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Cold Atomic Ensembles in the Strong Coupling Regime of Cavity QED

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. Incorporating the long lived motional coherence of ultacold atoms should yeild new possibilities for physical studies and quantum control.

To implement this, we have constructed a novel mm-scale magnetic trap (pdf) to cool and tightly confine magnetically-trapped, ultracold atoms in an optical cavity. We affectionately call it the "millitrap." In practice we use these mm-scale electromagnets to form a time-orbiting potential (TOP) trap, in which we may form BECs of ~40,000 atoms.

The electromagnets are coaxial and surround a high-finesse optical Fabry-Perot cavity of 194 µm length. We trap atoms in the mode of the cavity with a Far off resonant optical standing wave at 850 nm. This laser is also used to stabilize the length of the cavity. Atoms occupy ~300 lattice sites in the cavity, and have a temperature of ~800 nK.

Dispersive Cavity QED: We probe the cavity dispersively ~10-100GHz from the ⁸⁷Rb atomic resonance. In this limit the presence of each atom contributes a small amount of dispersive material to the cavity, changing the index of refraction.

Nonlinear Optics

Nonlinear optical phenomena typically occur at high optical intensities, as conventional materials mediate only weak coupling between photons. Under the condition of strong coupling, atomic saturation leads a host of nonlinear effects. In this system we observe significant nonlinearity due to collective motion of the atomic medium

The Fluctuation Bolometer

In a cavity, the density of states of the electromagnetic field is altered by the boundary conditions which the mirrors impose. Here, temporal fluctuations then take on the spectrum of the electromagnetic vacuum, being accentuated near the cavity resonances, and suppressed away from the resonances. Using the ultracold atomic medium in the cavity we have performed a Measurement of quantum fluctuations.

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