Quantum enhancement of momentum diffusion in the delta-kicked rotor - art.no. 074102

We present detailed observations of the quantum delta-kicked rotor in the v icinity of a quantum resonance. Our experiment consists of an ensemble of c old cesium atoms subject to a pulsed off-resonant standing wave of light. W e measure the mean energy and show clearly that at the quantum resonance it is a local maximum. We also examine the effect of noise on the system and find that the greatest sensitivity to this occurs at the resonances. This m akes these regions ideal for examining quantum-classical correspondence. A picture based on diffraction is developed which allows the experiments to b e readily understood.