We create atom-molecule superpositions in a Bose-Fermi mixture of ${}^{87}\text{R}\text{b}$ and ${}^{40}\text{K}$ atoms. The superpositions are generated by ramping an applied magnetic field near an interspecies Fano-Feshbach resonance to coherently couple atom and molecule states. Rabi- and Ramsey-type experiments show oscillations in the molecule population that persist as long as $150\mu \text{s}$ and have up to 50% contrast. The frequencies of these oscillations are magnetic-field dependent and consistent with the predicted molecule binding energy. This quantum superposition involves a molecule and a pair of free particles with different statistics (i.e., bosons and fermions) and furthers exploration of atom-molecule coherence in systems without a Bose-Einstein condensate.

• Received 10 October 2008

DOI:https://doi.org/10.1103/PhysRevA.80.030701