  We observe the quantum coherent dynamics of atomic spinor wavepackets in the
double well potentials of a far-off-resonance optical lattice. With appropriate
initial conditions the system Rabi oscillates between the left and right
localized states of the ground doublet, and at certain times the wavepacket
corresponds to a coherent superposition of these mesoscopically distinguishable
quantum states. The atom/optical double well potential is a flexible and
powerful system for further study of mesoscopic quantum coherence, quantum
control and the quantum/classical transition.
