  We have created a dark quantum superposition state of a Rb Bose-Einstein
condensate (BEC) and a degenerate gas of Rb$_2$ ground state molecules in a
specific ro-vibrational state using two-color photoassociation. As a signature
for the decoupling of this coherent atom-molecule gas from the light field we
observe a striking suppression of photoassociation loss. In our experiment the
maximal molecule population in the dark state is limited to about 100 Rb$_2$
molecules due to laser induced decay. The experimental findings can be well
described by a simple three mode model.
