Bulletin of the American Physical Society
40th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 54, Number 7
Tuesday–Saturday, May 19–23, 2009; Charlottesville, Virginia
Session B3: Matter Waves |
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Chair: Michael G. Moore, Michigan State University Room: Gilmer Hall 190 |
Wednesday, May 20, 2009 10:30AM - 10:42AM |
B3.00001: Near and far field studies of coherence in scalar Bose-Einstein condensates Kater Murch, Jennie Guzman, Mukund Vengalattore, Dan Stamper-Kurn We have studied the coherence properties of scalar $^{87}$Rb condensates. Far field images, obtained in long time-of-flight revealed phase fluctuations of the condensate as modulations in the density of the gas. Near field images were obtained in short time of flight by interfering portions of the condensate separated by~a variable distance. The decay of the contrast of this interference was related to the coherence length of the condensate. Using these dual techniques we have studied the coherence of scalar Bose gasses during and after condensate formation. [Preview Abstract] |
Wednesday, May 20, 2009 10:42AM - 10:54AM |
B3.00002: Dynamics and Relative Phase of Fragmenting BECs Douglas K. Faust, William P. Reinhardt Recent BEC experiments\footnote{Y. Shin et al. PRL 93, 050405 (2004)}$^,$\footnote{M. Albeiz et al. PRL 95, 010402 (2005)} have shown that an initially coherent condensate, when spatially fragmented, can exhibit phase-driven phenomena such as the Josephson effect and controllable interference patterns analogous to those of a Mach-Zehnder interferometer. A theoretical treatment of the dynamics of such systems is difficult as two models are appropriate in different regimes: Mean-field theory for the initial unfragmented state and a Hubbard model for the particle number dynamics as localized lobes of the cloud form. We present a method which correctly describes dynamics of both spatial and Fock-space variables for a fragmenting condensate. This method shows the effect of non-adiabaticity on interference patterns, stability of Josephson oscillations and the degree of number squeezing in specific trap geometries. Further, this technique yields the order parameter (nor rigorously defined in mean-field theory) and gives a context in which to discuss phase uncertainty - the ultimate limit on the quality of interferometry schemes. [Preview Abstract] |
Wednesday, May 20, 2009 10:54AM - 11:06AM |
B3.00003: Low-momentum Bragg Spectroscopy of a Strongly Interacting $^{85}$Rb Bose-Einstein Condensate Juan Pino, Rob Wild, Deborah Jin, Eric Cornell Bragg spectroscopy of a weakly interacting Bose-Einstein condensate (BEC) in the low-k limit has shown phonon-like dispersion (J. Steinhauer {\it et al.}, PRL {\bf 88}, 120407 (2002)). We report on Bragg spectroscopy of a strongly interacting BEC where we expect a divergence from the Bogoliubov spectrum (S. Papp {\it et al.}, PRL {\bf 101}, 135301 (2008)). We access the strongly interacting regime via a magnetic-field Feshbach resonance. Recent efforts focus on low-momentum excitations, and for this work we have implemented a shot-noise limited photon detection scheme. Additionally, we are working with a new, spherical trap that will allow us to interrogate the atoms in the strongly interacting regime for longer times than was possible in our previous work. [Preview Abstract] |
Wednesday, May 20, 2009 11:06AM - 11:18AM |
B3.00004: A large momentum beam-spitter using Bloch oscillations Pierre Clad\'e, Saida Guellati-Kh\'elifa, Fran\c cois Nez, Lucile Julien, Fran\c cois Biraben The sensitivity of an intertial sensor based on a Ramsey Bord\'e interfermometer is proportional to the velocity separation of atoms in the two arms of the interferometer. In this contribution we will describe how Bloch oscillations can be used to increase this separation using a large momentum transfer (LMT) beamsplitter. We experimentally demonstrate a separation of 10 recoil velocities. A numerical model is develloped to calculate the sensitivity of the interferometer to phase fluctuations and to intensity fluctuations. We demonstrate that the later can be significantly decreased by using a suitable combination of LMT pulses. We finally show how one can further increase the separation. [Preview Abstract] |
Wednesday, May 20, 2009 11:18AM - 11:30AM |
B3.00005: Direct Measurement of Atom Number Fluctuations in an RF Dressed Double Well Alma B. Bardon, Lindsay J. LeBlanc, Marcius H.T. Extavour, Jason McKeever, Joseph H. Thywissen Harnessing the interactions in a BEC can lead to a number-squeezed state in a double-well system for low enough temperature. Starting with a single BEC trapped with an atom chip, we dress the atoms with a time-varying radio-frequency magnetic field which deforms this harmonic magnetic trap into a double-well potential, splitting the BEC in two halves. For further control of our potential we have added an optical dipole trap, creating a hybrid rf-dressed magnetic and optical potential, which allows us to alter the aspect ratio and thus dimensionality of the trap. The fluctuation in the relative atom number between the two wells is measured directly by counting the number of atoms in each well using time-of-flight absorption imaging for many splitting trials. The measured fluctuations are compared to the shot noise limit of binomial statistics, the expected result for an ideal gas. We intend to measure these fluctuations as a function of temperature and splitting time. [Preview Abstract] |
Wednesday, May 20, 2009 11:30AM - 11:42AM |
B3.00006: Coherent Control of Atomic Transport in Spinor Optical Lattices Brian Mischuck, Ivan Deutsch, Poul Jessen The coherent transport of atoms in optical lattices is essential for quantum computation and quantum simulations involving controlled collisions between the atoms. By applying the techniques of quantum control, we study protocols for evolving the motional wave function in the ground band using applied external fields, and well-designed lattices. Through a combination of spin dependent optical lattices, external gradients and microwave controls we can couple the atom's spin and motional degrees of freedom. Borrowing well developed ideas from the control of the atoms' spin allows us to explore the controllability of the spin and the spatial wavefunction jointly. We examine explicit constructions for synthesizing specific unitary maps. We also explore extensions for control of multiple particles or multiple bands. [Preview Abstract] |
Wednesday, May 20, 2009 11:42AM - 11:54AM |
B3.00007: An open quantum system study of atomic transport through time-dependent optical lattices Ronald Pepino, Dana Anderson, Murray Holland Atomic transport in a static optical lattice can only effectively occur between adjacent sites that are resonant. In our atomtronic schematic for a flip-flop, an immediate problem is that we require effective transport across energetic gaps. Such transport may be enhanced by modifying the lattice so that it has oscillatory coupling links between off-resonant sites. Here we discuss our results on the investigation of an optical lattice, with oscillatory coupling, connected to atomic reservoirs. [Preview Abstract] |
Wednesday, May 20, 2009 11:54AM - 12:06PM |
B3.00008: Interference of Two Molecular Bose-Einstein Condensates Christoph Kohstall, Stefan Riedl, Edmundo R. Sanchez Guajardo, Leonid A. Sidorenkov, Johannes Hecker Denschlag, Rudolf Grimm Interference of Bose-Einstein condensates (BECs) strikingly demonstrates the wave nature of matter. In this talk, we present the observation of interference of BECs made of molecules. The molecules are weakly bound dimers consisting of fermonic lithium atoms close to the 834-G Feshbach resonance. We condense these molecules in a double well potential. After release, the clouds overlap and we record interference fringes by absorption imaging. We explore different scenarios that affect the contrast of the interference fringes. (1) As expected, the fringes vanish above the critical temperature for BEC. (2) Contrast is also reduced with further increasing the interaction strength between the molecules. (3) The contrast changes periodically in time when we excite collective modes along the direction of imaging. [Preview Abstract] |
Wednesday, May 20, 2009 12:06PM - 12:18PM |
B3.00009: Implementation of a Bose Einstein condensate gyroscope John H.T. Burke, Charles A. Sackett Atom interferometers using Bose Einstein condensates have been demonstrated in linear geometries and have given promising results. These interferometers often use magnetic fields to confine the atoms and to support them against gravity. Here we demonstrate a two-dimensional interferometer in harmonic magnetic trap. Such an interferometer can take advantage of the Sagnac effect for rotation and make gyroscopic measurements. Compared to free space interferometers, much larger interactions times and enclosed areas can in principle be achieved, since the atoms are not falling. In our implementation, we induce the atoms to oscillate along one direction by displacing the trap center. We then split and recombine the atoms along an orthogonal direction, using an off-resonant optical standing wave. The combination of the two motions produces an enclosed area. We observe interferometric contrast for areas up to 0.05 square mm, a value limited by the oscillation amplitude that we can reliably impart and by the coherence time of our linear interferometer. [Preview Abstract] |
Wednesday, May 20, 2009 12:18PM - 12:30PM |
B3.00010: Ultra stable Matter wave gyroscopy using Orbital Angular Momentum induces atomic vortices Sulakshana Thanvanthri, Kishor Kapale, Jonathan Dowling It has long been known that matter-wave gyroscopes are orders of magnitude more sensitive that optical gyroscopes. The creation of matter-wave currents that can achieve such sensitivity is a continuing challenge. We propose the use of Optical Angular Momentum (OAM) induced vortices in Bose-Einstein Condensates (BECs) as an ideal candidate for quantum gyroscopy. Coherent superpositions of left and right rotating quantum states of a trapped condensate lead to an interference pattern that rotates when the trap rotates---in accordance with the Sagnac effect. Two important benchmarks for any gyroscope are it's sensitivity and stability. Atomic beam gyroscopes while having high sensitivity (10$^{-9}$s$^{-1}$ Hz$^{-1/2})$, also suffer from instability due to drift caused by difficulties in beam pointing and thermal expansion of atom beams. Since the sensitivity of a gyroscope utilizing the Sagnac effect is directly proportional to the area (or atomic beam path lengths) of the interferometer, there is trade-off between sensitivity and stability. While focusing on the new application of BEC vortex superposition, we find that it leads to a highly stable gyroscope. We will also comment on increasing the sensitivity of the gyroscope without sacrificing stability. [Preview Abstract] |
Wednesday, May 20, 2009 12:30PM - 12:42PM |
B3.00011: High sensitivity atom interferometry measurement of the atom-surface interaction Vincent Lonij, Alex Cronin, Steven Lepoutre, Haikel Jelassi, G\'erard Tr\'enec, Matthias B\"uchner, Jacques Vigu\'e Atom interferometers are renowned for their ability to measure phase shifts with great precision. We have improved an atom interferometer experiment to measure phase shifts due to Van der Waals atom-surface interactions with enough precision to detect an unusual velocity dependence. We used standing waves of light, as beam splitters, and a nano-fabricated structure as a phase shifter. One arm of the Mach-Zehnder atom interferometer was transmitted through a nano-structure with 50 nm wide openings. Phase shifts due to this nano-structure exhibit a velocity dependence that is different from other, previously known, dispersive elements in atom-optics, such as electric fields or dilute gasses. The phase shifts for lithium atoms in the velocity range 700 to 2000 m/s depends on velocity to the power -0.49 (whereas for electric fields the phase shift depends on velocity to the power -1, and a dilute gas causes phase shifts that undulate as a function of velocity). We discuss the origin of this newly observed velocity dependence, and the utility of this experiment to measure Van der Waals C3 coefficients. [Preview Abstract] |
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