Experimental evidence of dynamical localization and delocalization in a quasiperiodic driven system

This paper presents the first experimental evidence of the transition from dynamical localization to delocalization under the influence of a quasiperi odic driving on a quantum system. A quantum kicked rotator is realized by p lacing cold atoms in a pulsed, far-detuned, standing wave. If the standing wave is periodically pulsed, one observes the suppression of the classical chaotic diffusion, i.e., dynamical localization. If the standing wave is pu lsed quasiperiodically, dynamical localization is observed or not, dependin g on the driving frequencies being commensurable or incommensurable. One ca n thus study the transition from the localized to the delocalized case as a function of the effective dimensionality of the system.