Toroidal and ring-shaped traps

One of our projects aims at confining ultracold gases in a ring-shaped trap or even at the surface of a hollow torus. In this way we want to realize a two-dimensional matter wave with periodic boundary conditions. Usually, ultracold gases are trapped using harmonic potentials, which often imposes restrictions on the validity of theoretical models and their predictions. The new trapping potentials will be locally flat in two dimensions and resemble the homogeneouscase more closely by not requiring, e.g., local density approximations. A major ingredient to our experiments are radio-frequency (rf) dressed potentials. By exploiting the vector type coupling between atoms and rf-fields, we gain control over atomic motion, and let atoms counterpropagate in two rings. This setup can be used as a matter wave Sagnac interferometer, sensitive to rotation. This movie depicts the potential we create for such an application.