Efficient creation of translational cold heteronuclear dimers in the rovibrational ground state from ultracold atoms via photoassociation followed by optical pumping

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Ultracold heteronuclear RbCs dimers are produced via photoassociation. These molecules are in highly excited vibrational states. This project is concerned with the transfer of the excited molecules to the lowest rovibrational level of the electronic ground state, i.e., the absolute ground state. Only deeply bound heteronuclear dimers carry a significant dipole moment, which makes experiments in the strongly interacting regime possible. Via this interaction, such molecules may serve as q-bits for future quantum computers. This project investigates two possibilities for improving the efficiency of the transfer and the resultant larger number of ground state molecules in the absolute ground state: The first technique, applying Stimulated Raman Adiabatic Passage (STIRAP) allows for a complete transfer between two states if two laser fields are applied in a well controlled sequence. The second technique is selecting appropriate levels to increase the efficiency, which is of particular interest for a transfer between singlet and triplet manifold via a mixed level. Another aspect of the transfer process is the hyperfine state of the molecule, which is of particular importance for possible quantum computers. The different hyperfine states are degenerate for the absolute ground state, but the preparation of a pure hyperfine state is essential for quantum computing and can be addressed in the transfer scheme.