Bulletin of the American Physical Society
40th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 54, Number 7
Tuesday–Saturday, May 19–23, 2009; Charlottesville, Virginia
Session E1: Poster Session I (4:00 - 6:00 pm) |
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Room: Newcomb Hall Ballroom |
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E1.00001: SPECTROSCOPY, LIFETIMES, OSCILLATOR STRENGTHS |
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E1.00002: Observation of the $^{85}$Rb$_{2}$ a $^{3}\Sigma _{u}^{+}$ State by PFOODR Resolved Fluorescence Spectroscopy Bediha Beser, Jianmei Bai, Ergin Ahmed, Vladimir Sovkov, Valery Ivanov, Feng Xie, Li Li, Marjatta Lyyra Perturbation Facilitated Optical Optical Double Resonance (PFOODR) resolved fluorescence from a single rovibronic level of an excited triplet state ($^{3}\Pi _{g }$ or $^{3}\Sigma _{g}^{+}$) was used to characterize the a $^{3}\Sigma _{u}^{+}$ ground triplet state of $^{85}$Rb$_{2}$. A thermal Rubidium heatpipe source was used with a Titanium Sapphire pump laser and with a Toptika DL100 diode laser as the probe. The two color excitation was performed using an intermediate level with mixed singlet-triplet character belonging to the $A \quad ^{1}\Sigma _{u}^{+}\sim \quad b \quad ^{3}\Pi _{u}$ system. We have recorded resolved fluorescence from the PFOODR upper level to the a $^{3}\Sigma _{u}^{+}$ state using a combination of a SPEX 1404 double monochromator (resolution $\sim $0.2cm$^{-1})$ and a DA8 BOMEM FTIR (resolution $\sim $0.015cm$^{-1})$ interferometer. The multi-parameter Morse Long Range potential method was used to analyze the observed bound-bound and bound-free components of the spectra to construct the $a^{3}\Sigma _{u}^{+}$ potential curve. [Preview Abstract] |
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E1.00003: Bound-free Emission in the NaK Molecule B.M. McGeehan, S. Ashman, S.J. Sweeney, C.M. Wolfe, J.P. Huennekens, A.P. Hickman We report the analysis of bound-free emission from the $4\,^3\Sigma^+$ electronic state to the $a(1)\,^3\Sigma^+$ repulsive state of the NaK molecule. Taken together with the previous experiments of Burns {\it et al.} [J. Chem.~Phys. {\bfseries 119} 4743--4754 (2003)], recent measurements have provided data for a sufficiently large range of initial vibrational levels (up to $v = 34$ of the $4\,^3\Sigma^+$ state) to probe the behavior of the transition dipole moment function $M(R)$ in the range $R \sim 3.5$ to 6.4~\AA. This range includes a region where theoretical calculations have predicted sharp structure due to an avoided crossing. Using a modified inner repulsive wall for the $a(1)\,^3\Sigma^+$ potential and a refined IPA potential for the $4\,^3\Sigma^+$ state, we have calculated bound free spectra and have adjusted $M(R)$ to fit the experimental data. The work was performed with a version of R. J. Le~Roy's code BCONT that we modified. Preliminary results confirm the sharp structure predicted in $M(R)$, and further work is in progress that will include both bound-free and bound-bound spectra in the analysis. [Preview Abstract] |
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E1.00004: Energy levels and mid-infrared spectrum of Rydberg states of triatomic hydrogen Jia Wang, Viatcheslav Kokoouline, Chris Greene In previous studies[1] of the dissociative recombination of ${H_3^+}$, the rigid rotator approximation, and in some cases the adiabatic hyperspherical approximation as well, were adopted by calculations of the rovibrational states of $\rm{H_3^+}$. In this work, the Coriolis interaction is considered, and accurate rovibrational energy levels of $\rm{H_3^+}$ are calculated, with the aim of eventually improving the approximations presently used in recombination theory. We also use these accurate rovibrational states of $\rm{H_3^+}$ to study the energy levels and mid-infrared spectrum of nonpenetrating $\rm{H_3}$ Rydberg states. [1] V. Kokoouline and C. H. Greene, Phys. Rev. A 68, 012703 (2003). [Preview Abstract] |
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E1.00005: Franck-Condon factor of the A-X(0-0) transition of CaF measured by the saturation of laser-induced fluorescence B.E. Sauer, T.E. Wall, J.J. Hudson, D. Cho, M.G. Boshier, E.A. Hinds, M.R. Tarbutt We describe a method\footnote{T. E. Wall et al., Phys. Rev. A \textbf{78}, 062509 (2008)} for determining the radiative decay properties of a molecule by studying the saturation of laser-induced fluorescence and the associated power broadening of spectral lines. The fluorescence saturates because the molecules decay to states that are not resonant with the laser. The amplitudes and widths of two hyperfine components of a spectral line are measured over a range of laser intensities and the results compared to a model of the laser-molecule interaction. Using this method we measure the lifetime of the A(v'=0) state of CaF to be $\tau=19.2\pm0.7$ ns, and the Franck-Condon factor for the transition to the X(v=0) state to be $Z=0.987_{-0.019}^{+0.013}$. In addition, our analysis provides a measure of the hyperfine interval in the lowest-lying state of A(v'=0), $\Delta_e=4.8\pm1.1$ MHz. A Franck-Condon factor close to 1 opens the possiblity of implementing a cycling transition with a small number of additional repump frequencies. We discuss possible schemes of laser cooling CaF or other alkaline earth monofluorides. [Preview Abstract] |
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E1.00006: Global analysis of data on the $A\ ^{1}\Sigma^{+}$ $\sim$ $b\ ^{3}\Pi$ states of NaK Houssam Salami, Thomas Bergeman, Amanda Ross NaK electronic states have been extensively studied over recent years. Many of these studies have involved the lowest excited states, $A\ ^{1}\Sigma^{+}$ and $b\ ^{3}\Pi$, as they offer pathways to higher states. These states have regained attention as they are used as intermediaries in the production of ultracold molecules. Recently, the $b\ ^{3}\Pi_{0}$ $\sim$ $A\ ^{1}\Sigma^{+}$ spin-orbit interactions have been examined [1,2]. However analysis was based on band-by-band local deperturbation which is not consistent with experimental errors limits. In this study, we collect existing (published and unpublished) data from various experiments (FT-LIF, PLS and PFOODR) performed at Orsay and Lyon (Ross et al.), Warsaw (Kowalczyk et al.) and Lehigh (Huennekens et al.) universities. Transitions from $D\ ^{1}\Pi$, $B\ ^{1}\Pi$, and $C\ ^{1}\Sigma^{+}$ states simultaneously to the $A$ $\sim$ $b$ and $X$ states constitute the bulk of the data as the upper term energy values can be deduced precisely from the well known $X$ state parameters. Combined data will be modeled using a global deperturbation approach employing the discrete variable representation (DVR) so as to fit potential energy and spin-orbit functions.\\ 1. P.~Burns et al., J.~Chem.~Phys. {\bf 122}, 074306 (2005). \\ 2. R.~Ferber et al., J.~Chem~.Phys.{\bf 112}, 5740 (2000). [Preview Abstract] |
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E1.00007: Robust laser frequency locking by dispersion of atoms in a transverse magnetic field Taro Hasegawa, Mitsuyasu Deguchi A robust laser frequency locking scheme to an atomic transition is proposed and experimentally demonstrated. In this scheme, dispersion (real part of electric susceptivity) of the Zeeman-shifted atoms is employed as an error signal for feedback, whereas in the DAVLL (dichroic atomic vapor laser lock, Appl. Opt. {\bf 37}, 3295(1998)), absorption (imaginary part of electric susceptivity) is. Magnetic field transverse to the laser beam is applied to the atoms. The error signal of the proposed scheme provides a wide locking range, depending on the parameters and the energy level structure. Experimental demonstration with transition between $5d$ $^2D_{3/2}$ and $6p$ $^2P_{1/2}$ of Ba$^+$ is carried out for a grating-feedback external-cavity laser diode at 650 nm. [Preview Abstract] |
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E1.00008: ABSTRACT WITHDRAWN |
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E1.00009: Measuring the Nuclear Magnetic Octupole Moment of a Single Trapped Barium-137 Ion Adam Kleczewski, Norval Fortson, Boris Blinov Recent measurements of hyperfine structure in the cesium-133 atom resolved a nuclear magnetic octupole moment $\Omega $ much larger than expected from the nuclear shell model[1]. To explore this issue further, we are undertaking an experiment to measure the hyperfine structure in the 5D manifold of a single trapped barium-137 ion which, together with reliable calculations in alkali-like Ba$^{+}$, should resolve $\Omega $ with sensitivity better than the shell model value [2]. We use a TmHo:YLF laser tuned to 2051 nm and a fiber laser tuned to 1762 nm to drive the 6S$_{1/2}$ to 5D$_{3/2}$ and 6S$_{1/2}$ to 5D$_{5/2}$ electric quadrupole transitions. These lasers allow us to selectively populate any hyperfine sub-level in the 5D manifold. We will then perform RF spectroscopy on the 5D states to make a precision measurement of the hyperfine frequency intervals. We report on the development of the laser and RF spectroscopy systems. [1] V. Gerginov, A. Derevianko, and C. E. Tanner, Phys. Rev. Lett. 91, 072501 [2] K. Beloy, A. Derevianko, V. A. Dzuba, G. T. Howell, B. B. Blinov, E. N. Fortson, arXiv:0804.4317v1 [physics.atom-ph] 28 Apr 2008 [Preview Abstract] |
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E1.00010: Isotope shift calculations and the variation of fundamental constants Julian Berengut, Victor Flambaum We present recent \emph{ab initio} calculations of isotope shift in many-electron atoms using a combination of configuration interaction and many-body perturbation theory. These calculations are necessitated by current searches for variation of fundamental constants in laboratory and astrophysical systems. We show that very good accuracy can be obtained for a variety of ions. [Preview Abstract] |
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E1.00011: FUNDAMENTAL SYMMETRIES AND PRECISION MEASUREMENTS |
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E1.00012: Polarized atoms in a far-off-resonance YAG laser optical dipole trap Fang Fang, Haiyan Wang, David Feldbaum, David Vieira, Xinxin Zhao Optical trapping of radioactive atoms has a great potential in precision measurements for testing fundamental physics such as electric dipole moment (EDM), atomic parity non-conservation (PNC) and parity violating beta-decay correlation coefficients. One challenge that remains is to polarize the atoms to a high degree and to measure the polarization of the sample and its evolution over time. In this paper we report on the polarization study of Rb atoms in a yttrium-aluminum-garnett (YAG) laser optical dipole trap using both Faraday rotation polarimetry and resolved Zeeman spectroscopy techniques. We have prepared a cold cloud of polarized atoms and observed that its spin relaxation due to light scattering is suppressed in the YAG dipole trap. The spin polarization is further purified and maintained when the two-body collision loss rate between atoms in mixed spin states is greater than the one-body trap loss. These advancements are an important step towards a new generation of precision measurement with polarized trapped atoms. [Preview Abstract] |
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E1.00013: PROBING MOLECULES WITH ULTRA-FAST LASERS |
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E1.00014: Complete momentum spectrum of H$_2^+$ ionization by short laser pulses from model Born-Oppenheimer calculations Fatima Anis, B.D. Esry We have performed one dimensional Born-Oppenheimer (BO) calculations for H$_2^+$ ionization in intense laser pulses. Here, one dimensional implies one degree of freedom each for the electron and the internuclear distance. Our scheme allows us to clearly separate dissociation and ionization without making any further approximation within the model. The results have been analyzed to qualitatively answer several important questions about different approximations and models proposed for interpreting and predicting the Kinetic energy spectrum of the protons following ionization, in particular above threshold Coulomb explosion (ATCE). [Preview Abstract] |
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E1.00015: Using the Time-dependent Floquet Method to Study Below-threshold Dissociation and Zero-photon Dissociation Jianjun Hua, Brett Esry Below-threshold dissociation (BTD) and zero-photon dissociation (ZPD) are two important nonadiabatic phenomena occurring during molecular dissociation in an ultrashort intense laser field. BTD is a single-photon dissociation mechanism initiated by a photon carrying less energy than the minimum required for the dissociation to occur. Zero-photon dissociation (ZPD) is a special case of BTD, occurring when the net number of photons absorbed is zero. We have employed the time-dependent Floquet method to investigate BTD and ZPD. We found that the vibrational states whose energy lies in the vicinity of one-photon and three-photon crossings make major contributions to BTD and ZPD. [Preview Abstract] |
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E1.00016: Spinning CO$_{2}$ Molecules into High Rotational States with an Optical Centrifuge Amy S. Mullin, Liwei Yuan, Sam Teitelbaum, Allison Robinson We have performed the first spectroscopic measurements of molecules in an optical centrifuge. The optical centrifuge is a means to generate molecules in very high rotational states using a pulsed laser. The optical centrifuge consists of two ultrafast laser pulses with reverse chirp and circular polarization that are combined to generate an intense electric field that undergoes angular acceleration. Molecules with polarizability anisotropy are driven by the field into high rotational states. We have used an optical centrifuge to promote CO$_{2}$ molecules into high rotational states (J$\sim $200) and monitored the effect of the centrifuge on different quantum states using high-resolution transient IR diode laser absorption at $\lambda $=4.3 $\mu $m. The depletion of low angular momentum (J=14) states and the appearance (and subsequent depletion) of middle-J (J=76) states that are populated by a collisional cascade have been observed and characterized. Direct detection of CO$_{2}$ molecules in states near J=200 will allow further characterization of the centrifuge. Transient signals were observed only in the presence of both optical centrifuge pulses and for pulses with circular polarization. The ability to control molecular rotation using the optical centrifuge opens a new realm of investigation into the behavior of energized molecules. [Preview Abstract] |
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E1.00017: ION-ATOM AND ION-ION COLLISIONS |
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E1.00018: Inelastic- collision cross sections for the interactions of $H^{+}$, $He^{2}+$ and $C^{6+}$ ions with liquid water Mario Bernal, Jacinto Liendo Monte Carlo codes for ion-nanodosimetry in tissue-like media require a detailed knowledge of the ionization cross sections. Secondary electrons play a main role in the radiobiological effectiveness of any radiation. The HKS and CDW-EIS formalisms are implemented to determine single ionization cross sections (SICS) corresponding to the impact of $H^{+}$, $He^{2+}$ and $C^{6+}$ ions on liquid water, for incident energies from 0.3 to 10 MeV/u. Corrected expressions for the HKS method have been used. The same kind of initial electron wave functions and binding energies have been used with both models, in order to compare the formalisms themselves. Double and single differential as well as total SICS of liquid water have been calculated by use of both methods and comparisons have been made between their theoretical predictions. Also, these results have been compared with experimental values reported previously for ionization of water vapor due to protons and alpha particles. The excitation cross sections are included to determine electronic stopping cross sections in liquid water. The results based on the CDW- EIS method provide the best agreement when stopping powers are compared with corresponding data published in ICRU reports, obtaining discrepancies of about 9 \%, 16 \% and 19 \% for incident protons, alpha particles and carbon ions respectively. [Preview Abstract] |
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E1.00019: Electron Capture in Collisions between Protons and Hydrogen Atoms Thomas Winter Cross sections have been determined for electron transfer as well as direct excitation and ionization in $p$-H collisions using the symmetric double-center Sturmian bases $\leq 16 (s,p,d)$ on each center (176 states in all) and $\leq 13(s,p,d,f)$ on each center (220 states in all) for proton energies $1-100$ keV, substantially expanding pioneering Sturmian calculations carried out thirty years ago.\footnote{R.Shakeshaft, J. Phys. B {\bf 8}, 1114 (1975); Phys. Rev. A {\bf 18}, 1930 (1978).} At energies $100-1000$ keV, Sturmian calculations have been carried out with the asymmetric basis $\leq 30(s,p,d,f)$ centered on the target nucleus and only $1s$ centered on the projectile. The computer code for arbitrary nuclear charges, recently applied to $\alpha$-H collisions,\footnote{T.G. Winter, Phys. Rev. A {\bf 76}, 062702 (2007).} has been specialized to the homonuclear case, halving the computing time. The results may be compared with large basis, double-center Gaussian results\footnote{N. Toshima, Phys. Rev. A {\bf59}, 1981 (1999).}; triple-center results\footnote{T. G. Winter and C.D. Lin, Phys. Rev. A {\bf29}, 567 (1984).}; double-center, even-tempered basis results\footnote{J. Kuang and C. D. Lin, J. Phys. B {\bf29}, 1207 (1996).}; other theoretical results; and numerous experimental results. [Preview Abstract] |
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E1.00020: Vortices in electron momentum distributions Serguei Ovchinnikov, Joseph Macek, James Sternberg Recent computations of the electron distributions for proton impact ionization of hydrogen atoms have shown unexpected ``holes,'' which are associated with vortices in the continuum part of time-dependent wavefunctions [1]. We find that the electron distributions calculated in the framework of the Impact-Parameter-Born approximation have the same holes. In contrast, the electron distributions in the Born approximation have no vortices but they appear in the Coulomb Born approximation. \\[4pt] [1] J.H. Macek, J.S. Sternberg, S.Y. Ovchinnikov, T-G. Lee, and D.R. Schultz, submitted for publication. [Preview Abstract] |
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E1.00021: Testing theoretical ion-atom interaction potentials by precise measurements of gas-phase ionic mobilities Rainer Johnsen, Larry Viehland, Timothy Wright High-level computations now predict ion-atom potentials over a wide range of inter-atomic distances, from the potential minimum up to the dissociation asymptote. Hence, their reliability needs to be tested by experiments that probe the potentials over a commensurate range of distances, which often exceeds the range accessible to spectroscopy. In a collaborative project, the authors have recently tested several theoretical potentials by comparing measured gas-phase ionic mobilities to those derived from computed potentials and state-of-the-art ion transport theory. Here we present results on the ion-atom systems O$^{+}$-He, O$^{+}$-Ne, O$^{+}$-Ar, as well as He$^{+}$-Ne and Ne$^{+}$-He. A selected-ion drift tube mass spectrometer was used that determines mobilities with an accuracy of about 2 to 3 {\%}, after corrections for ``end-effects''. While the calculated mobilities agree quite well with their measured values over a wide range of E/n (the electric-field to gas-density ratio), more accurate mobility measurements (at the 1{\%} level) are needed to test for finer details of the interaction, e.g. effects arising from spin-orbit coupling. We plan to (a) further improve the accuracy and (b) to incorporate a laser-ablation source in order to study metal-ion/molecule pairs that are of interest for molecular structure calculations. [Preview Abstract] |
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E1.00022: A Novel Merged-Beam Apparatus for Studying Anion-Neutral Reactions K. Miller, H. Bruhns, H. Kreckel, M. Lestinsky, W. Mitthumsiri, B. Schmitt, M. Schnell, B. Seredyuk, D.W. Savin, X. Urbain, M.E. Bannister, C.C. Havener, A. Dorn, M.L. Rappaport We have developed a novel apparatus at the Columbia Astrophysics Laboratory to study anion-neutral reactions. Beginning with an anion beam, we use photodetachment to generate a self-merged, anion- neutral beams arrangement. Laboratory beam energies are in the keV range. Because the beams run co-linear, center-of-mass energies from the meV to keV range are achievable. Our proof-of-principle measurement is the associative detachment (AD) reaction ${\rm H}^- + {\rm H} \to {\rm H}_2 + {\rm e}^-$. Published values for this process differ by almost an order of magnitude. With theory and experiment unable to reach a consistent description for this fundamental molecular formation reaction, it raises questions of how can we expect to do better for anion-neutral reactions involving more complicated systems? Measurements using our novel apparatus will help to resolve this fundamental issue in physics and chemistry. We observe the AD reaction by detecting fast H$_2^+$ ions formed through ionizing collisions of the AD-generated H$_2$ with He inside a gas cell. Here we present the current status of the project and discuss our future plans. [Preview Abstract] |
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E1.00023: Quantum mechanical models for the Fermi shuttle James Sternberg, S. Yu. Ovchinnikov, J.H. Macek Although the Fermi shuttle was originally proposed as an explanation for highly energetic cosmic rays, it is also a mechanism for the production of high energy electrons in atomic collisions [1]. The Fermi shuttle is usually thought of as a classical effect and most models of this process rely on classical or semi-classical approximations. In this work we explore several quantum mechanical models for ion-atom collisions and examine the evidence for the Fermi shuttle in these models. \\[4pt] [1] B. Sulik, Cs. Koncz, K. Tok\'esi, A. Orb\'an, and D. Ber\'enyi, Phys Rev. Lett. {\bf 88} 073201 (2002) [Preview Abstract] |
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E1.00024: Ionization of helium by proton and anti-proton impact: a finite-element discrete-variable approach Xiaoxu Guan, Klaus Bartschat We have modified our finite-element discrete-variable approach [1] to describe the response of a helium atom to an intense short laser pulse to allow for the treatment of a charged projectile. This requires the replacement of the electric dipole operator by the Coulomb interaction between the target and the projectile, which we assume to move along a straight line with a fixed impact parameter. The initial state is propagated in time using an efficient Arnoldi-Lanczos scheme. Calculations for single and double ionization of He by proton and anti-proton impact yield good agreement with experiment~[2-4] and theoretical predictions from other sophisticated non-perturbative approaches~[5,6]. In addition to angle-integrated observables, angle-differential cross sections as well as linear-momentum and energy distributions for double ionization will be presented. [1] Xiaoxu~Guan, K. Bartschat, and B.I.~Schneider, Phys. Rev. A~{\bf 77} (2008), 043421. [2] L.~H. Andersen {\it et al.}, Phys. Rev. A~{\bf 41} (1990), 6536. [3] P.~Hvelplund {\it et al.}, J. Phys. B~{\bf 27} (1990), 925. [4] H.~Knudsen {\it et al.}, Phys. Rev. Lett.~{\bf 101} (2008), 043201. [5] M.~Foster {\it et al.}, Phys. Rev. Lett.~{\bf 100} (2008), 033201. [6] M.~Foster {\it et al.}, J. Phys. B~{\bf 41} (2008), 111002. [Preview Abstract] |
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E1.00025: Final-state-resolved charge exchange in O$^{7+}$ + H collisions J. Nolte, P.C. Stancil, A. Watanabe Charge transfer between the solar wind ion O$^{7+}$ and neutral interstellar hydrogen is thought to be a significant contributor to the heliospheric component of the soft x- ray background, as the resultant highly excited O$^{6+}$ ion emits an x-ray photon in the electron's cascade to the ground state. Models of the heliospheric x-ray emission thus require accurate cross section data for this particular collision system. Experimental studies of this system, however, are rare and suffer from limited energy resolution and tend to focus on only the total cross section. In this study, we perform fully quantum calculations for the scattering system over a range of collision energies from 10 eV/u to 50 keV/u for all important n, l, and S-resolved states. In particular, we focus on the distribution of electron capture into the n=4, 5, and 6 manifolds, for both singlet and triplet states. [Preview Abstract] |
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E1.00026: Collisions of O+ with He at low energies Dwayne C. Joseph, B.C. Saha, L.B. Zhao We have investigated the following charge transfer process$O^+({ }^4S^0,{ }^2D^0,{ }^2P^0)+He\to O({ }^3P)+He^+-\Delta E$ using the full quantum [1] and semi-classical molecular [2]orbital close-coupling (MOCC) approximations. The quantum MOCC equations are solved numerically in the adiabatic representation [3]. Using MRD-CI package [4] the \textit{ab initio} configuration interaction calculation is carried out for potential energies. Details of our findings will be reported in the conference. [1] B. H. Bransden and M. R. C. McDowell, ``Charge Exchange and the Theory of Ion-Atom Collisions'', Clarendon Press, Oxford, 1992. [2] M. Kimura and N. F. Lane, At. Mol. Opt. Phys 26, 79 (1990). [3] J. P. Braga and J. C. Belchoir, J. Comput. Chem 17, 1559 (1996). [4] R. J. Buenker, ``Current Aspects of Quantum Chemistry 1981, Vol 21, edited by R. Carbo (Elsevier, Amsterdam), p 17. [Preview Abstract] |
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E1.00027: Theoretical Fully Differential Cross Sections for Transfer-Excitation Collisions A.L. Harris, M. Schulz, J.L. Peacher, D.H. Madison Theoretical fully differential cross sections (FDCS) will be compared with experimental results for transfer-excitation occurring in proton-helium collisions. In the experiments, the incident proton captures one electron from a helium atom, and the remaining electron is left an excited bound state of the helium ion. The theoretical approach we use is a full four-body approach, taking each particle and interaction into account. The calculations will address the effects of the projectile-target atom and projectile-residual ion interactions, as well as electron correlation. [Preview Abstract] |
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E1.00028: Kinematically complete studies of collisions between simple molecular ions and neutral gas targets Nora G. Johnson, A.M. Sayler, Ben Berry, Wania Wolff, B. Gaire, M. Zohrabi, J. McKenna, K.D. Carnes, I. Ben-Itzhak Collision-induced dissociation, dissociative capture, and target ionization (with or without projectile fragmentation) from few keV molecular ions impinging on various gas targets have been studied using a coincidence 3D momentum imaging technique. The newly installed apparatus employs a cold target jet configuration within a longitudinal spectrometer allowing for imaging of the molecular fragments, including neutrals and molecular ions that survive hard collisions, as well as the recoil ion on a single detector. Such detection capabilities enable kinematically complete studies for the dissociative capture channel and near-kinematically complete studies of all other channels. The results of, for example, 3 keV H$_{2}^{+}$+Ar collisions will be presented. [Preview Abstract] |
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E1.00029: COLLISIONS INVOLVING SURFACES |
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E1.00030: Creating reactive potentials for particle-surface interactions: C, H, Li P.S. Krstic, P. Kent The reliability of the molecular dynamic simulations of particle-surface interactions strongly depends on the quality of the ground electronic state potentials which determine classical forces for dynamics of all heavy particles particles in the system. Using multidimensional optimization techniques we improve the quality of the existing hydrocarbon potentials [Brenner et al, J. Phys: Condens. Matter 14, 783 (2002)] for the close-nuclei encounters. In addition, we present initial results for a new potential developed for carbonized lithium surfaces and apply for both chemical and physical sputtering yields. [Preview Abstract] |
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E1.00031: The effect of surface interaction on the performance of submillimeter atomic magnetometers K.F. Zhao, M. Schaden, Z. Wu We have studied the effect of surface interaction on the performance of submillimeter atomic magnetometers. We use an evanescent wave magnetometer with a coated cell of adjustable length. The cell length varies from a few millimeters to less than 100 $\mu m$. Two kinds of antirelaxation coatings are used: octadecyltrichlorosilane (OTS) and dichlorooctamethyltetrasiloxane (Surfasil). Sub-kHz linewidth can be achieved for a 100 micron thick OTS-coated cell. Magnetometers with coated ultra thin cells have superior performance in inhomogeneous magnetic fields, and can achieve a spatial resolution of better than 25~$\mu m$. [Preview Abstract] |
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E1.00032: Ionization of Rydberg atoms at metal surfaces Dennis Neufeld, Yu Pu, F. Barry Dunning The behavior of Xe(nf) Rydberg atoms at metal surfaces is being explored to probe the response of a Rydberg atom to the presence of a nearby surface and to determine the atom-surface separation at which ionization occurs through resonant tunneling of the excited electron into a vacant level in the metal. Although measurements yield average ionization distances that are in good agreement with theoretical predictions their spread is somewhat larger than expected. A variety of factors that might account for this are being examined. Measurements with different high-$n$ ($n\sim $17-50) states and incident angles are being used to examine possible effects associated with the evolution of the excited states as the surface is approached. A selection of different surfaces is being employed to elucidate the effects of surface topography and surface potential variations, i.e., patch fields. [Preview Abstract] |
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E1.00033: Scattering of H$^{-}$ by plane and nano-stepped surfaces: Role of the ion speed for probing the surface band structure Himadri Chakraborty, Uwe Thumm Resonant charge transfer between ions and metal surfaces is a useful tool to explore the surface electronic structure. Using the Crank-Nicholson propagation method [1] we solve the time-dependent Schroedinger equation to simulate the dynamic electron redistribution during the scattering of a hydrogen anion from plane and nano-stepped metal surfaces. We calculate electronic evolution during the scattering and the final ion survival probability as a function of the projectile's incident angle. We find that the survival of the ion reflected off a plane surface is very sensitive to the component of the projectile speed perpendicular to the surface and analyze rich structure of the survival probability as a function of the perpendicular speed. For the stepped surfaces, conversely, the ion survival is found to depend critically on the ion speed parallel to the surface. [1] Chakraborty et al., \textit{Phys. Rev.} A \textbf{70}, 052903 (2004). [Preview Abstract] |
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E1.00034: Electron emission from condensed-phase targets induced by fast ion transmission R.A. McLawhorn, S.L. McLawhorn, M. Dingfelder, L.H. Toburen, J.L. Shinpaugh, K.D. Carnes Doubly differential electron emission yields from thin foil targets induced by fast ion impact are presented. Electron energy spectra were measured as a function of emission angle for transmission of 2 and 6 MeV protons and 1 MeV/u fluorine ions through 1-$\mu$m Al, Au, and Cu foils and thin layers of condensed gases frozen on a copper-foil substrate at 40 K. Electron time-of-flight energy analysis was used to focus on the low-energy range of the spectrum where electron emission is most sensitive to the phase of the target. Absolute doubly differential electron emission yields for thin films of amorphous solid water are compared to results from Monte Carlo track structure simulations for electron transport in liquid water. While the model shows excellent agreement with the experimental data for electron energies greater than approximately 60 eV, discrepancies are found at low electron energies. Since low-energy electrons dominate the emission spectrum, this can have important implications for modeling radiation damage in biological systems. [Preview Abstract] |
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E1.00035: QUANTUM INFORMATION AND QUANTUM MEASUREMENTS |
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E1.00036: Three-qubit quantum register and quantum nondemolition detection using a single nitrogen-vacancy center Liang Jiang, Jonathan Hodges, Jero Maze, Mikhail Lukin We experimentally demonstrate coherent control of a quantum register [1,2] consisting of three coupled spin qubits. In our experiments, the electronic spin of the nitrogen-vacancy (NV) center is the primary qubit that can be initialized/detected optically; the two proximal C-13 nuclear spins are ancillary qubits with long coherence times. We demonstrate the spin-exchange operation between the two C-13 nucleus, which enables the full control over three-qubit quantum register. In addition, we demonstrate repetitive quantum nondemolition detection (QND) of spin qubits. As an application, we discuss how such QND technique can improve the sensitivity of NV-based magnetometers [3,4]. [1] M. V. G. Dutt, et al., Science 316, 1312 (2007). [2] L. Jiang, et al., PRA 76, 062323 (2007). [3] J. R. Maze, et al., Nature 455, 644 (2008). [4] J. M. Taylor, et al., Nature Physics 4, 810 (2008). [Preview Abstract] |
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E1.00037: Progress Towards Quantum Networks Using Nitrogen Vacancy Center in Diamond Emre Togan, Yiwen Chu, Alexei Trifonov, M.V. Gurudev Dutt, Liang Jiang, Lily Childress, Alexander Zibrov, Philip Hemmer, Mikhail Lukin Nitrogen Vacancy (NV) centers are promising systems for the realization of quantum registers in scalable quantum networks. A key ingredient of such a network is the entanglement between photons and the spins of individual NV centers that can be used to generate entanglement between separate NV based registers. We describe recent progress toward demonstrating spin-photon time-bin entanglement with the NV and evaluate the feasibility of using this scheme to entangle many NV centers. [Preview Abstract] |
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E1.00038: Ion-trap single-photon source for quantum networks Tracy Northup, Helena Barros, Andreas Stute, Carlos Russo, Piet Schmidt Trapped ions coupled to an optical cavity are a promising route toward quantum networks, in which the quantum states of the ions could be mapped onto photon states for transportation over fiber pathways. We describe an ion-based cavity-QED system consisting of a single trapped $^{40}$Ca$^{+}$ ion coupled to the mode of a high-finesse optical resonator. Intra-cavity photons are generated in a vacuum-stimulated Raman process between two atomic states driven by a laser and the cavity vacuum field. We have observed Raman spectra as a function of drive laser frequency and find excellent quantitative agreement with theoretical simulations. Here we demonstrate and characterize single-photon generation: we evaluate the photon statistics of the source by measurements of the second-order correlation function $g^{(2)}(\tau)$, and the temporal profile of the photon exiting the cavity allows us to investigate the dynamics of the Raman transfer process. Furthermore, through comparisons with simulation, we assess the coherence of the process and discuss its application for entanglement protocols. [Preview Abstract] |
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E1.00039: Photonic qubits for remote quantum information processing P. Maunz, S. Olmschenk, D. Hayes, D.N. Matsukevich, L.-M. Duan, C. Monroe Quantum information processing between remote quantum memories relies on a fast and faithful quantum channel. Recent experiments employed both, the photonic polarization and frequency qubits, in order to entangle remote atoms [1, 2], to teleport quantum information [3] and to operate a quantum gate between distant atoms. Here, we compare the dierent schemes used in these experiments and analyze the advantages of the dierent choices of atomic and photonic qubits and their coherence properties. \\[4pt] [1] D. L. Moehring et al. Nature 449, 68 (2007).\\[0pt] [2] D. N. Matsukevich et al. Phys. Rev. Lett. 100, 150404 2008).\\[0pt] [3] S. Olmschenk et al. Science, 323, 486 (2009). [Preview Abstract] |
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E1.00040: Fast quantum gates with hyperfine qubit states Q. Quraishi, W. Campbell, J. Mizrahi, C. Monroe Recent work in coherent transfer of atomic quantum states demonstrated the novel integration of ultrashort pulsed lasers with trapped ions [1]. Building on this work, we propose an experimental scheme whereby a sequence of optical pulses is used for quantum state manipulation. Specifically, we envisage trapping a single ytterbium ion in a linear trap and then, using a series of nonresonant optical pulses, we plan on individually addressing its hyperfine qubit state [2]. By controlling the timing, phases and intensities between successive pulses we can optimize the fidelity of the qubit gate. Given a 10 ps pulse duration laser, centered at 355 nm (14 nm from resonance at 369 nm) with 4 W average power, we expect two optical pulses to be sufficient to perform a single qubit rotation. Additionally, we expect that by using counter propagating pulses having well defined relative RF frequency shifts, we can impart controllable spin-dependent forces. These results are relevant for motional or temporal gates involving multiple ions. [1] S. Olmschenk, et. al., Science (2009). [2] J. J. Garcia-Ripoll, et. al., Phys. Rev. Lett. 91, 157901 (2003). [Preview Abstract] |
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E1.00041: Integrated optics approach towards ion trap quantum computation Taehyun Kim, Caleb Knoernschild, Justin Migacz, Rachel Noek, Michael Silver, Jungsang Kim A recent proposal for realizing scalable quantum computation is based on a microfabricated ion trap and its integration with micro-optical components performing various functionalities required for state preparation, gate operation, and state detection. In this work, we present our recent progress in implementing a micro-cavity system integrated with an ion trap. In our scheme, a circular-symmetric planar Paul trap will be fabricated on a fiber tip, and a micro-cavity will be formed between the fiber tip and a micro-mirror fabricated on a silicon wafer by isotropic etching. This cavity can dramatically enhance the coupling efficiency into the fiber by the increased spontaneous emission rate into the cavity mode. The enhanced coupling increases the state detection efficiency of trapped ions and entanglement probability of two remote ions. The trapped ion inside a cavity can also allow us to implement cavity QED system between the ion and photons inside the fiber. [Preview Abstract] |
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E1.00042: Quantum optomechanics with Cold atoms Zhaoyuan Ma, Kater Murch, Dan Stamper-Kurn Cavity QEDs with cold atoms have shown the potentials in realizing quantum simulation and quantum computing. As a new application of a system like it, we demonstrate the cold atoms transported into a high-finesse cavity is also a realization of quantum optomechanics where the collective motion of an atomic ensemble serves the role of a moveable optical element in an optical resonator. Experimental investigations of optomechanical effects, such as the bistability of collective atomic motion, the quantification of quantum backaction and the approach to the standard quantum limit measurement, will be presented, along with the comparison of our system to other optomechanical systems, such as those incorporating nanofabricated cantilevers or the large cavity mirrors of gravitational observatories. [Preview Abstract] |
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E1.00043: Direct spatial imaging of blockade effects in a cold Rydberg gas Andrew Schwarzkopf, Rachel Sapiro, Georg Raithel Recently, there has been interest in blockade effects in cold Rydberg gases. Previously, the dipole blockade has been shown to cause a saturation of the Rydberg atom number in atom samples, as well as a narrowing of the excitation number statistics. In the experiment described in this poster, it is planned to measure structures in the Rydberg pair correlation function predicted in [1]. To achieve sufficient spatial magnification, we use the principle of field ion microscopy. In our apparatus, a tungsten tip is placed close to a cold atom cloud in which several Rydberg excitations are prepared using a narrow- linewidth laser. To read out the sample, the tip voltage is suddenly switched to a high value. The Rydberg atoms are field- ionized, and the resultant ions are projected onto a nearby position-sensitive detector. Image analysis reveals structures in the spatial pair correlation function. [1] F. Robicheaux and J. Hernandez, ``Many-body wave function in a dipole blockade configuration,'' Phys. Rev. {\bf A 72}, 63403, 1-4 (2005). [Preview Abstract] |
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E1.00044: Coulomb blockade in a cold Rydberg gas measured by Ramsey Fringes Jianing Han, Tom Gallagher Dipole blockade, the suppression of the excitation of neighboring atoms, at higher principle quantum number n has been studied in a cold Rydberg gas. Free ions, often ignored, exist in a cold Rydberg gas, which can shift the energy levels and contribute the blockade effect. Accurately measuring this field is challenging. In this paper, Ramsey fringes driving the d to f transition, a transition between two electric field sensitive states, are used to estimate this field and the excitation suppression will be presented. [Preview Abstract] |
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E1.00045: COLD ATOMS, MOLECULES, AND PLASMAS |
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E1.00046: Progress with Ultracold Rydberg Atoms in Electric Fields J.E. Johnson, I. Arakelyan, Tao Hong, S.L. Rolston We present progress toward realizing a gas of ultracold Rydberg atoms with defined dipole-dipole interactions. A two-photon process excites a transition in a magneto-optical trap of cold $^{87}$Rb, during which we apply an electric field to orient the dipole moment of the atoms. We have observed Autler-Townes splitting and the Stark shift of the Rydberg excitation energy, and report progress toward exciting polarized Rydbergs in an optical trap and optical lattice. These techniques have applications to neutral atom quantum computing, as well as studying the Extended Bose-Hubbard Model. [Preview Abstract] |
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E1.00047: Electric field effects on cold Rydberg atom nD-nD pair collisions Donald W. Booth, Arne Schwettmann, James P. Shaffer, Jader S. Cabral, Luis F. Gon\c{c}alvez, Luis G. Marcassa Rydberg atom interactions are important for quantum information processing due to the dipole blockade effect. Collisions between Rydberg atoms provide an experimental method for making sensitive tests of these interactions as well as aiding our understanding of Rydberg atom pair excitation processes. We present experimental results that show a significant yield of (n+2)P atoms after the excitation of nD Rydberg atoms in a Rb MOT, where 27$\le $n$\le $41. These results can be attributed to binary collisions between Rydberg atoms. We compare these results to calculations using the Landau-Zener method to calculate transition probabilities at avoided crossings in the two-atom potential energy curves, taking into account the effects of AC Stark shift due to the laser pulse and DC Stark effect due to the background electric field. The calculations indicate that binary collisions between nD-nD pairs result in some transfer into (n+2)P-(n-2)F pairs. \newline [Preview Abstract] |
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E1.00048: Rydberg tagging time-of-flight imaging to study 3-body Recombination Jonathan Tallant, Arne Schwettmann, Donald W. Booth, James P. Shaffer With Rydberg tagging time-of-flight imaging of cold atoms, we have achieved a velocity resolution of $\sim $ 2.5 cm/s. This resolution allows accurate measurements of state-to-state differential cross-sections for ultracold collision processes. With the addition of a dipole trap and a Zeeman slower to our current apparatus, these methods may be implemented to study state-to-state differential cross-sections for 3-body recombination to gain insight into the physics of Efimov states. We present data on the current status of our apparatus and ongoing experiments. Detection methods and associated Frank-Condon factors will be presented. \newline [Preview Abstract] |
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E1.00049: Simulations using echo sequences to observe coherence in a cold Rydberg gas Jes\'us V. Hern\'andez, Francis Robicheaux We simulate the effect of special excitation pulses on a cold gas of atoms. First a rotary echo sequence is used to examine the coherent nature of a frozen Rydberg gas. If collective excitation and de-excitation is present with little or no source of dephasing, after these pulses the system should be returned to a state with few excitations, and a strong echo signal should occur. We investigate systems that should display a perfect echo and systems where the interaction between atoms reduces the echo signal. A spin echo sequence is also used on a system of coherent hopping excitations, and we simulate how the strength of a spin echo signal is affected by thermal motion. [Preview Abstract] |
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E1.00050: Coherent formation of ultracold molecules in the ground rovibrational state Elena Kuznetsova, Marco Gacesa, Philippe Pellegrini, Robin C\^ot\'e, Mikhail D. Lukin, Susanne F. Yelin Ultracold molecular gases can provide new insights into fundamental physics and lead to exciting applications. Dense samples of polar molecules in the ground rovibrational state v=0, J=0 are required for many of these studies. We discuss several coherent techniques, based on Stimulated Raman Adiabatic Passage (STIRAP), to produce molecular gases in v=0, J=0 state starting from either a bound Feshbach state or directly from atomic scattering states. The coherent formation process is highly efficient and preserves high phase-space density of an initial atomic gas. In one of the techniques a Feshbach molecule is brought to v=0, J=0 state through several intermediate vibrational states coupled by Raman transitions. It avoids the difficulty of finding an intermediate electronically excited state with favorable wave function overlap with both a highly delocalized Feshbach and a tightly localized v=0 state, and minimizes population in all intermediate levels. In another approach STIRAP is combined with photoassociation close to a Feshbach resonance, allowing to convert nearly the entire atomic population to v=0, J=0 molecules using low intensity laser pulses. [Preview Abstract] |
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E1.00051: A quantum gas of ground state molecules in an optical lattice Johann Danzl, Manfred Mark, Elmar Haller, Mattias Gustavsson, Russell Hart, Hanns-Christoph N\"agerl Ultracold samples of molecules are ideally suited for fundamental studies in physics and chemistry. For many of the proposed experiments full molecular state control and high phase space densities are needed. We create a dense quantum gas of ground state Cs$_{2}$ molecules trapped at the wells of a 3D optical lattice, i.e. a molecular Mott-insulator-like state with ground state molecules with vibrational quantum number $v = 0$. We first efficiently produce weakly bound molecules with $v \approx 155 $ on a Feshbach resonance out of an atomic Mott-insulator state that is obtained from a Bose-Einstein condensate (BEC) of Cs atoms. These molecules are then (coherently) transferred to the ground state by two sequential two-photon STIRAP processes via the intermediate vibrational level $v \approx 73 $ $^{1}$. The molecule production efficiency and the single-step STIRAP transfer efficiency reach 50\% and 80\%, respectively. We discuss the stability of the system and our progress towards the creation of a BEC of ground state molecules, which is expected to form when the molecular Mott-like state is ``melted'' upon lowering the lattice depth and releasing the molecules from the wells into a large volume trap. \newline $^{1}$J. G. Danzl, E. Haller, M. Gustavsson, M. Mark, R. Hart, N. Bouloufa, O. Dulieu, H. Ritsch, H.-C. N\"agerl, Science \textbf{321}, 1062 (2008). [Preview Abstract] |
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E1.00052: Cold collisions of Stark decelerated ND$_{3}$ molecules and magnetically trapped $^{87}$Rb atoms Noah Fitch, Paul Parazzoli, Dan Lobser, Heather Lewandowski Stark deceleration is a proven technique for decelerating polar molecules using time-varying inhomogeneous electric fields. This technique allows for precise control over both external and internal degrees of freedom. This high level of molecular control is particularly useful for collision studies where precise tuning of the center of mass collision energy is required. Measuring collision thresholds is one particular example where this control is critically important. We use this technique to study the energy dependence of inelastic collision cross sections between decelerated deuterated ammonia (ND$_{3}$) molecules and magnetically trapped Rb atoms. [Preview Abstract] |
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E1.00053: BOSE-EINSTEIN CONDENSATES |
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E1.00054: Quantum Dynamics of Photoassociation of an Atomic Bose-Einstein Condensate in a Driven Optical Cavity J. Mauricio Campuzano, Christopher P. Search We seek to compare various formulations of the quantum field dynamics for cavity assisted photoassociation of an atomic Bose-Einstein Condensates inside of a driven optical resonator. Specifically, our Heisenberg equations of motion describe the dynamics of the three coupled bosonic fields for atom, molecules, and photons in which atoms are converted to quantum degenerate molecules via two photon Raman photoassociation. To solve for the nonlinear quantum dynamics, we go beyond mean field theory (MFT) by truncating the BBGKY hierarchy of equations first at second order products of the field operators but also at fourth order products of the operators with the assistance of a pseudo-angular momentum representation (PAM). The approximate quantum dynamics of these higher order beyond-MFT equations are contrasted to exact numerical solutions of the density matrix equations.~ We show how the beyond-MFT equations are sufficient to describe the initial conversion of atoms into molecules via spontaneous emission of a photon into the cavity mode, which is outside of the scope of MFT. We also analyze squeezing and non-classical cross-correlations between the molecular and cavity fields. [Preview Abstract] |
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E1.00055: Zero-temperature phase diagram of a two-species atomic Bose-Einstein condensates with an interspecies Feshbach resonance Lu Zhou, Jing Qian, Han Pu, Weiping Zhang, Hong Y. Ling We consider a mixture of two-species atomic Bose-Einstein codensates coupled to a bound molecular state at zero temperature via interspecies Feshbach resonance. The interspecies Feshbach coupling precludes the possibility of doubly mixed phases while enables not only the pure molecular superfluid but also the pure atomic superfluids to exist as distinct phases. We construct the phase diagram and show that this system is able to support a rich set of phase separations, including that between two distinct mixed atom-molecule phases. We pay particular attention to the effects of the Feschbach coupling and the particle collisions on the miscibility of this multi-component condensate system. [Preview Abstract] |
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E1.00056: A complete basis for a perturbation expansion of the general N-body problem W. Blake Laing, David W. Kelle, Martin Dunn, Deborah K. Watson We introduce a basis set to calculate perturbation coefficients in an expansion of the general $N$-body problem. This basis has two advantages. First, the basis is complete order-by-order for the perturbation series. Second, the number of independent basis tensors spanning the space for a given order does not scale with $N$, the number of particles, despite the generality of the problem. At first order, the number of basis tensors is 23 for all $N$ although the problem at first order scales as $N^6$. The perturbation series is expanded in inverse powers of the spatial dimension. This results in a maximally symmetric configuration at lowest order which has a point group isomorphic with the symmetric group, $S_N$. The resulting perturbation series is order-by-order invariant under the $N!$ operations of the $S_N$ point group which is responsible for the slower than exponential growth of the basis. We perform the first test of this formalism including the completeness of the basis through first order by comparing to an exactly solvable fully-interacting problem of $N$ particles with a two-body harmonic interaction potential. [Preview Abstract] |
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E1.00057: A Dipolar Bose-Einstein Condensate as an Anisotropic Superfluid Ryan Wilson, Shai Ronen, John Bohn We consider a harmonically trapped dipolar Bose-Einstein condensate that is polarized by an external field. For a range of dipole-dipole interaction strengths and polarization angles, we calculate the quasiparticle spectrum of this system. In a quasi-two dimensional geometry where the condensate is free to move in a plane, the condensate exhibits a continuous dispersion relation that depends on the direction of wave propagation with respect to the field. The gas therefore exhibits an anisotropic superfluid velocity, as defined by the Landau criterion. Even for a pancake-shaped trap where atoms are confined in all directions, we can identify a ``discrete dispersion relation,'' with consequences for sound propagation in this kind of gas. [Preview Abstract] |
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E1.00058: Dipolar BEC in a double-well potential M. Asad-uz-Zaman, D. Blume The long-range and anisotropic nature of dipole-dipole interactions makes a dipolar BEC a promising and exciting play ground for physicists. This work considers the stability and dynamics of a dipolar BEC in a cylindrically symmetric double-well potential. We are particularly interested in the structure formation, the self-trapping and the Josephson oscillation in the double-well potential and how these behaviors differ from a system with s-wave interactions only. We are using the symmetric and antisymmetric solution of the time-independent Gross-Pitaevskii equation as the basis for the calculation of the Josephson oscillation frequency and compare it with that obtained by solving the time-dependent Gross-Pitaevskii equation. [Preview Abstract] |
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E1.00059: Formation of Solitons During the BEC Phase Transition JiaJia Chang, Chris Hamner, Peter Engels During the formation of a Bose-Einstein condensate, local differences in the emerging phase and interferences can lead to topological defects. In our experiment we analyze these dynamics in an elongated geometry and observe a pronounced appearance of solitons when the phase transition from a cloud of classical $^{87}$Rb atoms to a BEC in a cigar-shaped trap is crossed sufficiently rapidly. The spontaneous formation of such topological defects is a general feature of continuous phase transitions. Recent and ongoing results will be discussed. [Preview Abstract] |
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E1.00060: The onset of superfluid turbulence in Bose-Einstein condensates Tyler Neely, Edward Samson, Ashton Bradley, Matthew Davis, Brian Anderson We explore the onset of superfluid turbulence in Bose-Einstein condensates held in highly oblate traps. In our procedure, highly oblate BECs are first created in a combined optical and magnetic trap with an approximately 11:1 aspect ratio. We then modulate the the harmonic trapping frequency, introducing vortices and turbulence into the trapped gas. We explore the onset of superfluid turbulence in BECs held in both harmonic and multiply connected potential wells, comparing the characteristics of turbulence in both traps. By studying various excitation methods and re-thermalization of the gases as well as comparisons between experimental and numerical results, transitions to turbulence of ultra-cold trapped gases can be quantitatively characterized. [Preview Abstract] |
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E1.00061: Decay of rotational flow of a Bose-Einstein condensate in an optical toroidal potential Anand Ramanathan, Sergio Muniz, Kristian Helmerson, William Phillips An interacting Bose-Einstein Condensate (BEC) is expected to exhibit superfluidity, and persistent currents in a magnetically trapped, toroidal shaped BEC have been seen lasting up to 10 seconds [1]. We have recently performed experiments in a ring-shaped optical dipole trap, formed by the combination of a Laguerre-Gaussian beam intersecting a light sheet at normal incidence. We use evaporative cooling to create a quasi-2D, ring-shaped BEC. We induce rotational flow by transferring orbital angular momentum of light to the atoms [1]. The flow was observed to decay very rapidly, in less than a rotation period. We are concurrently investigating if the rapid decay is due to inhomogeneities in the optical potential or due to the quasi-2D character of the BEC. [1] C. Ryu, M. F. Andersen, P. Clad\'{e}, Vasant Natarajan, K. Helmerson, and W. D. Phillips, Physical Review Letters, 99 260401 (2007). [Preview Abstract] |
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E1.00062: Creating arbitrary optical potentials to study and manipulate Bose-Einstein Condensates. Sergio Muniz, Chandra Raman, Kristian Helmerson, William Phillips There is a lot of interest in studying degenerate quantum gases in various types of confining potentials, to explore effects ranging from quantum transport to quantum information. More recently, spatial light modulators have been proposed to produce generalized optical potentials. Here we present a particular kind of spatial-light modulation technique that we are investigating, based on acousto-optic devices, to produce arbitrary time-averaged optical potentials in 2D. This approach can be combined with other magnetic or optical confinement to create various trapping potentials in 3D as well. In particular, we will discuss the case of a Bose- Einstein condensate (BEC) in a toroidal trap in two different regimes: the quasi-2D and 3D limits. The approach proposed here allows for \emph{in-situ} corrections of the desired potential, after diagnosing any imperfections or aberrations caused by the propagation of the beams through the optical system. In addition, it may be a very promising method to create dynamically varying potentials. We will also discuss the application of this method to the study of macroscopic persistent currents using sodium BEC. [Preview Abstract] |
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E1.00063: Resolving and addressing independent Bose-Einstein condensates (BECs) in individual sites of a CO$_{2}$ laser optical lattice Eva Bookjans, Chris D. Hamley, Peyman Ahmadi, Michael S. Chapman We realize the production of an array of 10-30 independent $^{87}$Rb spin-1 BECs in the standing wave potential of a CO$_{2}$ laser by extending the single focus trap geometry of our all-optical BEC to a one-dimensional lattice. The period of the optical lattice created by the CO$_{2}$ laser is 5.3$\mu $m and is therefore large enough to optically resolve the individual sites and to selectively address them. By applying a high magnetic field gradient, we are able to manipulate single sites using microwave transitions between the different hyperfine states. We will present our experimental data together with theoretical simulations and discuss applications to studies of small condensates and their interactions. [Preview Abstract] |
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E1.00064: Charged impurities in a BEC Rachel Sapiro, David Anderson, Rui Zhang, Georg Raithel We present an apparatus for studying the interactions between a 87Rb BEC and ions or other impurity particles. Our system is unique among BEC machines in that we have the ability to cancel stray electric fields with high precision. This allows us to do controlled experiments in which a single or small number of charged impurities interact with a BEC for a significant amount of time. Furthermore, this system allows for sub-micron- resolution spatial imaging of ions or Rydberg atoms. This creates the possibility of high-resolution tomography of structures in a BEC or a cold atom cloud. [Preview Abstract] |
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E1.00065: Achieving and Analyzing the Cold Atoms in a dilute Atomic Gas Jina Park, Dahyun Yum, Wonho Jhe We investigate a quantum statistical phenomenon of Bose-condensed gas of alkali atoms in a magnetic trap. In double MOT system, Rubidium 87 atoms are captured at a gathering chamber and then transferred to a glass chamber. Trapped atomic clouds are cooled and loaded into a time-averaged orbiting potential applied by the superposition of a big spherical quadrupole field using anti-helmholtz coil and a small rotating bias field at 7kHz. In each step, we check the temperature and the density obtained by time of flight (TOF) distribution of trapped atoms. Through this process, we optimize our system including a trap design or experimental time sequence. In this presentation, we will describe how to improve our setup and show some progress. Future experiments related with the dynamical properties of cold atoms in the magnetic trap will be also proposed. [Preview Abstract] |
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E1.00066: When the Vacuum is a Drag Andrew Sykes, Matthew Davis, David Roberts Superfluidity is a remarkable macroscopic quantum phenomenon that was discovered in 1938 in liquid helium below 2.17 K by Kapitza, Allen and Misener. London was the first person to make the connection with the theory of Bose-Einstein condensation (BEC) and degenerate Bose gases developed by Einstein in 1924, and BEC is now understood to be an important ingredient of superfluidity. One of the features of a superfluid is that it exhibits frictionless flow below a certain ``critical'' velocity, and this is well understood at the level of mean-field theory. However, the inclusion of quantum fluctuations gives rise to a puzzle that has a connection to the Casimir force between two dielectrics in vacuum. Calculations suggest that the scattering of quantum fluctuations lead to a non-zero drag force at any velocity. Here I will discuss our recent work on calculating the drag force on an obstacle moving through a 1D Bose gas. [Preview Abstract] |
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E1.00067: DEGENERATE FERMI GASES |
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E1.00068: Controlling spin current in a trapped Fermi gas Xu Du, Yingyi Zhang, Jessie Petricka, Le Luo, Bason Clancy, John Thomas We observe fundamental new features of spin current in a weakly interacting Fermi gas of $^6$Li. By creating a spin current and then reversing its flow, we demonstrate control of the spin current. This reversal is predicted by an undamped spin wave theory, which we have developed to explain our previous observation of spin segregation in a trapped Fermi gas. Numerical calculations based on this theory are in very good agreement with the experimental results both in amplitude and temporal evolution. The theory provides a simple physical description of the origin of the spin current and suggests that broad control of the spin current is possible. {References:} [1] X. Du \textit{et al.}, Phys. Rev. Lett. 101, 150401 (2008). [Preview Abstract] |
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E1.00069: All-optical methods for cooling $^{6}$Li to quantum degeneracy P.M. Duarte, J.M. Hitchcock, T.A. Corcovilos, R.G. Hulet We present an all-optical production of a degenerate Fermi gas of $^{6}$Li. The sample is produced by evaporating a spin mixture of the two lowest ground state magnetic sublevels at unitarity in a 1064 nm optical dipole trap. We have modeled new methods for enhancing the evaporation rate and lowering the final temperature by tilting the optical trapping potential with the addition of an off-axis beam. The degenerate spin mixture will be loaded into a 3D simple cubic lattice with the purpose of studying the phase boundary of the antiferromagnetic ground state as a function of interactions and nearest neighbor tunneling. [Preview Abstract] |
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E1.00070: Strongly Interacting Quantum Mixtures of Ultracold Atoms Cheng-Hsun Wu, Ariel Sommer, Ibon Santiago-Gomez, Peyman Ahmadi, Martin Zwierlein In what forms does matter organize itself under the influence of interaction? This is the fundamental question of many-body physics, which arises at all length scales: from the dense quark matter present in the beginning of our Universe, to the atomic nucleus, the electrons inside a metal, and the inner workings of a neutron star. However, strong interactions between particles do not allow for a simple description of such systems. Strongly interacting mixtures of ultracold atoms will allow us to realize complex many-body systems relevant to the description of High-T$_C$ and Giant Magnetoresistance materials and which cannot be simulated theoretically. We are constructing a new apparatus that will allow to cool three different species of atoms, two of them fermionic, $^6$Li and $^{40}$K, and one of them bosonic, $^{23}$Na. A two-species Fermi-Fermi mixture close to a Feshbach resonance realizes an unusual form of fermionic superfluid with unequal masses. A mass- and number imbalanced Fermi mixture might give access to new states of fermionic matter, such as the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase of Cooper pairs with non-zero momentum. [Preview Abstract] |
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E1.00071: Radio-Frequency Spectroscopy of strongly interacting Fermi gases Andre Schirotzek, Cheng-Hsun Wu, Ariel Sommer, Martin Zwierlein Strongly interacting Fermi gases exhibit a rich phase diagram in the BEC-BCS crossover. In recent experiments we have used radio frequency spectroscopy to probe two physically very different regimes: 1.) We have observed Spin-Polarons in a highly imbalanced Fermi mixture. A single spin down atom immersed in a spin up Fermi sea dresses itself with a cloud of majority atoms, thus forming a Spin-Polaron. rf spectroscopy can directly reveal the polaron and allows for an experimental measure of the quasiparticle residue $Z$ and the chemical potential $\mu$ of this Fermi liquid. At a critical interaction strength, the transition to two-particle molecular binding is observed. 2.) rf spectroscopy of quasiparticles in a polarized superfluid allowed us to determine the superfluid gap $\Delta$ and has demonstrated the importance of the Hartree energy $U$ in rf spectra [1]. [1] Andre Schirotzek, Yong-il Shin, Christian H. Schunck and Wolfgang Ketterle, Phys. Rev. Lett. 101, 140403 (2008) [Preview Abstract] |
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E1.00072: Strongly Interacting Fermi and Bose-Fermi Gases Caleb A. Christensen, Jae H. Choi, Gyu-boong Jo, Ye-ryoung Lee, Tony H. Kim, Tout Wang, David E. Pritchard, Wolfgang Ketterle We study ultracold gases of $^6$Li and $^{23}$Na near homonuclear and heteronuclear Feshbach resonances. By sympathetically cooling Li with Na and loading the gases into optical dipole traps, we can obtain quantum degenerate samples with more than 10$^6$ atoms of either or both species. We study Fermi gases of Li in the two lowest hyperfine states or Bose-Fermi mixtures of Li and Na in the hyperfine ground states. We measure loss rates and use in situ imaging to study the effects of strong interactions. Our versatile apparatus also offers the possibility to load these strongly interacting gases into optical lattices of various geometries. [Preview Abstract] |
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E1.00073: Viscosity Measurements in an Ultracold, Strongly-Interacting, Fermi Gas Chenglin Cao, Jessie Petricka, James Joseph, Ethan Elliot, Bason Clancy, Le Luo, John Thomas Experiments and preliminary results measuring the viscosity in an ultracold Fermi gas are presented. An optically prepared, degenerate cloud of Fermionic $^6$Li placed in an external magnetic field tuned to the location of a scattering (Feshbach) resonance produces a strongly interacting gas. Rotation and subsequent expansion follows a rigorous hydrodynamic form at zero temperature. Experiments at the lowest temperatures confirm this behavior. At higher temperatures perturbative models involving viscous forces can provide an estimate of the temperature dependent viscosity of our sample. The predicted and observed motion is a deviation from perfect hydrodynamic behavior involving slowed expansion along the narrow trap dimensions and accelerated expansion along the long dimension. Attributing the observations solely to our viscosity model shows nearly zero viscosity up to energies of E=Ef. Above this energy, the viscosity rises with a nearly T$^{3/2}$ scaling. We discuss our ongoing analysis and the consistency of our model within fluid mechanics and examine possible extensions necessary to explain observed shape changes within the cloud. [Preview Abstract] |
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E1.00074: Inelastic Collisions of a Fermi Gas in the BEC-BCS Crossover regime Yingyi Zhang, Xu Du, John Thomas We measure inelastic collisions of a Fermi gas of $^6$Li in the BEC-BCS crossover regime. We load the ultracold atoms of $^6$Li into a CO$_2$ laser standing wave, forming a two dimensional Fermi gas. Atomic density in the 2-D system is 20 times higher than that in a 3-D Fermi gas, which leads to a significant increase in atom loss. At energy $E/E_F\simeq1.8$, data shows a dominant three-body decay process. We measure the magnetic field dependence of the three-body inelastic collision coefficients. At $E/E_F\simeq0.7$, data shows coexistence of two-body and three-body decay processes on and below the Feshbach resonance. We suggest the two-body decay may involve pairs of atoms and determine the two-body inelastic collision coefficients. [Preview Abstract] |
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E1.00075: Sound propagation in an elongated unitary gas Munekazu Horikoshi, Shuta Nakajima, Yasuhisa Inada, Swarupananda Pradhan, Masahito Ueda, Takashi Mukaiyama We have measured temperature dependence of a speed of sound waves propagating along the axial direction in an elongated unitary Fermi gas of $^6$Li atoms in an optical trap where the magnetic field is tuned at the Feshbach resonance. The measurement is repeated at various temperatures, and the data shows a notable change of the speed below the superfluid phase transition temperature which is determined by an additional experiment using a technique of projection. Under the universal hypothesis and an isentropic process, the speed of sound can be given by the temperature and the ratio of the interaction energy to the kinetic energy, which is defined as $\beta ^* = E_{int}/E_{kin}$. Whereas $\beta$ is normally defined only for $T=0$, we introduce (*) to denote that the system is at a finite temperature. Since the temperature of the unitary gas can be determined from the cloud width, we can estimate the $\beta ^*$ value from the speed and the temperature which are obtained experimentally. The result shows that the estimated $\beta ^*$ values start to change dramatically at the critical temperature and it implies the existence of two $\beta ^*$ values below the critical temperature, which are $\beta _n ^*$ for the normal component and $\beta _n ^*$ for the superfluid component. [Preview Abstract] |
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E1.00076: Exact numerical simulations of interacting fermions in 1D trapping potentials Bernd Schmidt, Dominik Muth, Alexander Mering, Michael Fleischhauer We discuss p-wave interacting spin-polarized fermions in a 1D trapping potential for arbitrary interaction strength. Using a boson-fermion mapping in 1D, interacting fermions with p-wave interaction strength $g_{1D}^F$ can be mapped to bosons with s-wave interaction strength $g_{1D}^B$ = -1/g$_{1D}^F$. As a consequence a weakly interacting Fermi gas behaves in local properties like a strongly interacting Bose gas and vice versa. We derive a proper discretized model for the interacting fermions and compare its predictions with that obtained by the Bose-Fermi mapping using DMRG and TEBD simulations. We calculate the realspace and momentum distributions of the fermions for the whole range of interaction strength starting at a weakly interacting gas going to the Fermi-Tonks limit and compare the results to predictions from field theoretical approaches. [Preview Abstract] |
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E1.00077: DYNAMIC AND OUT-OF-EQUILIBRIUM PHENOMENA IN COLD ATOMS |
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E1.00078: Measurement of interaction strength for spontaneous symmetric breaking in a parametrically modulated magneto-optical trap Geol Moon, Myoung-Sun Heo, Yonghee Kim, Heung-Ryoul Noh, Wonho Jhe We study on the attractive interaction between two atomic clouds, which leads to Spontaneous Symmetric Breaking (SSB) of atomic populations in the parametrically modulated magneto- optical trap (MOT). The parametric modulation is performed by periodically changing the intensity of laser beam along the axis of the anti-Helmholtz coils. In this parametrically modulated system, the two atomic clouds vibrate along the axis with the phase difference of $\pi$. The collective behavior observed in a single cloud of MOT also exists between the two clouds and the shadow effect which is one of the collective behavior brings about an attractive interaction between the two clouds. In special, this attractive interaction contributes to SSB which happens when the total atomic number is above a critical value. We measure the interaction strength by observing the change of vibration amplitude of each cloud. We also report on the various factors which affect the interaction strength between the two clouds. [Preview Abstract] |
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E1.00079: Mediated interactions in a dilute Bose-Einstein condensate and Fermi gas mixture Deborah Santamore, Eddy Timmermans We develop a diagrammatic perturbation treatment to calculate the zero-temperature equation of state of the dilute gas mixture of a single spin component Bose-Einstein condensate (BEC) and a normal Fermi gas of single spin fermion particles. We find that the mean-field description breaks down near the mechanical instability related to the phase separation phenomenon. Our analysis shows that the instability is caused by the competition of the usual short-range and fermion-mediated boson-boson interactions, which result in a boson compressibility that diverges. In the low BEC-density limit, we show that the diagrammatic analysis simplifies, we sum part of the higher order diagrams, and we discuss the effects of other higher-order contributions. Our results suggest that careful experimental measurements near the phase separation transition of fermion-boson mixtures can explore fundamentally interesting quantum many-body behavior. [Preview Abstract] |
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E1.00080: Modeling a sodium spinor condensate Stephen Maxwell, Thomas Hanna, Yingmei Liu, Eite Tiesinga, Paul Lett An optically trapped condensate of F=1 sodium atoms shows coherent oscillations of the spin populations. These oscillations are well described by a theory based on the assumption that the three spin projections of the condensate share a single spatial mode [1]. Some time after the initial state preparation the oscillations damp and the system arrives in a state consistent with the ground state predictions of this theory. The transition from coherent oscillations to a ground state, however, is not understood. In this poster we describe a numerical model based on a three- component coupled Gross Pitaevskii equation that simulates the behaviour of the gas. The model shows a coupling of spin interactions to motional degrees of freedom and shows behaviour similar to that seen in experiment. We also describe our efforts to produce an analytic model of this system. [1] W. Zhang et al, Phys. Rev. A, 72, 013602 (2005) [Preview Abstract] |
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E1.00081: Stripe formation and anomalous dynamics of a dual species Bose-Einstein condensate in an optical lattice Uttam Shrestha, Juha Javanainen, Janne Ruostekoski We study the dynamical instability of a dual species Bose-Einstein condensate in an optical lattice in the limit of weak atom-atom interactions. The time evolution of the density distributions shows the mixing and demixing behavior between the two species, in contrast to the common belief that the instability leads to phase separation. We also observe a striation pattern when one species is allowed to move. The number of striations is equal to the relative phase winding of the two species. For larger flow velocity we observe a sudden jump in the overlap of the state with the initial state. This may be explained in terms of phase slip during the flow, a phenomenon closely related to Landau instability. [Preview Abstract] |
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E1.00082: Comprehensive study of parametric resonance of high-density ultracold $^{87}$Rb atoms in an optical dipole trap A. Win, S. Balik, M.D. Havey We report a comprehensive experimental study of parametric resonance in a sample of high-density and ultracold $^{87}Rb$ atoms confined to a far off resonance optical dipole trap. The imaged and expanded ultracold atom cloud after parametric excitation shows significant modification, with higher sensitivity than traditional measurements of parametrically-driven trap loss. Detailed comparison of the two approaches also suggests that an imaging approach is more sensitive to the atoms near the energy minimum of the trap, and thus can provide more precise information about the harmonic part of the optical trapping potential. [Preview Abstract] |
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E1.00083: LASER COOLING AND TRAPPING |
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E1.00084: ABSTRACT WITHDRAWN |
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E1.00085: Laser cooling of rubidium atoms in an integrating sphere Liang Liu, Huadong Cheng, Wenzhuo Zhang, Ling Xiao, Yuzhu Wang Recently laser cooling of atoms directly from the vapor background in diffuse laser light has received a lot of attention because of its application to making a compact, cold atom clock. In this work we describe an experiment on laser cooling of $^{87}$Rb atoms directly from the vapor background in diffuse light. Diffuse light is produced in a ceramic integrating sphere by multiple scattering of two laser beams injected through multi-mode fibers. We measured the absorption spectra of cold atoms by scanning the frequency of a probe beam. We also measured the time dependence of the absorption of a probe beam after the cooling light is switched off. With this method, we can eliminate the saturation effect of the cooling light on the cold atoms, and observe the real absorption of probe beam. In order to increase the number of captured cold atoms, we injected two frequency cooling lasers. Atoms with high velocity are cooled by large-detuned light, and those with low velocity by small-detuned light. A combination of two frequency lasers leads to a larger cooling range, and thus can capture more cold atoms. In our experiment, two frequency cooling captured cold atoms two times more than single frequency cooling, and up to $4\times 10^9$ cold atoms are obtained. [Preview Abstract] |
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E1.00086: Pyramidal Magneto-Optical Atom Traps on a Chip Samuel Pollock, Joseph Cotter, Athanasios Laliotis, Fernando Ramirez-Martinez, Michael Trupke, Ed Hinds We demonstrate the fabrication and development of scalable arrays of pyramidal magneto-optical micro-traps in silicon as an elegant and simple way of capturing atoms from a thermal vapour directly on the surface of atom chips. The integration of these devices offers good prospects for reducing the cost and complexity of atom-chip experiments. Potential applications range from using an array of small cold atom clouds to map local magnetic field variations or sensing inertial forces. The micropyramids could also serve as single-atom sources for loading integrated optical cavities, allowing for production of single photons on demand for applications in QIP. We form the pyramids using an anisotropic etching process, preferentially etching the {100} plane to produce hollow pyramids in the surface of the wafer. Further processes have been developed to effectively smooth the rough mirror surfaces resulting from the anisotropic etch whilst maintaining the planar structure. We have recently demonstrated that these microfabricated pyramids can trap atoms from a thermal vapour. We present experimental data and associated theoretical models to describe the capture and loss processes of the MOT, as well as the properties of the cold atomic sample in the sub-mm$^3$ trapping region of the micropyramids. [Preview Abstract] |
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E1.00087: Progress toward the magneto-optical trapping of dysprosium Seo Ho Youn, Mingwu Lu, Ushnish Ray, Benjamin Lev We present details of an apparatus intended for the magneto-optical trapping (MOT) of dysprosium, a lanthanide (rare-earth) atom with an unsurpassed magnetic moment of 10 Bohr magnetons. The laser cooling and trapping of highly magnetic atoms with complex level structure opens a new frontier for ultracold dipolar physics, atom chip microscopy, and quantum information processing. While lanthanides do not generally have closed optical transitions beneficial for laser cooling, their large magnetic moments enable magnetic confinement in a repumper-less MOT region while the excited state population recycles to the ground state; such a scheme was recently successful for the laser cooling and trapping of atomic Er [1], and Dy should be amenable to sub-$\mu$K laser cooling as well. We discuss both the UHV system---including high temperature oven, Zeeman slower, and trapping region---and the stabilized 421 nm laser system for the slower, MOT, and imaging light. [1] J. J. McClelland and J. L. Hanssen,``Laser Cooling without Repumping: A Magneto-Optical Trap for Erbium Atoms," Phys. Rev. Lett., 96, 143005 (2006). [Preview Abstract] |
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E1.00088: Limitations to the Number of $^{85}$Rb and $^{87}$Rb Atoms Simultaneously Confined in a Shallow Optical Trap. Anthony Gorges, Mathew Hamilton, Jacob Roberts Simultaneously loading $^{85}$Rb and $^{87}$Rb into an optical trap has led to the observation of unexpected interferences. Not only will the presence of one species reduce the load rate into the trap of the other, but additionally the maximum number which can be loaded into the trap is greatly reduced as well. The reduction in maximum number is greater than expected from the measured light-assisted collisional loss rate. Rather, the presence of atoms in the trap interferes with subsequent loading. We present our observations characterizing the interference in the loading of atoms into the shallow optical trap. [Preview Abstract] |
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E1.00089: Characterization of LIAD loaded sodium MOT Tetsuya Ishikawa, Matthew Gibbs, Gustavo Telles, Chandra Raman We present a compact ultrahigh vacuum (UHV) vapor cell for magneto-optical trapping (MOT) of sodium atoms.~ Our system features light-induced atomic desorption (LIAD) loading. LIAD at short wavelengths (375 nm and 455 nm) was used, allowing for fast switching and control of the sodium vapor pressure. We have used a single laser beam which passes through an electro-optic modulator to provide repump light and then splits into three retro-reflected beams to create a 50 million atom MOT. Our results are in good agreement with the model presented on [1,2] and demonstrate the utility of vapor cell MOTs for ultracold experiments using atomic sodium. \newline \newline 1. C. Monroe et al., Phys. Rev. Lett. 65, 1571 (1990); \newline 2. S. Bartalini et al., Eur. Phys. J. D 36, 101 (2005) [Preview Abstract] |
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E1.00090: Closed-loop stabilization of a quasi-electrostatic trap Dwight Whitaker, Alex Zylstra We use a the signal from a solid-state infrared optical detector to control the power of a CO$_2$ laser, which is used to trap and cool a collection of rubidium-87 atoms. Atoms are loaded from a vapor cell MOT into a variable size QUEST produced by a single focused CO$_2$ laser beam. The atoms are then cooled by lowering the laser power with an acousto-optical modulator. In this poster we will discuss the effects of laser stabilization, provided by a closed-loop servo circuit between the solid-state detector and the AOM, on the temperature stability of evaporatively cooled atoms and discuss the possibility of experiments on temperature controlled, ultracold samples. [Preview Abstract] |
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E1.00091: Progress towards a continuous atom laser Mallory Traxler, Cornelius Hempel, Varun Vaidya, Georg Raithel We report on progress towards a continuous atom laser. In a previous design, $^{87}$Rb atoms are guided in a high-gradient, linear magnetic guide with a transverse temperature of 420 $\mu $K, a longitudinal temperature of 1 mK, and a flux of 3 x 10$^{7}$ atoms s$^{-1}$. This setup is currently being used to study the dynamics of Rydberg atoms and cold plasmas in extreme magnetic field configurations. In the present poster, we summarize results obtained in this guide. We have begun constructing an improved guide setup that enables a larger and colder atomic flux by addressing key problems associated with the continuous flow of cold atoms, such as atom heating during injection into the guide and atom losses due to laser-cooling stray light along the guide. In the poster, we outline the methods employed in the new guide setup to eliminate these issues. [Preview Abstract] |
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E1.00092: Optical Sidebands in Extended Cavity Diode Lasers Timothy Roach, Josh Ryor, Paul Oxley We have measured the amplitude of optical sidebands produced by RF current modulation of extended cavity diode lasers and studied its dependence on laser drive current, modulation frequency, and external cavity length. The modulated laser light is used in our work for optical repumping for laser cooling (Rb) and atomic beams (Li), but this can be (and is) a broadly applicable method for producing easily controlled optical sidebands. We require the linewidth and stability provided by an extended cavity; this is known to affect sideband amplitude but is not well studied. We found that sideband amplitude in a 780nm diode laser increased significantly in the modulation frequency range 2.8 to 3.3GHz, with a more pronounced effect at higher laser drive current. The same effect was seen with the external cavity removed, so this is likely due to a relaxation effect in the semiconductor. The external cavity reduced the sideband amplitude, in comparison to the bare laser, but no strong dependence on cavity length was seen for cavity lengths from 2 to 4cm. Further investigations to look for effects near the cavity free spectral range using higher modulation frequencies (~6.8GHz) and other cavity lengths are ongoing. [Preview Abstract] |
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E1.00093: Sympathetic Heating Spectroscopy with Ca$^{+}$ Isotopes Craig Clark, Yatis Dodia, James Geoders, Grahame Vittorini, Ricardo Viteri, Kenneth Brown Sympathetic heating spectroscopy is a promising technique to obtain ultrahigh-resolution spectra of molecular ions. The basis for this technique is to monitor the evolution of the fluorescence of a two-body Coulomb crystal in a Paul linear trap as one of the ions is excited. This crystal consists of an atomic ion which can be trapped and laser cooled (control ion), and a sympathetically cooled molecular or atomic ion (spectroscopy ion). We use isotopes of Ca$^{+}$ for the development of sympathetic heating spectroscopy because excitation schemes are well understood. We use $^{40}$Ca$^{+}$ for the control ion and $^{44}$Ca$^{+}$ for the spectroscopy ion. Heating of the $^{40}$Ca$^{+}$ is-achieved by driving the S$_{1\backslash 2}$-P$_{1\backslash 2}$ transition, detuned to the blue. We characterize the sympathetic heating spectroscopy for a variety of detunings, laser intensities, and for both open and closed optical transitions. [Preview Abstract] |
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E1.00094: Trapping and Optical Detection of Doubly-charged Ytterbium Ions Martin Schauer, Jeremy Danielson, David Feldbaum, Saidur Rahaman, BaoZhou Sun, Xinxin Zhao, Justin Torgerson Forbidden optical transitions in trapped ions are of great interest for high precision spectroscopic applications. The insensitivity to ambient fields of the $^{1}$S$_{0}$ -- $^{3}$P$_{0}$ transition in Yb$^{2+}$ coupled with the isolation from the environment provided by trapped ions makes this system particularly appealing. We report on trapping and optical detection of isotopically-pure, laser-cooled samples of doubly-charged Ytterbium ions. We discuss future work to be done with these and singly-charged Ytterbium ions in the same apparatus. [Preview Abstract] |
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E1.00095: Observation of recoil-induced resonaces and electromagnetically induced absorption of cold atoms in diffuse light Liang Liu In this paper we report an experiment on the observation of the recoil-induced resonances (RIR) and electromagnetically induced absorption (EIA) of cold $^{87}$Rb atoms in diffuse light in an integrating sphere. The atoms are first cooled in diffuse light and a probe beam is inserted to observe nonlinear spectra of cold atoms. The pump light of RIR and EIA comes from the diffuse light, which also serves the cooling light. The probe light beam is a weak laser split from the cooling laser in order to keep the cooling and probe lasers coherent. We measured the nonlinear spectra varying with detuning of the diffuse laser light, and studied the mechanism of RIR and EIA in the configuration with diffuse-light pumping and laser probing. The differences of nonlinear spectra of cold atoms between diffuse-light cooling and a magneto-optical trap (MOT) are also discussed. We present the theoretical models of the RIR and EIA of cold atoms in diffuse laser light. The theoretical results are in good agreement with the experimental ones when the light intensity distribution in the integrating sphere is considered. [Preview Abstract] |
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E1.00096: ANTIMATTER |
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E1.00097: A New Form of Matter -- Unmatter, Composed of Particles and Anti-Particles Florentin Smarandache Besides \textit{matter }and \textit{antimatter }there must exist \textit{unmatter }(as a new form of matter) in accordance with the neutrosophy theory that between an entity $<$A$>$ and its opposite $<$AntiA$>$ there exist intermediate entities $<$NeutA$>$. Unmatter is neither matter nor antimatter, but something in between. An atom of unmatter is formed either by (1): electrons, protons, and antineutrons, or by (2): antielectrons, antiprotons, and neutrons. At CERN it will be possible to test the production of unmatter. The existence of unmatter in the universe has a similar chance to that of the antimatter, and its production also difficult for present technologies. [Preview Abstract] |
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E1.00098: Low Energy Rydberg States in Dipositronium Joseph DiRienzi, Richard Drachman Previously the possible resonances in positronium hydride, PsH, [1] were studied, assuming a positronium ion, Ps$^{-}$, interacting with a proton, H$^{+}$, as the prime configuration. This study will look at the first resonances of dipositonium, Ps$_{2}$, in a similar manner. In this situation a variational method is used to determine the radial function of the bound state. First, the model system consisting of Ps$^{-}$ and a positron, e$^{+}$is investigated by including electron exchange but no positron exchange. Then the antisymmetrization of the two positrons is considered giving rise to a non-local potential. The full symmetrization of a system such as Ps$_{2}$ involves not only exchanging electrons and exchanging positrons, but also the charge conjugation of the two interacting ions in our model. Thus, in this second approach we construct a wave function that includes representations of both the Ps$^{-}$ + e$^{+}$ and Ps$^{+}$ + e$^{- }$channels to provide a complete description of this resonant system. From the calculations, the lowest energy singlet Rydberg resonant states are determined. A comparison will be made with results using group-theory analysis [2]. [1] J. Di Rienzi, R. J. Drachman, Phys. Rev. A \textbf{76}, 032705 (2007). [2] J. Usukura and Y. Suzuki, Phys. Rev. A \textbf{66}, 010502(R) (2002); C. G. Bao and T. Y. Shu, Phys. Rev. A \textbf{67}, 042505 (2003). [Preview Abstract] |
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E1.00099: QUANTUM OPTICS WITH NANOSTRUCTURES |
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E1.00100: Dissipation Assisted Quantum Memory with Coupled Spin Systems Liang Jiang, Frank Verstraete, Ignacio Cirac, Mikhail Lukin Dissipative dynamics often destroys quantum coherences. However, one can use dissipation to suppress decoherence. A well-known example is the so-called quantum Zeno effect, in which one can freeze the evolution using dissipative processes (e.g., frequently projecting the system to its initial state). Similarly, the undesired decoherence of quantum bits can also be suppressed using controlled dissipation. We propose and analyze the use of this generalization of quantum Zeno effect for protecting the quantum information encoded in the coupled spin systems. This new approach may potentially enhance the performance of quantum memories, in systems such as nitrogen-vacancy color-centers in diamond. [Preview Abstract] |
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E1.00101: Preparation of Non-equilibrium Nuclear Spin States in Quantum Dots Michael Gullans, Jacob Krich, Jacob Taylor, Bertrand Halperin, Amir Yacoby, Michael Stopa, Mikhail Lukin We examine how dynamical nuclear polarization (DNP) in quantum dots can lead to the emergence of novel non-equilibrium configurations of the lattice nuclear spins. Specifically, by integrating out the electron spin dynamics and course graining the evolution over one DNP cycle we derive an effective master equation for the nuclear spins, which we then solve using time-dependent mean field theory. This analysis provides a preliminary theoretical explanation for the observation of both reduced [1], and enhanced [2], Overhauser gradient magnetic fields seen in recent experiments. [Preview Abstract] |
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E1.00102: Optical levitation of quantum nano-mechanical resonators Darrick Chang, Cindy Regal, Scott Papp, Dalziel Wilson, Jun Ye, Peter Zoller, Oskar Painter, Jeff Kimble There recently has been great interest in being able to observe quantum signatures in the motion of small mechanical systems. One major obstacle in many of the current approaches is the large coupling of these systems to a thermal environment, which tends to rapidly drive these systems back to a classical state. We propose to overcome this difficulty by levitating a nano-scale, dielectric mechanical resonator inside a high-finesse cavity via an optical dipole force, thus effectively removing any external thermal contact and creating a highly isolated system. The dipole force creates a mechanical potential for the center-of-mass motion and an effective ``optical spring'' for various internal degrees of freedom, whose strengths can be widely tuned simply by changing the optical field intensity. Using standard sideband cooling techniques, we show that ground-state cooling of these degrees of freedom is easily achievable under realistic conditions. Furthermore, we show how the tunability can be used to realize even more exotic signatures of quantum mechanical behavior, including quantum state transfer between two mechanical degrees of freedom and strong squeezing of mechanical motion. [Preview Abstract] |
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E1.00103: Quantum gates between superconducting and atomic qubits Mark Saffman, Frank Wilhelm, Robert McDermott We propose methods for performing entangling gate operations between superconducting phase qubits and neutral atom hyperfine qubits. The gate is mediated by mapping the superconducting qubit onto a microwave excitation of a coplanar waveguide resonator (CPW). The large transition dipole moments of atomic Rydberg states at microwave frequencies enable bidirectional entanglement between a single atom and a single CPW photon. Specific gate protocols and fidelity calculations are presented for experimentally realistic geometries. [Preview Abstract] |
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E1.00104: Quantum gates between atoms coupled by surface plasmons of a nanowire David Dzsotjan, Michael Fleischhauer We investigate the long-range coupling of single atoms placed close to the surface of a metallic nanowire. Putting the emitter close to the surface of the wire, a strong Purcell effect can be observed: the emitter will decay into the guided surface plasmon modes of the wire, with a rate exceeding that of free space by a large factor. The strength of the coupling originates from the extremely small mode volume of the surface plasmon modes, because they are tightly confined near the wire surface. We find furthermore that there is an optimal, sub-wavelength emitter-wire distance where the coupling is maximal, due to the losses originating from circulating currents. Placing two emitters along the wire, we observe a strong, wire-mediated long-range interaction between them. As a result, super- and subradiance can occur over distances large compared to the resonant wavelength. Using this effect, one can construct quantum gates and induce entanglement among qubits along the wire. As a specific application, we propose a scheme for constructing a phase gate by a wire-mediated interaction of two lambda atoms. [Preview Abstract] |
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E1.00105: Strong coupling between an electronic spin qubit and a nano-mechanical resonator Peter Rabl, Paula Cappellaro, Gurudev Dutt, Liang Jiang, Jeronimo Maze, Mikhail Lukin We discuss the coupling between a nano-mechanical resonator and a spin qubit associated with a nitrogen-vacancy center. The coupling is achieved via a magnetic tip on the resonator which leads to an oscillating Zeeman shifts of the spin states. Under realistic conditions the shift per quantum of motion can approach 100 kHz and exceed both the spin coherence time ($T_2 \sim 1$ ms) and the motional heating rate of high-$Q$ mechanical resonators. The spin then becomes strongly coupled to mechanical motion in analogy to strong coupling of cavity QED. We first show how this regime can be accessed in a practical setting by a preparation of dressed spin states which eliminate fast dephasing ($T_2^* \sim 1 \,\mu$s) of the spin due to interactions with the nuclear spin bath. Optical spin preparation and readout techniques then allow quantum ground state cooling and the generation and detection of arbitrary superpositions of motional states. We extend this scheme to a whole resonator array where charged resonators interact with each other capacitively and thereby mediate spin-spin interactions over distances up to a few 100 $\mu$m. We discuss the implementation of basics gate operations in this setup and propose a scalable quantum computing architecture for a general class of isolated spin qubits. [Preview Abstract] |
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E1.00106: Enhancing the feedback signals used in closed-loop control of molecular fragmentation Michael A. Todt, Nick Smolnisky, Nathan Jastram, Bethany Jochim, N.G. Wells, E. Wells, J. Mckenna, A.M. Sayler, B. Gaire, Nora G. Johnson, M. Zohrabi, K.D. Carnes, I. Ben-Itzhak Using CO as a prototype system, the role of the feedback signal is examined in a closed-loop coherent control technique utilizing ultrafast laser pulse shaping coupled to a genetic algorithm. We control the fragmentation branching ratio of CO$^{+}$ or CO$^{2+}$ with a feedback signal obtained from a time-of-flight spectrometer. Optimization of the ratio of (C$^{+}$ + O)/(C + O$^{+})$ using a signal that integrated all of the C$^{+}$ fragments produced a different optimal pulse than when the kinetic energy release was used to separate the C$^{+}$ + O and C$^{+}$ + O$^{+}$ channels. Feedback signals obtained using particle counting detection rather than current mode were used to optimize low-probability channels, such as CO$^{2+}$, suggesting the possibility of incorporating coincidence measurements into feedback loops. [Preview Abstract] |
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E1.00107: Near-field Electrical Detection of Optical Surface Plasmons and Single Plasmon Sources Frank Koppens, A. Falk, C. Yu, K. Kang, N. de Leon, A. Akimov, M. Jo, M. Lukin, H. Park Surface plasmon polaritons (SPs) are a promising basis for nanoscale photonic circuits and allow for strong coupling between single photon emitters and propagating plasmon modes. However, there is a general tradeoff between the localization of an SP and the efficiency with which it can be detected with conventional far-field optics. In this talk, I will discus a nanoscale all-electrical SP detection technique based on the near-field coupling between propagating surface plasmons and a nanowire field-effect transistor. The detection scheme consists of an Ag nanowire (NW) crossing a Ge NW field-effect transistor. The Ag NW guides SPs to the Ag/Ge junction, where they are converted to electron-hole (e-h) pairs and detected as current through the Ge NW. We use our detectors to electrically detect the plasmon emission from an individual colloidal quantum dot coupled to a SP waveguide. The detectors are highly efficient (0.1 electrons/plasmon), and a plasmonic gating effect can be used to amplify the signal even higher (up to 50 electrons/plasmon). These results enable new and efficient on-chip optical sensing applications and fulfill a key requirement for 'dark' optical frequency nanocircuits in which SPs can be generated, manipulated, and detected without involving far-field radiation. [Preview Abstract] |
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E1.00108: A Nanoscale Quantum Interface for Single Atoms Jeff Thompson, Darrick Chang, Alexander Zibrov, Mikhail Lukin Single atoms are ideal quantum systems, but a scalable, efficient method to exchange information between single atoms and photonic modes is an outstanding challenge. Recently [1], it was proposed that surface plasmon modes in metallic nanowires can couple efficiently to an atom if the atom lies within the plasmon evanescent mode volume. In this poster, we extend this work and show that a nanowire can also be used to generate a dipole trap for the atom within the efficient coupling region. The confinement is extremely tight ($\sim $ 100 MHz), very close to the nanowire surface and stable against attractive atom-surface interactions. We also present experimental progress toward constructing a MOT-loaded nanowire trap. [1] Chang, D.E. et al., PRB \textbf{76}, 035420 (2007). [Preview Abstract] |
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E1.00109: Quantum Optics With Integrated Plasmonic/Optical Systems Brendan Shields, Alexey Akimov, Frank Koppens, Chun Yu, Parag Deotare, Darrick Chang, Phillip Hemmer, Alexander Zibrov, Marko Loncar, Hongkun Park, Mikhail Lukin We present an experimental observation of strong optical coupling between individual, nanocrystal CdSe/ZnS quantum dots, and the guided surface plasmon modes of a proximal silver nanowire. The plasmonic excitation is then evanescently coupled to the modes of an adjacent Si$_3$N$_4$ waveguide aligned parallel to the wire, resulting in high collection efficiency. The strong coupling between emitter and field is enabled by the unique properties of the plasmon modes on the nanowires. In particular, due to the small size of the nanowires ($\sim$100nm in diameter), the surface plasmons are localized transversely to dimensions well below the diffraction limit. Efficient out-coupling of the plasmon-enhanced quantum dot emission and photon correlations consistent with a single-photon source are observed. [Preview Abstract] |
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E1.00110: Atom number counting and cavity optomechanics on an integrated atom chip - cavity QED apparatus Daniel Brooks, Thomas Purdy, Thierry Botter, Dan Stamper-Kurn We have developed an atom chip based cavity QED apparatus. Atoms have been cooled, trapped, and transported to cavities on the atom chip. The cavities, a pair of high-finesse optical resonators in the single-atom, strong-coupling regime of cavity QED, sandwich an atom waveguide on the chip. A pair of holes were micromachined through the silicon chip substrate for the optical resonators. Microfabricated thick copper wires, capable of producing magnetic traps with tight confinement, allow for atoms to be precisely positioned relative to the standing-wave cavity mode. This provides for the capability to tune the coupling between mechanical and optical degrees of freedom of the atom-cavity system. Narrow-linewidth lasers are being developed to reduce noise on cavity-trapped atoms. We will also outline the experiments we plan to pursue related to cavity optomechanics and~atom number counting. [Preview Abstract] |
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E1.00111: Supercontinuum-Excited Z-scan Spectroscopy of CdSe/ZnS Semiconductor Coreshells JaeTae Seo, Qiguang Yang, William Yu, Wanjoong Kim, Sungsoo Jung Ultrafast and large nonlinear optical properties of semiconductor nanocrystals are of great interest because of their photonic applications. An ultrafast and white-light continuum Z-scan analysis provides, rapidly and simultaneously, the electronic contribution spectra of nonlinear absorption and dispersive nonlinear refraction of CdSe/ZnS colloidal coreshells, and laser intensity and excitation wavelength. CdSe/ZnS coreshells exhibited different polarities of nonlinear optical properties with resonant and nonresonant excitations which imply existence of electronic two-step absorption and two-photon absorption processes. This work at Hampton University was supported by the National Science Foundation (HRD-0734635, HRD-0630372, and ESI-0426328/002) and the U.S. Army Research Office (W911NF-07-1-0608). [Preview Abstract] |
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E1.00112: NEW EXPERIMENTAL TECHNIQUES |
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E1.00113: Edge enhancement in optically pumped Rb vapor Z. Wu, K.F. Zhao, M. Schaden We report the first observation of edge enhancement in optically pumped Rb vapor. We use evanescent waves to probe Zeeman polarization in the vicinity ($\sim 10^{-4} $~cm) of cell surface. Under certain experimental conditions, the magnetic resonance signal consists of two peaks localized near the cell surfaces in frequency space (edge enhancement). The excellent signal-to-noise ratio allows us to make a quantitative comparison between experimentally measured and theoretically calculated line shapes. Unlike the symmetric edge enhancement peaks observed in traditional NMR experiments, the peaks observed in the present experiment have different height owing to the fact that the evanescent beam probes only the polarization near the front surface. The asymmetry between the front and back peaks strongly depends on surface characteristics. Therefore the line shape of the edge enhanced peaks provides a sensitive way to determine surface interaction parameters of spin-polarized atoms. In particular, we are able to deduce the dwell time $\tau_s$ and the spin relaxation probability $\xi_s$ of Rb atoms on coated Pyrex glass surfaces. [Preview Abstract] |
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E1.00114: Millimeter-wave Velocity Modulation Spectroscopy as a Technique to Selectively Detect Molecular Ions DeWayne Halfen, Lucy Ziurys Molecular ions are usually very unstable and reactive species. As a result, their spectroscopic features can be difficult to identify and distinguish from those of neutral species, which tend to be more stable and thus have stronger signals. The technique of velocity modulation allows this disadvantage to be removed. This method uses the alternating plus and minus polarity of an electric field created by an AC discharge, which also produces the molecular ions, to selectively detect the molecular ions, while eliminating the neutral features. This technique has been applied at infrared and optical wavelengths for many years with much success. Recently, we designed and built a millimeter-wave velocity modulation spectrometer, the first ever constructed. This instrument has been used to create and study multiple molecular ions, including metal-bearing molecular ions. The rotational spectrum of these species, such as TiCl$^{+}$, VCl$^{+}$, TiF$^{+}$, FeO$^{+}$, FeCO$^{+}$, and SiCl$^{+}$, has been investigated with this new machine in our laboratory. Results of these studies along with a description of the velocity modulation technique and instrument will be presented. [Preview Abstract] |
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E1.00115: Pseudo-single beam FM spectroscopy for fast, minimally destructive, high SNR detection of Bose-Einstein condensates Chad Fertig, Mary Locke, Ken Kansky Frequency modulation spectroscopy (FMS) is a sensitive method of detecting dilute atomic gases. In FMS, the refractive index of an atomic cloud is sensed by an interferometric measurement of the differential phase shift between upper and lower sidebands of a frequency modulated probe laser. In the standard configuration, the probe beam's carrier component acts as both phase reference and amplifier---the electronic beat signal being proportional to $\sqrt{I_{\textrm{carrier}}}$. This creates a dilemma for using FMS for minimally destructive measurements: a brighter carrier produces a larger signal, but at the cost of greater spontaneous heating. We have developed a new method of FMS which solves the dilemma with an optical analog of a PLL FM-radio receiver. We extract the atomic density information encoded in the probe sidebands by beating the probe against a separately synthesized ``local-oscillator'' (LO) laser that is optically phase-locked to the probe's carrier component. Here, we report a demonstration of this scheme using an optical cavity as a stable, tunable, stand-in for cold atoms. [Preview Abstract] |
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E1.00116: Two-Step Dichroic Atomic Vapor Laser Lock Using Electromagnetically Induced Transparency and Absorption Francisco E. Becerra, Richard T. Willis, Steven L. Rolston, Luis A. Orozco We demonstrate a technique to lock the frequency of a laser to a two-photon transition of Rb vapor in the presence of a weak magnetic field. We use a ladder configuration from specific hyperfine sublevels of the 5S$_{1/2}$, 5P$_{3/2}$, and 5D$_{5/2}$ levels. This transition shows Electromagnetically Induced Transparency and Absorption processes. The error signal comes from the difference in the transparency or absorption felt by the two orthogonal polarizations of the probe beam. A simplified model is in good quantitative agreement with the observed signals for the experimental parameters. We have used this technique to lock the frequency of the laser up to 1.5 GHz off atomic resonance. [Preview Abstract] |
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E1.00117: A widely tunable laser frequency offset lock with digital counting Joshua Hughes, Chad Fertig We have developed a hybrid analog+digital electronic lock to stabilize a dynamically tunable RF frequency offset between two lasers. Our method features an 80~MHz capture range, $\pm$7~GHz tuning range, frequency agility of 1~MHz/$\mu$s, and low ($<30$~ppm) drift in the absolute optical frequency difference after $\sim$1000~s. With this scheme, multiple slave lasers can easily be referenced to one stable master laser, while each remains rapidly and accurately tunable over the wide frequency ranges encountered in typical laser cooling and trapping experiments. We present the results of experiments assessing the stability, accuracy and agility of the lock, as well as a theoretical analysis of the performance limits set by quantization error due to digital sampling. [Preview Abstract] |
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E1.00118: Producing and Diagnosing Chirped Nanosecond Pulses C.E. Rogers III, J.L. Carini, J.A. Pechkis, P.L. Gould We report on the production and characterization of phase- and amplitude-modulated pulses generated with the aid of fiber-based electro-optic modulators. Arbitrary frequency chirps are produced using an arbitrary waveform generator to drive a phase modulator within a fiber delay loop which also contains a self-injection-locked 780 nm diode laser [1]. To control the pulse amplitude, the light is then sent through a fiber-based electro-optical amplitude modulator, also driven with an arbitrary waveform generator. The resulting chirped pulses are then amplified using a tapered amplifier system. The frequency chirp, including residual phase modulation from the amplitude modulator, is characterized by heterodyning the output pulse with a fixed-frequency reference laser. Such pulses will be useful in controlling collisions between ultracold Rb atoms. This work is supported by DOE. \newline \newline [1] C.E. Rogers III, et al., J. Opt. Soc. Am. B 24, 1249 (2007). [Preview Abstract] |
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E1.00119: Optical monitoring of a wavelength-scale mechanical resonator via cavity scattering Ako Chijioke, John Lawall Phase-sensitive Fabry-Perot interferometry provides high-sensitivity optical monitoring of mechanical motion, but is restricted to objects with lateral dimensions many times the optical wavelength. For objects that are wavelength-scale or smaller, approaches based on scattering are appropriate. We demonstrate an enhanced-sensitivity scattering-based scheme for optical readout of the motion of a wavelength-scale mechanical beam, by exploiting the loss it induces when placed in a high-finesse Fabry-Perot cavity. This is of interest for optical probing of nanomechanical resonators. Static calibration, dynamic monitoring and feedback cooling are presented. [Preview Abstract] |
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E1.00120: A data acquisition system based on a novel microcontroller B.A. deHarak, T.G. Porter, N.L.S. Martin \newcommand{\prop}{Propeller\ } \newcommand{\propTM}{Propeller\texttrademark\ } We are currently investigating electron impact autoionization in the presence of a pulsed laser field. In these experiments, carried out with a continuous electron beam, it is necessary to record the arrival times of ejected electrons relative to the laser pulse, in order to distinguish between {\it laser on} and {\it laser off} events. A simple, versatile data acquisition system (DAQ) based on the \propTM microcontroller has been developed. The DAQ has a number of digital and analog I/O lines. Each piece of data received by the DAQ is given a \textit{timestamp} to indicate the time (relative to an external start pulse) that the data was received; the timestamps are precise to within 12.5 ns. Although the \prop provides for relatively easy, rapid development of complex applications, its use has not heretofore appeared in scientific literature. The \prop chip contains eight seperate processors (cogs) that can operate independently while sharing common resources -- most notably a single system clock which keeps all cogs synchronized. Various attributes of the \prop will be highlighted in the process of providing an in- depth description of our DAQ system. [Preview Abstract] |
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E1.00121: Combining lattice clocks with cavity QED: Prospects for a mHz-linewidth laser Dominic Meiser, Jun Ye, Murray Holland Optical atomic clocks based on ultracold alkaline-earth atoms confined in a lattice potential are competitive with the most stable and accurate time and frequency standards. The main bottleneck that prevents these clocks from achieving still better precision is the linewidth of the laser used to interrogate the clock transition. We propose to utilize the ultra-narrow atomic transition by making the atoms emit photons on that line collectively into the mode of a high Q-resonator in a laser-like fashion. A power level of order $10^{-12}$~W is possible, sufficient for phase-locking a slave optical local oscillator. We find that the linewidth of the radiation can be on the order of or even narrower than that of the clock transition due to collective effects. Achieving this major breakthrough will improve the stability of the best clocks by two orders of magnitude. [Preview Abstract] |
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E1.00122: Determining the spectral width of an ultrashort light pulse with a diffraction grating-based spectrometer J. Bruce Johnson A method is presented to determine the corrected linewidth of a pulse of light measured with a diffraction grating-based spectrometer. The correction is only necessary when working near the limit of resolution of the spectrometer. The analysis presented in this work includes the evaluation of the corrected linewidth for various pulse widths, numbers of grooves in the grating, and widths of the entrance slit. Although the method of correction is demonstrated with pulses possessing a Gaussian profile, the calculations are easily repeated for any profile of interest. [Preview Abstract] |
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E1.00123: Neutral Atom Lithography Using a Bright Metastable Helium Beam Claire Allred, Jason Reeves, Chris Corder, Harold Metcalf We have performed neutral atom lithography using a bright beam of metastable 2$^3$S$_1$ Helium (He*) that is collimated with the bichromatic force, followed by three optical molasses velocity compression stages. Because bichromatic collimation makes such an intense He* beam, our exposure time is measured in minutes instead of hours. We have exploited \nolinebreak the focusing and channeling of the He* beam into lines by the dipole force the atoms experience while traversing a standing wave of $\lambda$ = 1083 nm light tuned 500 MHz below the 2$^3$S$_1 \rightarrow$ 2$^3$P$_2$ transition. Focused He* atoms damage the molecules of a self assembled monolayer (SAM) of nonanethiol by depositing their 20 eV of internal energy on its surface. The undisturbed SAM then protects a 200 \AA \, layer of gold that has been evaporated onto a prepared Silicon wafer from a wet chemical etch. Samples created with this method have an edge resolution of 63 nm that was observed using an atomic force microscope. The lines are separated by $\lambda/2$ and cover the entire exposed length of the substrate, about 3 mm. They are about 3 mm long, corresponding to about twice the beam waist of the laser standing wave. Thus there are $\sim 6 \times 10^3$ lines of length $\sim 1500 \lambda$. These results agree with our numerical simulations of the experiment. [Preview Abstract] |
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E1.00124: Spatial light modulators for cold atom manipulation: guiding into a Laguerre-Gaussian mode Laurence Pruvost, Michael Mestre, Fabienne Diry, Bruno Viaris de Lesegno Spatial Light Modulators (SLM's) are programmable optical elements that can act as dynamical holograms. They provide a flexible method to create by holography any distribution of laser intensity. It only requires a good determination of the phase-hologram to apply to the laser beam. Such a method allows one to generate a large variety of optical potentials and to foresee applications for cold atom manipulation. In this context, with helical phase-holograms we have first generated almost-pure Laguerre-Gaussian laser modes of k order (LG0k). Then we have applied the obtained beam to a cold -10 micro-Kelvin- sample of rubidium atoms. Using a blue-detuned laser light we have confined the atoms inside the dark region of the LG mode. We present a quantitative study of the guidance efficiency versus the laser detuning, the order of the Laguerre-Gaussian beam and the beam dimension. We propose a two-dimensional capture model to interpret the results. We discuss also future possible development of this work. [Preview Abstract] |
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