Coherent Tunneling and Quantum Control in AN Optical Double-Well Potential

Quantum coherence and tunneling of a particle in a double-well potential is central to our understanding of many physical phenomena. We have developed a laboratory realization of this "toy model", based on laser cooled Cs atoms in a one-dimensional optical lattice. The system states are spinor wavepackets with highly entangled internal and external degrees of freedom, allowing us to use the atomic spin as a "meter" to observe the center-of-mass motion. With appropriate initial condition the system Rabi oscillates between right- and left-localized states of the ground doublet. In a separate experiment we have measured the entire density matrix of the atomic angular momentum, thereby extending the use of the spin as a meter and opening up new possibilities to study phenomena such as quantum chaos and decoherence in the double-well system.