Bulletin of the American Physical Society
43rd Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 57, Number 5
Monday–Friday, June 4–8, 2012; Orange County, California
Session H5: Unconventional Atom Trap Geometries |
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Chair: Trey Porto, NIST Room: Garden 3 |
Wednesday, June 6, 2012 10:30AM - 10:42AM |
H5.00001: Quantized decay of high charge superflow in an annular BEC Scott Beattie, Stuart Moulder, Rob Smith, Naaman Tammuz, Zoran Hadzibabic We have studied superfluid flow using a holographically generated Laguerre-Gauss (LG) beam to trap and rotate Bose-Einstein condensates of $^{87}$Rb atoms. ~The LG beam allows phase windings with arbitrary choice of charge to be imprinted on the atomic cloud. The transferred angular momentum can be measured both interferometrically and mechanically. We have observed high charge vortices persist for long times ($>$40s) and decay stochastically in a quantized fashion. We also discuss our latest results on the application of artificial gauge potentials to our annular BEC. [Preview Abstract] |
Wednesday, June 6, 2012 10:42AM - 10:54AM |
H5.00002: Driving phase slips in an annular Bose-Einstein condensate with a rotating weak link Kevin C. Wright, R.B. Blakestad, C.J. Lobb, W.D. Phillips, G.K. Campbell We have created a toroidal atomic Bose Einstein condensate, stirred by a rotating barrier potential which creates a weak link. Varying the rotation rate and critical current of the weak link, we observe two main regimes of behavior. At low rotation rates, and small critical current, we observe phase slips between well-defined persistent current states. At higher rotation rates, vortices penetrate into the bulk of the condensate, and discrete phase slips between well-defined persistent current states no longer occur. The response of the condensate can be compared to that of superconducting ring with a weak link in an external magnetic field. [Preview Abstract] |
Wednesday, June 6, 2012 10:54AM - 11:06AM |
H5.00003: Decay of a superfluid current of ultra-cold atoms in a toroidal trap Amy Mathey, Charles W. Clark, Ludwig Mathey Using a numerical implementation of the truncated Wigner approximation, we simulate the experiment reported by Ramanathan {\it et al.}, Phys. Rev. Lett. \textbf{106}, 130401 (2011), in which a Bose-Einstein condensate is created in a toroidal trap and set into rotation via a Gauss-Laguerre beam. A potential barrier is then placed in the trap to study the decay of the superflow. We find that the current decays via thermally activated phase slips, which can also be visualized as a vortex crossing the barrier region in radial direction. Adopting the notion of critical velocity used in the experiment, we determine it to be lower than the local speed of sound at the barrier. This result is in agreement with the experimental findings, but in contradiction to the predictions of the Gross-Pitaevskii equation. [Preview Abstract] |
Wednesday, June 6, 2012 11:06AM - 11:18AM |
H5.00004: Cylindrical vector modes in tapered optical fibers for atom nanotraps Fredrik K. Fatemi, Jonathan E. Hoffman, Sylvain Ravets, Guy Beadie, Luis A. Orozco, Steven L. Rolston Atoms confined to evanescent-field traps or lattices near tapered optical fibers are strongly coupled to photons propagating through the fiber. This strong coupling is ideal for quantum technologies and sensors. Previously, light propagation and strong atom-photon interactions have been demonstrated in fibers with submicron diameters, small enough to admit only the HE$_{11}$ mode. Higher order cylindrical vector modes, which have azimuthally-varying polarization profiles, open another set of trapping geometries in fibers with diameters slightly above the HE$_{11}$ cutoff value. In this work, we discuss propagation experiments in tapered fibers that allow the first excited family of modes. We have observed stable transmission of the TE$_{01}$, TM$_{01}$, and HE$_{21}$ modes in 1.2-micron-diameter fiber, currently with 25{\%} throughput. Transmitted power and beam profiles monitored during the drawing process show interesting power exchange between core and cladding modes, and by adjusting the drawing parameters we have experimentally probed the propagation behavior. Work supported by ONR, ARO, the Fulbright Foundation and the NSF through the PFC at JQI. [Preview Abstract] |
Wednesday, June 6, 2012 11:18AM - 11:30AM |
H5.00005: Low photon scattering rates and large optical depths of atoms in donut modes of hollow core optical fibers Joseph A. Pechkis, Fredrik K. Fatemi We have guided cold rubidium atoms in blue-detuned hollow optical modes of a hollow fiber. These higher order modes allow large optical depth, low scattering rates, and efficient use of guide laser power. Atoms are transported through a 3-cm-long hollow fiber with a 100 micron diameter using the first three optical modes of the fiber. We compare guiding properties in the red-detuned, fundamental HE$_{11}$ mode with the blue-detuned TE$_{01}$ (first order) and HE$_{12}$ (second order) modes. Using guide laser powers below 50 mW and detunings below 1.5 nm, we have directly measured recoil scattering rates in the three different guides and found that atoms in the HE$_{12}$ mode typically have a 10x lower recoil scattering rate compared to the red-detuned HE$_{11}$ mode for equal guide peak intensity. Furthermore, we have observed optical depths of $\sim$20 for the blue-detuned guides with recoil scattering rates below 10 Hz. We will discuss our ongoing experiments using the atoms in these guides. This work supported by the Office of Naval Research and the Defense Advanced Research Projects Agency. [Preview Abstract] |
Wednesday, June 6, 2012 11:30AM - 11:42AM |
H5.00006: Acoustic Spectroscopy in a Toroidal Bose-Einstein Condensate G. Edward Marti, Ryan Olf, Gabe Dunn, Dan Stamper-Kurn Sound waves in a Bose-Einstein condensate are long-lived excitations that probe the atomic density distribution. Measuring the frequencies, damping rates, and mode structures reveal perturbations of the atomic density and the underlying distortion of the trap. We excite azimuthal standing sound waves in a Bose-Einstein condensate that fills an all-optical toroidal trap. Frequency spectroscopy measures the speed of sound in the toroidal channel and corrugations of the potential. We demonstrate a proof-of-concept sonic rotation sensor that is fairly insensitive to errors in the optical potential and density effects. [Preview Abstract] |
Wednesday, June 6, 2012 11:42AM - 11:54AM |
H5.00007: Berry-gauge tuned Bose-Einstein condensate gyroscope Rudra Kafle, Eddy Timmermans If stable, the many-body ground state of a dilute gas of ultra-cold, bosonic atoms occupying a superposition of two internal states is a Bose-Einstein condensate(BEC)of effective spin $1/2$ bosons. The superfluid BEC dynamics admits long-lived quantized vortex states in which the complex phase of the superfluid order parameter, which we call the charge phase, undergoes an integer number of $2\pi$ windings along a multiply connected path - a closed trajectory that encloses a region in which the superfluid density vanishes. In response to an overall rotation of the ring, a quantization event can occur which can be used to sense rotation. Unfortunately, the sensitivity of the ring BEC gyroscope would be limited as the quantization event sets in at a rotation frequency that is not as low as the frequencies measured by other devices such as ring laser gyroscopes. We show that the recently realized synthetic magnetic fields, in which the controlled position dependence of the spin results in an effective gauge field, can tune the BEC ring gyroscope to trigger a quantization event at much smaller rotation frequency. In addition, the effective gauge field can undergo its own quantization events in which the spin vector undergoes an integer number of $2\pi$ or $4\pi$ windings. [Preview Abstract] |
Wednesday, June 6, 2012 11:54AM - 12:06PM |
H5.00008: Fundamental Atomtronic Circuit Elements Jeffrey Lee, Brian McIlvain, Christopher Lobb, Wendell T. Hill III Recent experiments with neutral superfluid gases have shown that it is possible to create atomtronic circuits analogous to existing superconducting circuits. The goals of these experiments are to create complex systems such as Josephson junctions. In addition, there are theoretical models for active atomtronic components analogous to diodes, transistors and oscillators. In order for any of these devices to function, an understanding of the more fundamental atomtronic elements is needed. Here we describe the first experimental realization of these more fundamental elements. We have created an atomtronic capacitor that is discharged through a resistance and inductance. We will discuss a theoretical description of the system that allows us to determine values for the capacitance, resistance and inductance. The resistance is shown to be analogous to the Sharvin resistance, and the inductance analogous to kinetic inductance in electronics. This atomtronic circuit is implemented with a thermal sample of laser cooled rubidium atoms. The atoms are confined using what we call free-space atom chips, a novel optical dipole trap produced using a generalized phase-contrast imaging technique. We will also discuss progress toward implementing this atomtronic system in a degenerate Bose gas. [Preview Abstract] |
Wednesday, June 6, 2012 12:06PM - 12:18PM |
H5.00009: Conduction of Ultracold Fermions Through a Mesoscopic Channel David Stadler, Jean-Philippe Brantut, Jakob Meineke, Sebastian Krinner, Tilman Esslinger In a mesoscopic conductor electric resistance is detected even if the device is defect-free. We engineer and study a cold-atom analog of a mesoscopic conductor. It consists of a narrow channel connecting two macroscopic reservoirs of fermions that can be switched from ballistic to diffusive. We induce a current through the channel and find ohmic conduction, even for a ballistic channel. An analysis of in-situ density distributions shows that in the ballistic case the dissipation is localized at the entrance and exit of the channel, revealing the presence of contact resistance. In contrast, a diffusive channel with disorder displays dissipation over the whole channel. Our approach opens the way towards quantum simulation of mesoscopic devices with quantum gases. [Preview Abstract] |
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