Spin transport in coupled spinor Bose gases

We report direct measurements of spin transport in a trapped, partially condensed spinor Bose gas. Detailed analyses of spin flux in this out-of-equilibrium quantum gas are performed by monitoring the flow of atoms in different hyperfine spin states. The main mechanisms for motion in this system are exchange scattering and potential energy inhomogeneity, which lead to spin waves in the normal component and domain formation in the condensate. We find a large discrepancy in domain formation timescales with those predicted by potential-driven formation, indicating strong coupling of the condensate to the normal component spin wave

A CLASS OF SEPARABILITY FLEXIBLE FUNCTIONAL FORMS

Quadratic flexible forms, such as the translog and generalized Leontief, are separability inflexible. That is, separability restrictions render them inflexible with regard to separable structures. A class functional forms is proposed that is flexible with regard to general production structures and remains flexible regarding weakly separable structures when separability restrictions are imposed, thus permitting tests of the separability hypothesis. Additionally, the restricted forms are parsimonious; that is they contain the minimum number of parameters with which flexibility can be achieved.Research Methods/ Statistical Methods,

Thermally Induced Losses in Ultra-Cold Atoms Magnetically Trapped Near Room-Temperature Surfaces

We have measured magnetic trap lifetimes of ultra-cold Rb87 atoms at distances of 5-1000 microns from surfaces of conducting metals with varying resistivity. Good agreement is found with a theoretical model for losses arising from near-field magnetic thermal noise, confirming the complications associated with holding trapped atoms close to conducting surfaces. A dielectric surface (silicon) was found in contrast to be so benign that we are able to evaporatively cool atoms to a Bose-Einstein condensate by using the surface to selectively adsorb higher energy atoms.Comment: Improved theory curve eliminates discrepancy. JLTP in pres

Quantum Interference to Measure Spacetime Curvature: A Proposed Experiment at the Intersection of Quantum Mechanics and General Relativity

An experiment in Low Earth Orbit (LEO) is proposed to measure components of the Riemann curvature tensor using atom interferometry. We show that the difference in the quantum phase $\Delta\phi$ of an atom that can travel along two intersecting geodesics is given by $mR_{0i0j}/\hbar$ times the spacetime volume contained within the geodesics. Our expression for $\Delta\phi$ also holds for gravitational waves in the long wavelength limit.Comment: 7 pages LaTeXed with RevTeX 4.0, 2 figures. Submitted to the 2003 Gravity Research Foundation Essay Contes

Decoherence-driven Cooling of a Degenerate Spinor Bose Gas

We investigate the relationship between the coherence of a partially Bose-condensed spinor gas and its temperature. We observe cooling of the normal component driven by decoherence as well the effect of temperature on decoherence rates.Comment: 4 pages, 2 figure

The Mystery of the Ramsey Fringe that Didn't Chirp

We use precision microwave spectroscopy of magnetically trapped, ultra-cold 87Rb to characterize intra- and inter-state density correlations. The cold collision shifts for both normal and condensed clouds are measured. The results verify the presence of the sometimes controversial "factors of two", in normal-cloud mean-field energies, both within a particular state and between two distinct spin species. One might expect that as two spin species decohere, the inter-state factor of two would revert to unity, but the associated frequency chirp one naively expects from such a trend is not observed in our data.Comment: Proceedings of the 18th International Conference on Atomic Physics (ICAP 2002

Optical excitation of nonlinear spin waves

We demonstrate a technique for exciting spin waves in an ultracold gas of Rb-87 atoms based on tunable AC Stark potentials. This technique allows us to excite normal modes of spin waves with arbitrary amplitudes in the trapped gas, including dipole, quadrupole, octupole, and hexadecapole modes. These modes exhibit strong nonlinearities, which manifest as amplitude dependence of the excitation frequencies and departure from sinusoidal behavior. Our results are in good agreement with a full treatment of a quantum Boltzmann transport equation.Comment: 11 pages, 5 figure

Localized collapse and revival of coherence in an ultracold Bose gas

We study the collapse and revival of coherence induced by dipolar spin waves in a trapped gas of Rb-87 atoms. In particular we observe spatially localized collapse and revival of Ramsey fringe contrast and show how the pattern of coherence depends on strength of the spin wave excitation. We find that the spatial character of the coherence dynamics is incompatible with a simple model based only on position-space overlap of wave functions. This phenomenon requires a full phase-space description of the atomic spin using a quantum Boltzmann transport equation, which highlights spin wave-induced coherent spin currents and the ensuing dynamics they drive.Comment: 5 pages, 4 figure