Atom chips allow for a great variety of trapping geometries for atomic ensembles by means of magnetic, electric, optical, microwave and radio-frequency potentials. Our research aims at the creation of multiply connected topologies, like rings, tori, and cylinders. These traps are used to investigate the low temperature behaviour of ultracold quantum gases when the dimensionality of the trapping geometry changes. Of particular interest are studies of low dimensional systems (2D and 1D) with periodic boundary conditions.
Two-dimensional quantum gases do not show a true Bose-Einstein condensation (BEC) in homogenous systems, but rather a Berezinskii-Kosterlitz-Thouless (BKT) type transition. A BEC can still occur in harmonic traps though, hence providing a "mixture" of BEC and BKT physics. A quasi-homogenous geometry as provided by the torus trap will enable the study of pure BKT physics.
Our current atom chip generation will produce cylinder-symmetric traps by using a combination of dc and radio-frequency fields. Further to the investigation of low-dimensional systems the chip can be used to dynamically split an elongated cloud of ultracold atoms. This "unzipping" of the cloud is intended to be used as a quantum simulator for effects of the Fulling-Davies-Unruh type.