General Physics Colloquium

Fundamental Physics with Quantum Matter in Microgravity

Wolfgang Ertmer, for the QUANTUS cooperation
QUEST, Institut für Quantenoptik, Leibniz Universität, Hannover, Germany

Coherent matter wave sources and coherent matter wave optics have reached a level of
performance where gravity based effects may impose severe perturbations. Thus,
microgravity can open new areas in which energy levels in the femto Kelvin regime get into
reach. In addition, microgravity will allow new fundamental tests and new regimes of
quantum metrology.
In my talk I will report on the implementation of a Bragg-type interferometer operated with a
chip-based atom laser for Rubidium ??Rb in microgravity. With a chip based atom laser we
can generate thermal ensemble as well as Bose-Einstein condensates (BEC). With the help of
delta kick cooling, implemented via the atom chip, we can further slow down the expansion
of thermal and condensed atoms, reducing tremenduously the expansion of the atomic
ensemble. In addition, the chip allows to transfer atoms in the individual Zeeman states of the
two Hyperfine groundstates, in particular into the non-magnetic state. With this toolbox we
could extend the observation of a BEC of 10000 atoms to macroscopic time scales
approaching two seconds. Benefiting form the extended free fall in microgravity we could
combine this with an asymmetric Mach-Zehnder type interferometer over hundreds of
milliseconds to study the coherence and to analyse the delta kick cooling with the help of the
observed interference fringes. This experiment can be considered as a double slit experiment
in microgravity.
A novel generation of atom chips allows to improve the performance of these flexible
devices. We could demonstrate loading of the chip with far more than 10? atoms in roughly a
second in a setup of the size of a shoebox. We discuss as a possible spin-off a chip based
quantum gravimeter for ground based applications, recently demonstrated with our device.
The design is employed for a rocket based test of such an interferometer and will demonstrate
the feasibility of a satellite based tests of Einsteins principle of equivalence as pursued by the
STE-QUEST mission.

Coffee/tea and cake will be served at 3 p.m.