H. E. Saunders-Singer

arXiv2005

Asymmetric diffusion in the delta-kicked rotor with broken symmetries

We report an experimental investigation of momentum diffusion in the delta-function kicked rotor where time symmetry is broken by a two-period kicking cycle and spatial symmetry by an alternating linear potential. The momentum diffusion constant is thus modified by kick-to-kick correlations which show a momentum dependence. We exploit this, and a technique involving a moving optical potential, to create an asymmetry in the momentum diffusion that is due entirely to the chaotic dynamics.

physics.atom-ph↗

arXiv2003

Shifting the boundaries: pulse-shape effects in the atom-optics kicked rotor

We present the results of experiments performed on cold caesium in a pulsed sinusoidal optical potential created by counter-propagating laser beams having a small frequency difference in the laboratory frame. Since the atoms, which have average velocity close to zero in the laboratory frame, have non-zero average velocity in the co-moving frame of the optical potential, we are able to centre the initial velocity distribution of the cloud at an arbitrary point in phase-space. In particular, we demonstrate the use of this technique to place the initial velocity distribution in a region of phase-space not accessible to previous experiments, namely beyond the momentum boundaries arising from the finite pulse duration of the potential. We further use the technique to explore the kicked rotor dynamics starting from a region of phase-space where there is a strong velocity dependence of the diffusion constant and quantum break time and demonstrate that this results in a marked asymmetry in the chaotic evolution of the atomic momentum distribution.

quant-ph↗