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 solid-state 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 three-dimensional optical lattice. This approach includes the possible coupling between center-of-mass and relative motion coordinates in a configuration-interaction (also called exact diagonalization) type of approach. Furthermore, the atoms are allowed to interact by their full inter-atomic 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 inter-atomic interaction strength. [Preview Abstract] |
Friday, May 30, 2008 2:12PM - 2:24PM |
Q4.00002: Probing higher-order interactions with an array of double-well optical-lattice 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 higher-order interactions usually neglected in Bose-Hubbard models of optical lattice physics. In addition to potentially revealing new and interesting physics, these higher-order interactions could also be an important source of dephasing in lattice-based 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 Bose-Condensed Cesium Atoms in an Optical Lattice Chen-Lung Hung, Xibo Zhang, Nathan Gemelke, Cheng Chin We describe methods to investigate universality in few-body systems derived from Bose-condensed 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 time-of-flight measurement, and suggest remedies based on Feshbach-mediated control of interactions, and possible application of spin-echo techniques to matter-wave revival. To reach this goal, we have recently demonstrated Bose-Einstein 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 two-dimensional optical lattice. This single-layer 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: Self-trapped atom corrals Jean-Felix Riou, David S. Weiss We will describe an experiment with a coupled array of 1D quantum degenerate gases in the mean-field regime. Transverse tunneling is suppressed when there is a sufficiently large difference in the mean-field energy of adjacent tubes. This phenomenon of self-trapping 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 self-trapped 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 self-trapped corral gives way, and the atoms expand in all directions. [Preview Abstract] |
Friday, May 30, 2008 2:48PM - 3:00PM |
Q4.00005: Matter-wave interference due to interactions Mattias Gustavsson, Elmar Haller, Manfred Mark, Johann Danzl, Russell Hart, Hanns-Christoph 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 time-varying regular interference pattern in the first Brillouin zone. We further demonstrate the coherence through a reversal of the phase evolution analogous to spin-echo experiments, by switching the interaction strength to zero and applying an external potential. We also observe long-lived 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 neutral-atom 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 neutral-atom $\sqrt{\rm SWAP}$ gate using exchange oscillations in a dynamically-deformable double-well optical lattice. This result demonstrated the feasibility of quantum gates driven by controlled exchange interactions. The observed oscillations, while long-lived, 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 magnetic-field issues. We present observations of this improved operation, as well as exploration of stroboscopic deformation of the double-well lattice. [Preview Abstract] |
Friday, May 30, 2008 3:12PM - 3:24PM |
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 Bose-Hubbard Model Matthew White, Matthew Pasienski, David McKay, Brian DeMarco Despite application of the disordered Bose-Hubbard (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 fine-grained disorder to a three-dimensional optical lattice using an optical speckle field. The speckle field is fine-grained 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 $n = 1$ Mott-insulator lobe. These measurements, in conjunction with theoretical and computational work in progress, are expected to place constraints on the disordered Bose-Hubbard 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] Wei-Khim Ng and Rajesh R. Parwani, e-print 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 four-level ``tripod" variant of the usual setup for stimulated Raman adiabatic passage (STIRAP) has been proposed for generating non-Abelian gauge fields [1]. Dirac-like Hamiltonians, which exhibit ZB, are simple examples of such non-Abelian 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 double-well trap located inside a high-Q optical resonator. Using a Monte-Carlo 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 Mott-insulator state. The two-time correlation functions of the scattered light and its entanglement with the matter waves are also discussed. [Preview Abstract] |
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