Bulletin of the American Physical Society
2005 36th Meeting of the Division of Atomic, Molecular and Optical Physics
Tuesday–Saturday, May 17–21, 2005; Lincoln, Nebraska
Session L4: Laser Trapping and Cooling |
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Chair: Siu Au Lee, Colorado State University Room: Burnham Yates Conference Center Hawthorne |
Friday, May 20, 2005 1:30PM - 1:42PM |
L4.00001: Multidimensional laser cooing on broad and narrow line transitions Han Pu, Daniel Phalen, Su Yi We investigate theoretically the properties of multidimensional laser cooling of a $J_g=0 \leftrightarrow J_e=1$ dipole transition. When the transition linewidth is broad (i.e., much larger than the single photon recoil frequency), we can use the semi-classical method to calculate both analytically and numerically the light pressure forces in a two-dimension (2D) $\sigma^+$-$\sigma^-$ laser configuration. From the results, we identify unique multidimensional features that cannot be captured by a 1D theory. For the narrow line transition, we have to adopt a full quantum theory in which the atomic center-of-mass motion is also quantized. For the same 2D laser field, we use a Monte Carlo Wavefunction simulation to obtain the atomic momentum distribution. We expect that these calculations can provide guidance and motivation for current experimental efforts on laser cooling of alkaline earth atoms such as $^{88}$Sr, which possesses both broad and narrow line $J_g=0 \leftrightarrow J_e=1$ transitions. [Preview Abstract] |
Friday, May 20, 2005 1:42PM - 1:54PM |
L4.00002: Loading of NH molecules into a magnetic trap Laurens van Buuren, Wesley Campbell, Katsunari Enomoto, Michael Gottselig, Edem Tsikata, John Doyle Trapped polar molecules are predicted to be valuable for the study of new collective quantum effects, collisional processes, searches for T-violation, and as candidates for quantum bits in a robust quantum computer. We are working toward magnetic trapping of large numbers of NH radicals and evaporatively cooling them into the ultracold regime. Previously, we demonstrated that up to 10$^{12}$ NH molecules in their ro-vibrational and electronic ground-state can be produced in cryogenic buffer gas, using a beam loading technique [1]. Recently, this technique has been employed to load NH molecules into the bore of a superconducting magnet that runs entirely in vacuum. Free-flight molecular beam spectra show resolvable hyperfine splittings, and thermalization with cryogenic $^{4}$He buffer gas has been observed. The Zeeman splitting of the ground state, obtained in uniform field, agrees with the calculated spectra. Enhanced diffusion lifetimes for molecules in low field seeking states are observed at $\sim $ 2.5 K in the trapping field of the magnet operated in anti-Helmholtz configuration. The apparatus is currently being upgraded to operate below 500 mK in preparation for trapping and evaporative cooling. [1] D. Egorov \textit{et al.}, Eur. Phys. J. D 31 (2004) 307. [Preview Abstract] |
Friday, May 20, 2005 1:54PM - 2:06PM |
L4.00003: Magnetic trapping of the rare earths at milliKelvin temperatures: Pr, Nd, Tb, Dy, Ho, Er, and Tm Matthew Hummon, S. Charles Doret, Cindy Hancox, Linjiao Luo, John Doyle We report magnetic trapping of non-S-state rare-earth atoms (Pr, Nd, Tb, Dy, Ho, Er, and Tm). We observe a suppression of the interaction anisotropy in collisions of rare-earth atoms with atomic helium. The rare-earth atoms behave effectively like S- state atoms because their unpaired electrons are shielded by two outer filled electronic shells that are spherically symmetric. For each rare-earth species, $(0.2-2)\times 10^{12}$ atoms are trapped at densities of $(0.2-8) \times 10^{12}$~cm$^{-3}$ and temperatures of $\sim800$~mK. Our results suggest that the creation of quantum degenerate gases with non-S-state atoms in a magnetic trap is possible. [Preview Abstract] |
Friday, May 20, 2005 2:06PM - 2:18PM |
L4.00004: A general cold atomic and molecular beam source Stephen Maxwell, Nathaniel Brahms, Robert deCarvalho, David Patterson, John Doyle, David Glenn, Jessie Patricka, David DeMille We have demonstrated and characterized a high-flux beam source for cold, slow atoms or molecules. The desired species is vaporized using laser ablation, then cooled by thermalization in a cryogenic cell filled with $\sim1$~mTorr ($\sim2\times10^{15}$~cm$^{-3}$) of helium buffer gas. The beam is formed by particles exiting a 3~mm hole in the buffer gas cell. We have characterized the properties of the beam (flux, forward velocity, translational and internal temperatures) for both an atom (Na) and a molecule (PbO) under varying buffer gas density at a cell temperature of $\sim4$~K. We have constructed a magnetic guide to separate the beam from the helium buffer gas and show that the source could be used to load a variety of traps with a wide range of atoms and molecules. We also plan to reduce the cell temperature below 1~K with additional cryogenic refrigeration. [Preview Abstract] |
Friday, May 20, 2005 2:18PM - 2:30PM |
L4.00005: Symmetry breaking between two dynamic attractors in the parametrically-driven magneto-optical trap Kihwan Kim, Myoung-Sun Heo, Kihwan Lee, Kiyoub Jang, Wonho Jhe, Heung-Ryoul Noh Nowadays there have been lots of studies about fluctuation-induced transitions in equilibrium and far from equilibrium states. The double well structure of those systems is very similar to that of the box separated into two compartments of the same section. When there are diffusions which come from thermal noise or spontaneous emissions the populations of both states are nearly same except some fluctuations. Surprisingly, in our parametrically driven magneto-optical trap we have observed the symmetry of the number of atoms in both states was broken at certain experimental conditions. Because the atoms in each state are nearly non-interacting ideal gas, which is much different from the granular particles, symmetry breaking (SB) of populations in our system is very strange and need to understand the underlying mechanism. We have found the most important factor of SB was the total number of atoms in both states. The critical numbers have been measured experimentally. We also developed the theoretical model that explains the phenomena very well, and quantitative simulation results compared to the experiments. [Preview Abstract] |
Friday, May 20, 2005 2:30PM - 2:42PM |
L4.00006: ``T''-junction and multizone ion traps for scalable quantum computation W.K. Hensinger, D. Stick, M. Acton, K.-A. Brickman, D. Hucul, R. Kohn, J. Burress, J.A. Rabchuk, L. Deslauriers, P.J. Lee, P.C. Haljan, M. Madsen, K. Schwab, C. Monroe Trapping and shuttling trapped ions in complex multizone trap structures is critical for scaling the trapped ion quantum computer. We have demonstrated a 10-zone linear ion trap consisting of 49 electrodes in a three-layer geometry, and have shuttled cold Cd$^{+}$ ions between several zones. This trap features a ``T''-junction that should allow shuttling around a corner, possibly enabling the controlled swapping of ion positions within a linear crystal. This trap topology may be a fundamental building block towards implementing complex entanglement algorithms on an ion trap quantum computer. We will discuss several nontrivial aspects regarding the trapping region near the junction. We will also report progress on the operation of micron-scale planar ion traps fabricated from epitaxially-grown GaAs/AlGaAs layers and shaped with chemical and dry etching techniques. Development of this fabrication process may allow scaling elementary ion trap quantum processors to a large number of qubits. This work is supported by the U.S. National Security Agency and the Advanced Research and Development Activity under Army Research Office contract, and the National Science Foundation ITR Program. [Preview Abstract] |
Friday, May 20, 2005 2:42PM - 2:54PM |
L4.00007: Al\textsuperscript{+} Spectroscopy via Sympathetic Cooling and Quantum Information Transfer using Be\textsuperscript{+} T. Rosenband, P. O. Schmidt, Y. Kobayashi, C. Langer, W. M. Itano, S. A. Diddams, J. C. Bergquist, D. J. Wineland A single \textsuperscript{9}Be\textsuperscript{+} ion and a single \textsuperscript{27}Al\textsuperscript{+} ion are simultaneously trapped in order to perform optical spectroscopy on the Al\textsuperscript{+} ion. The ion pair is cooled near its motional ground state by laser-cooling the Be\textsuperscript{+} ion. We then apply spectroscopy pulses to interrogate the cold Al\textsuperscript{+} ion. The effect of these pulses is measured by transferring the Al\textsuperscript{+} internal quantum state to the Be\textsuperscript{+} hyperfine state with motional sideband laser pulses, where it is detected with high efficiency. This two-ion technique allows laser spectroscopy on cold ions that do not possess suitable transitions for laser cooling or state detection. We present results that demonstrate the effectiveness of this intra-species quantum information transfer. As a first application of the technique we have measured the \textsuperscript{27}Al\textsuperscript{+} \textsuperscript{1}S$_0 $ $\rightarrow$ \textsuperscript{3}P$_{1}(F=7/2)$ transition frequency to be $1,122,842,857,335(1)$kHz, which represents an improvement in accuracy over previous measurements by six orders of magnitude. * This work was supported by ONR and NIST [Preview Abstract] |
Friday, May 20, 2005 2:54PM - 3:06PM |
L4.00008: Progress toward an Ytterbium Optical Clock Zeb Barber, Chad Hoyt, Chris Oates, Leo Hollberg We report progress toward an optical frequency standard based on the narrow $^{1}$S$_{0} \quad \leftrightarrow \quad ^{3}$P$_{0}$ transition of odd ytterbium isotopes at 578 nm. Recoil-free spectroscopy of neutral atoms tightly confined to an optical lattice could support fractional frequency instabilities of 10$^{-18 }$in one second. Loading the lattice from cold atomic clouds will provide large numbers of atoms and good signal-to-noise. ~We present initial results of two stage cooling and trapping experiments. ~The first stage consists of collecting and cooling atoms from an atomic beam using the broad 399 nm line and InGaN diode lasers. Second stage cooling to $\sim $50 mK is performed on the 556 nm intercombination line using frequency-doubled light from a narrow linewidth infrared fiber laser. A single pass of 1 W fundamental power through a periodically-poled lithium niobate crystal produces $\sim $30 mW of 556 nm light. With a fast linewidth of $\sim $60 kHz, locking the laser frequency to the atomic beam fluorescence is sufficient for cooling on this $\sim $180 kHz transition. This all-solid-state laser architecture enables simple and robust production of large numbers of atoms at ultracold temperatures for precision spectroscopy in a lattice. [Preview Abstract] |
Friday, May 20, 2005 3:06PM - 3:18PM |
L4.00009: Variable electrode micron-scale ion trap Louis Deslauriers, Jie Li, Kathy-Anne Brickman, Paul Haljan, Winni Hensinger, Patricia Lee, Martin Madsen, Jim Rabchuk, Dan Stick, Christopher Monroe We describe a novel ion trap geometry formed with two needle-like electrodes mounted on linear translation stages, allowing for the trap electrode spacing to be varied in-situ over a range of separations between 20-1000$\mu $m. The variable electrodes may allow for the systematic study of a host of ion trap properties at the micron scale, such as electrode surface noise and ion heating. The results of this study may impact the design and construction of future ion trapping apparatus relevant to quantum information applications, and the open geometry of the trap may be suitable for interfacing cold trapped ions with other quantum systems. This work is supported by the U.S. National Security Agency and the Advanced Research and Development Activity under Army Research Office contract, and the National Science Foundation ITR Program. [Preview Abstract] |
Friday, May 20, 2005 3:18PM - 3:30PM |
L4.00010: Toward Quantum Degeneracy in Strontium S.B. Nagel, Y.N. Martinez, P.G. Mickelson, A.D. Saenz, Y.C. Chen, T.C. Killian We present recent work toward achieving quantum degeneracy in Strontium. A MOT operating on the strong ($\Gamma $= (2$\pi $ )* 32 MHz), $^{1}$S$_{0}$ $\rightarrow ^{1}$P$_{1 }$transition cools 2.5*10$^{8}$ atoms to 2 mK in the first stage of cooling. Then, approximately 40{\%} of these atoms are transferred to a MOT operating on the weaker ($\Gamma $= (2$\pi $ )* 7.5 kHz) $^{1}$S$_{0 }\rightarrow ^{3}$P$_{1}$ intercombination transition, further cooling the sample to 5 $\mu $K. Here we discuss transferring this sample to a dipole trap and using evaporative cooling techniques to reach quantum degeneracy. [Preview Abstract] |
Friday, May 20, 2005 3:30PM - 3:42PM |
L4.00011: Critical Slowing Down Near Bifurcation Point in Parametrically-driven Magneto-optical Trap Myoung-Sun Heo, Kihwan Kim, Kiwhan Lee, Wonho Jhe, Heung-Ryoul Noh, Robin Kaiser Equilibrium phase transitions have been studied extensively over the last five decades. But on the other hand, critical phenomena in systems far from equilibrium are still challenging subjects and known to have some correspondences with those in equilibrium. And In this case the system of interest is usually nonlinear for it reveals extra abundant features such as bifurcation and chaos including non-equilibrium phase transition. Our parametrically driven magneto-optical trap of neutral atoms has these natures; it is an anharmonic trap and induces Hopf bifurcation. For the first step to study non-equilibrium phase transition we focused on the critical slowing down of the relaxation time occurring near bifurcation point. Experimentally we have seen it by measuring the time taken for atoms to move from non-steady to steady state, and obtained the dynamic critical exponent. Estimated values from Monte Carlo simulation were also compared with above results. [Preview Abstract] |
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