  We demonstrate perfect coherence preservation in an atom interferometer
perturbed by kicks from off-resonant standing wave pulses. Under most
conditions, the decoherence induced by the pulses reduces the signal; however,
the coherence is perfectly preserved when the kicking period is equal to the
rational fraction of the inverse atomic recoil frequency, independent of the
number or the randomness of the strength of the applied kicks. The width
narrowing of coherence revival as a function of increasing kick number and
strength provides a new accurate measurement of the recoil frequency.
