Hamburg 2009 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 51: Quantengase: Gitter und Tunneln II

Q 51.5: Talk

Thursday, March 5, 2009, 17:30–17:45, Audi-A

Directed Transport of Ultracold 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, D-53859 Bonn

Ratchets are considered as a tool, which generate a directed motion of particles in the absence of any gradients or net forces. The ratchet effect can be realized for instance in a fluctuating environment as a physical mechanism of microbiological motion. In order to observe a directed transport of atoms, one has to break the space-time symmetry of the system [1]. Here we report on the realization of a quantum ratchet in the absence of dissipative processes (Hamiltonian regime) within the interaction time.

We load a ⁸⁷Rb Bose-Einstein condensate into a sawtooth-like asymmetric optical lattice potential, which is realized by superimposing an optical standing wave with λ/2 spatial periodicity with a fourth-order potential with λ/4 spatial periodicity, where λ denotes the wavelength of the used laser [2]. Besides the spatial, also the temporal symmetry of the system is broken by modulation of the lattice potential depth. We experimentally observe directed transport of atoms arising from Hamiltonian ratchet transport in the quantum regime.
S. Denisov et al., Phys. Rev. A 75, 063424 (2007)
G. Ritt et al., Phys. Rev. A 74, 063622 (2006)