Our research is focussed on ultra-cold atoms and Bose-Einstein condensates in micro-structured trapping potentials. With so-called atom chips, we are able to shape and generate magnetic fields that allow us to cool and control gases of neutral atoms at micrometer distances from a material surface.
Quantum optics and light-matter interfaces
We investigate techniques to map the quantum states of light pulses into the spin degrees of freedom of atomic ensembles and vice versa. Using their long coherence times, the atoms serve as a quantum memory, enabling, e.g., long-distance quantum communication.
On the other hand, mapping quantum states of matter onto light makes them accessible to well established quantum optical techniques like photon counting and homodyne detection. These can then be used as analytical tools for a variety of strongly correlated many-body states. We plan to trap very elongated clouds of atoms inside the small hollow core of a photonic crystal fibre, which will lead to strong interactions with the light field even for gases containing only a few hundred atoms.
Toroidal and ring-shaped matterwaves
Another line of experiments will make use of atom chip based traps with non-trivial topologies. By confining an ultracold gas to the surface of a hollow torus, we want to realise a two-dimensional matter wave with periodic boundary conditions.
This will help overcoming certain restrictions to the validity of theoretical models, which are encountered when using harmonic trapping potentials. 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 will be
able to let atoms counterpropagate in two rings. Such a setup can be used as a matter wave Sagnac interferometer that is extremely sensitive to rotation.