One-dimensional Bose-Einstein condensates in micro-traps

A novel wire-based magneto-optical trap has been demonstrated which enables to collect up to 3x10^8 cold atoms close to the reflecting surface of an atom chip. These atoms are subsequently transferred to micro-traps generated by wires mounted on the atom chip and Bose-Einstein condensation has been achieved. The Bose-Einstein condensates (BECs) created in the micro-traps form in the one-dimensional Thomas-Fermi regime. The cross-over between three-dimensional and one-dimensional BECs has been investigated by monitoring the transverse size of the BEC after ballistic expansion. Good agreement to theory has been found. As an application, one-dimensional BECs have been used to implement a microscopic magnetic field sensor. This sensor enables field measurements in a region which is not accessible for today's state-of-the-art sensors. A field sensitivity of 4 nT at a spatial resolution of 3 micrometer has been demonstrated. To investigate the phase-properties of a one-dimensional BEC, coherent splitting of a one-dimensional BEC has been achieved and interferometry on an atom chip has been demonstrated