Optical billiards for atoms

One of the central paradigms for classical and quantum chaos in conservative systems is the two-dimensional billiard in which particles are confined to a closed region in the plane, undergoing elastic collisions with the walls and free motion in between. We report the first realization of billiards using ultracold atoms bouncing off beams of light. These beams create the desired spatial pattern, forming an "optical billiard." We find excellent agreement between theory and our experimental demonstration of chaotic and stable motion in optical billiards, establishing a new testing ground for classical and quantum chaos.     

Direct observation of sub-Poissonian number statistics in a degenerate bose gas

We report the direct observation of sub-Poissonian number fluctuation for a degenerate Bose gas confined in an optical trap. Reduction of number fluctuations below the Poissonian limit is observed for average numbers that range from 300 to 60 atoms.     

Compression of atomic phase space using an asymmetric one-way barrier

We show how to construct asymmetric optical barriers for atoms. These barriers can be used to compress phase-space of a sample by creating a confined region in space where atoms can accumulate with heating at the single photon recoil level. We illustrate our method with a simple two-level model and then show how it can be applied to more realistic multilevel atoms.     

Precise spectroscopy for fundamental physics

We have applied experimental techniques that were developed for use in atomic frequency standards andclocks to investigations of local Lorentz invariance, the linearity of quantum mechanics, andanomalous long-range spin-dependent forces. These experiments used a hyperfine transition in⁹Be⁺ ions in a Penning trap. Recently, we have studied hyperfine transitions in¹⁹⁹Hg⁺ ions in a linear rf trap. Hg⁺ ions might be used for similar investigations in the future.Work of the National Institute of Standards andTechnology. Not subject to US copyright.     

Quantum transport of ultracold atoms in an accelerating optical potential

Received: 8 July 1997     

Shape of the quantum diffusion front

We show that quantum diffusion has well-defined front shape. After an initial transient, the wave packet front (tails) is described by a stretched exponential P(x,t) = A(t)exp(-absolute value of [x/w](gamma)), with 1 < gamma < infinity, where w(t) is the spreading width which scales as w(t) approximately t(beta), with 0 < beta < or = 1. The two exponents satisfy the universal relation gamma = 1/(1-beta). We demonstrate these results through numerical work on one-dimensional quasiperiodic systems and the three-dimensional Anderson model of disorder. We provide an analytical derivation of these relations by using the memory function formalism of quantum dynamics. Furthermore, we present an application to experimental results for the quantum kicked rotor.