Quantum Optics and Experimental Gravitation

The PRIMUS project takes an all-optical approach for BEC generation in microgravity. Therefore, an optical dipole trap is set-up in a drop tower experiment for use in the Bremen drop tower. The key component is a far-off resonant, high power fiber laser (45W, 1064nm) used to implement a crossed optical dipole trap. After transferring the atoms to the dipole trap subsequent evaporative cooling is used to create a Bose-Einstein condensate. On the path to the Bose-Einstein condensation in the drop tower, efficiency is key. Therefore, so-called painted optical potentials are implemented. Here the trapping beam is spatially modulated in order to dynamically control the trapping volume. This also provides the opportunity to use potential shapes substantially differing from the harmonic potentials typically used in BEC experiments. Box-shaped potentials will allow to study quantum gases of homogenous density. Here microgravity is crucial in order to overcome buoyance forces disturbing the distribution in ground-based experiments.

Atomic clocks onboard Earth orbiting satellites are exposed to large modulations in velocity and gravitational potential. Thus, they allow for sensitive tests of principles and predictions of Special and General Relativity. In our group we investigate various such scenarios for current and future opportunities to perform such tests. For example we could make use of two satellites of the European GNSS Galileo that were accidentally injected into eccentric orbits to obtain a sensitive test of the gravitational redshift. Along this line, we are investigating whether other aspects of General Relativity such as gravito-magnetism could be probed from such systems as well.