John Obrecht

Measurement of the Temperature Dependence of the Casimir-Polder Force

We report on the first measurement of a temperature dependence of the Casimir-Polder force. This measurement was obtained by positioning a nearly pure 87Rb Bose-Einstein condensate a few microns from a dielectric substrate and exciting its dipole oscillation. Changes in the collective oscillation frequency of the magnetically trapped atoms result from spatial variations in the surface-atom force. In our experiment, the dielectric substrate is heated up to 605 K, while the surrounding environment is kept near room temperature (310 K). The effect of the Casimir-Polder force is measured to be nearly 3 times larger for a 605 K substrate than for a room-temperature substrate, showing a clear temperature dependence in agreement with theory.

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.

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

A magnetically trapped

Measuring electric fields from surface contaminants with neutral atoms

^{87}\mathrm{Rb}

Cold collisions between NH molecules and Rubidium atoms

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,

Measurement of the temperature dependence of the Casimir-Polder force

^{87}\mathrm{Rb}

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

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

\mathrm{Rb}

Casimir-Polder force measurements with Bose-Einstein condensates

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.