title: Experimental control of transport resonances in a coherent quantum rocking ratchet.
abstract: The ratchet phenomenon is a means to get directed transport without net forces. Originally conceived to rectify stochastic motion and describe operational principles of biological motors, the ratchet effect can be used to achieve controllable coherent quantum transport. This transport is an ingredient of several perspective quantum devices including atomic chips. Here we examine coherent transport of ultra-cold atoms in a rocking quantum ratchet. This is realized by loading a rubidium atomic Bose-Einstein condensate into a periodic optical potential subjected to a biharmonic temporal drive. The achieved long-time coherence allows us to resolve resonance enhancement of the atom transport induced by avoided crossings in the Floquet spectrum of the system. By tuning the strength of the temporal modulations, we observe a bifurcation of a single resonance into a doublet. Our measurements reveal the role of interactions among Floquet eigenstates for quantum ratchet transport.
authors: Institut für Angewandte Physik der Universität Bonn, Wegelerstr. 8, 53115 Bonn, Germany.
authors: Christopher
authors: C
authors: Grossert
authors: Institut für Angewandte Physik der Universität Bonn, Wegelerstr. 8, 53115 Bonn, Germany.
authors: Martin
authors: M
authors: Leder
authors: Department of Applied Mathematics, Lobachevsky State University of Nizhny Novgorod, Nizhny Novgorod 603950, Russia.|Institut für Physik, Universität Augsburg, Universitätsstr. 1, 86159 Augsburg, Germany.|Sumy State University, Rimsky-Korsakov Street 2, 40007 Sumy, Ukraine.
authors: Sergey
authors: S
authors: Denisov
authors: Department of Applied Mathematics, Lobachevsky State University of Nizhny Novgorod, Nizhny Novgorod 603950, Russia.|Institut für Physik, Universität Augsburg, Universitätsstr. 1, 86159 Augsburg, Germany.|Nanosystems Initiative Munich, Schellingstr. 4, D-80799 München, Germany.
authors: Peter
authors: P
authors: Hänggi
authors: Institut für Angewandte Physik der Universität Bonn, Wegelerstr. 8, 53115 Bonn, Germany.
authors: Martin
authors: M
authors: Weitz