Rubidium BEC Project

Ultracold Rb atoms and molecules in an optical lattice

Experimental Setup

View into the Rubidium laboratory at the Institute of Quantum Matter:


As a starting point for our experiments we create a Bose–Einstein condensate (BEC) of about 106 ultracold 87Rubidium atoms. This BEC is then typically loaded into a 3D optical lattice creating a Mott-insulator state with a well defined atom number per lattice site. Using Feshbach resonances, the Rb atoms can be converted into molecules.

Left: False-colour absorption imaging of a Rubidium BEC released from a weak optical 3D lattice. Right: Rb molecules captured in a deep optical lattice.

Ultracold molecules

We have demonstrated a scheme to efficiently transfer the Rb molecules, which are initially very weakly bound, to the ro-vibrational ground state of the triplet potential, creating a quantum gas of ultracold deeply bound molecules.

We have mapped out in detail the vibrational, rotational, hyperfine, and Zeeman structure with an absolute accuracy of about 50 MHz. These results will be relevant for future experiments with ultracold Rb2 molecules, e.g. cold collisions and molecular BEC.

In the future we will

  • investigate the triplet groundstate and the first excited state as they are of special interest: They are not easily accessible in conventional set-ups and they exhibit a magnetic moment
  • investigate the collisional properties of these molecules
  • produce molecular BEC
  • carry out controlled ultracold chemistry with molecules
  • perform precision spectroscopy to test theoretical models and predictions


Condensed matter phenomena with cold bosonic atoms

Ultracold atomic gases in optical lattices allow for creating intriguing physical systems of strongly correlated particles. A quantum lattice gas of cold atoms is a practically perfect realization of a Hubbard model and can be used to mimic and explore interesting condensed matter physics. Using bosonic ultracold 87Rb atoms, which are held in a 3D optical lattice, we plan to explore regimes which are not accessible to conventional condensed matter systems and investigate novel quantum phases as well as their properties and their dynamics. In doing so, we will also develop techniques that can be used for quantum information applications.


Previous experiments of the Rb BEC project

The following experiments were carried out within Rudi Grimm’s group at the Institut für Experimentalphysik, Universität Innsbruck, before our team moved to Ulm: