Cooling in RF dressed state potentials
With the long lifetimes, no additional heating, and high collision rates, evaporative cooling to quantum degeneracy in the RF-induced potentials is possible. This is accomplished by applying a sweep of an additional weak RF field tuned to energy differences in the dressed state level scheme. The observed RF induced evaporative cooling is as stable and efficient as in the original magnetic trap, and allows easy and fast creation of pure Bose Einstein Condensates in the dressed state potentials.
The ability to cool atomic samples in the RF-double well potential allows us to prepare two fully independent condensates from a split thermal cloud, and compare them with the coherently split BEC in identical potentials. In both cases we start with thermal atoms in the static single well potential. In the case of coherent splitting, the sample is first cooled to degeneracy and then the potential is deformed into a double well by increasing the amplitudes of the RF fields. Alternatively, we apply the RF dressing field first, splitting the thermal cloud. We then cool the two separate samples to degeneracy. The height of the potential barrier between the two wells was U ~ 80 µm in this experiment, ensuring that the two samples were truly separated long before condensation began.
The coherently split BEC shows a narrow phase distribution, the independently created BEC’s interfere with a random phase.
