Cooling atomic ensembles with Maxwell's demon

Bannerman, Stephen Travis
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This dissertation details the development and implementation of novel experimental techniques for cooling neutral atoms. Based on a method first proposed by Maxwell in a nineteenth century thought experiment, these techniques reduce the entropy of an ensemble by allowing unidirectional transmission through a barrier and thus compressing the ensemble without doing work or increasing its temperature. Because of their general nature, these techniques are much more broadly applicable than traditional laser and evaporative cooling methods, with the potential to cool the vast majority of the periodic table and even molecules.

An implementation that cools in one dimension is demonstrated for an ensemble of magnetically trapped rubidium atoms which are irreversibly transferred to a gravito-optical trap. Analysis of the experimental results confirms that phase-space is completely compressed in one dimension. The results also indicate that the overall cooling performance is limited only by the dynamics of atoms in the magnetic trap and may be improved with a more ergodic system.

Three-dimensional cooling may be accomplished with a modified technique which substitutes a radio-frequency-dressed magnetic trap for the gravito-optical trap. Application of this technique to atomic hydrogen and progress toward building an experimental apparatus are discussed.