excitation. Despite the strong interactions the evolution can still be reversed by a simple phase shift in the excitation laser field. We experimentally prove the coherence of the excitation in the strong blockade regime by applying an "optical rotary echo" technique to a sample of magnetically trapped ultracold atoms, analogous to a method known from nuclear magnetic resonance. We additionally measured the dephasing time due to the interaction between the Rydberg atoms.
authors.affiliation: 5. Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany. u.raitzsch@physik.uni-stuttgart.de
authors.forename: Ulrich
authors.initials: U
authors.lastname: Raitzsch
authors.forename: Vera
authors.initials: V
authors.lastname: Bendkowsky
authors.forename: Rolf
authors.initials: R
authors.lastname: Heidemann
authors.forename: Björn
authors.initials: B
authors.lastname: Butscher
authors.forename: Robert
authors.initials: R
authors.lastname: Löw
authors.forename: Tilman
authors.initials: T
authors.lastname: Pfau