Bulletin of the American Physical Society
41st Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 55, Number 5
Tuesday–Saturday, May 25–29, 2010; Houston, Texas
Session C6: Methods of Ultracold Atoms |
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Chair: David Hall, Amherst College Room: Arboretum IV-V |
Wednesday, May 26, 2010 2:00PM - 2:12PM |
C6.00001: Scanning electron microscopy of ultracold atoms Peter W\"urtz, Andreas Vogler, Tatjana Gericke, Herwig Ott We have adapted a scanning electron microscope for the study of ultracold quantum gases. The technique allows for \textit{in situ} imaging of single atoms with a resolution of better than 150 nm. Thus, it can readily be applied to study quantum gases in optical lattices. The dissipative interaction of the electron beam with the atoms can be used to selectively remove atoms. In this way, one can create arbitrary patterns of occupied lattice sites. In the future, we want to exploit the single atom sensitivity to study temporal and spatial correlation functions. The system is also an interesting experimental platform to study electron-atom scattering processes and cold ion-atom collisions. [Preview Abstract] |
Wednesday, May 26, 2010 2:12PM - 2:24PM |
C6.00002: Probing Aton-Atom correlations by Single Atom Detection R. Buecker, A. Perrin, St. Manz, I. Mazets, T. Schumm, J. Schmiedmayer We built a single atom camera that allows imaging of ultra cold quantum gases in expansion (R. B\"{u}cker, et al. NJP, \textbf{11,} 103039 (2009)). After release from a confining potential, atoms fall through a sheet of resonant excitation laser light and the emitted fluorescence photons are imaged onto an amplified CCD camera using a high numerical aperture optical system. The imaging system reaches an extraordinary dynamic range, not attainable with conventional absorption imaging. We demonstrate single-atom detection for dilute atomic clouds with high efficiency where at the same time dense Bose-Einstein condensates can be imaged without saturation or distortionIn the talk we will give examples of how these detectors can be used to probe atom-atom correlations in ultra cold degenerate quantum many body systems. [Preview Abstract] |
Wednesday, May 26, 2010 2:24PM - 2:36PM |
C6.00003: Probing Noise and Coherence in 1d Quantum Systems T. Betz, St. Manz, A. Perrin, T. Schumm, I. Mazets, J. Schmiedmayer We investigate experimentally and theoretically the interference between two one-dimensional quasi-condensates of ultra cold atoms, either independent or tunnel-coupled. The coherence, the noise and their dynamics in these 1d quantum systems is revealed by the full distribution function of the shot to shot variation of the interference patterns. We find that the universal behavior of the contrast distribution can be characterized by two dimensionless parameters related to the ratio of the thermal coherence length to the sampling length or to the coupling-induced phase-locking length, respectively. We compare numerically three models based on the Luttinger liquid theory, Bogoliubov theory, and Ornstein-Uhlenbeck stochastic-process method and estimate the range of parameters where the fundamental quantum noise is important. The ``semi-classical'' approach (\underline {arXiv:0910.5337}) is found to be an accurate approximation in the typical range of experimental parameters. [Preview Abstract] |
Wednesday, May 26, 2010 2:36PM - 2:48PM |
C6.00004: Density Fluctuations in Ultracold Gases Christian Sanner, Ralf Gommers, Wujie Huang, Aviv Keshet, Edward Su, Wolfgang Ketterle Many interesting quantum phases like the Mott insulator are characterized by their incompressibility and suppression of density fluctuations. Directly measuring these fluctuations around the average can provide important information about the quantum phase. We report on experiments that directly measure the density fluctuations in an ultracold Fermi gas. [Preview Abstract] |
Wednesday, May 26, 2010 2:48PM - 3:00PM |
C6.00005: Imaging of Multi-Level Atoms in Deep Optical-Micro Traps Tzahi Grunzweig, Andrew Hilliard, Matt McGovern, Peter McDowall, Mikkel F. Andersen By tightly focusing a far off-resonance laser beam, we can form an optical dipole trap with large oscillation frequencies. Such systems are desirable both for applications in quantum information processing [1] and for investigating quantum mechanics at the single event limit [2]. Our setup is based on the atomic tweezers concept, in which an objective lens is used both to focus the trapping beam, and to image the fluorescence from the trapped atoms. In this talk I will describe our experimental setup and present our recent results on efficient detection and imaging of dense samples of Rb85 atoms in the micro-trap. We address imaging issues resulting from the multi-level structure of the atoms, the different shifts to the various internal states induced by the trapping beam and various loss mechanisms associated with the on-resonance detection process. Detailed understanding of the in-situ detection processes may allow for loss-free, number counting of the trapped atoms. [1] A. Ga\"etan et. al. Nature Physics 5, 115 - 118 (2009); E. Urban et. al., Nature Physics 5, 110 - 114 (2009). [2] Th. Sauter et. al., Phys. Rev. Lett. 57, 1696 - 1698 (1986). [Preview Abstract] |
Wednesday, May 26, 2010 3:00PM - 3:12PM |
C6.00006: Photon Counting for Bragg Spectroscopy of Quantum Gases Juan Pino, Robert Wild, Philip Makotyn, Deborah Jin, Eric Cornell Spectroscopy of low-energy excitations has proved to be an invaluable tool in understanding the many-body physics of ultracold quantum gases. Typically for these measurements, the quantum gas is driven by some field, and the response measured through time-of-flight images of the gas. Often overlooked, however, is the response of the field itself due to its interaction with the gas. We present a method for measuring the response of a light field used to create excitations for Bragg spectroscopy. We describe the techniques used to achieve shot-noise limited detection of this light-field, and also present Bragg spectroscopy of a Bose-Einstein condensate using this novel technique. [Preview Abstract] |
Wednesday, May 26, 2010 3:12PM - 3:24PM |
C6.00007: How to create macroscopic superposition states of cold bosons in an asymmetric double well Miguel-\'Angel Garc\'Ia-March, Lincoln Carr The quantum models of the behavior of cold bosons in a double well attribute self trapping of an initial maximal population imbalance, i.e. all atoms localized initially in one of the wells, to exponentially long tunneling times. We show that this self trapping can also be attributed to the presence of a small tilt. Nevertheless, when the tilt is increased this tunneling reappears periodically for certain resonant values of the tilt. The higher the value of the resonant tilt is, the higher the deviations around it the initial state supports without self trapping in one of the wells and the quicker the period of the tunneling is. Therefore, a properly prepared tilt around one of the resonances allows the experimental observation of the quantum sloshing of the atoms initially localized in one of the wells. We show that macroscopic superposition states, that take the form of NOON or NOON-like states, are realized periodically along the quantum sloshing of the cold bosons, thus paving the way for their experimental observation. [Preview Abstract] |
Wednesday, May 26, 2010 3:24PM - 3:36PM |
C6.00008: Coherent control of population transfer between Wannier-stark states in an optical lattice via one- and two- phonon interference Chao Zhuang, Christopher Paul, Samansa Maneshi, Luciano Cruz, Aephraim Steinberg We demonstrate coherent control of population transfer between quantum vibrational states in an optical lattice by using interference between a 2-phonon excitation at $\omega$ and a 1-phonon excitation at $2\omega$. By varying the relative phase between phase modulation (PM) of the lattice at $\omega$ and amplitude modulation (AM) at $2\omega$, we observe oscillations in the branching ratio between transition to the first excited state and higher excited states. We will present experimental data showing the quantum interference between a 2-PM-phonon and a 1-AM-phonon for different excitation amplitudes. Our best result, by tuning the excitation amplitude and relative phase, shows an improvement of coupling into the first excited state by $23\%$ and the branching ratio by a factor of $3.5\pm0.7$, when the total population in the higher excited states is reduced to our measurement noise level. [Preview Abstract] |
Wednesday, May 26, 2010 3:36PM - 3:48PM |
C6.00009: Quasiparticle Spectrum of 2-d Dirac Vortices in Optical Lattices Laith Haddad, Lincoln Carr Bose-Einstein condensates (BEC's) in a honeycomb optical lattice are described by a nonlinear Dirac equaton (NLDE) in the long wavelength, mean field limit [1]. The bipartite structure of the lattice appears as pseudospin in the multi-component BEC with states above and below the Dirac point playing the roles of particles and antiparticles. Although much work has been done on NLDE's, the bulk of the literature deals with models with Poincare invariant nonlinearites. In contrast our equations break Poincare symmetry providing an opportunity to study phenomenological models in cosmology and particle physics where this symmetry is not manifest. We present the associated linear stability equations and apply them to the case of weak contact interactions to obtain the quasiparticle energies, states, and stabilities of vortex solutions of the mean field equations. We discuss future applications of our results to problems at the interface between condensed matter and particle physics.\\[4pt] [1] L. H. Haddad and L. D. Carr, ``The Nonlinear Dirac Equation in Bose-Einstein Condensates: Foundation and Symmetries,'' Physica D: Nonlinear Phenomena, v. 238, p. 1413 (2009). \underline {http://arxiv.org/pdf/0803.3039v1} [Preview Abstract] |
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