David Murray Harber

Measurement of the Casimir-Polder force through center-of-mass oscillations of a Bose-Einstein condensate

We have performed a measurement of the Casimir-Polder force using a magnetically trapped {sup 87}Rb Bose-Einstein condensate. By detecting perturbations of the frequency of center-of-mass oscillations of the condensate perpendicular to the surface, we are able to detect this force at a distance {approx}5 {mu}m, significantly farther than has been previously achieved, and at a precision approaching that needed to detect the modification due to thermal radiation. Additionally, this technique provides a limit for the presence of non-Newtonian gravity forces in the {approx}1 {mu}m range.

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

We have measured magnetic trap lifetimes of ultra-cold 87Rb atoms at distances of 5–1000 µm 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.

Observation of anomalous spin-state segregation in a trapped ultracold vapor

We observe counterintuitive spin segregation in an inhomogeneous sample of ultracold, noncondensed rubidium atoms in a magnetic trap. We use spatially selective microwave spectroscopy to verify a model that accounts for the differential forces on two internal spin states. In any simple understanding of the cloud dynamics, the forces are far too small to account for the dramatic transient spin polarizations observed. The underlying mechanism remains to be elucidated.

Alkali-metal adsorbate polarization on conducting and insulating surfaces probed with Bose-Einstein condensates

A magnetically trapped

Spatial Resolution of Spin Waves in an Ultracold Gas

^{87}\mathrm{Rb}

Decoherence-Driven Cooling of a Degenerate Spinor Bose Gas

Bose-Einstein condensate is used as a sensitive probe of short-range electrical forces. In particular, the electric polarization of, and the subsequent electric field generated by,

Normal-Superfluid Interaction Dynamics in a Spinor Bose Gas

^{87}\mathrm{Rb}

Effect of cold collisions on spin coherence and resonance shifts in a magnetically trapped ultracold gas

adsorbates on conducting and insulating surfaces is measured by characterizing perturbations to the magnetic trapping potential using high quality factor condensate excitations. The nature of the alterations to the electrical properties of

Measurement of the temperature dependence of the Casimir-Polder force through collective excitations of a Bose-Einstein condensate

\mathrm{Rb}

Measurement of the effects of the Casimir-Polder force using dipole oscillations of a magnetically trapped Bose-Einstein condensate

adsorbates is studied on titanium (metal) and silicon (semiconductor) surfaces, which exhibit nearly identical properties, and on glass (insulator), which displays a smaller transitory electrical effect. The limits of this technique in detecting electrical fields and ramifications for measurements of short-range forces near surfaces are discussed.