title: Extended coherence time on the clock transition of optically trapped rubidium.
abstract: Optically trapped ensembles are of crucial importance for frequency measurements and quantum memories but generally suffer from strong dephasing due to inhomogeneous density and light shifts. We demonstrate a drastic increase of the coherence time to 21 s on the magnetic field insensitive clock transition of (87)Rb by applying the recently discovered spin self-rephasing [C. Deutsch et al., Phys. Rev. Lett. 105, 020401 (2010)]. This result confirms the general nature of this new mechanism and thus shows its applicability in atom clocks and quantum memories. A systematic investigation of all relevant frequency shifts and noise contributions yields a stability of 2.4×10(-11)τ(-1/2), where τ is the integration time in seconds. Based on a set of technical improvements, the presented frequency standard is predicted to rival the stability of microwave fountain clocks in a potentially much more compact setup.
authors.affiliation: Institut für Quantenoptik, Leibniz Universität Hannover, Hannover, Germany. kleinebuening@iqo.uni-hannover.de
authors.forename: G Kleine
authors.initials: GK
authors.lastname: Büning
authors.forename: J
authors.initials: J
authors.lastname: Will
authors.forename: W
authors.initials: W
authors.lastname: Ertmer
authors.forename: E
authors.initials: E
authors.lastname: Rasel
authors.forename: J
authors.initials: J
authors.lastname: Arlt
authors.forename: C
authors.initials: C
authors.lastname: Klempt
authors.forename: F
authors.initials: F
authors.lastname: Ramirez-Martinez
authors.forename: F
authors.initials: F
authors.lastname: Piéchon
authors.forename: P
authors.initials: P
authors.lastname: Rosenbusch