Bulletin of the American Physical Society
42nd Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 56, Number 5
Monday–Friday, June 13–17, 2011; Atlanta, Georgia
Session U2: Matter Wave Interferometry |
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Chair: John Burke, Air Force Research Laboratory Room: A602 |
Friday, June 17, 2011 10:30AM - 10:42AM |
U2.00001: Coherent control of atomic motion in an optical lattice for precise measurements of gravity Marco Giacinto Tarallo, Andrea Alberti, Nicola Poli, Marco Prevedelli, Fu-Yuan Wang, Guglielmo M. Tino Coherent control of atomic motion inside an optical lattice allows precise measurement of forces by means amplitude-modulation (AM) driven resonant tunneling. We report about the recently-performed high precision measurements of gravitational acceleration using ultracold strontium atoms trapped in an AM driven vertical optical lattice.\footnote{A. Alberti \textit{et al.}, New J. Phys. 12, 065037 (2010).} We reached an uncertainty $\Delta g/g \approx 10^{-7}$ by measuring at the 5$^{th}$ harmonic of the Bloch oscillation frequency.\footnote{N. Poli \textit{et al.}, Phys. Rev. Lett. 106, 038501 (2011).} We analyzed the systematic effects induced by the trapping optical lattice, such as the intensity gradient and the lattice frequency-induced shift. We accurately measured the lattice frequency by means of an fiber link with a home-made frequency comb. The value of $g$ obtained with this microscopic quantum system is consistent with the one we measured with a classical absolute gravimeter. Short-distance measurements of gravity near dielectric surfaces are discussed. These results prospect a new way to new tests of gravity at micrometer scale. [Preview Abstract] |
Friday, June 17, 2011 10:42AM - 10:54AM |
U2.00002: Atom interferometry with large momentum transfer Shau-Yu Lan, Pei-Chen Kuan, Brian Estey, Holger M\"uller The sensitivity of light-pulse atom interferometers can be greatly improved by large momentum transfer (LMT) beam splitters and long interrogation times. Large momentum space separation $\Delta $p between two interferometric arms result in increased phase shift proportional to $\Delta $p or even ($\Delta $p)$^{2}$, and therefore leads to superior tools for precision measurements. ``BBB'' beam splitters, using high order Bragg diffraction combined with Bloch oscillations, have already been demonstrated and are scalable, as their momentum transfer is not limited by the available laser power. By running an additional conjugate interferometer at the same time, noises common to both interferometers can be eliminated. We will present our work aiming at further improvements, which would allow applications requiring extremely large enclosed areas, such as test of the Einstein equivalence principle, measurements of fundamental constants, or searching for new gravitational effects. [Preview Abstract] |
Friday, June 17, 2011 10:54AM - 11:06AM |
U2.00003: Inertially sensitive light pulse atom interferometry at short interrogation times David Butts, Krish Kotru, Joseph Kinast, Brian Timmons, Richard Stoner The use of cold atoms in any sensor operating in a dynamic environment requires that the measurement cycle be conducted before the atom cloud escapes the interaction region. Under multiple-g accelerations, it is desirable to complete measurements in millisecond time scales, especially when laser beams are used to interrogate the atoms. We demonstrate high-contrast atom interferometry in a small vapor cell using stimulated Raman transitions at millisecond interrogation times. Laser-cooled cesium atoms are interrogated with a sequence of three Raman pulses and the interferometer phase is read out in the same region in which the atoms are trapped. Our system achieved over 70{\%} contrast with a Doppler insensitive interferometer and over 40{\%} contrast with a Doppler sensitive interferometer, in an environment normally considered adverse to high-contrast atom interferometry (e.g., no retroreflector stabilization and no magnetic shielding). We also report evidence of a potential inertial sensor error mechanism and present a method for inertial sensor scalefactor enhancement at short interrogation times. [Preview Abstract] |
Friday, June 17, 2011 11:06AM - 11:18AM |
U2.00004: Momentum-space engineering of Bose-Einstein condensates Brandon Benton, Jeffrey Heward, Mark Edwards, Charles Clark We show how the momentum distribution of gaseous Bose--Einstein condensates can be shaped by applying a sequence of standing--wave laser pulses. We present a theory, whose validity was demonstrated in an earlier experiment,\footnote{L.\ Deng, et al., PRL {\bf 83}, 5407 (1999)} of the effect of a two--pulse sequence on the condensate wave function in momentum space. We generalize the previous result to the case of $N$ pulses having arbitrary pulse areas and separated by arbitrary time intervals and show how these parameters can be engineered to produce a desired final momentum distribution. We find that several momentum distributions, such as single--state distributions or a range of momentum states which are important in initial state selection in atom--interferometry applications, can be engineered with high fidelity with two or three pulses. We present several examples of such distributions and show how the fidelity improves as more pulses are added. We also give some ideas of how these momentum distributions can be applied to atom interferometry. [Preview Abstract] |
Friday, June 17, 2011 11:18AM - 11:30AM |
U2.00005: Atomic Interaction Effects in Precision Bose-Einstein Condensate Interferometry Alan O. Jamison, J. Nathan Kutz, Vladyslav V. Ivanov, Anders H. Hansen, Alexander Khramov, William H. Dowd, Subhadeep Gupta We propose to measure $h/m$ and $\alpha$ to sub-ppb precision with a Bose-Einstein condensate (BEC) interferometer. Since atomic interactions are among the most pernicious systematic effects in a BEC, we present theoretical tools for predicting and reducing the effects of atomic interactions in a broad class of BEC interferometry experiments. To address mean-field shifts during free propagation, we derive a robust scaling solution that reduces the three-dimensional Gross-Pitaevskii equation to a set of three simple differential equations valid for any interaction strength. To model the other common components of a BEC interferometer---condensate splitting, manipulation, and merging---we generalize the slowly-varying envelope reduction, providing both analytic handles and dramatically improved simulations. Applying these tools to a contrast interferometry setup, we demonstrate the potential for a sub-ppb determination of $h/m$ and $\alpha$, even for atomic species with relatively large scattering lengths. These tools can make BEC interferometry a viable scheme for a broad class of precision measurements. Our experimental progress will be reported. [Preview Abstract] |
Friday, June 17, 2011 11:30AM - 11:42AM |
U2.00006: Progress towards a test of the universality of free fall using a $^6$Li/$^7$Li atom interferometer Geena Kim, Paul Hamilton, Dennis Schlippert, Holger M\"{u}ller Many extensions of the standard model of physics, e.g. Kaluza- Klein theories, string theory, and supersymmetry, introduce new interactions which lead to violations of the universality of free fall (UFF). We discuss progress towards a proposed dual matter- wave interferometer which will measure the differential acceleration of $^6$Li and $^7$Li atoms. The difference in the baryon-to-lepton number ratio and nuclear binding energy for these two species gives higher sensitivity than many other proposed tests of UFF. However, the high thermal velocity of lithium, due to its light mass, leads to large atom loss in a traditional interferometer. To overcome this, an optical lattice will confine the lithium atoms during the interferometry sequence. Manipulations of the optical lattice will split the matter waves and hold the arms of the interferometer apart for many seconds in a compact apparatus. This large separation time leads to an anticipated accuracy of $10^{-14}$ g in the differential acceleration. We discuss possible systematic effects and show that many will be common mode to the two species. Finally we will review technical progress on the experiment and recent investigations into novel cooling techniques for lithium. [Preview Abstract] |
Friday, June 17, 2011 11:42AM - 11:54AM |
U2.00007: Design for a compact CW atom laser Erik Power, Georg Raithel We present a design for a compact continuous-wave atom laser on a chip. A 2D spiral-shaped quadrupole guide is formed by two 0.5 mm x 0.5 mm wires carrying 5 A each embedded in a Si wafer; a 1.5 mm x 0.5 mm wire on the bottom layer carries -10 A, producing a horizontal $\mathbf{B}$-field that pushes the guiding channel center above the chip surface. The center-to-center separation between the top wires is varied from 1.6 mm at the start of the guide to 1 mm at the end, decreasing the guide height from $\sim 500~\mu\textrm{m}$ to $\sim 25~\mu\textrm{m}$ above the surface as the atoms travel the 70 cm-long guide. The magnetic gradient of the guiding channel gradually increases from $\sim 100~G/\textrm{cm}$ to $\sim 930~G/\textrm{cm}$. These features result in continuous surface adsorption evaporative cooling and progressive magnetic compression. Spin flip losses are mitigated by a solenoid sewn around the guide to produce a longitudinal $\mathbf{B}$-field. $^{87}\textrm{Rb}$ atoms are gravitationally loaded into the guide. A far off-resonant light shift barrier at the end of the guide traps the atoms and allows formation of a BEC. Tuning the barrier height to create a non-zero tunneling rate equal to the loading rate completes the implementation of a CW atom laser. Two options for atom interferometry are implemented on the first-generation chip (matter-wave Fabry-Perot interferometer and guide-based Mach-Zehnder interferometer). Current construction status and challenges will be discussed, along with preliminary results. [Preview Abstract] |
Friday, June 17, 2011 11:54AM - 12:06PM |
U2.00008: Atom guidance in the TE$_{01}$ donut mode of a large-core hollow fiber J.A. Pechkis, F.K. Fatemi We report on our progress towards low-light-level nonlinear optics experiments by optically guiding atoms in the TE$_{01}$ donut mode of a hollow fiber. Atoms are transported over 12 cm from a ``source'' magneto-optical trap (MOT) through a 100-$\mu$m-diameter hollow fiber and are recaptured by a ``collection'' MOT situated directly below the fiber. For red-detuned guiding, we compare the guiding efficiency between the fundamental (Gaussian-like) mode and this donut mode, which has a larger guiding area but lower peak intensity. We also discuss our progress in transporting atoms in the dark core of this mode using blue-detuned light, which has more stringent constraints to atom guidance compared to red-detuned light. [Preview Abstract] |
Friday, June 17, 2011 12:06PM - 12:18PM |
U2.00009: Enhanced atom interferometry through quantum information science Mark Edwards, Brandon Benton, Michael Krygier, Charles Clark New designs for atom interferometers can be inspired by quantum information science (QIS). QIS--inspired atom interferometer (AI) designs have the potential for producing AIs with enhanced sensitivity and robustness. We compare the sensitivity of a standard Mach--Zehnder (M--Z) Bragg AI with an AI whose design is based on the idea of decoherence--free subspaces (DFS).\footnote{D.A.\ Pushin, M.\ Arif, and D.G.\ Cory, Phys.Rev.\ A {\bf 79}, 053635 (2009)} We studied the performance of both atom interferometers using an enhanced version of a previously developed Bragg interferometer prototyping model.\footnote{S.E.\ Simsarian et al., Phys.\ Rev.Lett.\ {\bf 85}, 2040 (2000).} This model approximates the effect on the condensate of multiple Bragg pulses separated by time delays using two elements: the effect of a single pulse and condensate evolution between pulses. The overall effect is rapidly approximated by following the steps of the interferometric process. We describe this model and then present the comparison of the performance of the M--Z interferometer with that of the DFS--inspired interferometer. [Preview Abstract] |
Friday, June 17, 2011 12:18PM - 12:30PM |
U2.00010: Arbitrarily shaped high-coherence electron bunches from ultracold plasma R.E. Scholten, A.J. McCulloch, D.V. Sheludko, M. Junker, S.C. Bell, S.D. Saliba, K.A. Nugent Sources of inherently cold electrons extracted from laser cooled atoms have the potential to transform electron imaging. These sources promise both the spatial coherence and high current required for picosecond molecular scale imaging. Here we demonstrate arbitrary and real-time control of electron bunch shape and thus realise a major step towards alleviation of electron source brightness limitations due to Coulomb explosion. The ability to dynamically shape the electron source itself and to observe that pattern in the propagated electron bunch provides a remarkable experimental demonstration of the intrinsically high spatial coherence of a cold electron source. [Preview Abstract] |
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