  The sensitivity of the fidelity in the kicked rotor to an acceleration is
experimentally and theoretically investigated. We used a Bose-Einstein
condensate exposed to a sequence of pulses from a standing light wave followed
by a single reversal pulse in which the standing wave was shifted by half a
wavelength. The features of the fidelity "spectrum" as a function of
acceleration are presented. This work may find application in the measurement
of temperature of an atomic sample.
