Observation of Robust Quantum Resonance Peaks in an Atom Optics Kicked Rotor with Amplitude Noise

The effect of pulse train noise on the quantum resonance peaks of the Atom Optics Kicked Rotor is investigated experimentally. Quantum resonance peaks in the late time mean energy of the atoms are found to be surprisingly robust against all levels of noise applied to the kicking amplitude, whilst even small levels of noise on the kicking period lead to their destruction. The robustness to amplitude noise of the resonance peak and of the fall--off in mean energy to either side of this peak are explained in terms of the occurence of stable, $\epsilon$--classical dynamics [S. Wimberger, I. Guarneri, and S. Fishman, \textit{Nonlin.} \textbf{16}, 1381 (2003)] around each quantum resonance.