Sub-Fourier Characteristics of a δ-kicked-rotor Resonance

We experimentally investigate the sub-Fourier behavior of a delta-kicked-rotor resonance by performing a measurement of the fidelity or overlap of a Bose-Einstein condensate exposed to a periodically pulsed standing wave. The temporal width of the fidelity resonance peak centered at the Talbot time and zero initial momentum exhibits an inverse cube pulse number (1/N(3))-dependent scaling compared to a 1/N(2) dependence for the mean energy width at the same resonance. A theoretical analysis shows that for an accelerating potential the width of the resonance in acceleration space depends on 1/N(3), a property which we also verify experimentally. Such a sub-Fourier effect could be useful for high precision gravity measurements.