Laboratoire de Physique Théorique
Toulouse - UMR 5152

In a recent letter published in Physical Review Letters (the Fig. 2 was the cover of the december 16, 2011 issue), a collaboration between Bertrand Georgeot from LPT and the experimental cold atoms group of LCAR (David Guery-Odelin and Gianluca Gattobigio) has demonstrated an experimental setup to study the effect of classically chaotic potentials on coherent matter waves.

The domain of quantum chaos studies the behaviour of wave systems for which the classical (short-wavelength) limit is chaotic. In this case, complex interference phenomena take place and can be observed. In this recent work, the Toulouse team has studied how a matter wave propagating in a guide can be modified by the presence of an out-of-center defect with controllable characteristics. The matter wave is produced from a Bose-Einstein condensate, i.e. a gas at sufficiently low temperature that the atoms behave as a single wave of macroscopic size.

For a small defect, the trajectories are slightly perturbed. For a stronger defect, the system displays complex trajectories. This study enabled to observe experimentally a transition predicted by numerical simulations between a regular regime and a chaotic regime. The latter is characterized in particular by a large dispersion of results for nearby initial conditions. This work at the same time helps us to better understand guided atom optics and gives us a new model to study chaotic behaviour in the context of quantum mechanics.

A more detailed exposition (in French) can be seen at the CNRS website.