Bulletin of the American Physical Society
2006 37th Meeting of the Division of Atomic, Molecular and Optical Physics
Tuesday–Saturday, May 16–20, 2006; Knoxville, TN
Session K3: Laser Cooling and Trapping |
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Chair: Phillip Gould, University of Connecticut Room: Knoxville Convention Center 301D |
Thursday, May 18, 2006 8:00AM - 8:12AM |
K3.00001: Generation of large clouds of ultracold metastable helium S. Charles Doret, Scott V. Nguyen, Colin B. Connolly, Robert A. Michniak, Wolfgang Ketterle, John M. Doyle Metastable helium is buffer-gas cooled, magnetically trapped and evaporatively cooled in large numbers. $10^{11}$ $^{4}He^{*}$ atoms are trapped at an initial temperature of 400 mK and evaporatively cooled into the ultracold regime, resulting in a cloud of $2x10^{9}$ atoms at 1.4 mK. Efficient evaporation indicates low collisional loss for $^{4}He^{*}$ in both the ultracold and multi-partial-wave regime, in agreement with theory. Further evaporative cooling to quantum degeneracy should be attainable after transfering the cloud to an Ioffe-Pritchard trap and implementing RF evaporation. [Preview Abstract] |
Thursday, May 18, 2006 8:12AM - 8:24AM |
K3.00002: Laser cooling of trapped ytterbium ions with an ultraviolet diode laser David Kielpinski, Marko Cetina, Jonathan Cox, Franz Kaertner We demonstrate an ultraviolet diode laser system for cooling of trapped ytterbium ions. The laser power and linewidth are comparable to previous systems based on resonant frequency doubling, but the system is simpler, more robust, and less expensive. We use the laser system to cool small numbers of ytterbium ions confined in a linear Paul trap. From the observed spectra, we dudce final temperatures $< 270$ mK. [Preview Abstract] |
Thursday, May 18, 2006 8:24AM - 8:36AM |
K3.00003: Magneto-optical trapping of erbium atoms: trapping without repumping J.J. McClelland, J.L. Hanssen We will discuss recent observations of a robust magneto-optical trap (MOT) for erbium atoms that operates without repumping, despite many ``optical leaks'' from the excited state. The surprisingly high trap population of over $10^6$ atoms is explained by a novel recycling mechanism, in which (1) excited atoms decay to metastable states that are confined by the quadrupole magnetic field of the MOT because of their high spin, (2) a large fraction of these metastables eventually decay to the ground state, remaining in the magnetic trap, and (3) these cold ground state atoms are recaptured by the MOT. A simple rate equation model of this recycling mechanism shows excellent agreement with measurements of the time dependence of MOT fluorescence, indicating validity of the model. In addition to showing it is possible to trap atoms with optical leaks without repumping, this demonstration of an erbium MOT opens a wide range of new possibilities for practical applications and fundamental studies with cold atoms, impacting such diverse fields as quantum optics, quantum information processing, ultra-precise frequency standards, quantum degenerate gases, cold collisions, trace atom detection, nanostructure fabrication, and atom-by-atom doping of materials. [Preview Abstract] |
Thursday, May 18, 2006 8:36AM - 8:48AM |
K3.00004: Reabsorption Mitigation Using Frequency-Broadened Light Anthony Gorges, Ansel Foxley, David French, Jacob Roberts The reabsorption of photons in optically thick gases of ultracold atoms presents a critical limitation to the efficient optical pumping of these gases. In particular, this limitation severely hampers many laser-based cooling schemes. We present measurements that show that the reabsorption probability can be reduced by using light with a broad frequency spectrum. This reduction is expected since reabsorption depends on a two-photon spontaneous Raman scattering processes that involves a spontaneously emitted photon and a pump photon with the same frequency, and in a sufficiently broad source this condition is met for only a fraction of the light. In one set of measurements, we observed the reduction in reabsorption by comparing the amount of heat imparted to ultracold $^{85}$Rb atoms in an optically thick cloud by two independent lasers as compared to the heat imparted by these lasers individually while keeping the total intensity constant. Also, experiments to reduce the reabsorption with a single laser whose frequency is broadened using an AOM and multiple RF drive frequencies were also performed. The results suggest that the frequency broadening of an optical pumping laser is beneficial for the efficient optical pumping of optically thick ultracold gases. [Preview Abstract] |
Thursday, May 18, 2006 8:48AM - 9:00AM |
K3.00005: Magic wavelengths for the $ns-np$ transitions in alkali-metal atoms Bindiya Arora, M.S. Safronova, Charles W. Clark Extensive calculations of the electric-dipole matrix elements in alkali-metal atoms are conducted using the relativistic all-order method. This approach is a linearized version of the coupled-cluster method, which sums infinite sets of many-body perturbation theory terms; it is one of the most accurate methods currently being used in atomic structure calculations. All allowed transitions between four lowest $s, p_{1/2}, p_{3/2}$ states and three lowest $d_{3/2}, d_{5/2}$ states are considered and an estimate of the accuracy of the calculation is conducted. The results are used for the high-precision calculation of the frequency-dependent polarizabilities of the alkali-atoms in excited states. We find ``magic'' wavelengths in alkali-metal atoms for which the $ns$ and $np_{1/2,3/2}$ atomic levels have the same ac-Stark shifts, which facilitates state-insensitive optical cooling and trapping. [Preview Abstract] |
Thursday, May 18, 2006 9:00AM - 9:12AM |
K3.00006: Cold atom confinement in hollow laser beams with high charge number Fredrik Fatemi, Mark Bashkansky We investigate experimentally and numerically the focusing properties of hollow laser beams suitable for cold atom confinement, and use these properties to confine atoms in a blue-detuned optical trap. A Gaussian beam modified by a spatial light modulator to have an azimuthally varying phase exp(i$n\phi )$ creates a hollow laser beam with charge number $n$. When focused through an imaging lens, these hollow beams are found to attain peak intensity farther from the focal plane as $n$ is increased. We demonstrate the properties of these beams by confining atoms in a box potential with steep intensity walls formed by crossed blue-detuned hollow beams with high charge number. [Preview Abstract] |
Thursday, May 18, 2006 9:12AM - 9:24AM |
K3.00007: Bichromatic transverse cooling and guiding in hollow beams Frank A. Narducci Optical guiding of atoms, especially in hollow core fibers, usually consists of a far off resonant field so that the effects of spontaneous emission can be minimized yet the dipole force can be utilized. However, bichromatic fields driving coherent population trapping can shut off the spontaneous emission. In this paper, I analyze the possibility of using bichromatic fields for transverse cooling, confinement and guiding in hollow light tubes and compare the results to the single field case. Experimental progress will be discussed. [Preview Abstract] |
Thursday, May 18, 2006 9:24AM - 9:36AM |
K3.00008: Open-Channel fluorescence imaging of atoms in a high-gradient magnetic guide Rahul Mhaskar, Spencer Olson, Georg Raithel We present a novel method of imaging atomic distributions in high-gradient trapping fields. A probe laser tuned to an open transition is used to illuminate the atomic distribution. The resultant fluorescence yield per atom is largely fixed throughout the trap volume, independent of the trapping field. This enables a reliable conversion of fluorescence images into atomic-density profiles. The method is applied to measure distributions of $^{87}$Rb atoms in a high-gradient (2.7~kGauss/cm) magnetic atom guide. We characterize the parameters for which the open-transition imaging method performs best. Quantum Monte Carlo simulations are used to test the underlying assumptions of the method. The method can be applied to image cold atoms trapped by permanent fields, continuously trapped or guided atoms, and species that do not have a suitable closed transition. [Preview Abstract] |
Thursday, May 18, 2006 9:36AM - 9:48AM |
K3.00009: Scaling and Suppression of Heating in an Adjustable Ion Trap Steven Olmschenk, Louis Deslauriers, Dan Stick, Winfried Hensinger, Jon Sterk, Christopher Monroe One of the major hurdles in the realization of large entangled states among trapped ions is anomalous heating of trapped ion motion [1].~ We implement a novel rf ion trap featuring moveable electrodes that has enabled a controlled investigation of this motional decoherence.~ First, we characterize heating as a function of electrode proximity, related to the geometry of noisy potentials on the electrode surface. Second, we cool the electrodes via contact with a liquid nitrogen reservoir and observe that the decoherence rate is suppressed by an order of magnitude.~ The insight gained through these experiments may have relevance to scaling the ion trap quantum information processor. 1.~ Q. A. Turchette, et. al., Phys. Rev. A 61, 063418 (2000). [Preview Abstract] |
Thursday, May 18, 2006 9:48AM - 10:00AM |
K3.00010: Ion Trap in a Semiconductor Chip Dan Stick, Winfried Hensinger, Steven Olmschenk, Martin Madsen, Keith Schwab, Chris Monroe Current ion trap research is largely driven by the quest to build a quantum information processor, where quantum bits of information are stored in individual atomic ions and connected through a common interaction with their collective motion$^{1}$. Semiconductor processing techniques, particularly photolithography on integrated structures, allows the fabrication of ion traps which can host large numbers of qubits and shuttle ions between many separated trapping zones$^{2}$. Here we discuss the trapping of a single ion in an rf Paul trap fabricated on a monolithic GaAs heterostructure. Of particular note is that this trap is integrated on a chip and does not require any alignment or manual assembly. In addition to discussing the processing steps and electrical characteristics of the trap, we report measurements of heating of a single ion in the trap$^{3}$. Work supported by the Disruptive Technology Office under Army Research Office contract \newline and the National Science Foundation ITR Program. 1. Cirac, J. I. {\&} Zoller, P. Quantum computations with cold trapped ions. \textit{Phys Rev. Lett.} \textbf{74}, 4091-4094 (1995). 2. Kielpinski, D., Monroe, C., Wineland D. J. Architecture for a large scale ion trap quantum computer. \textit{Nature} \textbf{417}, 709-711 (2002). 3. D. Stick, W. K. Hensinger, S. Olmschenk, M. J. Madsen, K. Schwab, C. Monroe. \textit{Nature Phys.} \textbf{2}, 36-39 (2006). [Preview Abstract] |
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