We experimentally investigate the effect of atomic delta-kicked rotor potentials on the mutual coherence between wavepackets in an atom interferometer, and demonstrate fidelity saturation in phase-space displacement echoes at quantum resonance.
We show that the quantum fidelity is accessible to cold atom experiments for a large class of evolutions in periodical potentials, properly taking into account the experimental initial conditions of the atomic ensemble. We prove analytically that, at the fundamental quantum resonances of the atom-optics kicked rotor, the fidelity saturates at a constant, time-independent value after a small number of kicks. The latter saturation arises from the bulk of the atomic ensemble, whilst for the resonantly accelerated atoms the fidelity is predicted to decay slowly according to a power law.
We show that the quantum fidelity is accessible to cold atom experiments for a large class of evolutions in periodical potentials, properly taking into account the experimental initial conditions of the atomic ensemble. We prove analytically that, at the fundamental quantum resonances of the atom-optics kicked rotor, the fidelity saturates at a constant, time-independent value after a small number of kicks. The latter saturation arises from the bulk of the atomic ensemble, whilst for the resonantly accelerated atoms the fidelity is predicted to decay slowly according to a power law.
We investigate the dynamics of the atom-optics δ-kicked rotor in the vicinity of quantum resonance. Although small deviations from resonant conditions lead to a negligible change in the momentum space probability density, they lead to a significant relative phase change between the different momentum states taking part in the dynamics. By adding a tailored pulse to the kicked rotor pulse sequence, one can measure the overlap between the resonant state and any other state, i.e. perform a fidelity measurement. Using this sequence, we predict a narrow peak around quantum resonance with a width that scales as 1/ N 3 with N being the number of pulses in the kicked rotor sequence. This method may be of interest to precision measurements, such as h / M .
We propose an atom optics experiment to measure the stability of the quantum kicked rotor under perturbations of the Hamiltonian. We avail ourselves of the theory of Loschmidt echoes, i.e., we consider the overlap of a quantum state evolved in a perturbed and an unperturbed potential. Atom interferometry allows us to determine the overlap integral in amplitude and phase. A numerical analysis of the kicked rotor in various regimes shows that the quantum signatures of specific classical properties can be detected experimentally.
We use an atom interferometer to investigate the dynamics of matter waves in a periodically pulsed optical standing wave: an atom optics realization of the quantum kicked rotor that exhibits chaotic classical dynamics. We experimentally show that a measure of the coherence between the interferometer diffraction orders can revive after a quick initial loss, and can approach a finite asymptote as the number of kicks increases. This observation demonstrates that quantum fidelity of a classically chaotic system can survive strong perturbations over long times without decay.