# Hannover 2010 – wissenschaftliches Programm

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# Q: Fachverband Quantenoptik und Photonik

## Q 58: Quantum Gases: Lattices II

### Q 58.1: Vortrag

### Freitag, 12. März 2010, 10:30–10:45, E 001

**Dynamics of Atoms in a Hamiltonian Quantum Ratchet** — •Tobias Salger, Carsten Geckeler, Sebastian Kling, Tim Hecking, and Martin Weitz — Institut für Angewandte Physik der Universität Bonn, Wegelerstr. 8, 53115 Bonn, Germany

Ratchets are devices, that are able to generate a directed motion of
particles in a fluctuating environment without gradients or net
forces. In order to observe the ratchet effect, one has to break the
spatiotemporal symmetry of the system [1]. Here we report on the first
realization of a pure "Hamiltonian Quantum Ratchet" in the absence of
dissipation [2]. A ^{87}Rb Bose-Einstein condensate is loaded into a
sawtooth-like lattice potential, which is realized by superimposing an
optical standing wave with λ/2 spatial periodicity with a
four-photon lattice with λ/4 spatial periodicity [3]. Besides
the spatial, also the temporal symmetry is broken by asymmetrically
modulating the amplitude of the ratchet potential. We observe a directed
motion of atoms arising from Hamiltonian ratchet transport at the
quantum limit.

In more recent experiments we have investigated the dynamics of atoms in a
Hamiltonian Quantum Ratchet under the influence of weak
gradients. Absolute negative mobility, which describes the possibility
to transport a particle against an external field, could be observed
in the experiment.

S. Denisov et al., Phys. Rev. A **75**, 063424 (2007)

T. Salger et al., Science **326**, 1241 (2009)

T. Salger et al., Phys. Rev. Lett. **99**, 190405 (2007)