Saijun Wu

Splitting matter waves using an optimized standing-wave light-pulse sequence

In a recent experiment [1], it was observed that a sequence of two standing wave square pulses can split a BEC at rest into +/- 2 h_bar k diffraction orders with almost 100% efficiency. By truncating the Raman-Nath equations to a 2-state model, we provide an intuitive picture that explains this double square pulse beamsplitter scheme. We further show it is possible to optimize a standingwave multi square pulse sequence to efficiently diffract an atom at rest to symmetric superposition of +/- 2n h_bar k diffraction order with n>1. The approach is considered to be qualitatively different from the traditional light pulse schemes in the Bragg or the Raman-Nath region, and can be extended to more complex atomic optical elements that produce various tailored output momentum states from a cold atom source.

Time domain de Broglie wave interferometry along a magnetic guide

Abstract.Time domain de Broglie wave interferometry [Phys. Rev. Lett. 79, 784 (1997)] is applied to Rb87 atoms in a magnetic guide. A standing wave light field is carefully aligned along the guiding direction of the magnetic trapping potential from a soft-ferromagnetic 4-foil structure. A sequence of two standing wave pulses is applied to the magnetically trapped atoms. The backscattered light at the atomic density grating revival time is collected and detected via a heterodyning technique. In addition to the observed recoil oscillations that fit the interferometer theory for atoms in free space, we observe a decay of the interferometer contrast on a millisecond time scale with unexpected millisecond-scale oscillations. We find that the oscillating decay is explained by a residual variation of the linear trapping potential along the standing wave direction.

Atom Interferometry Using Wave Packets with Constant Spatial Displacements

A standing-wave light-pulse sequence is demonstrated that places atoms into a superposition of wave packets with precisely controlled displacements that remain constant for times as long as 1 s. The separated wave packets are subsequently recombined, resulting in atom interference patterns that probe energy differences of {approx_equal}10{sup -34} J and can provide acceleration measurements that are insensitive to platform vibrations.

Demonstration of a multipulse interferometer for quantum kicked-rotor studies

We demonstrate perfect coherence preservation in an atom in terferometer perturbed by kicks from offresonant standing wave pulses. Under most conditions, the d ecoherence 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 num ber or the randomness of the strength of the applied kicks. The width narrowing of coherence revival as a functio n of increasing kick number and strength provides a new accurate measurement of the recoil frequency.

Perfect coherence preservation in an atom interferometer perturbed by optical standing wave pulses acting as a kicked rotor

We experimentally studied the effect of standing wave pulses on an atom interferometer. Despite the external field perturbations the coherence is perfectly preserved for the conditions similar to quantum resonances of a quantum kicked rotor.

Observation of fidelity saturation in a δ-kicked rotor potential

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.