We use laser-cooled cesium atoms in atomic fountains to perform precision measurements. Efforts have been ongoing for about a decade to measure the fine structure constant a and local gravity g with sensitivity and accuracy higher than any previous method.
Atoms in magneto-optic traps are launched in moving optical molasses with a temperature of about 2 mK. The temperature can further be reduced through Raman sideband cooling in a moving optical lattice to about 150 nK. These atoms then enter a magnetically well-shielded region where atom interferometry is performed.
Beamsplitters and mirrors for the interferometer are formed by pulses of laser light which drive velocity selective stimulated Raman transitions between magnetic field insensitive hyperfine ground states. The use of ultra-cold atoms, atomic fountains and hyperfine ground states allow interrogation time of up to 1 second thereby improving the precision of such measurements by orders of magnitude. Details>> [Top]
We are currently working on producing a BEC of 87Rb. Our apparatus has several unique features which should allow us to produce Bose-condensed atoms at an unprecedented rate: First, we will use 3D Raman Sideband cooling in optical lattices as a precooling stage to evaporation in a conventional magnetic trap. We hope to demonstrate that a large BEC can be produced fast enough to permit the use of a single vapor cell with modest background pressure, removing the need for complicated double MOT or Zeeman slower-based systems. Our apparatus also incorporates a double magnetic trap design, which will give us the possibility of extreme adiabatic compression of our sample before evaporation, potentially shortening the evaporation time even further.
After producing BEC we plan to study many-body physics in optical lattices. Specifically, we plan to study quantum phase transitions, Such as the famous Mott-insulator to Superfluid transition (recently observed by the groups of T. Hansch and M. Kasevich) with a particular interest in their critical behavior at the transition itself. We are also thinking about experiments involving the effects of reduced dimensionality and disorder on the phase transition, as well as spinor condensates in optical lattices. Details>> [Top]
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Last modified 01/13/2009 by Sheng-wey Chiow