In a spinor Bose-Einstein condensate the atoms can be in a superposition of internal quantum states. Thus, a BEC of spin-1 particles, like the F = 1 ground state of Na atoms, can be thought of as being a single condensate with the atoms in a superposition of the three spin projections mF = -1, 0, and +1, or equivalently, the superposition of three coupled BECs with the same spatial wavefunction, one in each of these spin states.
I will report on the spinor BEC experiment in Na atoms at NIST, Gaithersburg. Here we use microwave-dressing to create a nonlinear matter-wave amplifier that can be used to produce spin-squeezed states. We examine weak coherent seeds and show that the populations distribution after an evolution time can be used as a large amplitude measurement initial seed. This kind of measurement may be important in achieving high phase sensitivity in Heisenberg-limited matter-wave interferometers.
Ultracold atoms in optical lattices are a versatile tool to investigate fundamental properties of quantum many body systems. We demonstrate how the control of such systems can be extended down to the most fundamental level of single atomic spins at specific lattice sites. Using a high-resolution optical imaging system, we were able to obtain fluorescence images of strongly interacting bosonic Mott insulators with single-atom and single-site resolution  and addressed the atomic spins with sub-diffraction-limited resolution . In addition, we directly monitored the tunneling quantum dynamics of single atoms in the lattice, and observed quantum-correlated particle-hole pairs  and spreading of correlations after a parameter quench , and the quantum dynamics of spin-impurities. Our results open the path to a wide range of novel applications from observation of entropy transport, implementation of novel cooling schemes, and engineering of quantum many-body phases to quantum information processing.
 J. F. Sherson, C. Weitenberg, M. Endres, M. Cheneau, I. Bloch, S. Kuhr, Single-atom-resolved fluorescence imaging of an atomic Mott insulator, Nature 467, 68 (2010).
 C. Weitenberg, M. Endres, J. F. Sherson, M. Cheneau, P. Schauß, T. Fukuhara, I.Bloch, S. Kuhr, Single-spin addressing in an atomic Mott insulator, Nature 471, 319 (2011).
 M. Endres, M. Cheneau, T. Fukuhara, C. Weitenberg, P. Schauß, C. Gross, L. Mazza, M.C. Banuls, L. Pollet, I. Bloch, S. Kuhr, Observation of Correlated Particle-Hole Pairs and String Order in Low-Dimensional Mott Insulators, Science 334, 200 (2011).
 M. Cheneau, P. Barmettler, D. Poletti, M. Endres, P. Schauß, T. Fukuhara, C. Gross, I. Bloch, C. Kollath, S. Kuhr, Light-cone-like spreading of correlations in a quantum many-body system, Nature 481, 484 (2012).