Stamper-Kurn Group
UC Berkeley Ultracold Atomic Physics Group

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Cavity QED with Magnetically Trapped Atoms
(a.k.a. Rubidium-87 BEC... too?)


Cavity QED to date has yielded many tantalizing results, including the creation of atom-photon entanglement, single-atom microscopy, and long-lived optical trapping of a single atom in a resonant optical cavity. Magnetic trapping of atoms inside a high-finesse cavity is an attractive avenue for deterministic CQED as it allows a large reservoir of atoms to be held in the strongly-coupled regime, providing for such experimental possibilities as resonant atom counting and photon Fock-state generation. Utilizing the unique atom-probing capabilities of cavity QED may also provide new windows into many-atom, ultra-cold phenomena such as Bose-Einstein condensation.

To implement this, we have constructed a novel mm-scale Ioffe-Pritchard (IP) trap to tightly confine magnetically-trapped, ultracold atoms in an optical cavity. We affectionately call it the "millitrap."

We have produced ~5 billion atom 87Rb MOTs, loaded from a recirculating oven and Zeeman slower source. We have magnetically trapped 1/3 of these in the |1,-1> state in a quadrupole magnetic field. We are able to transfer these 100 µK atoms within one second to the cavity quadrupole trap (400 G/cm). The millitrap has performed well to-date, and has produced condensates of over 1 million atoms.


Separately, we have constructed a high-finesse optical Fabry-Perot cavity of 170 µm length and stabilized it to within a fraction of its linewidth (< 1 picometer). Passive isolation for high frequencies is provided by a two-stage spring-mass vibration isolation system. Low frequency noise (< 10 kHz) is actively suppressed with electronic feedback to a PZT. The cavity satisfies the requirements for strong coupling. We have also built and stabilized a “transfer” cavity to transfer the locking wavelength away from the atomic resonance. The integration of magnetically trapped ultracold atoms and the high finesse optical cavity will be accomplished in the very near future.

Please see our recent publications and presentations to get the latest info on what we're up to!


Now playing on E2 cinema:



BEC on E2!



Cold atoms filling a
quadrupolar ring trap



Circular waveguide
for BECs

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