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 B5: Cold Plasmas and Optical Lattices |
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Chair: Michael S. Chapman, Georgia Institute of Technology Room: Burnham Yates Conference Center Arbor |
Wednesday, May 18, 2005 10:30AM - 10:42AM |
B5.00001: Electron Screening Effects in a Strongly Coupled Ultracold Neutral Plasma C.E. Simien, Y.C. Chen, S. Laha, P. Gupta, Y.N. Martinez, P.G. Mickelson, S.B. Nagel, T.C. Killian We study equilibration of strongly coupled ions in an ultracold neutral plasma produced by photo-ionizing laser-cooled and trapped atoms. By varying the electron temperature, we show that electron screening modifies the equilibrium ion temperature. Even with few electrons in a Debye sphere, the screening is well described by a model using Yukawa ion-ion potential. We also observe damped oscillations of the ion kinetic energy that are a unique feature of equilibration of strongly coupled plasma. [Preview Abstract] |
Wednesday, May 18, 2005 10:42AM - 10:54AM |
B5.00002: Dipole-Dipole Excitation and Ionization in a Frozen Rydberg Gas Paul Tanner, Wenhui Li, Thomas Gallagher In cold dense Rydberg atom samples, the dipole-dipole interaction strength is effectively resonant at the typical interatomic spacing in the sample, and the interaction has a 1/R$^{3}$ dependence on interatomic spacing R. The dipole-dipole attraction leads to ionizing collisions of initially stationary atoms, which produces hot atoms and ions and initiates the evolution of initially cold samples of neutral Rydberg atoms into plasmas. More generally, the strong dipole-dipole forces lead to motion, which must be considered in proposed applications. [Preview Abstract] |
Wednesday, May 18, 2005 10:54AM - 11:06AM |
B5.00003: Kinetic Energy oscillations in ultracold plasma Sampad Laha, Y.C. Chen, P. Gupta, Y.N. Martinez, P.G. Mickelson, S.B. Nagel, A.D. Saenz, C.E. Simien, T.C. Killian After imaging ultracold Sr plasma using 422 nm light, we investigate temporal and spatial variation of kinetic energy of the ions before it has reached global thermal equilibrium. The spatial resolution of our imaging system allows us to probe the annular regions of the plasma and it is found that kinetic energy of the ions undergoes damped oscillations before reaching global thermal equilibrium. [Preview Abstract] |
Wednesday, May 18, 2005 11:06AM - 11:18AM |
B5.00004: Formation of antihydrogen positive ions D. Vrinceanu, S. X. Hu, S. F. Mazevet, L. A. Collins We have performed molecular dynamics (MD) simulations of an ultracold positron-antiproton plasma in a strong magnetic field (5.4 Tesla). Three-body recombinations produce magnetized cold antihydrogen atoms. Besides the neutral antihydrogen atoms, we also observed the formation of antihydrogen positive ions - two positrons bind to an antiproton. Similar to negative hydrogen ions, this new antimatter form is important because it can be trapped by the existing fields, which confine the positrons. The production of positive H-bar ions is enhanced by the magnetic field. [Preview Abstract] |
Wednesday, May 18, 2005 11:18AM - 11:30AM |
B5.00005: Study of the Expansion of Ultracold Strontium Plasma Priya Gupta, Clayton Simien, Sampad Laha, Yenny Martinez, Pascal Mickelson, Sarah Nagel, Ying-Cheng Chen, Thomas Killian We probe the expansion of ultracold strontium plasma with spectroscopy of the $^{2}$S$_{1/2}-^{2}$P$_{1/2}$ transition of Sr+ at 422nm. The absorption spectrum is Doppler broadened, which gives a measure of the ion velocity. The expansion is driven by the electron pressure, and the ion acceleration gives a measure of the electron temperature. We will present the result of the study of the expansion of ultracold plasma including the effects of adiabatic expansion, recombination, and evaporation on the temperature of the electrons. [Preview Abstract] |
Wednesday, May 18, 2005 11:30AM - 11:42AM |
B5.00006: Neutral Atoms in an Optical Lattice for Quantum Information Processing Chad Fertig, Johnny Huckans, Ian Spielman, Jennifer Sebby-Strabley, Marco Anderlini, Steven Rolston, William Phillips, James Porto We experimentally study Bose-Einstein Condensates in optical lattices as a promising candidate for scalable quantum information processing. We study the superfluid-to-Mott-insulator transition as a means of initializing a quantum register of singly occupied lattice sites. The fidelity of the Mott state can be assessed using vibrational spectroscopy. Single q-bit operations can be realized using a 3-photon stimulated Raman coupling field. We conduct experiments to realize 2-qubit operations in a 3D lattice of double-well potentials, where the strength of the barrier is tunable in real-time. [Preview Abstract] |
Wednesday, May 18, 2005 11:42AM - 11:54AM |
B5.00007: Progress toward a Sr optical atomic clock in an optical lattice A. D. Ludlow, T. Ido, M. M. Boyd, M. Nottcutt, T. Zelevinsky, S. Blatt, S. Foreman, J. Ye We report our recent progress toward an optical atomic clock based on the Sr $^{1}$S$_{0}-^{3}$P$_{0}$ transition in an optical lattice. In order to probe the doubly forbidden intercombination transition, we have developed a compact and highly stabilized diode laser source at 698 nm. This laser can serve as the local oscillator for an atomic clock based on $^{87}$Sr or on a newly proposed clock scheme exploiting electromagnetically induced transparency in $^{88}$Sr. The diode laser is locked to an ultra high finesse cavity which has an innovative vertical mounting geometry. This geometry provides a common mode rejection of cavity length changes due to accelerations. The locked laser system exhibits in-loop frequency noise of $\sim $60mHz/$\surd $Hz from 100 Hz to 30 kHz. In order to measure the laser linewidth, we compare this laser system with a highly stabilized Nd:YAG system which has already demonstrated a sub-hertz linewidth. We do so by phase locking an octave spanning, self-referenced femtosecond comb to a Nd:YAG laser at 1.064 $\mu $m and beating our 698 nm stabilized laser with the narrow (Hz level) comb mode at 698 nm. After having trapped, cooled, and efficiently loaded the strontium atoms into an optical lattice at the magic wavelength of ac stark shift cancellation, we report preliminary spectroscopic measurements. [Preview Abstract] |
Wednesday, May 18, 2005 11:54AM - 12:06PM |
B5.00008: Studies of the \textbf{\textit{5s$^{21}$S$_{0}$-- 5s5p$^{3}$P$_{1}$}} Transition in Atomic Strontium Yenny Natali Martinez, Ying-Cheng Chen, Pascal Mickelson, Sarah Nagel, Thomas C. Killian The importance of the $5s^{21}S_{0 }-- 5s5p^{3}P_{1}$ intercombination line of strontium (Sr) as a possible candidate for optical frequency standards requires precise knowledge of the properties of this transition. Using the established electron-shelving technique on a cloud of laser cooled and trapped Sr atoms, we measured the lifetime of the $^{3}P_{1}$ state. Studies of the linewidth of the transition allowed us to determine the linewidth of the pumping laser used in the experiment, which is important for future applications in laser cooling. [Preview Abstract] |
Wednesday, May 18, 2005 12:06PM - 12:18PM |
B5.00009: Rapid Molecular Transport in Pulsed Optical Lattices Peter Barker, Ray Fulton, Alexis Bishop, Mikhail Shneider We show that molecules can be rapidly transported using large optical lattices (500 K) using high intensity (2 x 10$^{16}$ W/m$^{2})$ far off resonant pulsed optical lattices. Using this method we have decelerated benzene molecules from a cold (2.3 K) molecular beam from 320 m/s to 243 m/s, exceeding earlier results using a single focused Gaussian beam$^{[1]}$.$^{ }$This corresponds to an average deceleration of 10$^{9}$g, reducing the translational energy of the benzene molecules by 48{\%}. These results indicate that if the field is rapidly switched-off a significant fraction of the molecules could be brought to rest in a single 2 ns pulse. References: [1] R. Fulton, A.I. Bishop, P.F. Barker. Phys. Rev. Lett. \textbf{93}, 243004 (2004) [Preview Abstract] |
Wednesday, May 18, 2005 12:18PM - 12:30PM |
B5.00010: Quantum control of ultracold atomic collisions in optical lattices Ivan Deutsch, Rene Stock We present a new method for robustly controlling collisions of ultra-cold atoms in optical lattices based on the ``trap-induced shape resonance'' (TISR) [1]. Like the magnetic Feschbach resonance, in the TISR a weakly-bound molecular state is made resonant with a trap vibrational state through the trapping potential energy. The TISR allows for strong interaction between trapped but separated atoms, providing new avenues for robust encodings of quantum information, protected from fluctuations in control parameters. A particularly promising candidate species is $^{133}$Cs, whose dimer potential posses an extremely weakly bound state near dissociation. Scattering lengths on the order of 100nm are possible for appropriate choices of encodings, larger that the typical trapped wavepacket, and thus leading to very strong interaction. To deal with the complexity of the multichannel scattering problem at short range, and the trapping potential at long range, we have developed a generalized multichannel energy-dependent Fermi pseudo-potential, including higher partial waves, and second order spin-orbit coupling [2]. [1] R. Stock \textit{et al.}, Phys. Rev. Lett. \textbf{91}, 183201 (2003). [2] R. Stock \textit{et al.}, Phys. Rev. Lett. \textbf{94}, 023202 (2005). [Preview Abstract] |
Wednesday, May 18, 2005 12:30PM - 12:42PM |
B5.00011: Period doubling and the growth of swallowtails in Bose-Einstein condensates trapped in a lattice potential Brian Seaman, Lincoln Carr, Murray Holland The band structure for a Bose-Einstein condensate on a lattice is shown to be both qualitatively and quantitatively independent of the exact structure of the underlying lattice by examining sinusoidal, Jacobi elliptic, and Kronig-Penney potentials. The appearance of swallowtails in the band structure is then analyzed in terms of the adiabatic growth of a shorter period lattice using analytic period doubled solutions of a Kronig-Penney potential. Since the results are independent of the potential used, these properties hold for the experimental sinusoidal potential as well. [Preview Abstract] |
Wednesday, May 18, 2005 12:42PM - 12:54PM |
B5.00012: Motional Two-Qubit Gate in an Optical Lattice Mark Edwards, Kristen Kasprak, Adam Bozeman, Trey Porto, Charles W. Clark By crossing two pairs of counterpropagating laser beams at right angles, an optical potential consisting of a periodic array of separated double--wells can be created. In this experiemental arrangement, both the barrier height between the wells and the difference in the well depths (called the ``tilt'') can be independently varied. If a Bose--Einstein condensate is subjected to this lattice potential and the overall depth is increased, it is possible to trap exactly two particles in each double well. We have modeled this system with a potential consisting of two square wells separated by a square barrier. Using this model we studied the dynamics of controlled motion of two interacting particles moving in this potential as the tilt is varied by solving the time--dependent Schr\"odinger equation. The goal of the study is to explore the motion of the atom to controllably place and extract two atoms in the same site in order to affect interactions. Such controlled motion and interactions can form the basis for two--qubit gate. We present the results of our simulations and comment on the feasibility of implementing a two--qubit gate in the laboratory. [Preview Abstract] |
Wednesday, May 18, 2005 12:54PM - 1:06PM |
B5.00013: Quantum fluctuations of a 1D bosonic gas in an optical lattice Janne Ruostekoski, Lorenzo Isella We numerically study the quantum dynamics of a 1D bosonic gas in a shallow optical lattice for both static and time-dependent lattices. In particular, we model the strongly damped dipole oscillations which have recently been observed experimentally at NIST by Fertig et al. cond-mat/0410491. We find a qualitative agreement with the experimentally observed damping rates which can be explained as being due to zero temperature quantum fluctuations. [Preview Abstract] |
Wednesday, May 18, 2005 1:06PM - 1:18PM |
B5.00014: Raman Optical Lattice Rui Zhang, Natalya Morrow, Paul Berman, Georg Raithel It is shown that sub-Doppler cooling occurs in an atom-field geometry that can lead to reduced period optical lattices. Four optical fields are combined to produce a standing wave Raman field that drives transitions between two ground state sublevels. Semi-classical solutions of the atomic momentum distribution are calculated and compared with both experimental results and Quantum Monte Carlo Wavefunction simulations. [Preview Abstract] |
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