Bulletin of the American Physical Society
39th Annual Meeting of the APS Division of Atomic, Molecular, and Optical Physics
Volume 53, Number 7
Tuesday–Saturday, May 27–31, 2008; State College, Pennsylvania
Session Q4: Atoms in Optical Lattices 
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Chair: Markus Greiner, Harvard University Room: Nittany Lion Inn Ballroom AB 
Friday, May 30, 2008 2:00PM  2:12PM 
Q4.00001: Exact theoretical description of two ultracold atoms in a single site of a 3D optical lattice Alejandro Saenz, Sergey Grishkevich Ultracold atoms in optical lattices are exciting systems to study, e.g., phenomena of solidstate physics, since the lattice resembles in some sense the periodicity of a crystal potential. These systems are furthermore supposed to be of great interest for quantum information purposes. We have developed a theoretical approach that allows for an exact numerical description of a pair of ultracold atoms trapped in a threedimensional optical lattice. This approach includes the possible coupling between centerofmass and relative motion coordinates in a configurationinteraction (also called exact diagonalization) type of approach. Furthermore, the atoms are allowed to interact by their full interatomic interaction potential that is, presently, only limited to be central. With the aid of the newly developed method deviations from the harmonic approximation are discussed. The developed method is also used to model recent experimental data [C. Ospelkaus et al., Phys. Rev. Lett. {\bf 97}, 120402 (2006)]. In that experiment heteronuclear molecules were created in an optical lattice and their binding energies were measured close to a Feshbach resonance as a function of the magnetic field and thus of a variable interatomic interaction strength. [Preview Abstract] 
Friday, May 30, 2008 2:12PM  2:24PM 
Q4.00002: Probing higherorder interactions with an array of doublewell opticallattice interferometers Philip Johnson, Eite Tiesinga, Carl Williams In the double well optical lattice number (squeezed) states can be loaded into individual wells via the Mott insulator phase transition, and then the wells can be dynamically split or merged in a variety of ways. One simple picture for the subsequent splitting and merging of wavefunctions is to view the system as an array of beam splitters. We show how this system can be used as an array of interferometers for sensitively probing higherorder interactions usually neglected in BoseHubbard models of optical lattice physics. In addition to potentially revealing new and interesting physics, these higherorder interactions could also be an important source of dephasing in latticebased quantum computers. Characterizing them is an important step toward mitigating any unwanted effects and potentially exploiting new types of interactions. [Preview Abstract] 
Friday, May 30, 2008 2:24PM  2:36PM 
Q4.00003: Studying Universality with BoseCondensed Cesium Atoms in an Optical Lattice ChenLung Hung, Xibo Zhang, Nathan Gemelke, Cheng Chin We describe methods to investigate universality in fewbody systems derived from Bosecondensed atoms in optical lattices. In particular, we describe how precise spectroscopy and the collapse and revival of matter wave coherence may be used as a sensitive probe of collision properties and correlations. We discuss limitations on the technique due to lattice inhomogeneity and hydrodynamic timeofflight measurement, and suggest remedies based on Feshbachmediated control of interactions, and possible application of spinecho techniques to matterwave revival. To reach this goal, we have recently demonstrated BoseEinstein condensation of $\sim 10^5$ cesium atoms in a novel crossed beam dipole trap configuration, which allows us to adiabatically transfer atoms from a harmonic trapping potential into a single layer of twodimensional optical lattice. This singlelayer 2D lattice will allow us to directly and simply monitor the density distribution of atoms, and provide a large number of subsystems to sensitively probe coherence. [Preview Abstract] 
Friday, May 30, 2008 2:36PM  2:48PM 
Q4.00004: Selftrapped atom corrals JeanFelix Riou, David S. Weiss We will describe an experiment with a coupled array of 1D quantum degenerate gases in the meanfield regime. Transverse tunneling is suppressed when there is a sufficiently large difference in the meanfield energy of adjacent tubes. This phenomenon of selftrapping is strongest near the edge the bundle of tubes, where the tube occupation gradients are largest. With the right parameters, atoms that start to expand transversely from the central tubes are reflected by a selftrapped corral. The resulting ring structures do not correspond to any features of the trapping potential. As the atoms expand along the tubes, their density gradients drop until suddenly the selftrapped corral gives way, and the atoms expand in all directions. [Preview Abstract] 
Friday, May 30, 2008 2:48PM  3:00PM 
Q4.00005: Matterwave interference due to interactions Mattias Gustavsson, Elmar Haller, Manfred Mark, Johann Danzl, Russell Hart, HannsChristoph N\"agerl A BEC in a lattice potential undergoes Bloch oscillations when subject to an external force. If the force is strong enough, dynamical instabilities are suppressed and the interacting matter wave dephases in a coherent way, which we observe as a timevarying regular interference pattern in the first Brillouin zone. We further demonstrate the coherence through a reversal of the phase evolution analogous to spinecho experiments, by switching the interaction strength to zero and applying an external potential. We also observe longlived Bloch oscillations when the effect of interactions is balanced by a harmonic trapping potential. Furthermore, we explore the limit of vanishing interaction. In this regime we can follow more than 20000 oscillations over 12 s. [Preview Abstract] 
Friday, May 30, 2008 3:00PM  3:12PM 
Q4.00006: Exploring a neutralatom SWAP gate with clock states Nathan Lundblad, Patricia Lee, John Obrecht, William Phillips, Trey Porto Recent work in our group demonstrated the essential components of a neutralatom $\sqrt{\rm SWAP}$ gate using exchange oscillations in a dynamicallydeformable doublewell optical lattice. This result demonstrated the feasibility of quantum gates driven by controlled exchange interactions. The observed oscillations, while longlived, had limited contrast due to a multitude of experimental issues. We have moved our operating qubits from the $F=1,m_F=1\rangle$, $F=1,m_F=0\rangle$ pair to the hyperfine clock state, eliminating considerable concern over magneticfield issues. We present observations of this improved operation, as well as exploration of stroboscopic deformation of the doublewell lattice. [Preview Abstract] 

Q4.00007: ABSTRACT WITHDRAWN 
Friday, May 30, 2008 3:24PM  3:36PM 
Q4.00008: Raman excitation of ultracold atoms to higher vibrational bands in an optical lattice Patricia Lee, Nathan Lundblad, John Obrecht, William Phillips, Trey Porto Cold atoms with orbital degrees of freedom in an optical lattice could lead to novel effects and quantum phases. We present experiments using stimulated Raman transition to excite atoms initially in the ground band to higher vibrational bands in a 3D optical lattice while simultaneously changing the hyperfine state of the atoms. The combination of spin and vibrational coupling allow us to create higher orbital states with different spins and observe the dynamics of such a system. [Preview Abstract] 
Friday, May 30, 2008 3:36PM  3:48PM 
Q4.00009: Experiments on the 3D Disordered BoseHubbard Model Matthew White, Matthew Pasienski, David McKay, Brian DeMarco Despite application of the disordered BoseHubbard (BH) model to many physical systems, the nature of the ground state phase diagram for this model has remained unsettled for nearly two decades. In order to experimentally test the properties of the disordered BH model, we have added finegrained disorder to a threedimensional optical lattice using an optical speckle field. The speckle field is finegrained in that the correlation in disorder between neighboring sites is small along every lattice direction. We have measured the change in condensate fraction as a function of disorder strength for several different values of lattice depths above and below the onset of the $n = 1$ Mottinsulator lobe. These measurements, in conjunction with theoretical and computational work in progress, are expected to place constraints on the disordered BoseHubbard phase diagram. [Preview Abstract] 
Friday, May 30, 2008 3:48PM  4:00PM 
Q4.00010: A Nonlinear Dirac Equation in Ultracold Bosons in an Optical Lattice Lincoln D. Carr, Laith Haddad We present a relativistic generalization of the nonlinear Schrodinger equation, the nonlinear Dirac equation (NLDE). Although different versions of a nonlinear Dirac equation have appeared in numerous fields in the past (for a recent summary, see [1]), we present a novel version of the NLDE which is of immediate experimental relevance in ultracold quantum gases and has a ``speed of light'' ten orders of magnitude slower than $c$. We discuss the symmetry properties of this new equation. [1] WeiKhim Ng and Rajesh R. Parwani, eprint arXiv:0707.1553 (2007). [Preview Abstract] 
Friday, May 30, 2008 4:00PM  4:12PM 
Q4.00011: Observing Zitterbewegung with Ultracold Atoms J.Y. Vaishnav, Charles W. Clark We propose an optical lattice scheme which would permit the experimental observation of {\it Zitterbewegung} (ZB) with ultracold, neutral atoms. A fourlevel ``tripod" variant of the usual setup for stimulated Raman adiabatic passage (STIRAP) has been proposed for generating nonAbelian gauge fields [1]. Diraclike Hamiltonians, which exhibit ZB, are simple examples of such nonAbelian gauge fields; we show how a variety of them can arise, and how ZB can be observed, in a tripod system. We predict that the ZB should occur at experimentally accessible frequencies and amplitudes. We also discuss how the tripod STIRAP setup can be used to generate atomic versions of various spintronic devices. \newline [1] J. Ruseckas, G. Juzeli{\=u}nas, P. \"{O}hberg, M. Fleischhauer, {\it Physical Review Letters} {\bf 95}, 010404 (2005). [Preview Abstract] 
Friday, May 30, 2008 4:12PM  4:24PM 
Q4.00012: Cavity QED determination of atomic statistics in optical lattices  power spectrum and entanglement Wenzhou Chen, Pierre Meystre We study theoretically the interaction between a quantized light field and ultracold bosonic atoms in a doublewell trap located inside a highQ optical resonator. Using a MonteCarlo wave function method to account for dissipation we show that the statistical properties of the scattered light reflect the state of the atomic field, allowing one to distinguish in particular between a superfluid from a Mottinsulator state. The twotime correlation functions of the scattered light and its entanglement with the matter waves are also discussed. [Preview Abstract] 
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