Bulletin of the American Physical Society
41st Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 55, Number 5
Tuesday–Saturday, May 25–29, 2010; Houston, Texas
Session M1: Poster Session II (4:00 pm - 6:00 pm) |
Hide Abstracts |
Room: Exhibit Hall |
|
M1.00001: COHERENT CONTROL |
|
M1.00002: Fluctuations in Yoked-Superfluorescence Delay Times Ariunbold Gombojav, Vladimir Sautenkov, Marlan Scully We study fluctuations in yoked-superfluorescence (YSF) generated in rubidium atomic vapor. The dense atomic vapor is initially excited to 5D from 5S state, via two-photon processes with femtosecond laser pulses through 5P intermediate level. The YSF emission on the 6P-5S transition at 420 nm is recorded using a streak camera with picosecond time resolution. The time duration of the generated YSF is tens of picoseconds which is much shorter than any time scale of the relaxation processes including spontaneous emissions and dephasing. The dependence of time delay between reference/input pulse and YSF is measured as atomic density and/or input power is varied. With the help of the secondary input pulse, the relative delay between pair of generated YSF pulses is studied experimentally. This may allow us to understand more deeply quantum fluctuations in YSF delay time. [Preview Abstract] |
|
M1.00003: Spontaneously generated coherence effects in an inverted Y-type atomic system coupled by three coherent fields Jianbing Qi We investigate the spontaneous emission from an inverted Y-type atomic system coupled by three coherent fields. We use the Schr\"{o}dinger equation to calculate the probability amplitudes of the wave function of the system and derive an analytical expression of the spontaneous emission spectrum to trace the origin of the spectral features. Quantum interference effects, such as the spectral line narrowing, spectrum splitting, and dark resonance, are observed. The number of spectral components, the spectral linewidth, and relative heights can be very different depending on the physical parameters. A variety of spontaneous emission spectral features can be controlled by the amplitude of the coupling fields and the preparation of the initial quantum state of the atom. We propose an ultracold atomic $^{87}$Rb system for experimental observation. [Preview Abstract] |
|
M1.00004: Population distribution in a three-level ladder system interacting with ultrafast laser pulses that have been subjected to a sinusoidal spectral phase modulation Hyounguk Jang, Bachana Lomsadze, Charles Fehrenbach, Eric Schultz, Brett DePaola Shaping the spectral phase in ultrafast laser pulses has led to greater understanding of the interaction between light and matter. In this work, a sinusoidal spectral phase is impressed upon ultrafast laser pulses using a pulse shaper. The effect of this phase on the level populations in three-level ladder excitation is measured. As is well known, if a sinusoidal spectral phase is added to a single pulse the result is a regularly spaced series of pulses in the time domain. The temporal spacing between the pulses, as well as the pulse-to-pulse phase difference is determined by parameters in the sinusoidal phase function. By varying these parameters, constructive or destructive interference can occur in the excitation probability of the transitions under study. In this work, the 5s-5p-5d system in atomic Rb was studied. Landscape maps were created that show measured population in the uppermost state of the ladder as a function of pulse-to-pulse spacing and phase. In some cases, these maps showed measured contrast ratios as high as 150. [Preview Abstract] |
|
M1.00005: Towards sub-femtosecond emission Roger Bach, Peter Hansen, Herman Batelaan, Shawn Hilbert To manipulate femtosecond pulses of electrons new electron optical elements are needed. For example, if a source has a lower limit in the duration of the electron pulses that it generates, then aan electron optical element that can reduce the pulse duration could be useful. An example of this is the proposed ``temporal lens '' [1]. To detect the short electron pulses one also needs new elements. Attempts to use the ponderomotive interaction between the electron pulse and a second laser pulse will be presented [2]. Alternatively, we have started to explore a plasmonics structure provided by the Capasso group to make a fast electron switch. This has the potential to be useful both for switching, shaping and detecting the electron pulse. Finally, the experimental parameters and detection ideas for quantum degeneracy will be discussed. [1] S. Hilbert, B. Barwick, K. Uiterwaal, H. Batelaan, A. Zewail, ``Temporal lenses for attosecond and femtosecond electron pulses'', Proceedings of the National Academy of Sciences, p. 10558, vol. 106, (2009). [2] L. Kreminskaya, C. Corder, V. Engquist, O. Golovin, P. Hansen, H. Batelaan, A. I. Khizhnyak, G. A. Swartzlander, Jr., ``Laser Beam Shaping: Donut Mode Formation by Interference.'' Laser Beam Shaping X (Proceedings Volume) Proceedings of SPIE Volume: 7430. [Preview Abstract] |
|
M1.00006: Towards sub-femtosecond emission Scot McGregor, Roger Bach, Ryan Hotovy, Herman Batelaan In earlier work we have shown that field emission tips can produce sub-100 femtosecond electron pulses upon illumination with a femtosecond laser pulse [1]. In later work we have shown that emission from a tungsten tip is limited to pulse durations longer than 5 femtoseconds [2]. For the purpose of reaching shorter duration pulses, we report the effect that different tip materials and operating conditions have on the pulse duration. Additionally, a method based on the phase relation between the first and second harmonic of the laser pulse is described that is thought to assist in the search for favorable operating conditions. This type of source is developed for a host of experiments including fundamental studies involving the Aharonov-Bohm effect [3], but also possible application such as enhancing pump-probe studies with temporal lenses [4]. [1] B. Barwick, C. Corder, J. Strohaber, N. Chandler-Smith,\textbf{ }C.~Uiterwaal and H. Batelaan, New J. Phys. 9, 142 (2007). [2] S. Hilbert, A. Neukirch, K, Uiterwaal, H. Batelaan, J. Phys. B, 141001, vol. 42 (2009). [3] H. Batelaan, A. Tonomura, Physics Today, (september issue of 2009). [4] S. Hilbert, B. Barwick, K. Uiterwaal, H. Batelaan, A. Zewail, Proc. Nat. Acad. Sci., p. 10558, vol. 106, (2009). [Preview Abstract] |
|
M1.00007: Quantum control of the spin-orbit coupling interaction using the AC Stark effect Ergin Ahmed, Sonia Ingram, Teodora Kirova, Omer Salihoglu, Yafei Guan, John Huennekens, Marjatta Lyyra The spin-orbit coupling plays an important role in the dynamics of excited states. It can cause natural mixing of potentials of different multiplicity leading to possible population exchange between them. Thus the ability to manipulate the degree of mixing of the multiplicity character opens up the possibility of exerting control on processes such as photodissociation and the rate of energy relaxation. It can be also applied to the preparation of spin switches, with potential application in quantum information storage or quantum information processing devices. Using a three laser excitation scheme in $^{7}$Li$_{2}$, we have demonstrated that AC Stark effect (Autler-Townes splitting) can be used to modify the mixing coefficients and thus the amount of singlet or triplet character of a pair of rovibrational G $^{1}\Pi _{g}$(v=12,J=21f)$^{ }$and 1$^{3}\Sigma _{g}$(v=1,N=21f) states perturbed by the spin-orbit interaction. The singlet triplet pair of levels is naturally separated by an energy gap of 750 MHz. The AC Stark splitting is due to a strong laser that couples the singlet G $^{1}\Pi _{g}$(v=12,J=21f) state to rovibrational level in the A$^{1}\Sigma _{u}^{+}$ state. [Preview Abstract] |
|
M1.00008: Complete Population Transfer in 4-Level System Via SU(2)$\times $SU(2)/Z$_{2}$ Coupling Dmitry Uskov, Haim Suchowski We describe a scheme for complete population transfer in a four-level system and identify its relation with the generating function of Pythagorean triples from number theory. In a simple case of the nearest-neighbor coupling the complete population transfer occurs if ratios between the coupling coefficients V$_{12}$ ,V$_{23}$ and V$_{34}$ match one of the Pythagorean triples. We find that both the structure of the evolution operator and the period of complete population transfer are determined by two frequencies, associated with two distinct SU(2) subgroups of the full SU(4) dynamical group. We demonstrate that our solution can be interpreted as a generalization of the two-level Rabi solution for a four-level system. [Preview Abstract] |
|
M1.00009: Inhibited Spontaneous Emission in a Time-Dependent Cavity David Branning In the process of inhibited spontaneous emission, an excited atom is prevented from spontaneously emitting radiation by a reflecting cavity that surrounds it. Quantum theory predicts that, when an atom is first placed into the cavity, it initially radiates at the free-space rate, and the interference from the returning radiation halts any further evolution of the atom into the ground state. To observe this initial radiation directly, a wall of the cavity must be quickly replaced with a photon-counting detector, but the femtosecond time scales involved make this observation impossible for atoms. Intsead, our experiment uses spontaneous parametric downconversion, a process in which a single ultraviolet photon from a laser is spontaneously converted into two lower-frequency photons in a nonlinear optical medium. The downconversion is inhibited using a mirror, at much greater distances than is possible for atoms, and the mirror is then ``replaced'' by a detector on a timescale of several nanoseconds using a Pockels cell as a switch. At the detector, the arrival time of the photons indicates whether or not they had existed in the cavity before the switch was activated. [Preview Abstract] |
|
M1.00010: The Defect on Electromagnetically Induced Transparency by Optical Pumping Chin-Chun Tsai, Yung-Yung Chang, Zong-Syun He, Ray-Yuan Chang, Ming-Tsung Lee, Yi-Chih Lee The V-type electromagnetically induced transparency (EIT) in a multi-level system of cesium atom at room temperature has been investigated. A defect on the EIT spectrum due to the optical pumping reducing the depth of transmission window is observed. In this experiment, the frequency of the probe laser is locked to the selected cesium $D_2$ transition,$|6S_{1/2}, F=3\rangle \rightarrow |6P_{3/2}, F=4\rangle$ and the coupling laser scans across the hyperfine transition, $|6S_{1/2}, F=3\rangle \rightarrow |6P_{3/2}, F=2, 3, 4\rangle$. The numerical simulations by solving the steady state density matrix, using dressed atom approach and the population transformation due to optical pumping fits well with the experimental profile. [Preview Abstract] |
|
M1.00011: Tuning the Scale Factor and Sensitivity of a Passive Cavity with Optical Pumping Krishna Myneni, David D. Smith, Jamiu A. Odutola, Charles A. Schambeau Recent measurements of mode pushing in a Fabry-Perot cavity, by an intra-cavity medium of atomic vapor, demonstrated that {\it both} the cavity scale factor, $S$, and the cavity sensitivity (defined by the ratio of $S$ to the mode width, $W$) may be enhanced in the region of anomalous dispersion associated with an absorption resonance of the vapor[1]. The enhancement is dependent on the net gain of the medium, even for a passive cavity. We demonstrate tuning the cavity scale factor and sensitivity for the passive cavity with an intra-cavity Rb87 vapor cell, using optical pumping between the two ground hyperfine levels. Since hyperfine pumping efficiency increases monotonically with the pump beam intensity, it is possible to achieve continuous tuning of the cavity scale factor from the region of finite enhancement, across its pole along the gain axis, and into the region of mode splitting with a fixed length vapor cell. [1] D.D. Smith, K. Myneni, J.A. Odutola, and J.C. Diels, Phys. Rev. A {\bf 80}, 011809(R) (2009). [Preview Abstract] |
|
M1.00012: Simultaneous EIT of two circularly polarized optical fields driven by a linearly polarized optical field in a $\omega$-system Cristian Bahrim We analyze the possibility of slowing down simultaneously two circularly polarized optical fields using a linearly polarized control field in a four level atom $\omega $-system placed in a weak magnetic field. The goal is to propose a new type of optical quantum memory [1] using binary recording. Our prototype $\omega $-system is an ensemble of alkali-atoms on the $\vert ^{1}$S$_{0}>$ground state and the three M = 0, $\pm $1 Zeeman states of the first excited atomic state, $\vert ^{1}$P$_{1}>$. The energy separation between the Zeeman states is set up with a weak magnetic field of 0.006 $<$ B $<$ 0.035 T chosen so that (1) the Larmor frequency does not exceed the characteristic time of the spin-orbit interaction between $\vert ^{1}$S$_{0}>$ and $\vert ^{1}$P$_{1}>$ states, and (2) the bandwidths of the $\vert ^{1}$P$_{1}$; M $>$ Zeeman states do not overlap. We report atomic coherences calculated from the density matrix master equation which includes the radiative relaxations $\vert ^{1}$P$_{1}$; M= 0, $\pm $1 $> \quad \to \quad \vert ^{1}$S$_{0}>$. We explain the mechanism of slowing down simultaneously two optical fields using a variable control field by adopting a dressed state representation. We also analyze the evolution of the Autler-Townes doublets associated to the two probe fields from a proto-EIT phase into a stable EIT phase [2]. [1] Lvovsky A I, Sanders B C and Tittel W 2009 \textit{Nature Photonics }\textbf{3} 706. [2] Fleischhauer M, Imamoglu A and Marangos J P 2005 \textit{Rev. Mod. Phys.}\textbf{ 77} 633. [Preview Abstract] |
|
M1.00013: Effective gaufe fields for dark-state polaritons Johannes Otterbach, Julius Ruseckas, Razmik G. Unanyan, Gediminas Juzeliunas, Michael Fleischhauer We discuss dynamical phenomena of light-matter quasi-particles, so-called dark-state polaritons (DSP). These particles arise in the Raman interaction of a weak probe field with a coherently driven atomic ensemble under conditions of electromagnetically induced transparency (EIT), and are the basis of phenomena such as slow-, stopped and stationary-light. We study the creation of an effective magnetic field for the DSP. In the limit of large a pulse length they behave as effective Schr\"odinger particles with an externally adjustable mass. By uniformly rotating the medium an effective magnetic field is created. With the proposed scheme degeneracies of the lowest Landau level of 100 and above is achievable. Thus the system can be used to study effects as the Lorentz force for neutral particles or, upon creating interactions between the DSP, the bosonic analogue of the fractional quantum Hall effect. [Preview Abstract] |
|
M1.00014: Refractive Index Enhancement in Atomic Media Nicholas Proite, Daniel Sikes, Deniz Yavuz We experimentally demonstrate a scheme where a laser beam experiences refractive index enhancement with vanishing absorption. The essential idea is to excite two Raman resonances with appropriately chosen strong laser beams in a far-off resonant atomic system. We have performed our experiments both in vapor cells and in ultracold atomic clouds. Additionally, we discuss a new scheme that achieves giant Kerr nonlinearities using refractive index enhancement. This scheme does not require an intense coupling laser and has the potential to produce all-optical switches and distributed Bragg reflectors at a total energy requirement of tens of photons per atomic cross section. [Preview Abstract] |
|
M1.00015: Negative Refraction in a Raman Chiral System Daniel Sikes, Deniz Yavuz We propose a new scheme to achieve negative refraction in an atomic system using laser-induced magnetoelectric cross-coupling. Our scheme uses a combination of one photon and Raman transitions to coherently drive the electric and magnetic responses for a probe beam according to a chiral approach for negative refraction. The energy level structure of this scheme has an advantage over other proposed schemes in that it does not require the existence of electric and magnetic dipole transitions at the same resonant frequency. This proposed scheme is a promising new approach to negative refraction at optical wavelengths with low absorption in an atomic system. [Preview Abstract] |
|
M1.00016: Slow and stored light propagation under the condition of resonant four-wave mixing Irina Novikova, Nathaniel Phillips We study the possibility of simultaneous storage of a resonant probe and off-resonant Stokes pulses in a hot Rb vapor cell. Specifically, under the conditions of electromagnetically induced transparency and resonant four-wave mixing the coupled propagation of both fields may be connected to the same dark state polariton. Experimental data and numerical simulations are presented. [Preview Abstract] |
|
M1.00017: Coupling a Spin Qubit in Diamond to the Motion of a Macroscopic Mechanical Cantilever Shimon Kolkowitz, Frank Koppens, Ania Bleszynski-Jayich, Peter Rabl, Mikhail Lukin, Jack Harris Nano electro-mechanical systems (NEMS) can be used as quantum transducers for electronic spin qubits, where spins are coupled to the motion of magnetized mechanical resonators via magnetic field gradients [1]. Provided that the mechanical system is charged, the magnetic moments associated with spin qubits can be effectively amplified to enable a coherent spin-spin coupling over long distances via Coulomb forces. We describe experimental progress to achieve strong coupling between the spin state of a Nitrogen Vacancy (NV) Center in diamond with the motional state of a magnetized mechanical resonator. \\[4pt] [1] Rabl, \textit{et al., }``A quantum spin transducer based on nano electro-mechanical resonator arrays,'' submitted to \textit{Nature Physics }(2009). Pre-print available: arXiv:0908.0316 [Preview Abstract] |
|
M1.00018: Strong-field optimal control with 2D learning algorithms Guan-Yeu Chen, Ben Crist, Wendell T. Hill, III Several years ago we introduced the first 4p-image spectrometer for studying strong-field dissociative-ionization processes (e.g., Coulomb explosion) in small molecular systems. We now employ imaging and this spectrometer, in conjunction with pulse-shaping and learning algorithms, to investigate strong-field control of dynamics with a two- dimensional fitness function. As an example, focusing on various patterns on images has allowed us to isolate for control a particular molecular mode to control, such as bending in carbon dioxide [1]. Two- dimensional fitness functions provide access to the dynamics that are either difficult to access or unrevealed through scalar fitness functions. As a consequence, exploiting these additional degrees of freedom is enabling us to make steps towards deciphering optimal control fields. In this poster we will provide details of image-based learning algorithms. We will give examples of using multi- dimensional fitness functions and discuss how they can be used to control molecular dynamics. \\[4pt] [1] G.-Y. Chen, Z. W. Wang, and W. T. Hill III, PRA 79, 011401 (R), 2009 [Preview Abstract] |
|
M1.00019: A Time-dependent Analysis of Few-Photon Coherent Control Schemes Shaohao Chen, Agnieszka Jaron-Becker, Andreas Becker Nowadays coherent quantum control is an important topic in atomic, molecular and optical physics as well as chemistry, due to recent development in ultrashort laser technology. Coherent control schemes have been proposed to realize dark or bright pulses with near-infrared wavelengths in the perturbative intensity regime for two-photon excitations in atoms. In this work, we investigate the coherent control of a non-resonant two-photon excitation and a 2+1 photon ionization process from the time-dependent perspective. To this end, we have solved the time-dependent Schrodinger equation for hydrogen atom interacting with a shaped ultrashort ultraviolet laser pulse. The time-dependent analysis offers complementary information about the control mechanisms from a direct comparison of the time evolution of the laser field with the instantaneous response of the quantum system for two control schemes based on the modulation of the spectral phase, i.e. symmetric/antisymmetric phase distribution and pi phase-step modulation. [Preview Abstract] |
|
M1.00020: STRONGLY INTERACTING FERMI GASES |
|
M1.00021: Finite-Temperature Phase Diagrams of an Atomic Bose and Two-Component Fermi Mixture Hong Ling, Michael Fodor The recent technological advancement in cooling and trapping neutral atoms has allowed the physics of degenerate Bose-Fermi mixture, which was traditionally limited to liquid isotopes of helium atoms, to be explored in atomic quantum gases under well-controlled conditions. While existing studies have focused mainly on mixtures of single-component species, we consider in this work mixtures between single-component bosonic atoms (b) and two-component [spin-up (u) and spin-down (d)] fermionic atoms of equal densities, using a model that incorporates both repulsive collisions involving the bosonic atoms: (bb), (bu) and (bd), and attractive collision (ud) between fermionic atoms of opposite spins. We perform a systematic study of the mean-field phase diagrams at finite-temperature, including the density profiles under the local density approximation. We find that the prospect of having correlated Fermi pairs can greatly enrich the possible phases and phase separations in this system. We strive to highlight the features that are generic to the phase diagrams of such a mixture. We show how these features can be explored to facilitate the idea of using the bosonic atoms as the probe to the properties of this interacting Bose-Fermi mixture. [Preview Abstract] |
|
M1.00022: Equation of State of the Unitary Gas: Theory and Experiment Felix Werner, Kris Van Houcke, Evgeny Kozik, Nikolay Prokofev, Boris Svistunov, Andre Schirotzek, Ariel Sommer, Mark Ku, Martin Zwierlein The equation of state of the balanced unitary gas is given by a dimensionless function of a single variable. We compute this function in the normal phase, from the high-temperature classical regime down to the quantum degenerate regime. We use a new Diagrammatic Monte-Carlo approach, where Feynman diagrams for the self-energy are sampled stochastically up to sufficiently high order so that the extrapolation to infinite order can be performed. The diagrammatic building blocks are bare propagators, and interaction lines that include the sum of all ladder diagrams. We will also present results obtained with the self-consistent `bold' Monte-Carlo scheme, where the diagrammatic building blocks are dressed propagators and vertex functions. We will compare these theoretical predictions with our experimental results for the equation of state, which we extract from column-integrated density profiles using a new procedure, the temperature and chemical potential of a cloud being determined by fitting its outer region with the virial expansion. Then, we will use our Monte-Carlo results to fit the outer region of colder clouds, for which the central part gives access to the equation of state down into the superfluid phase. [Preview Abstract] |
|
M1.00023: Oscillations of solitons in a trapped superfluid Fermi gas in the BCS-BEC crossover Franco Dalfovo, Lev Pitaevskii, Robin Scott, Sandro Stringari We investigate the dynamics of dark/grey solitons in a two-component superfluid Fermi gas in the BCS-BEC crossover. We numerical solve the time-dependent Bogoliubov-de Gennes equations for a gas confined in a quasi-1D trap. A soliton is generated by preparing the gas in two distinct wells and then merging them in a single harmonic trap. By varying the initial relative phase, we control the soliton motion, thereby creating an atom interferometer. For relative phases close to $\pi$, solitons are found to oscillate back and forth in the trap. The frequency of the oscillation changes smoothly by varying the strength and sign of the interaction along the crossover. On the BEC side we reproduce the dynamics a bosonic molecular condensate, where the solitons behaves as a particle having twice the mass of a molecule. We compare the numerical results with analytic predictions obtained in the hydrodynamic limit in the local density approximation. [Preview Abstract] |
|
M1.00024: One dimensional polarized paired Fermi gases on a Feshbach resonance Stefan Baur, Erich Mueller We study the effects of spin polarization on the BEC-BCS crossover in one spatial dimension(1D). To this end we model the system using the Bose-Fermi resonance model in 1D and, by solving the three-body problem of a dimer and an excess fermion, we give arguments for a possible phase transition between the FFLO phase characterized by an oscillating superfluid correlation function and a Bose-Fermi mixture featuring nodeless superfluid correlations [arXiv:0902.4653]. In addition, we explain recent experiments of the Rice group [arXiv:0912.0092] by solving thermodynamic Bethe ansatz equations for the Gaudin-Yang Hamiltonian. Work done in collaboration with Y.-A. Liao, A. S. C. Rittner, T. Paprotta, R. G. Hulet and J. Shumway. [Preview Abstract] |
|
M1.00025: BOSE-EINSTEIN CONDENSATES |
|
M1.00026: Spin waves in a spin-1 normal Bose gas Stefan Natu, Erich Mueller We present a theory of spin waves in a non-condensed gas of spin-1 bosons: providing both analytic calculations of the linear theory, and full numerical simulations of the nonlinear response. Although the spin-dependent contact interaction is small compared to the thermal energy, it sets the scale for low-energy, long-wavelength spin waves. We find which parameters lead to stable ferromagnetic or nematic order and study the dynamics of any resulting instabilities. For example, we show that ferromagnetic fluctuations render the polar state of $^{87}$Rb unstable, even in a thermal gas. We corroborate this result by explicit numerical simulations in a harmonic trap. We also explore coherent population dynamics in a collisionless transversely polarized gas, driven entirely by the spin-dependent contact interaction. [Preview Abstract] |
|
M1.00027: Simulating the Aharonov-Bohm effect in scattering of cold paramagnetic atoms in a cylindrically symmetric magnetic field Bernard Zygelman We consider the scattering of spin 1/2 atoms in a cylindrically symmetric magnetic field. Expanding the total wavefunction in a Born-Oppenheimer (or adiabatic) basis we obtain coupled equations in which a non-Abelian vector gauge potential is induced. For collision energies in which one of the Zeeman- split channels is closed, we show that the open-channel equation is equivalent to that describing Aharonov-Bohm scattering. We calculate the scattering amplitude, for the open channel, using the fully coupled equations and compare it to that predicted by Aharonov-Bohm scattering. We also discuss planar collisions of two spin-1/2 atoms that interact through the magnetic dipole-dipole interaction, and show the relationship with the system considered above. [Preview Abstract] |
|
M1.00028: Quantum Degenerate Gases of Strontium Brian DeSalvo, Natali Martinez de Escobar, Pacal Mickelson, Mi Yan, Thomas Killian We have produced quantum degenerate gases of three of the four stable isotopes of strontium. Using two-stage laser trapping and cooling followed by direct evaporative cooling in a far-off- resonance optical dipole trap (ODT), a stable Bose-Einstein Condensate (BEC) of $^{84}$Sr is formed. Via dual species trapping and sympathetic cooling in an ODT, an attractive BEC of $^{88}$Sr is created, as well as a degenerate Fermi gas of $^{87}$Sr. Differences in the evaporation scheme used to reach degeneracy for each isotope will be presented as well as the varied dynamics of the gases. [Preview Abstract] |
|
M1.00029: Macroscopic superposition states of cold bosons in an asymmetric double well with Orbital Degrees of freedom Miguel-\'Angel Garc\'Ia-March, Lincoln Carr We extend previous studies on cold bosons in double well potentials using a Hubbard-like Hamiltonian to two and three dimensions and relax the one-level assumption. We consider a tilted potential and all regimes, from a weak barrier to a strong barrier. We discuss the properties of Macroscopic Superposition (MS) states, i.e. NOON or NOON-like states, with a non-zero orbital angular momentum in such a Hamiltonian. We find that, as in the one dimensional case, these states are very sensitive to small imperfections in a symmetric potential. Despite their fragility, MS states with angular momentum reappear periodically as the tilt between both wells is increased. The tunneling dynamics of different initial states, ranging from maximal population imbalance in the lower level, to maximal population imbalance in the higher one, is also discussed. Intermediate situations include a variety of populations of both levels and maximal population imbalance in each one. [Preview Abstract] |
|
M1.00030: Miniature, Monolithic Ultra High Vacuum Cells for BEC Applications Sterling McBride, Joey Michalchuk, Dana Anderson, Evan Salim, Kai Hudek We have developed a miniature, monolithic ultra high vacuum cell with integrated atom source, gas and atom getters, ion pump and atom chip for applications in cold atom systems. The vacuum cell is a planar, multi-chamber system, fabricated on a single substrate and arranged to spatially separate a 2D MOT high pressure region containing the atom source, a 3D MOT region and a UHV atom chip region for BEC production. The chambers are fluidically connected by micro-channel structures to provide differential pumping between chambers. The vacuum cell is fabricated using novel planar batch fabrication techniques, which enables miniaturization, permits high bake-out temperature up to 300 $^{\circ}$C, shows pressure below 10$^{-10}$ Torr, and allows operation from room temperature to 300 $^{\circ}$C. Experiments demonstrate the production of a double MOT in the 2D and 3D MOT regions. Applications include portable and transportable BEC systems for applications in atom interferometry, inertial navigation systems and atomic clocks. [Preview Abstract] |
|
M1.00031: Observation of Quantized Flow of a BEC in a Toroidal Trap Changhyun Ryu, Kevin Henderson, Malcolm Boshier Quantized circulation, one of the most important consequences of Bose-Einstein condensation, is fundamental to the understanding of superfluid phenomena. In a toroidal trap, Bose- condensed atoms should flow with a well defined winding number, which makes it an ideal system to demonstrate the quantized nature of circulation. We used a scanning laser beam to create a toroidal trap [1]. To rotate the atoms, a small potential barrier within the toroidal trap was rotated at a certain frequency and then the barrier was lowered to create a quantized flow state. The winding number of the flow was determined by the diameter of the central hole seen in a time of flight image of the condensate. The measurement showed diameters increasing stepwise with the stirring frequency. We observed flows with winding number up to 5. This is a clear demonstration of the quantization of the flow of atoms in a toroidal trap. Further study of critical velocity and metastability of flow of atoms will be very important in understanding the nature of superfluidity of atoms in a toroidal trap, especially in a 1D limit.\\[4pt] [1] K. Henderson, C. Ryu, C. MacCormick, and M. G. Boshier, New Journal of Physics 11, 043030 (2009). [Preview Abstract] |
|
M1.00032: Tuning the structural and dynamical properties of a dipolar Bose-Einstein condensate: Ripples and instability islands M. Asad-uz-Zaman, D. Blume It is now well established that the stability of aligned dipolar Bose gases can be tuned by varying the aspect ratio of the external harmonic confinement. Our work extends this idea and demonstrates that a Gaussian barrier along the strong confinement direction can be employed to tune both the structural properties and the dynamical stability of an oblate dipolar Bose gas aligned along the strong confinement direction. In particular, our theoretical mean-field analysis, in which the condensate is described by a single macroscopically occupied wave function, predicts the existence of instability islands immersed in otherwise stable regions of the phase diagram. Dynamical studies indicate that these instability islands are associated with the going soft of a Bogoliubov-de Gennes excitation frequency with radial breathing mode character. Furthermore, we find dynamically stable ground state densities with ripple-like oscillations along the radial direction. These structured ground states exist in the vicinity of a dynamical radial roton-like instability. We are currently developing a complementary approach, in which the system is assumed to consist of two spatially separated clouds that are described by a set of coupled mean-field equations. [Preview Abstract] |
|
M1.00033: Formation of Magnetic Structure in a Spinor Bose Einstein Condensate A.N. Wenz, J. Guzman, K. Murch, D.M. Stamper-Kurn We report on recent experimental studies of $F=1$ $^{87}$Rb spinor Bose Einstein condensates. Utilizing in-situ magnetization sensitive phase contrast imaging we are able to temporally and spatially resolve the magnetization of the spinor BEC. Additionally, with time-of-flight absorption imaging we are able to measure the population in each Zeeman sublevel. With those techniques we investigate the formation and equilibration times of spatially modulated spin domains and spin mixing as a function of temperature and the quadratic Zeeman shift. [Preview Abstract] |
|
M1.00034: Detection of Small Spinor Condensates in Optical Traps Eva Bookjans, Chris Hamley, Michael S. Chapman We are interested in studying spinor physics of small BECs beyond the mean field regime. We investigate $^{87}$Rb Bose-Einstein condensates (BECs) with less than $<$100 atoms that are created in the optical lattice of a CO$_{2}$ laser. Measuring small numbers of atoms requires state of the art atomic detection techniques. We have explored the limits of absorption and fluorescence imaging techniques for observing small condensates. We will present the results of our investigation and discuss the applications to studies of small condensates and their spinor interactions. [Preview Abstract] |
|
M1.00035: 3D Roton-Excitations and Supersolid formation in Rydberg-excited BECs Nils Henkel, Rejish Nath, Thomas Pohl We study the behavior of a Bose-Einstein condensate in which atoms are weakly coupled to a highly excited Rydberg state. Since the latter have very strong van der Waals interactions, this coupling induces effective interactions between the dressed groundstate atoms. Albeit its asymptotic short-range nature the induced interaction is shown to have dramatic consequences, such as the appearance of a roton-maxon excitation spectrum and a transition to a super solid state in three dimensional condensates. The presented analysis of decoherence and loss mechanisms, suggests that these phenomena are observable with current experimental capabilities. [Preview Abstract] |
|
M1.00036: Variational Calculations for the Effects of Magnetic Dipole-Dipole Interaction in Bose-Einstein Condensates Abraham Olson, Yong P. Chen Employing previously developed variational calculation techniques [1, 2], we explore various possibilities for observing effects of magnetic dipole-dipole interaction (MDDI) in Bose-Einstein condensates (BECs). The effects of MDDI on both in-trap and time-of-flight expansion dynamics are investigated, as well as effects on condensate stability. The variational calculation has been verified to agree well with experimental data in Cr$^{52}$[3] and Li$^{7}$[4]. Using current knowledge of Feshbach resonances, we determine the experimental accessibility of observing MDDI effects for the bosonic alkalis and find most favorable results for Li$^{7}$, K$^{39}$, and Cs$^{133}$. We also present calculations for Dy and Er, motivated by advances in cooling such high magnetic moment species. These results would be useful to experimentalists working on dipolar quantum gases. \\[4pt] [1] S. Yi and L. You, Phys. Rev. A, \textbf{63}, 053607 (2001)\\[0pt] [2] T. Koch \emph{et al.} Nature Physcis \textbf{4}, 218-222 (2008)\\[0pt] [3] T. Lahaye \emph{et al.} Nature \textbf{448}, 672-675 (2007)\\[0pt] [4] S.E. Pollack \emph{et al.} Phys. Rev. Lett. \textbf{102}, 090402 (2009). [Preview Abstract] |
|
M1.00037: Phase winding a BEC into a soliton train Chris Hamner, JiaJia Chang, Peter Engels We present an experimental investigation studying the phase winding of a two spin component Bose-Einstein Condensate in an elongated optical dipole trap. The winding is generated by performing~near resonant Rabi oscillations in the presence of a weak magnetic gradient. We investigate the winding dynamics and experimentally show that the resulting spin domains can be converted into trains of filled solitons. [Preview Abstract] |
|
M1.00038: Transition properties of a Bose-Einstein condensate confined by a laser in a Laguerre-Gaussian mode Thomas Akin, Sharon Kennedy, Jeremy Marzoula, Jason Alexander, Eric Abraham An optical dipole force trap generated by lasers in a Laguerre-Gaussian (LG) mode facilitates a means to study the Bose-Einstein condensate (BEC) vortex states. The toroidal geometry and the intrinsic orbital angular momentum of the LG beam offers an ideal environment to support vortex states. An investigation is made on an ideal gas confined by a LG mode laser. We submit theoretical studies of the transition properties for a BEC in a LG external potential, and work toward mean field effects. Experimental results of laser cooled atoms confined in LG beams created by diffractive optics will be presented. [Preview Abstract] |
|
M1.00039: Ion-BEC Interactions David A. Anderson, Rachel E. Sapiro, Georg Raithel Recently, a significant amount of theoretical work on dilute atomic BEC has focused on how condensates interact with ultra- cold charged impurities. The phenomena one may expect to find include the formation of mesoscopic molecular ions via recombination of BEC atoms by ion-induced polarization potentials, ion-induced structures in the BEC wave-function, quantum charge diffusion, and self trapping of ions in BECs. Here, we present progress towards experimental studies of such ion-BEC interactions using a $^{87}$Rb BEC setup. It is paramount that the ions have a sufficiently long dwell time in the BEC (~100us) and move slowly to avoid unwanted BEC excitations. These conditions are met by (1) creating the ions via photo-ionization of ultra-cold atoms close to the photo- ionization limit, and (2) by minimizing stray electric fields in the interaction region using Stark spectroscopy of high- lying Rydberg states. The electric field of a small tip-like structure is used to extract and image the ions onto a micro- channel plate detector, allowing ion counting, time-of-flight analysis and spatial imaging. [Preview Abstract] |
|
M1.00040: DYNAMIC AND OUT-OF-EQUILIBRIUM PHENOMENA IN COLD ATOMS |
|
M1.00041: Dissipative Dynamics of a Bose-Einstein Condensate in an Optical Speckle Potential Paata Kakashvili, Satyan G. Bhongale, Han Pu, Carlos J. Bolech Progress in ultra-cold atomic physics allows to engineer and probe analogs of condensed matter systems, which are not plagued by imperfections. In addition, it is also possible to study effects of impurities and disorder, which can be controlled with a great precision. Disorder potential can be imposed by applying an optical-speckle field to a cloud of ultra-cold atoms. The optical speckle is produced by passing a laser beam through a diffusive piece of glass. We propose a theoretical model to understand the hydrodynamic transport of a Bose-Einstein condensate through an optical-speckle potential. Analytic expressions are derived to describe dissipation mechanisms in the limit of weak disorder, such that the depletion of the condensate induced by the speckle potential may be neglected. Comparison of our predictions with the experimental data for large-amplitude dipole oscillations of the condensate shows a striking agreement. Thus, the adequacy of the model in correctly capturing the essential aspects of dissipation in such transport experiments is demonstrated. [Preview Abstract] |
|
M1.00042: Thermalization in quenched spinor condensates Mukund Vengalattore, Ryan Barnett, Anatoli Polkovnikov Motivated by recent experiments on spinor Bose gases, we consider the dynamics of a spin-1 Bose condensate following a quantum quench from a polar phase to a ferromagnetic phase. We apply the truncated Wigner approximation (TWA) to the spinor system with all spatial and spin degrees of freedom. For short times following the quench, we find excellent agreement with the linearized Bogoliubov treatment showing, for instance, that the longitudinal magnetization density grows at twice the gain exponent as the transverse magnetization. In the saturated regime (where the linearized treatment fails), we provide evidence of thermalization. For large quenches, we interpret our results as a dynamical Berezinskii-Kosterlitz-Thouless transition resulting from the unbinding of vortices in the spin and charge degrees of freedom. [Preview Abstract] |
|
M1.00043: Characterizing the dynamics of an out-of-equilibrium 1D Bose gas Jean-Felix Riou, Aaron Reinhard, Phillip Schaefer, David S. Weiss We present experimental results on out-of-equilibrium quantum gases in optical lattices, where we trap Bose gases in one-dimensional tubes, and prepare them in an out-of-equilibrium state by modifying their momentum distribution. The lattice depth is a key experimental parameter, which gives us access to different regimes of evolution. We characterize the dynamics of the system using measures of the difference between observed distributions and various reference distributions, including what we determine to be the true equilibrium state of the system. This analysis requires us to quantitatively treat many effects specific to our experiment. In particular we discuss how the trapping parameters and the energy exchange in the system affect the dynamics. Finally, we show how we can gain insight into the processes involved in different regimes by keeping track of the density dependence of the evolution. [Preview Abstract] |
|
M1.00044: Dynamics of Anti-ferromagnetic Spin Order in Lattice-trapped $^{87}$Rb Karl Nelson, Radu Chicireanu, Steven Olmschenk, William Phillips, Trey Porto Optical lattices provide a controlled environment in which to model condensed-matter systems and study strongly-correlated many-body behavior. Starting with $^{87}$Rb deep in the Mott-insulating state, we use an effective staggered field to create an antiferromagnetically-ordered (AF) many-body state in a double-well optical lattice. In $^{87}$Rb, AF order has the highest energy of any $M=0$ spin configuration in the Mott-insulator state (where $M$ is the total magnetization). Decay from this state requires low-energy excitations that are unavailable due to the Mott-insulator gap. We study the spin dynamics by varying the tunnel coupling in the lattice, to determine how well decay to other spin configurations is suppressed by the Mott-insulator gap. [Preview Abstract] |
|
M1.00045: Equilibrium and out of equilibrium studies of ultracold fermions in an optical lattice Daniel Greif, Leticia Tarruell, Thomas Uehlinger, Robert Jordens, Niels Strohmaier, Henning Moritz, Tilman Esslinger In our experiment we use a two component Fermi gas in a 3D optical lattice to realize the Fermi-Hubbard model. This clean approach offers the advantage of posing well defined questions and accessing clean probes. Here we present recent measurements of equilibrium and out of equilibrium properties of this model system. Tuning the interaction via a Feshbach resonance over a broad range we investigate the crossover from a metallic to Mott insulating state. This is signaled by a drastic reduction of double occupancy and the appearance of a gapped mode in the doublon spectrum probed by lattice modulation. The resolution in double occupancy of our most recent measurements allows for precise comparison with both DMFT calculations and high-temperature series expansions. If the lattice modulation is sufficiently weak, the increase of doublons with time is well captured by linear response theory. In this regime the buildup rate of doublons is a measure for equilibrium properties such as the temperature sensitive local spin ordering. For long modulation times the system is driven into a far from equilibrium state with many additional doublons. We show that the dominant decay mechanism is a high-order scattering process with many single particles. [Preview Abstract] |
|
M1.00046: Optimal control of the dynamics of a BEC: optimizing splitting and squeezing J. Grond, U. Hohenester, G. von Winckel, A. Scrinzi, J. Schmiedmayer Number squeezed states are useful for atom interferometers and reduce phase diffusion in split Bose-Einstein condensates. In this paper we show that counter-intuitive splitting protocols allow efficient number squeezing on much shorter time scales compared to quasi-adiabatic splitting ( J. Grond et al., Phys. Rev. A \textbf{80}, 053625 (2009) ). This is achieved by controlling the interplay between tunneling and nonlinear interaction using optimal control theory (OCT) within the Multi-configurational time dependent Hartree equations for Bosons MCTDHB ( O. E. Alon, et al., Phys Rev. A \textbf{77}, 033613 (2008) ) method. We are seeking for maximal squeezing, while the condensates should be at rest and decoupled at the end of the splitting. We proceed with MCTDHB simulations with more than two modes. Condensate excitations are shown to affect number squeezing in some cases, but are found to be of little importance for our OCT control fields. From these results we obtain insight about the limits of two-mode descriptions. [Preview Abstract] |
|
M1.00047: Dynamics of a two-species Bose-Einstein condensate in a double well Bo Sun, M. Pindzola The dynamics of a two-species Bose-Einstein condensate in a double well is studied using the two-mode approximation. Such a system is characterized by the intraspecies and interspecies s-wave scattering as well as the Josephson tunneling between the two wells and the population transfer between the two species (i.e. two internal states in this study). We discuss the population dynamics for some interesting regimes where we can obtain closed-form results. To support our conclusions, we also present numerical results in each regime. A particularly interesting case is for vanishing intraspecies scattering lengths and a weak interspecies scattering length where we find collapses and revivals in the population dynamics. [Preview Abstract] |
|
M1.00048: Locally Induced Dynamics of Thin Cored Vortex Geometries with Application to Bose-Einstein Condensates Scott A. Strong, Lincoln D. Carr The self-induced dynamics of a vortex defect in a Bose-Einstein condensate (BEC) are well modeled by phenomenological hydrodynamics. At the macroscopic scale, vortex defects are thought to be precursory to turbulent fluid dynamics. However, at the microscopic scale, the vortex defects take on additional structure since some of their important features become quantized. While the study of vortex-tubes is most applicable for these phenomenon, nontrivial dynamics also manifests from idealized line vortices and are expressed by a concise asymptotic expansion consistent with the Euler equations relating the local dynamics of the defect to nonlinear Scr\"{o}dinger (NLS) evolution. This {\it local induction approximation} (LIA) states that a bent line-vortex generates a local velocity field with an asymmetry in the binormal direction. Binormal flows correspond to NLS, which is a completely integrable nonlinear PDE admitting soliton solutions whose amplitude and phase controls the line-vortex curvature and torsion, respectively. Our recent work, generalizing LIA, indicates that higher order expansions offer no new dynamics in the case of a line-vortex, which is in contrast to existing results relating the dynamics of slender vortex tubes to a hierarchy of integrable dynamics. We also discuss the applicability of these expansions to BEC vortex dynamics. [Preview Abstract] |
|
M1.00049: Nonlinear dynamics in the mixing and demixing of a two component BEC JiaJia Chang, Chris Hamner, Peter Engels We experimentally study the dynamics resulting from the controlled mixing/demixing of $^{87}$Rb Bose-Einstein condensates (BEC) in two different hyperfine states. Large and small scale domain formations are observed as well as the formation of nonlinear structures such as filled solitons. Recent and ongoing results will be presented. [Preview Abstract] |
|
M1.00050: Quantum Quenching in an Optical Lattice David Chen, Cecilia Borries, Carolyn Meldgin, Brian DeMarco We present measurements of an Rb-87 gas trapped in a 3D optical lattice that is rapidly ``quenched'' into a purely harmonic potential. We determine the excitation energy after the quench by measuring the deviation from a smooth profile in images taken after relatively long time-of-flight. We observe that the excitation energy grows as the initial lattice depth is increased beyond the critical value for atoms in the Mott-insulator phase to occupy the center of the lattice. The presence of structures similar to vortices in the images suggests that this process is similar to Kibble-Zureck mechanism for vortex formation. We discuss the effect of quenching rate on the excitations and analyze features in the image autocorrelation. [Preview Abstract] |
|
M1.00051: Towards Studying Transport Phenomena with Trapped Ions Michael Ramm, Thaned Pruttivarasin, Boyan Tabakov, Axel Kreuter, Nikos Daniilidis, Hartmut H\"affner Transport of charge and energy are key phenomena for many technological applications. The basic transport mechanisms, particularly in the quantum regime, offer rich physics. For instance, the conditions necessary for a fully quantum system to equilibrate are still under debate. We started an experimental effort to study energy transport in the quantum regime by placing single ions in microtraps formed by a standing wave inside an optical resonator. The resulting anharmonic quantum oscillators are weakly coupled to each other via the Coulomb interaction. Such oscillator chains often serve as model systems for studying quantum transport phenomena and thermalization. We will discuss our experimental goals of following the propagation of a single excitation within the ion chain. Furthermore, we will describe the experimental setup including the cavity for the optical standing wave, vacuum apparatus, and microfabrication of a planar ion trap using a lift-off technique. [Preview Abstract] |
|
M1.00052: The Memory of Initial Conditions in an Incompletely-Chaotic Quantum System Vladimir Yurovsky, Maxim Olshanii A system of two atoms in a circular, transversely harmonic waveguide in the multimode regime is analyzed [1]. While showing some signatures of the quantum-chaotic behavior, the system fails to reach a complete quantum chaos, even when the interaction between the atoms is infinitely strong. A relaxation from an initial state leads to a final state which is different from a thermal equilibrium; this state retains some memory of the initial conditions. The results inspire a more general theory of relaxation in incompletely-chaotic systems [2] of which our system is a particular case. \\[4pt] [1] V. A. Yurovsky and M. Olshanii, e-print:1001.0225.\\[0pt] [2] M. Olshanii and V. A. Yurovsky, e-print:0911.5587. [Preview Abstract] |
|
M1.00053: COLD AND ULTRA-COLD MOLECULES |
|
M1.00054: Triplet-singlet conversion in ultracold Cs$_2$ - production of ground state molecules Marin Pichler, Nadia Bouloufa, Olivier Dulieu We present theoretical calculations in molecular cesium for the conversion of ultracold triplet to singlet molecules through the $0_{u}^{+}$ system. We show that strong mixing of $A^{1}\Sigma_{u}^{+} \sim b ^{3}\Pi_{u}$ states facilitates the triplet-singlet conversion. The conversion opens additional channels for enhanced production of deeply bound ultracold molecules in the ground $X$$^{1}\Sigma_{g}^{+}$ state. In addition, our calculations reveal that due to this triplet singlet conversion, the optical pumping and subsequent vibrational cooling can not be applied to the ground triplet $a$$^{3}\Sigma_{u}^{+} $ molecules due in part to this loss mechanism. [Preview Abstract] |
|
M1.00055: LiYb molecule in traps: potential energies, long-range energies, dipole moments, ... H.R. Sadeghpour, P. Zhang, A. Dalgarno We employ multireference configurations interaction and coupled cluster techniques to determine the potential energy curves of the ground and low-lying excited states of the LiYb molecule. The scalar relativistic effects have been included by means of the Douglas-Kroll Hamiltonian and effective core potentials, and the spin-orbit couplings have been evaluated by the full microscopic Breit-Pauli operator. The dipole moment, static dipole polarizability, transition dipole moments, van der Waals coefficients, and Franck-Condon spectroscopy of the LiYb molecule have been determined. Perturbations to the vibrational spectrum due to the non-adiabatic interactions are included. Implications for double-MOT trapping of LiYb are discussed and we find that dimer of these molecules should easily form. [Preview Abstract] |
|
M1.00056: The Hyperfine Molecular Hubbard Hamiltonian Lincoln D. Carr, Michael L. Wall Recently, ultracold diatomic heteronuclear polar molecules were cooled to near quantum degeneracy [1]. We study the many body physics of such systems in optical lattices [1,2] in the presence of strong electric and magnetic fields. The molecules interact via an electric dipole-dipole interaction. Our main model is the Hyperfine Molecular Hubbard Hamiltonian, a generalization of Hubbard Hamiltonians for lattice physics which includes the internal degrees of freedom of molecules and external DC magnetic and electric and AC electric driving fields. Our main numerical method is time-evolving block decimation, which treats entangled quantum dynamics. We consider both fermionic and bosonic molecules. Our choice of a strong electric field plus a strong magnetic field prevents chemical reactions, thereby stabilizing the molecular ensemble. We find that tuning the electric AC driving field plus the angle between the DC electric and magnetic fields allows us to progressively include more molecular degrees of freedom, from spatial to rotational to nuclear hyperfine.\\[4pt] [1] L. D. Carr, David DeMille, Roman V. Krems, and Jun Ye, New J. Phys. v. 11, p. 055049 (2009).\\[0pt] [2] M. L. Wall and L. D. Carr, New J. Phys. v. 11, p. 055027 (2009). [Preview Abstract] |
|
M1.00057: Benchmark calculations for small rare gas clusters Vladimir Roudnev, Michael Cavagnero We present detailed calculations of dimers and trimers of He and other rare gas atoms to benchmark a non-relativistic three-body code currently in development for public distribution. For these systems, uncertainties in the fundamental constants can substantially exceed the errors of numerical calculations. For example, the near-threshold bound state of the He$_2$ dimer is quite sensitive to small variations of the nuclear mass. Our benchmark calculations include specific estimates of the numerical accuracy of the calculations, and also explore sensitivity to fundamental constants and their uncertainties. We provide detailed analysis of both numerical and physical uncertainties for the observable characteristics of bound states of small He and other rare gas two and three-atom clusters based on widely used ab initio and model potentials. [Preview Abstract] |
|
M1.00058: Aqueous, electrolytic Paul mictrotrap for control of biomolecules Jae Hyun Park, Weihua Guan, Mark Reed, Predrag Krstic We study dynamical trapping of the individual charged particles in an aqueous, electrolytic environment by a 2D quadrupole field of a microscale Paul nanotrap. Influence of the drag forces as well as of effective field of the electrolyte sub-system and thermal fluctuations to the stable confinement boundaries in the parametric space of the trap was investigated by solving the generalized Mathieu equation. The results of the theoretical analysis provided satisfactory comparison with the experimental observations at a planar aqueous electrodynamic trap on a chip, demonstrating a possibility for aqueous, electrolytic trapping and control of single bio-molecular ions. [Preview Abstract] |
|
M1.00059: Vibrational State Transfer in Ultracold NaCs Amy Wakim, Patrick Zabawa, Jennifer Hansen, Amanda Neukirch, Nicholas Bigelow Ultracold polar NaCs molecules are formed via photoassociation through a resonance 23 GHz detuned from the Cs 6$^{2}$P$_{3/2}$ asymptote from overlapped dark-spot Magneto-Optical Traps. Using a vibrational state selective detection method, we have determined the sample consists of $\nu $=4-19 in the X$^{1}\Sigma ^{+}$ electronic ground state. We will report on an optical pumping method designed to transfer this initial distribution of vibrational levels to maximize the $\nu $=0 population.~A simple model of optical pumping using the A$^{1}\Sigma ^{+}$ - b$^{3}\Pi $ complex is used to predict that the population will accumulate in the $\nu $=0 state if the sample is illuminated with light at roughly 1 micron with a 10 nm spectral range. Most importantly, the pulse frequency must be shaped to exclude transitions out of the $\nu $=0 level in order to create a dark state where the population will accumulate [1]. \\[4pt] [1] D. Sofikitis, et al. PRA 80 051401 (2009) [Preview Abstract] |
|
M1.00060: Ultracold Fermionic gases of Li atoms and LiNa molecules Caleb Christensen, Jae Choi, Ye-ryoung Lee, Gyu-boong Jo, Wolfgang Ketterle, Dave Pritchard We present recent data on the stability and basic properties of ultracold gases of $^6$Li and $^{23}$Na, including fermionic LiNa molecules. A cold, dense mixture of atoms is produced in an IR optical dipole trap. The magnetic field is brought to the vicinity of Feshbach resonances, and short lived states are populated by driving RF transitions from noninteracting to interacting states. Absorption imaging of the atoms is used to study the formation and lifetime of Feshbach molecules. We also present recent work on the potential for a ferromagnetic state of a gas of lithium atoms. [Preview Abstract] |
|
M1.00061: Toward Trapped Ultracold RbCs Molecules in the Absolute Ground State Mattias Gustavsson, Colin Bruzewicz, Alpha Ga\"{e}tan, Nathan Gilfoy, Stephan Falke, Toshihiko Shimasaki, David DeMille We report on an improved apparatus for production of ultracold, optically trapped RbCs molecules, aiming to achieve an ultracold sample of polar molecules in the rovibrational ground state. Starting with a spin-polarized sample of Rb and Cs atoms, molecules are formed by photoassociation and decay into high vibrational levels of the triplet ground state. We plan to transfer these molecules to the absolute ground state via an electronically excited state of mixed singlet and triplet character, as previously demonstrated in our lab with pulsed lasers. Currently, we are working on high resolution spectroscopy of this state using cw diode lasers, to identify a suitable level for a subsequent STIRAP transfer to the ground state with control over rotational and hyperfine structure. We will present our latest results, and will also report on efforts to directly image a molecular sample with resolution by photoionization and subsequent detection on a phospor screen behind a microchannel plate. [Preview Abstract] |
|
M1.00062: Progress Towards Laser Cooling and Trapping Strontium Monofluoride from a Cryogenic Beam Source John Barry, Edward Shuman, David DeMille We report on the continuing development of a cryogenic helium buffer-gas cooled molecular beam source which will ultimately be used to feed a trap for polar molecules. We have carefully characterized the properties of this source for strontium monofluoride (SrF) in a variety of buffer-gas flow regimes, ranging from the effusive (thermal mean velocity, moderate flux), to the deeply hydrodynamic (large forward velocity, high-flux, high collimation). Using this beam source we have demonstrated optical deflection and transverse cooling of our molecular beam, necessary steps to precool our beam before loading it into our trap. [Preview Abstract] |
|
M1.00063: Permanent dipole moment of alkali-strontium diatomic molecules Olivier Dulieu, Mireille Aymar, Romain Gu\'erout Ultracold gases of alkali atoms and alkaline-earth atoms are routinely created experimentally. Using a quantum chemistry approach based on effective core potentials, core polarization potentials, and full configuration interaction for the three valence electrons, we computed the electronic structure and the permanent dipole moment of the diatomic polar molecules composed of one alkali atom A=Li, Na, K, Rb, Cs and one strontium (Sr) atom. Properties for the lowest doublet and quartet states of each species are determined. We discuss the prospects for such polar molecules to be used to achieve dipolar quantum gases. [Preview Abstract] |
|
M1.00064: Ultracold gas of ground-state polar KRb molecules in 2D B. Neyenhuis, D. Wang, M.H.G. de Miranda, A. Chotia, J. Ye, D.S. Jin We report on our ongoing studies of dipolar interactions in ground-state KRb molecules prepared in the quantum regime. At large dipole moment we see a dramatic increase in the inelastic scattering rate due to attractive head-to-tail interactions between molecules [1]. To suppress this inelastic loss we are preparing a gas of polar molecules in a 2D confined geometry provided by a one-dimensional optical lattice. We will explore the effect of the 2D confinement on the lifetime of the trapped molecule gas. \\[4pt] [1] K.-K. Ni, S. Ospelkaus, D. Wang, G. Quemener, B. Neyenhuis, M. H. G. de Miranda, J. L. Bohn, J. Ye, D. S. Jin, Dipolar collisions of polar molecules in the quantum regime. arXiv:1001.2809. [Preview Abstract] |
|
M1.00065: Ultracold dipolar collisions of KRb molecules Goulven Quemener, John Bohn, Kang-Kuen Ni, Silke Ospelkaus, Dajun Wang, Brian Neyenhuis, Marcio de Miranda, Jun Ye, Deborah Jin Ultracold fermionic polar molecules of $^{40}$K$^{87}$Rb in their absolute rovibronic anf hyperfine state [1] have been recently created in a magnetic trap. This enables experiments to probe ultracold molecular chemistry of polar molecules [2] in well defined quantum states. In addition, KRb molecules are polar and can be manipulated by an electric field. We present theoretical predictions for ultracold dipolar collisions of indistinguishable KRb molecules in a presence of an electric field, using a simple Quantum Threshold model (QT model) [3]. We demonstrate that the KRb + KRb $\to$ K$_2$ + Rb$_2$ chemical reaction rate increases as the sixth power of the dipole moment induced by the electric field for fermionic KRb isotopes. We also estimate the temperature dependence of the chemical rates in zero electric field. These predictions are in excellent agreement with experimental data [2,4]. [1] Ni et al., Science 322, 231 (2008) ; Ospelkaus et al., Phys. Rev. Lett. 104, 030402 (2010). [2] Ospelkaus et al., arXiv:0912.3854, Science, in press (2010). [3] Qu{\'e}m{\'e}ner et al., Phys. Rev. A, in press (2010). [4] Ni et al., arXiv:1001.2809, submitted (2010). [Preview Abstract] |
|
M1.00066: Solid phases in atoms - polar molecules mixtures Barbara Capogrosso-Sansone We study solid phases of a mixture of atoms and polar molecules. On one hand we find that the presence of atoms facilitate the formation of a solid phase, which appears at lower dipole interaction strengths than in the absence of atoms. On the other hand, the presence of molecules allows for the realization of atomic solid phases at higher temperatures, than those required with e.g. multi-component atomic mixtures. [Preview Abstract] |
|
M1.00067: Resonant scattering of rotational excitons in optical lattices with polar molecules Marina Litinskaya, Felipe Herrera, Roman Krems We consider ultracold polar molecules in the ro-vibrational ground state trapped on an optical lattice with one molecule per lattice site. Rotational excitation of molecules produces rotational excitons that can propagate throughout the optical lattice due to long-range dipole-dipole interaction between molecules. Unlike excitons in most naturally occurring solids, these rotational excitons have a negative effective mass. Molecular impurities introduced into the lattice break the translational symmetry and scatter excitons. We show that the exciton-impurity interaction strength can be tuned by an external electric field, leading to exciton-impurity scattering resonances. This can be used to realize different kinetic regimes of exciton dynamics, from free propagation to Anderson localization. The negative effective mass of the excitons results in resonant scattering produced by repulsive, and not attractive, scattering potentials. [Preview Abstract] |
|
M1.00068: Toward Ultracold Mixtures and Polar Molecules from Lithium and Ytterbium Atoms Vladyslav Ivanov, Anders Hansen, Alexander Khramov, William Dowd, Subhadeep Gupta We are building a system for the combined cooling and trapping of lithium and ytterbium atoms. We plan to study interspecies interactions and also prepare diatomic polar LiYb molecules. Such molecules are important as novel strongly interacting quantum systems, for sensitive tests of the standard model of physics, and as building blocks for quantum computers. Our apparatus is based on separate effusive ovens and Zeeman slowers for the two species, a common ultrahigh vacuum chamber for simultaneous trapping of the two species, and the requisite magnetic and optical fields to induce strong interactions between trapped atoms. We will present our experimental setup including the achievement of simultaneous magneto-optical trapping of lithium and ytterbium atoms, and report on our latest experiments on dual species trapping and cooling in a far off resonance optical trap. [Preview Abstract] |
|
M1.00069: Rovibrational dynamics of ultracold heteronuclear molecules with tunable dipole-dipole interactions Philippe Pellegrini, la\"etitia Bomble, Mich\`ele Desouter-Lecomte Ultracold heteronuclear dimers have large permanent dipole moments and long-lived states that make them promising systems for quantum information processing. The implementation of logic gates using rovibrational levels often relies on the possibility of controlling the strong dipole-dipole interaction coupling neighboring molecules [1]. The stability of the encoded qubits under sudden variations of the dipole-dipole interaction if of particular importance for the realization of a practical quantum register with polar molecules. We present a theoretical study of the rovibrational dynamics of ultracold polar molecules when the interaction coupling them varies. Molecules with large dipole moments like NaCs are considered. The use of tunable interactions for scalable quantum computing will be discussed as well. \\[4pt] [1] E. Kuznetsova et al. Phys. Rev. A, 78, 012315 (2008) [Preview Abstract] |
|
M1.00070: ABSTRACT WITHDRAWN |
|
M1.00071: ENTANGLEMENT, DECOHERENCE, AND ERROR CORRECTION |
|
M1.00072: Quantum Entanglement Between Optical Photon and Solid-state Spin Qubit Emre Togan, Yiwen Chu, Alexei Trifonov, Liang Jiang, Jeronimo Maze, Lilian Childress, M.V. Gurudev Dutt, Anders Sorensen, Philip Hemmer, Alexander Zibrov, Mikhail Lukin Nonlocal quantum entanglement is among the most fascinating aspects of quantum theory. Motivated by the potential realization of quantum networks that require entanglement of remote quantum nodes with long-term quantum memory, we demonstrate nonlocal entanglement between a single optical photon and a solid-state qubit associated with the single electronic spin of a Nitrogen Vacancy impurity in diamond. Our experiments demonstrate a high degree of control over solid-state qubits in the optical domain and provide a fundamental building block for the realization of quantum optical networks based on long-lived electronic and nuclear spin memory in the solid-state. [Preview Abstract] |
|
M1.00073: Remote Spin Coupling and Room Temperature Quantum Computation with Diamond Color Centers Norman Yao, Liang Jiang, Alexey Gorshkov, Geza Giedke, Ignacio Cirac, Mikhail Lukin We propose an experimentally feasible architecture for a room-temperature solid-state quantum computer utilizing nitrogen-vacancy (NV) defects in diamond as qubits and demonstrate the possibility of high fidelity operations. At an implantation spacing of 20nm, magnetic dipole-dipole interactions are sufficiently strong to enable coherent coupling of qubits. We further investigate remote spin coupling as a candidate for reducing the experimental constraints on such implementations. This approach makes use of a two-dimensional array of nitrogen impurities with sparsely implanted NV center qubits. By utilizing nitrogen impurities to mediate quantum state transfer, it is possible to coherently couple spatially separated qubits using SWAP gate, spin chain, and quantum mirror techniques. [Preview Abstract] |
|
M1.00074: Progress towards room temperature quantum computation based on NV centers in diamond Peter Maurer, Nicholas Chisholm, Georg Kucsko, Liang Jiang, Jero Maze, Alexey Gorshkov, Norman Yao, Dirk Englund, Alexander Zibrov , Daniel Twitchen, Ronald Walsworth, Mikhail Lukin We report on recent progress towards the implementation of fundamental building blocks of a room temperature quantum computer based on an array of nitrogen vacancy (NV) centers in diamond. ~We use the nitrogen nuclear spin as a quantum memory due to its long coherence time, and the electronic spin of the NV center for manipulation and efficient read out of the qubit [Jiang, Science]. Coupling between individual NV centers, separated by $\sim $20nm, is provided by magnetic dipole-dipole interaction. Individual addressing is accomplished via a combination of magnetic field gradients and far-field sub-wavelength optical manipulation. Techniques for parallel manipulation of multiple NV centers will be discussed. [Preview Abstract] |
|
M1.00075: Few-electron physics in Double quantum dots in carbon nanotubes Javier von Stecher, Bernhard Wunsch, Mikahil Lukin, Eugene Demler, Ana Maria Rey Recent experimental progress on few-electron quantum dots (also known as artificial atoms) has allowed the controllable manipulation of the spin degrees of freedom of the confined electrons. Such control is at the heart of semiconductor-based spintronics and quantum-information proposals. Double-well quantum dot in~semiconducting carbon nanotubes exhibit rich physics due to the additional valley degree of freedom. Here, we study the few-electron spectrum of a carbon-nanotube double quantum dot with spin-orbit coupling. We find that Coulomb interactions can cause strong correlation effects which lead to different ground state transitions. In particular, we show that such strong correlations can produce the disappearance of the Pauli blockade in transport experiments and an interaction-induced ferromagnetic ground state. [Preview Abstract] |
|
M1.00076: A Scanning Cavity Nanoscope Brendan Shields, Dirk Englund, Kelley Rivoire, Fariba Hatami, Jelena Vuckovic, Hongkun Park, Mikhail Lukin Techniques for imaging and manipulating individual quantum emitters with high spatial resolution are essential in areas ranging from single molecule spectroscopy to interfacing emitters in quantum networks. Optical cavities enable strong light-matter interaction and, when coupled to suitable imaging platforms, enable new approaches for single-atom microscopy. Here we demonstrate a scanning cavity nanoscope (SCN), based on a photonic crystal cavity, that enables simultaneous nanoscale localization of solid-state quantum emitters and modification of emitter properties via the Purcell Effect. We illustrate the power of the SCN by coupling individual nitrogen vacancy (NV) centres in diamond to the nanocavity. Scanning over an NV results in strong position-dependent modification of the spontaneous emission (SE) spectrum, including a six-fold enhancement of the SE intensity at the cavity frequency. The scanning nanocavity overcomes the traditional trade-off between spatial resolution and collection efficiency of near-field optical probes and enables a deterministic photonic interface for a wide range of quantum emitters. [Preview Abstract] |
|
M1.00077: A Nanoscale Quantum Interface for Single Atoms Jeff Thompson, Alexey Akimov, Frank Koppens, Darrick Chang, Alexander Zibrov, Mikhail Lukin We propose and analyze a scheme to interface individual neutral atoms with nanoscale solid-state systems. The interface is enabled by optically trapping the atom via the strong near-field generated by a sharp metallic nanotip. We show that under realistic conditions, a neutral atom can be trapped with position uncertainties of just a few nanometers, and within tens of nanometers of other surfaces. Simultaneously, the guided surface plasmon modes of the nanotip allow the atom to be optically manipulated, or for fluorescence photons to be collected, with very high efficiency. Finally, we analyze the surface forces, heating and decoherence rates acting on the trapped atom. In this presentation, we discuss the general properties of these systems, schemes for loading and cooling atoms in very small traps, and current experimental progress toward loading nanowire traps from a Rb MOT. [Preview Abstract] |
|
M1.00078: Robust control of nuclear spins in diamond Lilian Childress, Benjamin Smeltzer Isolated nuclear spins offer a promising building block for quantum information processing systems, but their weak interactions often impede preparation, manipulation, and detection. Hyperfine coupling to a proximal electronic spin can provide a polarization and readout mechanism and enhance manipulation and interaction speed. Using the electronic spin of the nitrogen-vacancy center as an intermediary, we demonstrate robust initialization, fast manipulation, and direct optical readout of 13C, 14N, and 15N nuclear spins in diamond. These results pave the way for nitrogen nuclear spin-based architectures in isotopically purified diamond. [Preview Abstract] |
|
M1.00079: Title: Dynamics of Overhauser Field under nuclear spin diffusion in a quantum dot Zhe-Xuan Gong, Zhang-Qi Yin, Lu-Ming Duan The coherence of electron spin can be significantly enhanced by locking the Overhauser field from nuclear spins using the nuclear spin preparation. We propose a theoretical model to calculate the long time dynamics of the Overhauser field under intrinsic nuclear spin diffusion in a quantum dot. We obtain a simplified diffusion equation that can be numerically solved and show quantitatively how the Knight shift and the electron-mediated nuclear spin flip-flop affect the nuclear spin diffusion. The results explain several recent experimental observations, where the decay time of Overhauser field is measured under different configurations, including variation of the external magnetic field, the electron spin configuration in a double dot, and the initial nuclear spin polarization rate. [Preview Abstract] |
|
M1.00080: QUANTUM INFORMATION |
|
M1.00081: Two-fluid model of a Bose-Einstein condensate in the cavity optomechanical regime Dan Goldbaum, Keye Zhang, Pierre Meystre We analyze an atomic Bose-Einstein condensate trapped in a high-$Q$ optical cavity driven by a feeble optical field. The dynamics of the resulting collective density excitation of the condensate are formally analogous to the central model system of cavity optomechanics: a radiation pressure driven mechanical oscillator [Brennecke {\it et al}., Science \textbf{322}, 235 (2008)]. However, although BEC-based optomechanical systems have several desirable properties, one must also take into account the effect of atom-atom interactions. We treat these interactions via a two-fluid model that retains the intuitive appeal of the non-interacting two-mode description. We find that the Bogoliubov excitation spectrum of this system comprises a gapped upper branch and a lower branch that can include an unstable excitation mode. \\[4pt] D. S. Goldbaum, K. Zhang and P. Meystre, {\it Two-fluid model of a Bose-Einstein condensate in the cavity optomechanical regime}, arXiv:0911.3234. [Preview Abstract] |
|
M1.00082: Toward ion-photon entanglement with barium-138 ground state Zeeman levels Nathan Kurz, Matthew Dietrich, Gang Shu, Katherine Mitchell, Boris Blinov Robust generation of entangled ion-photon and multi-ion states is a crucial step to many quantum information processing protocols [1]. Using single barium-138 ions in a linear Paul trap, we propose a qubit scheme using the m=+1/2 and m=-1/2 Zeeman sublevels of the $6S_{1/2}$ ground state. We estimate the lower bound of the coherence time of this qubit at 200 $\mu$s based on measurements on the $6S_{1/2}-5D_{5/2}$ optical qubit at 1762 nm using a narrowband fiber laser at 1762 nm. Detection of the Zeeman qubit state can be performed by selectively shelving one of the Zeeman sublevels to the $5D_{5/2}$ level. A mode-locked Ti:Sapphire at 968 nm doubled to 493 nm on-resonance with the transition to $6P_{1/2}$ excites the ion, which subsequently emits a single photon whose polarization modes are entangled with the magnetic spin of the ion. Photonic qubit rotations are accomplished after the collection optics with waveplates, a polarizing beam splitter and photomultiplier tubes. \\[4pt] [1] R. Raussendorf and H. J. Briegel, PRL 86: 22, 5188-91 (2001). [Preview Abstract] |
|
M1.00083: A single ion anharmonic mechanical oscillator with nonlinear dissipation Nitzan Akerman, Shlomi Kotler, Yinnon Glickman, Anna Keselman, Yehonatan Dallal, Roee Ozeri A driven, damped, nearly harmonic oscillator with a small cubic term in the force, is known as the Duffing oscillator. The Duffing oscillator shows various interesting features of non-linear response such as bistability and hysteresis. Several features of the Duffing instability have been recently measured using superconducting qubits and nano-mechanical resonators. Linear Paul traps can be well approximated as harmonic but have a small an-harmonicity due to their deviation from an ideal quadruple geometry. We study the steady state motion of a single trapped Sr$^{+}$ ion, subject to a near-resonance drive and dissipation in a linear Paul trap with a small anharmonicity. The driving force is applied by an oscillating voltage on the trap end-caps. Dissipation is the result of laser Doppler cooling. We measure both the amplitude and phase of the driven oscillations and find a good agreement with the Duffing oscillator model. When the cooling laser is close to resonance the standard Duffing model has to be extended to account for non-linearity in the dissipative force. Both the linear and the nonlinear terms of the dissipative force for various cooling laser detunings are determined by the line-shape of the - cooling transition and the cooling laser intensity and can therefore be conveniently controlled. [Preview Abstract] |
|
M1.00084: A cryogenic ion trap for $^{9}$Be$^{+}$ Kenton R. Brown, Christian Ospelkaus, Yves Colombe, Dietrich Leibfried, David Wineland Ion traps with cryogenic electrodes present several advantages over their room temperature counterparts, including longer ion lifetimes, lower motional heating rates, and the possibility of coupling ions to other systems that function only at cryogenic temperatures. We have recently built a surface electrode ion trap for $^{9}$Be$^{+}$ ions (ion-to-surface distance = 40 $\mu $m) that incorporates electrodes cooled to 4.2 K, a bakeable copper vacuum enclosure surrounding the electrodes, and an achromatic, completely reflective, in-vacuum imaging objective. Preliminary results indicate an ion lifetime limited only by the stability of our cooling laser, effective shielding from magnetic field fluctuations, high radial trapping frequencies ($>$ 30 MHz), and a heating rate of 75 quanta/sec for the 2.3 MHz axial mode. We will present these results and discuss our plans for experiments taking advantage of the low heating rate realized in this apparatus. [Preview Abstract] |
|
M1.00085: Efficient ion-photon coupling with phase Fresnel lenses Erik Streed, Benjamin Norton, Till Weinhold, David Kielpinski Efficient ion-photon coupling is an important component for large-scale ion-trap quantum computing. We propose that arrays of phase Fresnel lenses (PFLs) are a favorable optical coupling technology to match with multi-zone ion traps. Both are scalable technologies based on conventional micro-fabrication techniques. The large numerical apertures (NAs) possible with PFLs can reduce the readout time for ion qubits. PFLs also provide good coherent ion-photon coupling by matching a large fraction of an ion's emission pattern to a single optical propagation mode (TEM$_{00})$. We report on progress towards experimentally integrating a large numerical aperture PFL (NA=0.64) with Yb$^{+}$ ions held in a needle style Paul trap. The PFL is designed for use with the 369.5 nm cycling transition in Yb$^{+}$ and was fabricated by a e-beam lithography a two level pattern on a fused silica substrate. The trap electrode spacing is adjustable and will allow us to measure the effect of the patterned dielectric PFL surface on the trap stability. The PFL was previously optically characterized to have a diffraction-limited spot w$_{0}$=350+/-15 nm (1/e$^{2}$ waist) with mode quality M$^{2}$= 1.08+/-0.05. [Preview Abstract] |
|
M1.00086: ABSTRACT WITHDRAWN |
|
M1.00087: High fidelity readout of a single electron spin Anna Keselman, Yinnon Glickman, Nitzan Akerman, Shlomi Kotler, Yehonatan Dallal, Roee Ozeri We use the two spin states of the valence electron of a single trapped $^{88}$Sr$^{+}$ ion as a physical qubit implementation. For qubit readout one of the qubit states is shelved to a metastable $D$ level using a narrow linewidth 674nm diode laser followed by state-selective fluorescence detection. Careful analysis of the resulting photon detection statistics allows for a minimal detection error of 2 $\cdot $ 10$^{-3}$, compatible with recent estimates of the fault-tolerance required error threshold. [Preview Abstract] |
|
M1.00088: Demonstration of an optical qubit in $^{137}$Ba$^{+}$ ions Thomas Noel, Matt Dietrich, Nathan Kurz, Gang Shu, Boris Blinov We present a demonstration of an optical qubit in $^{137}$Ba$^{+}$ ions. Isotope-selective ion loading, qubit state preparation, single-qubit rotation, and qubit state readout have been achieved with high fidelity. An infrared fiber laser at 1762 nm coherently drives the narrow 6S$_{1/2}$-5D$_{5/2}$ quadrupole transition, which has a natural line width of about 33 mHz. A Rabi frequency of 55 kHz has been achieved with about 5 mW of laser power, and a qubit coherence time of about 200 $\mu $s was observed. To accomplish this, we developed a novel microcontroller-based lock servo and modulation scheme for stabilization of the fiber laser. Using this laser we have also demonstrated an efficient adiabatic passage population transfer, which makes possible high fidelity readout of the ground state hyperfine and Zeeman qubits in $^{137}$Ba$^{+}$. [Preview Abstract] |
|
M1.00089: A Cold Strontium Ion Source Christopher J. Erickson, Mary Lyon, Kelvin Blaser, Stuart Harper, Dallin Durfee We present a cold ion source for strontium 87. The source is based off of a standard Low-Velocity-Intense-Source (LVIS) for strontium using permanent magnets in place of anti-Helmholtz coils. Atoms from the LVIS are then ionized in a two photon process as they pass a 20kV anode plate. The result is a mono-energetic beam of ions whose velocity is tunable. Applications for the ions include spectroscopy and ion interferometry. [Preview Abstract] |
|
M1.00090: Scalable neutral atom quantum computing with MEMS micromirrors Caleb Knoernschild, Felix Lu, Hoon Ryu, Michael Feng, Jungsang Kim In order to realize a useful atom-based quantum computer, a means to efficiently distribute critical laser resources to multiple trap locations is essential. Optical micro-electromechanical systems (MEMS) can provide the scalability, flexibility, and stability needed to help bridge the gap between fundamental demonstrations of quantum gates to large scale quantum computing of multiple qubits. Using controllable, broadband micromirrors, an arbitrary atom in a 1, 2, or 3 dimensional optical lattice can be addressed with a single laser source. It is straightforward to scale this base system to address n arbitrary set of atoms simultaneously using n laser sources. We explore on-demand addressability of individual atoms trapped in a 1D lattice, as well as investigate the effect the micromirrors have on the laser beam quality and phase stability. [Preview Abstract] |
|
M1.00091: Silicon surface-electrode ion traps for quantum information processing S. Charles Doret, Richart Slusher The Georgia Tech Research Institute (GTRI) is designing, building, and testing scalable surface-electrode ion traps for quantum information applications, fabricated using silicon VLSI technology. A wide range of trap architectures have been developed, including a linear trap capable of holding long chains of equally spaced ions, a 90-degree X-junction, and an integrated micromirror with collection efficiency approaching 20\%. Fabrication features that can be integrated with the surface electrodes include multilayer interconnects, optics for enhanced light collection, flexible optical access through beveled slots extending through the substrate, and recessed wire bonds for clear laser access across the trap surface. Traps are designed at GTRI using in-house codes that calculate trap fields, compute the full motion of ions confined in the trap, including micromotion, and optimize electrode shapes and transport waveforms using genetic algorithms. We will present designs and initial test results for several of these traps, as well as plans for their use in future experiments. [Preview Abstract] |
|
M1.00092: Integration of ion trap and optical cavity towards efficient entanglement generation between remote ions Taehyun Kim, Peter Maunz, Rachel Noek, Caleb Knoernschild, Emily Mount, Jungsang Kim Entanglement of remote ions [1] could lead to an alternative way to scale quantum information processing (QIP). The heralded entanglement generation relies on the collection and interference of two photons from different ions. In current experiments, the success probability of this protocol is very small mainly due to limited photon collection probability. Increasing the photon collection probability from a single ion is thus essential to make the remote entanglement protocol useful for scalable QIP. Here, we present progress towards an experiment in which a single trapped Ytterbium ion will be coupled to the mode of a small high finesse cavity. A surface ion trap will be patterned on a fiber ferrule to trap an ion in the center of a tightly focused light mode. The cavity will be formed by the fiber tip and a mirror with 5mm radius of curvature. We will analyze trap characteristics and the photon extraction probability that is realizable with available technology. \\[4pt] [1] S. Olmschenk et al., Science 323, 486 (2009). [Preview Abstract] |
|
M1.00093: Anharmonic Traps for Scalable Quantum Information Processing with Trapped Ions S. Korenblit, E.E. Edwards, K. Kim, K.R. Islam, L. Luo, J.D. Sterk, T.A. Manning, M.-S. Chang, C. Monroe, G.-D. Lin, L.-M. Duan, D. Stick, M.G. Blain, J. Amini, R.E. Slusher We report progress towards scalable quantum information processing using a linear crystal of 171Yb+ ions. Anharmonic traps can stably hold large numbers of nearly equally spaced ions. We implement novel, multi-segment micro- and surface-traps. These architectures may allow us to perform large-scale quantum computations and quantum simulations of systems that are classically intractable. [Preview Abstract] |
|
M1.00094: Entanglement and Non-Classical Correlations in Light-Harvesting Complexes Dmitry Uskov, Kamil Bradler, Mark Wilde, Sai Vinjanampathy This work belongs to the emerging field of quantum biology. The main direction of research in the quantum biological program is to identify and quantify the role of ``quantumness'' in basic biological processes, exploiting appropriate tools of quantum information theory. Using the tight-binding Hamiltonian and the Lindblad form of master equations, we calculate the time evolution of the density matrix of an exciton in the Fenna-Matthews-Olson (FMO) protein complex during the energy transfer from an antenna to a reaction center at cryogenic T=77$^{\circ}$K and physiological T=300$^{\circ}$K temperatures. The quantum information toolbox is then applied to analyze the resulting density matrix. We compute \textit{quantum discord functional} to identify the amount of non-classical quantum correlations and compare the result with \textit{relative entropy of entanglement}. We observe an interesting phenomenon that the value of discord is typically one order of magnitude larger than the value of relative entropy of entanglement, indicating that non-classical correlations may be more robust against phase decoherence than the quantum entanglement. [Preview Abstract] |
|
M1.00095: Suppression of collisional decoherence by dynamical decoupling in optically trapped dense atomic ensemble Yoav Sagi, Ido Almog, Nir Davidson An ensemble of two level quantum systems coupled to a fluctuating external environment is a common paradigm in many fields of study. This coupling leads to decoherence that limits the usefulness of these systems, e.g. as qubits in quantum computation systems. Application of external pulses can reduce the decoherence by utilizing symmetry properties of the coupling Hamiltonian to average out its effect, a method commonly referred to as dynamical decoupling. In the case of trapped atoms these techniques can be especially useful since the fluctuations are inherent to the desirable high densities required to achieve a good overall efficiency of quantum operations. Here we report on experiments with optically trapped $^{87}Rb$ atoms demonstrating a $20$-fold increase of the coherence time when a dynamical decoupling sequence with more than $200$ $\pi$-pulses is applied. By starting with different initial states and using state tomography we demonstrate that a dense ensemble with $OD\approx100$ can store an arbitrary superposition for more than $3$ seconds. [Preview Abstract] |
|
M1.00096: Entanglement of neutral atoms using Rydberg blockade Xianli Zhang, Larry Isenhower, Alex Gill, Thad Walker, Mark Saffman We report measurements of entanglement of two Rb atoms achieved with a Rydberg blockade mediated quantum gate. The entanglement fidelity is compared for two different gate protocols: one based on a Hadamard-$C_Z$-Hadamard sequence, and the other using a controlled amplitude swap operation. Entanglement fidelity $F>0.5$ is achieved after correction for atom loss during the gate operation. Progress towards deterministic entanglement, without correction for atom loss, will be presented. [Preview Abstract] |
|
M1.00097: Atoms Talking with SQUIDs Jeffrey Grover, Daniel Hemmer, Jonathan Hoffman, Saurabh Paul, Alex Dragt, Robert Anderson, Jacob Taylor, Chris Lobb, Steven Rolston, Fred Wellstood, Luis Orozco Recent proposals in quantum computing have centered on the creation of hybrid quantum processors [1]. Here we present a scheme to inductively couple a cloud of $^{87}$Rb atoms to a superconducting flux qubit. Conveniently, the flux qubit can be tuned to have the same energy level separation as the 6.8GHz hyperfine splitting in $^{87}$Rb. We will trap the atoms around a sub-wavelength optical fiber using a two-color, evanescent wave dipole trap [2]. This will allow us to bring the atoms less than 10$\mu$m above the superconductor's surface without producing excessive heating or changing magnetic fields. In addition to interfacing a stable quantum memory ($^{87}$Rb atoms) with a fast, scalable quantum processor (flux qubit), this setup lends itself to probing sources of decoherence in superconducting qubits.\\[4pt] [1] M. Wallquist \textit{et al.}, Phys. Scr. T137, 014001 (2009).\\[0pt] [2] F. L. Kien \textit{et al.}, Phys. Rev. A 70, 063403 (2004). [Preview Abstract] |
|
M1.00098: Micron-scale ion trap to interface atoms and photons J.D. Sterk, T.A. Manning, L. Luo, P. Maunz, C. Monroe Reflective optics placed near a trapped ion may potentially improve the success rate for probabilistic entangling schemes that rely on the collection and interference of single photons [1]. We successfully trapped an ytterbium ion at the focus of a $5$mm spherical reflector using an optically open trap with moveable electrodes and measured characteristic trap parameters. We present progress towards observing an enhancement of ion fluorescence collection off the spherical mirror over that of free space [2, 3]. We discuss the possibility of placing the ion in an asymmetric, micron-scale optical cavity ($\mathcal{F} \approx$ 4500) as well as describe various methods to generate ion-photon entanglement inside the cavity. This work is supported by IARPA under ARO contract, the NSF PIF Program, and the NSF Physics Frontier Center at JQI. \\[4pt] [1] D. L. Moehring, et al. \emph{Nature} \textbf{449}, 68 (2007) \newline [2] N. Lindlen, et al. \emph{Laser Physics} \textbf{17},927 (2007) \newline [3] G. Shu, et al. \emph{J. Phys. B} \textbf{42}, 154005 (2009); G. Shu, et al. ArXiv: 0911.4958 [Preview Abstract] |
|
M1.00099: All-optical cluster-state generation using Rydberg dipole blockade T. Bragdon, E. Kuznetsova, S.F. Yelin We analyze the generation of cluster-states, which are useful in one-way quantum computing architectures, in a 2D array of Rydberg atoms. Dipole blockade is used as a mechanism for controlled-Z operation between nearest neighbors. Applying an electric field gradient allows individual atomic addressing due to spatially dependent Stark-shifts. The latter combined with a train of optical pulses tailored to resonantly excite spatially selected pairs of atoms is proposed to entangle nearest neighbors. In order to efficiently generate a 2D cluster-state, we apply this protocol in parallel to non-interacting 1D chains of atoms. [Preview Abstract] |
|
M1.00100: Atom number squeezing and Rydberg level shifts near a magnetic film atom chip Atreju Tauschinsky, Caspar Ockeloen, Rutger Thijssen, Ben van Linden van den Heuvell, Shannon Whitlock, Robert Spreeuw We have produced a two-dimensional lattice of microscopic traps above a magnetic-film atom chip. A few hundred optically resolved microtraps, each holding tens to a few hundred $^{87}$Rb atoms, are cooled to quantum degeneracy in parallel. For any given site in the lattice we observe squeezing of the shot-to-shot atom number fluctuations to below the Poissonian level, due to strong three-body loss in these tightly confining microtraps. We aim to perform quantum information studies in mesoscopic ensembles in this lattice, using the dipole blockade of Rydberg atoms to mediate switchable, long-range interaction. In order to characterize the influence of the chip surface we are now using electromagnetically induced transparency (EIT) in a three-level ladder configuration. This allows us to study level shifts and broadenings of the Rydberg states in the proximity of the surface. Preliminary results show MHz level shifts at typical distances of $\sim $50 $\mu $m, and a strong dependence on the distance to the surface and the principal quantum number. The shifts are most likely caused by electric fields originating in the surface. Our lattice of mesoscopic ensembles has bright prospects for being developed as a scalable platform for quantum information science with neutral atoms. [Preview Abstract] |
|
M1.00101: Investigation of a quantum memory created by diffraction of laser light at an array of pinholes Katharina Gillen-Christandl, Bert Copsey, Glen D. Gillen We present computational results of the investigation of an array of pinholes as basis for a quantum memory. Our previous calculations [1] showed that the diffraction pattern of laser light behind a pinhole exhibits localized intensity maxima and minima that, for moderate laser intensities and commercially available pinholes, can serve as single atom traps for quantum computing. We also found that the traps stay intact for laser light incident on the pinhole at an angle. Thus, two laser beams incident at an angle can trap two atoms in separate wells. By exploiting the polarization-dependence of the atom trapping potential on the light polarization and the magnetic substate of the atom [2], we can controllably bring a pair of atoms together and apart for quantum operations. This is achieved by using two tilted laser beams with opposite circular polarizations to trap two atoms in different magnetic substates, and then moving the atoms arbitrarily close to each other by tilting the beams to normal incidence. We are currently exploring the scaling up of this approach to many pinholes to create an addressable 2D array of atoms for use as a quantum memory. [1] G. D. Gillen, et al., Phys. Rev. A 73, 013409 (2006); [2] I. H. Deutsch, et al., Phys. Rev. A, 57 (3), 1972-1986 (1998). [Preview Abstract] |
|
M1.00102: PHYSICS WITH ULTRA-INTENSE LASERS |
|
M1.00103: The atomic response to 10$^{18}$ W/cm$^2$ x-rays from the LCLS B. Kr\"assig, E.P. Kanter, A.M. March, Y. Li, S.T. Pratt, R. Santra, S.H. Southworth, L. Young, N. Rohringer, N. Berrah, L. Fang, M. H\"oner, L. DiMauro, G. Doumy, C.A. Roedig, P.H. Bucksbaum, J.P. Cryan, S. Ghimire, J.M. Glownia, D.A. Reis, M. Messerschmidt, C. Bostedt, J.D. Bozek The goal of this experiment was to characterize the response of a prototypical atom, neon, to the unprecedented flux of microfocussed x-rays produced at the Linac Coherent Light Source (LCLS) at the SLAC Linear Accelerator Laboratory. In agreement with results from theoretical modeling, we find atoms inside the focal volume to undergo multiple successive ionization events, leading to fully stripped Ne$^{10+}$ at 2-keV x-ray energies, and charge states up to Ne$^{8+}$ below the {\em K}-ionization threshold. We also observe photoproduction of hollow neon ions through successive {\em K}-shell ionization on timescales shorter than Auger decay. We demonstrate intensity-induced x-ray transparency as a consequence of ever slower vacancy decay clocks limiting an ion's consecutive {\em K} absorption within a single 200-fs x-ray pulse. [Preview Abstract] |
|
M1.00104: Characterization of LCLS X-Ray Pulses Using Atomic Spectroscopy A.M. March, L. Young, S.H. Southworth, E.P. Kanter, B. Kr\"assig, R. Santra, Y. Li, S.T. Pratt, N. Berrah, M. H\"oner, L. Fang, J.P. Cryan, J.M. Glownia, D.A. Reis, S. Ghimire, P. Bucksbaum, L. DiMauro, G. Doumy, C. Roedig, J.D. Bozek, C. Bostedt, M. Messerschmidt The first experiments at the LCLS succeeded in not only revealing the nature of interactions between intense x-rays and atomic or molecular systems, but also properties of the LCLS x-ray pulses. Our spectroscopic measurements of the interaction with neon atoms have revealed information on x-ray photon energy, the pulse duration, and the focal spot size. When analyzed in conjunction with diagnostics of the electron beam, the data yields information on the photon energy bandwidth and shot-to-shot photon energy jitter. The intrinsic bandwidth of the LCLS pulse is strongly dependent on the LINAC tuning, thus high resolution photoelectron spectroscopy is a valuable diagnostic that can be implemented in a pass through configuration. [Preview Abstract] |
|
M1.00105: Free-free transitions in the presence of laser fields at very low incident electron energy A.K. Bhatia, Chandana Sinha We study the free-free transition in electron-hydrogenic systems in ground state in presence of an external laser field at very low incident energies. The laser field is treated classically while the collision dynamics is treated quantum mechanically. The laser field is chosen to be monochromatic, linearly polarized and homogeneous. The incident electron is considered to be dressed by the laser in a nonperturbative manner by choosing a Volkov wave function for it. The scattering wave function for the electron is solved numerically by taking into account the effect of the electron exchange, short-range as well as of the long-range interactions to get the S and P wave phase shifts while for the higher angular momentum phase shifts, the exchange approximation has only been considered. We calculate the laser-assisted differential cross sections (LADCS) for the aforesaid free-free transition process for single photon absorption/emission. The laser intensity is chosen to be much less than the atomic field intensity. A strong suppression is noted in the LADCS as compared to the field free (FF) cross sections. Unlike the FF ones, the LADCS exhibit some oscillations having a distinct maximum at a low value of the scattering angle depending on the laser parameters as well as on the incident energies. [Preview Abstract] |
|
M1.00106: Orientation-Dependent High-Order Harmonic Generation of N$_{2}$ and F$_{2}$ in Intense 800~nm Laser Pulses Dmitry A. Telnov, Shih-I Chu We present time-dependent density functional calculations of high-order harmonic generation (HHG) of diatomic molecules N$_{2}$ and F$_{2}$ with arbitrary orientation of the molecular axis by intense linearly-polarized laser pulses with the wavelength 800~nm [1]. HHG is more intense for the orientations where multiphoton ionization reaches its maximum. This happens at the parallel orientation for N$_{2}$ and at the orientation 40$^{\circ}$ for F$_{2}$. The high-order harmonics are very sensitive to the interference of the contributions from multiple electronic shells. Due to one-photon resonance, the highest-occupied molecular orbital (HOMO) and the next occupied orbital (HOMO$-1$) in N$_{2}$ are strongly coupled by the laser field at nonparallel orientations, and the HHG radiation results from their combined response to the field. In any case, the account of the multielectron effects can change the resulting harmonic radiation energy by orders of magnitude, as compared with the HHG spectrum produced by HOMO only.\\ \noindent [1] D.~A.~Telnov and S.~I.~Chu, Phys.~Rev.~A \textbf{80}, 043412 (2009). [Preview Abstract] |
|
M1.00107: \textit{Ab Initio} Calculation of Double Photoexcitation of Helium below the $N =2$ Threshold in a Strong dc Electric Field John Heslar, Shih-I Chu We present a complex-scaling (CS)-generalized pseudospectral (GPS) method in hyperspherical coordinates (HSC) for an accurate \textit{ab initio} and accurate treatment of the electron structure and quantum dynamics of two-electron systems. The GPS method allows non-uniform and optimal spatial discretization of the two-electron Hamiltonian in HSC with the use of only a very modest number of grid points. The procedure is applied for the precision calculation of the energies and widths of doubly-excited Rydberg resonance states as well as the ionization rates of He atoms in an external electric field of $84.4$ \textit{kV/cm}. The effects of dc-field ionization rates on the 1$S^{e}$, 1$P^{o}$, and 1$D^{e}$ states where $n =10-20$ have been identified. [Preview Abstract] |
|
M1.00108: Oscillating ionization probability of hydrogen and helium atoms in a single XUV attosecond and delayed few-cycle infrared laser pulses Feng He, Uwe Thumm By solving the time-dependent Schr\"odinger equation, we study the ionization of hydrogen and helium atoms in a single attosecond pulse and a delayed few-cycle femtosecond laser pulse. The attosecond XUV pulse pumps the electron to a certain excited state, and the time-delayed femtosecond laser pulse ionizes the excited atom. The ionization probability is found to oscillate as a function of the time delay between such pump and probe pulses. The oscillation period of the ionization signal is half of the probe pulse period, regardless its wavelength. The ionization probability is largest when the attosecond pulse coincides with a peak of the carrier oscillation of the infrared probe pulse. In contrast, ionization is suppressed when the attosecond pulse coincides with a node of the laser electric field. [Preview Abstract] |
|
M1.00109: Quantum mechanical simulation of the dissociation dynamics of the N$_{2}$ (N$_{2}^{+}$, N$_{2}^{++})$ and O$_{2}$ (O$_{2}^{+}$, O$_{2}^{++})$ molecules* Maia Magrakvelidze, Irina Bocharova, Igor Litvinyuk, Uwe Thumm The nuclear dynamics of molecular nitrogen and oxygen in intense laser fields was studied by analyzing their fragment kinetic energy release (KER) spectra as a function of time$^{1}$. Typically, several intermediate states contribute to the same KER. Based on a quantum mechanical model, we calculated the time evolution of an initial (ground state) nuclear wave packet in N$_{2}^{+}$ and N$_{2}^{++}$ (O$_{2}^{+}$ and O$_{2}^{++})$ separately, for given adiabatic molecular potential curves, in order to assess the relevance of individual potential curves during the laser-induced fragmentation. By Fourier transformation of the nuclear probability density with respect to time, we derive internuclear distance (R) dependent power spectra$^{2}$ that allow us to identify vibrational frequencies associated with the bound motion of the vibrationally excited molecular ion. To include laser-induced dynamical couplings between molecular potential curves we are in the process of modeling (non)adiabatic transitions near curve crossings based on Landau-Zener transition rates and will compare our numerical results with existing measured KER- spectra. $^{1}$I. Bocharova et al., to be published. $^{2}$M. Magrakvelidze et al., PRA 79, 033410 (2009) *Supported by the US DOE. [Preview Abstract] |
|
M1.00110: Memory Effect on Multi-Photon Coherent Destruction of Tunneling in Electron Transport of Nanoscale Systems Driven by a Periodic Field: A Generalized Floquet Approach Hsing Ta Chen, Tak Son Ho, Shih I. Chu Time-dependent electron transport processes are often studied in the wide-band limit. We present a novel generalized Floquet approach beyond the wide-band limit (WBL), which is developed for the general treatment of memory effect on the virtually unexplored multi-photon (MP) coherent destruction of tunneling (CDT) phenomenon of periodically driven electrode-wire-electrode nanoscale systems. As a case study, we apply the new approach for a detailed analysis of the electron transport d.c. current in the electrode-quantum double dots-electrode system, showing the significance of the memory effect as well as illustrating the origin of the MP-CDT phenomenon. Furthermore, we study the effect on the contact between the single dot and the electrodes. Unlike in the WBL, the memory effect enables us to observe the MP-CDT phenomenon for larger bias voltages, due to the suppression of higher tunneling channels. By means of the nearly-degenerate perturbation method, we derive an analytical expression which can explain the shifting and sharpening of the transmission coefficient peaks. [Preview Abstract] |
|
M1.00111: Double Ionization of Hydrogen Molecule by Intense Attosecond Laser Pulses Teck-Ghee Lee, M.S. Pindzola, F. Robicheaux Time-dependent close-coupling calculations within the fixed nuclei approximation are carried out for the double ionization of H$_2$ induced by an intense attosecond laser pulse at a photon energy of 40 eV. We consider here the two-photon absorption processes and examine the response of the ejected electrons, particularly the single- and the double-electron energy distributions, to linearly and circularly polarized pulse at laser intensities between 10$^{15}$ W/cm$^2$ and 10$^{16}$ W/cm$^2$. We find that, for both the linearly and circularly polarized pulses, sequential peaks and non-sequential wells appear in both the single- and double-electron energy distributions that are generally akin to the analogous two electrons photoemission processes in He atom driven by a linearly polarized intense attosecond pulse [1,2]. Furthermore, a clear signature of the sequential double-electron above threshold ionization process can be seen in the single- and double-electron energy distributions when a linearly polarized pulse is being used.\\[4pt] [1] I. F. Barna, J. Wang, and J. Burgdorfer, Phys. Rev. A. 73, 023402 (2006) \\[0pt] [2] T-G Lee, M. S. Pindzola and F. Robicheaux, Phys. Rev. A. 79, 053420 (2009) [Preview Abstract] |
|
M1.00112: Suppressed strong field ionization of polyatomic molecules Agnieszka Jaron-Becker, Andreas Becker Suppressed strong field ionization of diatomic molecules has been attributed to Young type interferences of different contributions originating from atomic centers. The destructive or constructive interference depends on the symmetry properties of the active orbital. For polyatomic molecules the situations is more complex due to the variety of possible symmetries as well as the possibility that more than one orbital can be ionized by a strong laser source. We use S matrix theory for strong field ionization to analyze the suppressed ionization of several polyatomic molecules. We study in detail the influence of different molecular properties on the observed interference, by investigating the difference between coherent and incoherent sums of the atomic contributions. Finally, we discuss the dependence of the phenomenon of suppressed molecular ionization on the parameters of the laser field. [Preview Abstract] |
|
M1.00113: Collisional auto-ionization of clusters exposed to intense X-ray pulses Ulf Saalmann, Christian Gnodtke, Jan M. Rost An efficient multi-electronic ionization process mechanism in strong X-ray pulses is proposed. It occurs, e.g., in clusters or large molecules when photo-electrons, trapped in the strong Coulomb potential of the cluster ions, form a plasma with supra-atomic density and undergo multiple energy-exchanging collisions in the entire cluster volume producing fast electrons. As an example we discuss the electron spectrum obtained from a recent experiment where xenon clusters were exposed to strong femtosecond pulses of 90 eV photon energy at FLASH, causing mainly inner-shell ionization [1]. Such collisional auto-ionization is expected to be a general phenomenon occurring for strong atomic X-ray absorption in extended systems.\\[3mm] [1] Ch. Bostedt etal, submitted (2009). [Preview Abstract] |
|
M1.00114: Examining the role of the feedback signal in closed-loop control of molecular fragmentation B. Jochim, R. Averin, N. Gregerson, M. Todt, E. Wells, J. McKenna, S. De, M. Zohrabi, A.M. Sayler, B. Gaire, D. Ray, K.D. Carnes, M.F. Kling, I. Ben-Itzhak Closed-loop control schemes incorporating feedback algorithms and shaped ultrafast laser pulses have been used to control a number of molecular processes. Using carbon monoxide as a model system, we have examined how the type of feedback signal delivered to the algorithm can influence the level of control and in some cases, help provide a better understanding of how the control is accomplished. Several feedback methods were examined, including using time-of-flight to select dissociation channels by kinetic energy release, isolating the C$^+$ + O$^+$ channel using a coincidence time-of-flight technique and using velocity map imaging to provide multi-dimensional momentum information in the feedback loop. [Preview Abstract] |
|
M1.00115: Low kinetic energy release in the strong-field dissociation of H$_{3}^{+}$ B. Gaire, J. McKenna, M. Zohrabi, K.D. Carnes, B.D. Esry, I. Ben-Itzhak The triatomic hydrogen molecular ion is a fundamentally important system for the understanding of the laser-driven dynamics of polyatomic molecules. Recently, Alexander \textit{et al}. [J. Phys. B, \textbf{42}, 141004, (2009)] reported the laser-induced dissociation of D$_{3}^{+}$ as a function of the time the D$_{3}^{+}$ was stored in an electrostatic ion trap, using 30 fs, 800 nm pulses. They ascribed the detected low kinetic energy release neutral fragments to the D$_{2}^{+}$+D dissociation channel even though the neutral fragments D and D$_{2}$ could not be clearly distinguished in their measurement. Using coincidence 3D momentum imaging we clearly separate and distinguish between all fragments and measure kinetic energy release down to 0 eV. Our results suggest that the low kinetic energy release is associated with the H$^{+}$+H$_{2}$ dissociation channel of H$_{3}^{+}$. [Preview Abstract] |
|
M1.00116: Two-Color Coherent Control of $\mathbf{D_{2}^{+}}$ D. Ursrey, J.V. Hern\'andez, F. Anis, J. McKenna, M.A. Zohrabi, B. Gaire, D. Ray, K.D. Carnes, C.L. Cocke, I. Ben-Itzhak, B.D. Esry It has long been known that adjusting the delay between the colors in an intense two-color field can be used to coherently control molecular dynamics [1]. Because of this access to control, the study of two-color dissociation has become increasingly important. We present theoretical and experimental results for the dissociation of $\mathrm{D_{2}^{+}}$ in an intense two-color laser field. We have studied the nuclear kinetic energy release and the asymmetry of the dissociated fragments as a function of the delay between $\sim$40 fs long ultraviolet (395 nm) and infrared (790 nm) pulses. We solved the time-dependent Schrodinger equation in the Born-Oppenheimer representation including all degrees of freedom except ionization. \\[4pt] [1] P. Brumer and M. Shapiro, Annu. Rev. of Phys. Chem. 43, 257 (1992) [Preview Abstract] |
|
M1.00117: Optimal pulse sequences for population transfer in the three level lambda system Praveen Kumar, Vladimir Malinovsky, Svetlana Malinovskaya By means of the fields designed using optimal control theory, we study the dynamics of adiabatic population transfer and maximal coherence in a three-level lambda system. A family of solutions of the optimal pulse sequences is obtained using different numerical methods such as conjugate gradient method, Krotov method, and Zhu-Rabitz's iterative method. The minimum population transfer to the intermediate level is achieved via a functional constraint which depends on the state of the system at each instant of time. Optimal pulse sequences obtained is the well known STIRAP (stimulated Raman adiabatic passage) scheme for the complete population transfer and half-STIRAP method which only transfers half of the population between appropriate levels. We analyze the convergence properties of all the methods and demonstrate that the result of the Krotov method depends strongly on the choices of the reference field. [Preview Abstract] |
|
M1.00118: Hydrocarbon Bond Rearrangement Following Ionization by a Single Attosecond Pulse from a Fast Ion M.P. Jones, J.B. Williams, J. Watson, A. Fisher, M. Fogle, A.L. Landers, T. Austin When a polyatomic molecule is doubly ionized to form a dication that then dissociates, there can be some probability that the molecule rearranges to form new bonds in the resulting fragment ions. We have used a COLTRIMS arrangement to image in coincidence multiple ionic fragments ejected following the interaction of a fast ($\sim $few au) ion and molecules with fields and time scales similar to (or shorter than) current pulsed lasers. In addition to the branching ratio for final-state fragment pairs, we have measured the kinetic energy release and dissociation axis relative to the incident ion beam for two-body breakup channels. An overview of the program and particularly interesting results for small hydrocarbons (e.g. methane) will be highlighted. [Preview Abstract] |
|
M1.00119: Quantitative Comparison of H$_2^+$ Laser-Induced Dissociation in an Intense Ultrashort Pulse J.V. Hern\'andez, F. Anis, A.M. Sayler, J. McKenna, B. Gaire, M. Zohrabi, N.G. Johnson, K.D. Carnes, B.D. Esry, I. Ben-Itzhak We present a quantitative comparison between experimental measurements and theoretical calculations for laser-induced dissociation of H$_2^+$ in an intense ultrashort pulse. The 3D momentum distribution was measured for the dissociating fragments of an H$_2^+$ beam that has been exposed to a 10~fs, 790~nm pulse at intensities of 10$^{12}$ and 10$^{13}$~W/cm$^2$. We have solved the TDSE within the Born-Oppenheimer representation, including all degrees of freedom, but ionization. In order to produce a theoretical momentum distribution that can be directly compared to experimental measurements, the observables are averaged over the initial vibrational and thermal distributions as well as the intensity distribution of the laser within the focus. The experimental resolution in both energy and angle are also incorporated, which can finally be fit to the experimental data taking the effective source temperature to be a free parameter. Whether this parameter alone is sufficient to produce agreement will be discussed. [Preview Abstract] |
|
M1.00120: New determination of structure parameters in strong field tunneling ionization theory of molecules Song-Feng Zhao, Cheng Jin, Anh-Thu Le, T.F. Jiang, C.D. Lin In the strong field molecular tunneling ionization theory of Tong et al. [Phys. Rev. A 66, 033402 (2002)], the ionization rate depends on the asymptotic wavefunction of the molecular orbital from which the electron is removed. The orbital wavefunctions obtained from standard quantum chemistry packages in general are not good enough in the asymptotic region. Here we construct a one-electron model potential for several linear molecules using density functional theory (DFT). We show that the asymptotic wavefunction can be improved with an iteration method and after one iteration accurate asymptotic wavefunctions and structure parameters are determined. With the new parameters we examine the alignment-dependent tunneling ionization probabilities for several molecules and compare with other calculations and with recent measurements, including ionization from inner molecular orbitals. [Preview Abstract] |
|
M1.00121: Study of zero-photon dissociation of H$_{2}^{+}$ and its isotopes in ultrashort transform limited and chirped laser pulses B. Gaire, J.V. Hern\'andez, F. Anis, M. Zohrabi, J. McKenna, K.D. Carnes, B.D. Esry, I. Ben-Itzhak We have measured very low kinetic energy release (KER) in the dissociation of H$_{2}^{+}$ and its isotopes in intense ultrashort 800 nm laser pulses. Zero-photon dissociation is the mechanism responsible for this low-KER peak. Our results, obtained by using coincidence three dimensional momentum imaging, suggest some differences in the low kinetic energy release part of the dissociation spectra of HD$^{+}$, namely a difference between the two channels H$^{+}$+D and H+D$^{+}$. We also investigate the effect of the positive/negative chirped pulses on the zero-photon dissociation yields. The solutions of the time-dependent Schr\"{o}dinger equation, which are in good agreement with the experiment for transform limited pulses, show qualitative differences between positively and negatively chirped pulses. [Preview Abstract] |
|
M1.00122: Correlated electron-nuclear kinetic energy distribution following strong-field ionization of H$_2^+$ C.B. Madsen, F. Anis*, L.B. Madsen, B.D. Esry* Being the simplest molecule, understanding the behavior of H$_2^+$ in a strong laser field helps to understand more complex molecules. Theoretically, however, it is challenging to account for both electronic and nuclear motion in the ionization of even this simple molecule. Accordingly, calculating correlated electron-nuclear physical observables --- such as energy or momentum distributions --- has rarely been accomplished. Such calculations are needed to interpret recent measurements of coincidence momentum distributions of electrons and ions following the ionization of molecules by short intense laser pulses. We study how the energy absorbed from an intense laser pulse (400--800~nm, $\sim$10$^{14}$~W/cm$^2$, $\ge$10 cycles) is shared among the nuclei and the electron of H$_2^+$ by calculating the 2D electron-nuclei momentum distribution for a 1D model with soft-core Coulomb interactions. These 2D momentum plots reveal multiphoton structure with the energy shared between the nuclei and electron. This structure survives integrating out the nuclear energy, but not integrating out the electronic energy. $^*$Supported by the Chemical Sciences, Geosciences, and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U.S. DoE. [Preview Abstract] |
|
M1.00123: Laser-induced fragmentation of D$_{2}$: detection of metastable D$^{\ast}$ atoms M. Zohrabi, J. McKenna, J.J. Hua, A.M. Sayler, Nora G. Johnson, B. Gaire, K.D. Carnes, B.D. Esry, I. Ben-Itzhak In a recent Letter, Manschwetus \textit{et al.} [Phys. Rev. Lett. \textbf{102}, 113002 (2009)] reported experimental evidence for the formation of metastable H* fragments upon dissociative ionization of H$_{2}$ by a strong laser field. Their finding was explained using a frustrated tunnel ionization model. Here, we present our measurements of D* formation from D$_{2}$ that encompass the dependence of this process on pulse duration, intensity, ellipticity and angular alignment. We find that the mechanism suggested by Manschwetus \textit{et al.} is consistent with our experimental data. However, other mechanisms might also be consistent with the data. A few possible mechanisms have been eliminated by our theoretical work on the fragmentation of the transient D$_{2}^{+}$, and further investigation of other mechanisms is underway. Supported by the Chemical Sciences, Geosciences and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy. [Preview Abstract] |
|
M1.00124: Controlled double ionization of helium in ultrashort laser pulses Feng He, Aihua Liu, Camilo Ruiz, Andreas Becker, Uwe Thumm We study the double ionization of helium in an ultrashort laser pulse by solving a three dimensional time-dependent Schr\"odinger equation. In our model, the laser field first ionizes one electron and subsequently rescatters it one or several times on the parent ion to cause double ionization. We revisit the dependence of double ionization on the laser parameters and discuss a scheme for controlling the double ionization yield. [Preview Abstract] |
|
M1.00125: FUNDAMENTAL SYMMETRIES AND PRECISION MEASUREMENTS |
|
M1.00126: A K-Rb-Ne Co-magnetometer Lawrence Cheuk, Michael Romalis An atomic co-magnetometer consists of coupled spin ensembles of alkali atoms and noble gas atoms. With an appropriate external field, the noble gas polarization cancels external magnetic fields, rendering the co-magnetometer a sensitive probe for non-magnetic spin couplings. In the past we have used a K-$^{3}$He co-magnetometer as a gyroscope and to search for spin interactions beyond the Standard Model. In this work, we explore a K-Rb-Ne co-magnetometer. Due to a lower gyromagnetic ratio, the use of $^{21}$Ne provides a ten-fold increase in sensitivity to non-magnetic interactions compared to K-$^{3}$He co-magnetometers. We also use hybrid-pumping to polarize a K-Rb mixture ($n_{Rb}/ n_{K}\sim 100$). The K atoms are optically pumped, while the Rb atoms are polarized via spin-exchange collisions. The relatively low $n_K$ allows uniform polarization of K atoms. In turn, a uniform polarization of a dense Rb vapor ($\sim 10^{15}\mbox{cm}^{-3}$) is achieved. With the ten-fold increase in alkali density, the K-Rb-Ne co-magnetometer is expected to provide up to two orders of magnitude of improvement in inertial rotation sensing and searches for new physics. In addition, since $^{21}$Ne has nuclear spin $I=3/2$, it is sensitive to anomalous tensorial spin couplings that violate Lorentz symmetry but preserve CPT symmetry. [Preview Abstract] |
|
M1.00127: Autoionization of HfF for an electron EDM search Huanqian Loh, Russell Stutz, Matthew Grau, Eric Cornell The $^3\Delta_1$ state of HfF$^+$ has been proposed as a candidate for the search for an electron electric dipole moment (eEDM). Neutral HfF molecules are created upon laser ablation of a Hf target in the presence of Ar + 1\%SF$_6$, and cooled rotationally via supersonic expansion. The neutral molecules are optically excited with two photons to an autoionizing state, from which they decay to form ions. We report on progress to measure the rotational populations of the autoionization decay products, using laser-induced fluorescence of ions excited on the $^1\Sigma_0 \rightarrow ^3\Pi_1$ line. [Preview Abstract] |
|
M1.00128: Measuring the electron electric dipole moment using a cold molecular beam Elizabeth Petrik, Wesley Campbell, Yulia Gurevich, Paul Hess, Nicholas Hutzler, Emil Kirilov, Maxwell Parsons, Benjamin Spaun, Amar Vutha, David DeMille, Gerald Gabrielse, John Doyle A test of theories beyond the standard model is in progress using a cold beam of thorium monoxide (ThO) to improve the experimental limit on the electric dipole moment of the electron (eEDM). Improvements are expected on the current experimental eEDM limit because of the large internal electric field of polarized ThO, the long lifetime and magnetic field insensitivity of the metastable H state used in the experiment, the powerful systematic error canceling provided by the H state $\mathrm{\Omega}$-doublet structure, and the high-flux, well collimated molecular beam provided by a buffer gas-cooled beam source. We detail the progress of this experiment, including the development of techniques to produce the ThO emission source, cool and collimate the molecular beam, and create stable electric and magnetic field configurations. [Preview Abstract] |
|
M1.00129: Electron EDM searches based on alkali-metal- or alkaline-earth-metal-bearing molecules Edmund Meyer, John Bohn We introduce four new molecules - YbRb, YbCs, YbSr$^+$, and YbBa$^+$ - that may prove fruitful in experimental searches for the electric-dipole moment (EDM) of the electron. These molecules can, in principle, be prepared at extremely low temperatures by photoassociating ultracold atoms and therefore may present an advantage over molecular-beam experiments. Here we discuss properties of these molecules and assess the effective electric fields they contribute to an electron EDM measurement. [Preview Abstract] |
|
M1.00130: Relativistic many-body calculation of energies, lifetimes, hyperfine constants, multipole polarizabilities, and black-body radiation shift in $^{137}$Ba~II Ulyana Safronova Excitation energies of the [Xe]$ns_{1/2}$ [Xe]$np_j$, and [Xe]$nd_j$ ($n \leq$ 12 and [Xe]=$1s^22s^22p^63s^23p^63d^{10}4s^24p^634d^{10}5s^25p^6$) in Ba~II are evaluated. First-, second-, third-order, and all-order Coulomb energies and first- and second-order Coulomb-Breit energies are calculated. Electric-dipole ($6s_{1/2}\ -np_j$, $n$ = 6--26), electric-quadrupole ($6s_{1/2}\ -nd_j$, $n$ = 5--26), and electric-octupole ($6s_{1/2}\ -nf_j$, $n$ = 4--26) matrix elements are calculated to obtain the ground state E1, E2, and E3 static polarizabilities. Scalar polarizabilities of the $ns_{1/2}$, $np_j$and $nd_j$ states, and tensor polarizabilities of the $np_{3/2}$ and $nd_j$ excited states of Ba$^+$ are evaluated. All above-mentioned matrix elements are determined using all-order methods. We investigate the hyperfine structure in $^{137} $Ba~II. The hyperfine $A$- and B-values are determined for the first the first low-lying levels up to $n$ = 9. The quadratic Stark effect on hyperfine structure levels of $^{137}$Ba~II ground state is investigates. The calculated shift for the ($F$ = 2, $M$ =0) $\leftrightarrow$ ($F$ = 1, $M$ =0) transition is -0.2931~Hz/(kV/cm)$^2$, in agreement with previous theoretical result -0.284(3). These calculations provide a theoretical benchmark for comparison with experiment and theory. [Preview Abstract] |
|
M1.00131: Progress toward an EDM measurement in Ra-225 I.A. Sulai, W.L. Trimble, R.H. Parker, K. Bailey, J.P. Greene, R.J. Holt, W. Korsch, Z.T. Lu, P. Mueller, T.P. O'Connor, J. Singh We are developing an EDM search based on laser-cooled and trapped Ra-225 (half-life = 15 d) atoms. Due to octupole deformation of the nucleus, Ra-225 is predicted to be 2-3 orders of magnitude more sensitive to T-violating interactions than Hg-199, which currently sets the most stringent limits in the nuclear sector. In preparation of an EDM measurement, we have trapped radium atoms first in a MOT and then transferred them to a far-off-resonant optical dipole trap. We will report progress towards the EDM search and the measurements of relevant atomic properties. This work is supported by DOE, Office of Nuclear Physics, under contract No. DE-AC02-06CH11357. [Preview Abstract] |
|
M1.00132: Microwave cavity study for Anapole measurement in francium Jonathan Hood, Dong Sheng, Luis Orozco We present a detailed study of the mode structure and diffraction loses of a microwave spherical resonator using analytical and numerical methods. The resonator is an essential part of the apparatus to measure the anapole moment in francium [1]. The sensitivity of the measurement to polarization, alignment, and mode purity requires a study beyond the well-established paraxial methods. Our studies have found regions of parameter space where it is possible to satisfy the experimental requirements. Investigations of the coupling mechanisms of the radiation into the cavity point towards quasi-optical methods that can suppress the existence of traveling waves to acceptable methods. \\[4pt] [1] E. Gomez, S. Aubin, G. D. Sprouse, L. A. Orozco, and D. P. DeMille, ``Measurement method for the nuclear anapole moment of laser-trapped alkali-metal atoms,'' Phys. Rev. A \textbf{75}, 033418 (2007). [Preview Abstract] |
|
M1.00133: Progress on the measurement of the francium anapole moment Dong Sheng, Jonathan Hood, Steven Lynam, Luis Orozco, Eduardo Gomez, Seth Aubin, Gerald Gwinner, John Behr, Matthew Pearson, Peter Jackson, Dan Melconian, Victor Flambaum, Gene Sprouse We present the current status of the experimental effort towards the measurement of the anapole moment in francium. The anapole is a parity violating, time-reversal conserving nuclear moment that arises from the weak interaction among nucleons. The anapole moment is nuclear spin dependent (nsd) and sensitive to the configuration of nuclear structure. Our experimental scheme is to perform a direct measurement of the nsd parity violation, by driving a parity forbidden E1 transition between hyperfine ground states in a series of francium isotopes inside a blue detuned dipole trap at the electric anti-node of a microwave cavity. We explore theoretical aspects and experimental requirements on the possible tests using rubidium isotopes. The experiment will be at the ISAC radioactive beam facility of TRIUMF. Work supported by NSF and DOE USA, NSERC and NRC Canada, CONACYT Mexico. [Preview Abstract] |
|
M1.00134: A portable ultrasensitive atomic magnetometer for biomagnetic measurements Robert Wyllie, Ronald Wakai, Thad Walker We present a portable Rb cell atomic magnetometer suited for biomagnetic measurements. Working in the spin-exchange relaxation free regime, we demonstrate an initial white noise floor of 10 fT/(Hz)$^{1/2}$ above a 1/f noise bandwidth of 1 Hz. We show an adult magnetic cardiogram and demonstrate the feasibility of extending our measurements to fetal MCG. Based on previous experiments, we expect to be able to suppress nonmagnetic noise peaks by parametrically modulating the z-magnetic field, which also allows for the simultaneous measurement of the x and y field components using a single probe beam [1]. This work is supported by the NIH. \\[4pt] [1] Z Li, R T Wakai, and T G Walker, Appl. Phys. Lett. 89, 134105 (2006) [Preview Abstract] |
|
M1.00135: Birefringent Stability of a Monolithic High-Finesse Optical Cavity Francisco Monsalve, Michael Hohensee, Holger M\"uller We investigate the stability and achievable linewidths of high-finesse optical cavities made from monolithic blocks of fused silica (suprasil 3001). Since the cavity modes are entirely supported within the dielectric substrate, the resonances will be shifted and broadened by stress-induced birefringence, scattering from impurities and imperfections in the medium, Faraday rotation, and thermal variations in the cavity length. We study the relative stability of cavity resonances for light with two orthogonal polarizations. Since the two polarization modes spatially overlap, the effects of many external perturbations are common to both modes. This work has applications to fundamental tests of Lorentz Invariance for electrodynamics [1,2]. We also consider the use of total internal reflection cavities to circumvent the problem of thermal noise of mirror coatings, which presently limits the stability of the very best lasers [3].\\[4pt] [1] H. M\"uller, PRD 71, 045004 (2005).\newline [2] V.A. Kosteleck\'y and M. Mewes, PRD 80, 015020 (2009). \newline [3] M. Notcutt \emph{et al.}, PRA 73, 031804 (2006). [Preview Abstract] |
|
M1.00136: Experiment to measure the electric dipole moment (edm) of the electron using laser-cooled Cs atoms Yong-Sup Ihn, Daniel Heinzen The electron edm $d_{e}$ is known to be smaller in magnitude than $1.6\times 10^{-27}$\textit{e$\cdot $cm} [1]. We will describe progress on an ongoing experiment designed to be sensitive to an electron EDM $d_{e}$ as small as $10^{-29}$\textit{e$\cdot $cm.} The experiment will search for the resulting edm of the Cs atom, proportional to $d_{e}$, using laser-cooled Cs atoms held in an optical dipole force trap. Important features of the experiment include resonant optical cavities to accurately define the trapping laser field, in-vacuum high voltage electrodes, and methods to reduce magnetic noise to low levels, including the use of a novel titanium vacuum chamber \\[4pt] [1] B. C. Regan \textit{et al. }Phys. Rev. Lett. \textbf{88}, 071805 (2002) [Preview Abstract] |
|
M1.00137: Experimental determination of the dipole moment of the PbF molecule: Implications for an e-EDM measurement Tao Zheng Yang, Poopalasingam Sivakumar, Christopher McRaven, Priyanka Milinda Rupasinghe, Neil Shafer-Ray The lead mono-fluoride (PbF) molecule has many features that make it an attractive candidate for the measurement of the electron's electric dipole moment (e-EDM). These features include a large dipole moment combined with closely spaced levels of opposite parity. This situation greatly reduces the electric field required to become sensitive to the e-EDM. Here a new and highly sensitive multi-photon ionization technique (pseudo-continuous-REMPI) is used to carry out Stark spectroscopy of PbF for the first time. Data obtained are analyzed in terms of an effective spin-rotational Hamiltonian to determine the dipole moment of the molecule. This dipole moment is compared to theoretical prediction and implications for an e-EDM measurement are discussed. [Preview Abstract] |
|
M1.00138: Nuclear Spin-Dependent Parity Violation in Diatomic Molecules Sidney Cahn, David Rahmlow, Matthew Steinecker, Jeffrey Ammon, Emil Kirilov, Edward Deveney, Richard Paolino, David DeMille Nuclear spin-dependent parity nonconservation (NSD-PNC) effects arise from exchange of the $Z^{0}$ boson (parameterized by the electroweak coupling constants $C_{2{\{P,N\}}}$) between electrons and the nucleus and from the interaction of electrons with the nuclear anapole moment, a parity-odd magnetic moment. The latter scales with the nucleon number $A$ of the nucleus as $A^{\frac{2}{3}}$, while the $Z^{0}$ coupling is independent of A; the former will be the dominant source of NSD-PNC in nuclei with $A \ge 20$. The most precise result on NSD-PNC to date comes from a measurement of the hyperfine dependence of atomic PNC in $^{133}$Cs, but this effect can be dramatically enhanced in diatomic molecules by bringing two levels of opposite parity close to degeneracy in a strong magnetic field. Level crossings have been observed in $^{138}$BaF as a precursor to the test for parity violation in $^{137}$BaF. We report on our measurements and planned design improvements to improve sensitivity in preparation for the parity violation experiment. [Preview Abstract] |
|
M1.00139: $^{87}$Sr Optical Lattice Clock Yige Lin, Matthew Swallows, Michael Martin, Michael Bishof, Sebastian Blatt, Travis Nicholson, Benjamin Bloom, Jun Ye The JILA optical clock based on 1D lattice-confined $^{87}$Sr atoms operating on the ultra narrow $^1S_0$-$^3P_0$ transition has reached a fractional uncertainty of 1.4$\times 10^{-16}$.\footnote{A. D. Ludlow \textit{et al.,} Science, \textbf{319}(5871) pp. 1805-1808, 2008.} We have characterized a density dependent frequency shift, one of the largest sources of uncertainty in the JILA 1D lattice clock, at the $5\times 10^{-17}$ level.\footnote{G. K. Campbell \textit{et al.,} Science, \textbf{324}(5925) pp. 360-363, 2009.} We have implemented a 2D optical lattice confinement to further reduce this uncertainty. In addition, we report advances in characterizing and eliminating blackbody radiation-induced clock shifts, which currently dominate our systematic uncertainty. Direct optical frequency comparisons with the NIST Yb optical lattice clock demonstrate clock stability below $10^{-16}$ at 1000 s. [Preview Abstract] |
|
M1.00140: Short-term stability improvements of an optical frequency standard based on free Ca atoms Jeff Sherman, Chris Oates Compared to optical frequency standards featuring trapped ions or atoms in optical lattices, the strength of a standard using freely expanding neutral calcium atoms is not ultimate accuracy but rather short-term stability and experimental simplicity. Recently, a fractional frequency instability of $4 \times 10^{-15}$ at 1 second was demonstrated for the Ca standard at 657 nm~[1]. The short cycle time ($\sim$2 ms) combined with only a moderate interrogation duty cycle ($\sim$15 \%) is thought to introduce excess, and potentially critically limiting technical noise due to the Dick effect---high-frequency noise on the laser oscillator is not averaged away but is instead down-sampled by aliasing. We will present results of two strategies employed to minimize this effect: the reduction of clock laser noise by filtering the master clock oscillator through a high-finesse optical cavity~[2], and an optimization of the interrogation cycle to match our laser's noise spectrum.\\[4pt] [1] Oates et al., \emph{Optics Letters}, \textbf{25}(21), 1603--5 (2000)\\[0pt] [2] Nazarova et al., \emph{J.\ Opt.\ Soc.\ Am.\ B}, \textbf{5}(10), 1632--8 (2008) [Preview Abstract] |
|
M1.00141: Group Theory of Lorentz Symmetry in the Cosmological Expansion Felix T. Smith In the hyperbolic geometry of the Hubble expansion the Lorentz velocity boost symmetry is unimpaired, and it acquires a companion Lorentzian symmetry in hyperbolic position space. Hyperbolic translations generate a boost-like operator depending on $\delta \bf{r}/ct_{\mbox{H}}$, where $t_{\mbox{H}}$ is the Hubble time. Position and velocity participate in a doubly Lorentzian phase space. A direct product of two O(3,1) subgroups leads to a double Lorentz group with separate operators for velocity boosts and for hyperbolic translations. The resulting group theory will be outlined. (Cf. Smith, F. T., Ann. Fond. L. deBroglie, 30, 179 (2005).) Its representation requires $8\times 8$ matrices. Its Lie algebra is constructed, and compared to that of the Poincar\'e group. Its operators for velocity boosts operate on vectors of both velocity and position subspaces of a phase space, and so do its operators of hyperbolic translation. When the latter operate on position vectors they describe quantitatively the Hubble effect. Curvature effects in position and velocity spaces are of different magnitudes, and each produces its own angular momentum effects. A new angular momentum operator is encountered, with applications to the classification of angular momentum or particle states and their transitions. [Preview Abstract] |
|
M1.00142: Noise dynamics of a prism-based Cr:forsterite laser frequency comb Shun Wu, Brian Washburn, Kristan Corwin, Karl Tillman Mode-locked Cr:forsterite lasers are of significant interest as infrared frequency combs due to their ability to generate stable high repetition rate femtosecond pulses. However, self-referenced Cr:forsterite frequency combs tend to exhibit wide carrier-envelope offset frequency ($f_{0})$ linewidths. These large $f_{0}$ linewidths can be attributed to significant frequency noise across the comb's spectral bandwidth and result in broad comb teeth. We have stabilized a prism-based Cr:forsterite frequency comb and observed narrowing of the $f_{0}$ linewidth from $\sim $1 MHz down to $<$100 kHz when a knife edge is inserted into the intracavity beam as a spectral filter. This can also be further reduced after phase-locking the comb to a low-phase noise rf oscillator. Thus, the introduction of an intracavity knife edge significantly reduces the frequency noise of the system and enables more effective stabilization of the entire comb. A theoretical model has been used to investigate the noise dynamics of the phase-stabilized comb system. It includes: the pump laser power (P), the frequency dependence of the $f_{0}$ response to pump power changes ((d$f_{0}$/dP)($\nu ))$, and the frequency dependence of the femtosecond laser's relative intensity noise, RIN($\nu )$. Supported by AFOSR FA9950-05-1-0304 and NSF ECS-0449295 [Preview Abstract] |
|
M1.00143: Recent Results from the PbO Electron EDM Experiment Paul Hamilton, Emil Kirilov, Hunter Smith, David DeMille Observation of an electric dipole moment (EDM) of the electron would imply CP violation beyond the Standard Model. This experiment searches for the electron EDM using a metastable state of the PbO molecule. Several unique properties of this state, including closely spaced levels of opposite parity and a long coherence time, make it suitable for use in a vapor cell, which in turn enables high counting rates. The closely spaced levels of opposite parity are due to omega-doubling. Roughly speaking this doubling leads to states with oppositely directed internal electric fields but otherwise nearly identical properties. This reversal along with those of the lab electric and magnetic fields allow us to greatly reduce most systematics. We will discuss the statistical and systematic limits from a recent EDM data run as well as improvements in both our state preparation and detection schemes. [Preview Abstract] |
|
M1.00144: RYDBERG ATOMS I |
|
M1.00145: Enhanced electric field sensitivity of rf-dressed Rydberg dark states M. Tanasittikosol, M.G. Bason, A. Sargsyan, A.K. Mohapatra, D. Sarkisyan, R.M. Potvliege, C.S. Adams We demonstrate the formation of Rydberg dark states dressed by a radio frequency (rf) field. Microwave or rf dressing of Rydberg states has previously been observed using laser excitation and field ionization of an atomic beam or of cold atoms. Here, however, the resulting Floquet states are observed as EIT resonances in the absorption spectrum of the probe laser beam in a vapor cell. We show that these rf-dressed dark states have an enhanced sensitivity to dc electric fields compared to their bare counterparts. We also show that the strength of the dc electric field is encoded not only in the overall shift of the corresponding EIT feature but also in the shape of the transparency window. As a consequence, and as we illustrate by an actual measurement, rf dressing may help determine the dc field without absolute knowledge of the laser frequency i.e. the precise measurements of the dc field is independent of laser frequency fluctuations. In addition, our results suggest that space charges within the enclosed cell reduce electric field inhomogeneities within the interaction region. [Preview Abstract] |
|
M1.00146: Negative Ions from Ultracold Rydberg Atoms M. Ascoli, L. Aldridge, D.M. Karpov, E.E. Eyler, P.L. Gould We describe experiments looking for negative ions produced by ultracold Rb Rydberg atoms interacting with ground-state atoms. Starting with Rb atoms in a MOT, we excite a fraction of them to \textit{np} Rydberg states by use of a single UV photon at 297 nm. After a variable delay, we field ionize the sample with a high-voltage pulse and extract the negative charges, then detect them with to a discrete-dynode electron multiplier with single ion sensitivity. Negative ions are well separated in time-of-flight from the large number of electrons resulting from the field ionization. Similar measurements are being performed starting with an ultracold plasma instead of a Rydberg sample. We will also describe progress towards experiments involving direct excitation to high-lying states of the ion pair Rb$^{+}$-Rb$^{-}$. [Preview Abstract] |
|
M1.00147: Polarizabilites and Rydberg states in the presence of a Debye potential A.K. Bhatia, Richard J. Drachman Polarizabilities and hyperpolarizabilities, $\alpha_1$, $\beta_1$, $\gamma_1$, $\alpha_2$, $\beta_2$, $\gamma_2$, $\alpha_3$, $\beta_3$, $\gamma_3$, $\delta$ and $\epsilon$ of hydrogenic systems have been calculated by Drachman. We have now calculated these quantities by using pseudostates for the S, P, D and F states. All of them converge very fast as the number of terms in the pseudostates is increased, and are essentially independent of the nonlinear parameters. All the results are in good agreement with the results obtained by Drachman, except for $\delta$, which is of the third-order in perturbation formalism. We have calculated Rydberg states of He for high N and L. The effective potential is -$\alpha_1$/x$^4$+(6$\beta_1$- $\alpha_2$)/x$^6$, where x is the distance of the outer electron from the nucleus. The exchange and electron-electron correlations are unimportant because the outer electron is far away from the nucleus. This implies that the conventional variational calculations are not necessary. The results agree well with the results of Drachman. We have generalized this approach in the presence of a Debye potential. [Preview Abstract] |
|
M1.00148: Rydberg Atoms in Ponderomotive Optical Lattices Kelly Younge, Sarah Anderson, Georg Raithel Rydberg atoms in ponderomotive optical lattices present a unique platform to study properties and interactions of these highly excited atoms. Ponderomotive lattices tailored to trap Rydberg atoms will allow new experiments in quantum information physics and high-precision spectroscopy. Here, we have calculated the adiabatic potentials of Rydberg atoms in one-dimensional ponderomotive lattices for a variety of atomic states and lattice parameters. We have used these potentials to obtain ensembles of Rydberg-atom trajectories in the lattice, and to simulate the spectra of microwave transitions of Rydberg atoms moving through the lattice. We conclude that microwave spectroscopy presents a powerful technique to probe the motion and to verify trapping of the atoms in ponderomotive lattices. We further examine a novel optical lattice potential that provides a transverse trapping force in addition to the longitudinal trapping force normally provided by an optical lattice. [Preview Abstract] |
|
M1.00149: A spectroscopic study of resonant energy exchange among cold Rydberg atoms Emily E. Altiere, Thomas J. Carroll, Michael W. Noel Cold Rydberg atoms can exchange energy through long-range dipole-dipole interactions. The Stark effect allows us to tune the positions of the Rydberg states with a static electric field, which can bring into resonance this energy exchange. We present measurements of the spectrum of these resonant energy exchanges as the static field is varied for a broad range of initially excited Rydberg states and compare these measurements with calculated spectra. [Preview Abstract] |
|
M1.00150: Encoding and decoding information in high-$n$ circular wave packets S. Yoshida, C.O. Reinhold, J. Burgd\"orfer, B. Wyker, F.B. Dunning Information can be encoded in a Rydberg wave packet comprising a superposition of stationary eigenstates by control of the complex expansion coefficients. Protecting the encoded information against decoherence is a major challenge for high-$n$ states given the sensitivity to external perturbations and is necessary for information retrieval. We demonstrate theoretically and experimentally the extraction of detailed information on the density matrix of very-high-$n$ ($> 300$) near-circular Rydberg wave packets through Fourier analysis of the quantum beat and quantum revival signals. The remarkably long coherence times, $> 1~\mu$s, associated with circular wave packets facilitate the preservation and read-out of information encoded in this matrix. We illustrate the power of the method by determining the angular localization of the components of the wave packet. Research supported by the NSF, the Robert A. Welch Foundation, the OBES, U.S. DoE to ORNL, and by the FWF (Austria). [Preview Abstract] |
|
M1.00151: Precise manipulation of Rydberg wave packets B. Wyker, F.B. Dunning, C.O. Reinhold, S. Yoshida, J. Burgd\"orfer The creation and control of mesoscopic, very-high-$n$ ($n \sim 300$) near-circular Rydberg wave packets, whose quantum coherence can be maintained over hundreds of classical orbital periods, is described. We show that the $n$ distributions in such wave packets can be controlled during production by the size and shape of the generating field and further tailored through the application, after production, of precisely timed half-cycle pulses. The remarkable level of precision that can be achieved is demonstrated using time domain spectroscopy. The protocols employed are described with the aid of ``quantized'' classical trajectory Monte Carlo simulations. Research supported by the NSF, the Robert A. Welch Foundation, the OBES, U.S. DoE to ORNL, and by the FWF (Austria). [Preview Abstract] |
|
M1.00152: Rydberg excitation in Rb atoms using external cavity diode lasers Donald P. Fahey, Bonnie L. Schmittberger, Michael W. Noel Rubidium atoms were excited to Rydberg states by two different pathways using only external cavity diode lasers. In the first method we excited atoms from the 5S to 5P state with 780 nm light, and then from the 5P to 5D state with 776 nm light. Atoms fluoresce to the 6P state, where they are then excited to Rydberg states using a tunable diode laser with a center wavelength of 1015 nm. Although this method involves populating the 6P state through fluorescence from the 5D state, this did not appear to greatly hinder the pathway's efficiency in exciting Rydberg states. In the second method, pulsed 960 nm light from a diode laser was frequency doubled and used to excite Rydberg states directly from the 5P state. Measurement of Rydberg states using each method will be presented and details of the techniques discussed. [Preview Abstract] |
|
M1.00153: Absolute Measurement of STIRAP Efficiency Xiaoxu Lu, Yuan Sun, Claire Allred, Harold Metcalf Driving atoms from an initial to a final state of the same parity via an intermediate state of opposite parity is most efficiently done using STIRAP\footnote{U. Gaubatz et al., {\it J. Chem. Phys.}, \textbf{92}, 5363 (1990).}, because it doesn't populate the intermediate state. For optical transitions this requires appropriate pulses of light in the counter-intuitive order - first coupling the intermediate and final states. We populate Rydberg states of He ($n = 26$) in a beam of average velocity 1070 m/s by having them cross two laser beams in a tunable dc electric field of $\sim 100$ V/cm. The ``red" light near $\lambda =$ 796 nm connects the 3$^3$P states to the Rydberg states and the ``blue" beam connects the metastable 2$^3$S state atoms emitted by our source to their 3$^3$P states. By varying the relative position of these beams we can vary the order and overlap encountered by the atoms. We vary the dc field to sweep across several Stark states \nolinebreak of the Rydberg manifold. We measure the absolute efficiency using a curved wavefront beam of $\lambda = 1.083\, \mu$m light to deflect residual 2$^3$S atoms out of the beam, and we measure their flux with and without the STIRAP beams. This uncontaminated measurement has high absolute accuracy. [Preview Abstract] |
|
M1.00154: Atom-chip trap for Rydberg atom experiments Arne Schwettmann, Jonathon Sedlacek, Leah Trafford, James Shaffer We report on an atom-chip trap experiment designed to investigate the interactions between high-lying Rb Rydberg atoms (n$>$30) and the role of Rydberg atom impurities. A magnetic microtrap that can be transformed into a double-well potential is created by dc and rf currents running through microscopic wires on an atom chip. The two wells can be separated by several micrometers. The microtrap is loaded with ultracold Rb atoms from a mirror magneto-optical trap via an intermediate millimeter-size magnetic wire-trap. A home-built Rydberg excitation laser at $\sim $480 nm is used to excite Rydberg atoms in the magnetic trap. [Preview Abstract] |
|
M1.00155: Rydberg tagging time-of-flight imaging: An improved apparatus for studying many-body processes Jonathan Tallant, Donald Booth, Arne Schwettmann, James Shaffer With Rydberg tagging time-of-flight imaging of cold atoms, we have achieved a velocity resolution of $\sim $2.5 cm/s. The apparatus and resolution have already allowed us to observe ultralong-range electric field-induced Cs$_{2}$ molecules, and differentiate them from low-energy inelastic collisional processes. Addition of a Zeeman-slowed atomic beam and tapered amplifier system have given nearly two orders of magnitude increase in the number of atoms trapped in our MOT, making many-body processes, such as three-body recombination, much easier to detect. With the implementation of two crossed dipole trapping beams, the number density available in the trap has also increased by nearly two orders of magnitude. Data on nS$_{1/2}$+6S$_{1/2}$ Rydberg molecules and other ultracold collision processes will be presented. [Preview Abstract] |
|
M1.00156: ELECTRON - MOLECULE COLLISIONS |
|
M1.00157: Dissociation of multiply ionized small hetero-nuclear molecules through electron impact Pengqian Wang The dissociation of multiply ionized molecules is interesting in the areas such as plasma physics and planetary atmospheric chemistry. The study of the dissociation dynamics of molecular ions provides valuable information on the electronic states and the potential energy surfaces of the ions. Electron impact is a widely used method to excite and ionize molecules because of its simple construction and excellent tunability. Also the absolute cross sections for electron impact ionization of molecules are needed in the areas such as plasma modeling in semiconductor manufacturing. In this presentation we report the dissociation of some small singly to triply ionized hetero-nuclear molecules (OCS, NOCl, COFCl and HNCO), investigated by two- and three-dimensional covariance mapping techniques at an electron energy of 200 eV. The absolute cross sections for the various dissociation channels of up to triply ionized molecules have been measured. The dissociation mechanisms, such as sequential dissociation and metastable decays have been revealed from the covariance maps. Project supported by the WIU-URC grant. [Preview Abstract] |
|
M1.00158: Electron-impact excitation of atmospheric gases Charles P. Malone, Jason A. Young, Paul V. Johnson, Xianming Liu, Isik Kanik, Bahar Ajdari, Murtadha A. Khakoo Electron energy-loss and impact-induced emission techniques were used to investigate excitation of key features in molecular nitrogen and rare gases. Specifically, line and band emission intensities were investigated as a function of wavelength (at high resolution) and incident electron energy using various monochromator-detector combinations. In addition, electron energy-loss spectroscopy was utilized such that differential cross sections (DCSs) and integral cross sections (ICSs) were obtained. The emission cross sections, DCSs, and ICSs for these atmospheric species will be presented. [Preview Abstract] |
|
M1.00159: Comparative studies of dissociative electron attachment to CH$_2$Cl$_2$ and CF$_2$Cl$_2$ molecules Shavkat Mamatkulov, Ilya Fabrikant Experimental studies\footnote{K. Aflatooni and P. D. Burrow, Int. J. Mass Spectrom. {\bf 205}, 149 (2001).} of dissociative electron attachment to dichloroalkanes and chlorofluoromethanes have established a universal relation between the peak value of the cross section and the vertical attachment energy. The CH$_2$Cl$_2$ is the only compound that is substantially removed from the trend observed for all other compounds: its peak cross section is more than one order of magnitude lower than that predicted by the universal curve. In an attempt to understand this difference we calculated energies of the LUMO states for CH$_2$Cl$_2$ and CF$_2$Cl$_2$ anions as functions of the C-Cl distance and performed dissociative electron attachment calculations using one effective reaction coordinate corresponding to the C-Cl stretch. For the potential energy curve calculations we employed MP2 theory with 6-31+G(d) and 6-311++G(3df,3pd) basis sets. The calculations show that the ionic curve for CH$_2$Cl$_2$ is much less repulsive and crosses the neutral curve at substantially larger internuclear separation than for CF$_2$Cl$_2$. This explains qualitatively and semiquantitatively the much lower dissociative attachment cross section for CH$_2$Cl$_2$. This work was supported by the US National Science Foundation. and by a Fullbright fellowship. [Preview Abstract] |
|
M1.00160: R-matrix calculations of the electron collisions CF$_3$Cl in the fixed-nuclei approximation Michal Tarana, Ilya I. Fabrikant Previous studies on CF$_3$Cl show a resonance which lead to dissociative electron attachment under standard plasma conditions. Here the R-matrix method is used to treat electron collisions with the CF$_3$Cl molecule at its equilibrium geometry using a coupled states expansion. These calculations concentrate on obtaining low-energy, sub-6 eV, elastic cross sections and properties of the $^2A_1$ resonance. Present results are compared with previously published experimental data. [Preview Abstract] |
|
M1.00161: An Alternative Approach to the Non-local Theory of Low-Energy Electron-Molecule Collisions Karel Houfek The non-local theory of the nuclear dynamics of the resonant low-energy electron-molecule collisions [W. Domcke, Phys. Rep. 208, 97 (1991)] is reformulated in such a way that the driving equation describing of the nuclear motion in the non-local, complex, and energy-dependent (or time-dependent) potential is replaced by the infinite system of coupled differential equations for nuclear wave functions corresponding to the electronic discrete state and continuum states. This system is then reduced to a finite system using some appropriate discretization of the electronic continuum. For systems with two or more nuclear degrees of freedom like H$_2$0, the resulting system of coupled differential equations with local potentials and couplings could be easier to solve numerically that a single equation with nonlocal potential. We have tested this alternative approach on diatomic molecules. For numerical solution we have applied the FEM and DVR methods together with the exterior complex scaling method [T.N. Rescigno and C.W. McCurdy, Phys. Rev. A 62, 032706 (2000)]. The results have shown that even for relatively small number of the electronic states used for the discretization of the electronic continuum one can get reasonably accurate cross sections for processes of interest. [Preview Abstract] |
|
M1.00162: Electron-impact dissociative excitation and ionization of dihydride cations XH$_{2}^{+}$ (X=B, C, N, O, F) Michael Fogle, Mark Bannister, Randy Vane, Eric Bahati, Richard Thomas, Vitali Zhaunerchyk Absolute cross sections for electron-impact dissociation of XH$_{2}^{+}$ (X=B, C, N, O, F) cations forming XH$^{+}$ and X$^{+}$ ion fragments were measured in the 3-100 eV range using a crossed electron-ion beams technique at Oak Ridge National Laboratory. This electron energy range covers both dissociative excitation and ionization of these species. Large, resonant-type contributions are observed in the dissociative excitation channels of CH$_{2}^{+}$ --$>$ CH$^{+}$ and BH$_{2}^{+}$ --$>$ BH$^{+}$, however, the other species do not exhibit such an enhancement to the dissociative excitation cross sections. [Preview Abstract] |
|
M1.00163: Nuclear dynamics of dissociative electron attachment to water via the conically intersecting $^2$B$_2$ and $^2$A$_1$ states Daniel Haxton, Thomas Rescigno, C. William McCurdy We present theoretical results on the nuclear dynamics of dissociative electron attachment to the water molecule via the highest-energy $^2$B$_2$ electronic Feshbach resonance state of the anion. These results accompany the experimental results of Adaniya et al. The process in question is complex, involving a conical intersection of Born-Oppenheimer potential energy surfaces and several two-and three-body final fragment states. Surface-hopping classical trajectory calculations including the effect of autoionization are performed with previously calculated potential energy surfaces for the intersecting $^2$B$_2$ and $^2$A$_1$ states, and the amplitude for attachment as a function of nuclear geometry and incident angle of the electron in the molecular frame is also determined. This permits a reconstruction of the lab frame fragment angular distribution and the explanation of its features in terms of the multidimensional nuclear dynamics of the dissociation process. [Preview Abstract] |
|
M1.00164: Dielectronic Recombination Calculations of M-shell Ions Duck-Hee Kwon, Ming Feng Gu, Daniel Wolf Savin Understanding the properties of astrophysical and laboratory plasmas necessitates knowing the ionization balance of the observed or modelled source. This in turn depends on the underlying recombination and ionization processes. Of particularly importance are data for the electron-ion recombination process known as dielectronic recombination (DR) which is the dominant recombination mechanism for most ions. While much work has been carried out for K- and L-shell ions, little state-of-the-art theoretical results exist for M- shell ions. The aim of our work is to calcuate modern DR rate coefficients for all M-shell ions ranging from Mg to Zn. We use the the Flexible Atomic Code (FAC) which is a relativistic, multiconfigurational, distorted-wave atomic package and consider all $\Delta N=0$ and $\Delta N=1$ core electron excitations. All possible radiative decay and autoionization channels are taken into account. Configuration mixing effects and decay to autoionizing levels followed by radiative cascades (DAC) are also considered. [Preview Abstract] |
|
M1.00165: New Experimental Apparatus for Momentum Imaging of Electron-Impact Induced Molecular Dissociation Ali Moradmand, Chad Rose, Devin Kalafut, Allen Landers, Mike Fogle The construction of a new COLTRIMS-type momentum imaging apparatus is being built at Auburn University to examine dynamics and energetics of various dissociation pathways induced by electron impact. The new apparatus will consist of a skimmed, supersonic gas jet in a crossed-beam geometry with an electron beam capable of producing electrons with an energy range of $\sim$1 - 2000 eV. A timed electron beam pulse in concert with a pulsed electric field extraction system allows for the momenta and flight times of the various ion fragments to be measured by a position-sensitive, multi-hit detector. Processes such as dissociative single and double ionization as well as dissociative electron attachment will be studied with this new apparatus. [Preview Abstract] |
|
M1.00166: ATOM - ATOM MOLECULE COLLISIONS: ROOM TEMPERATURE |
|
M1.00167: Heating of atom ensembles in magnetic traps due to collisions with hot background gases Chenchong Zhu, James Booth, Kirk Madison It is well known that collisions between laser-cooled atoms in magnetic and magneto-optical traps with residual background gas particles result in atoms being lost from the traps, and modifies the energy distribution of the atoms remaining in the traps. The loss rate depends on both the collisional cross section between the trapped and background atoms and on trap depth. Our prior measurements of the collisional cross-section of trapped $^{85}$Rb and $^{87}$Rb atoms colliding with background Rb and Ar indicated that quantum-diffractive collisions contribute to approximately 50 \% of the total collisional cross-section [Phys. Rev. A 80, 022712 (2009)]. In deep traps, a single diffractive collision will not impart enough kinetic energy on the trapped atom to allow it to escape; instead, the atom remains in the trap with, on average, an increased kinetic energy. A series of such diffractive collisions may impart enough aggregate kinetic energy to eject atoms from deep traps. We present experimental measurements and numerical simulations of heating in magnetically trapped Rb ensembles as a function of background pressure. [Preview Abstract] |
|
M1.00168: Trap depth determination from background gas collision induced loss rates Janelle Van Dongen, James L. Booth, Kirk W. Madison We present experimental and theoretical characterizations of a novel technique to determine the depth of an atom trap from measurements of the loss rate induced by background gas collisions. It is well known that the lifetime of an atomic or molecular trap is ultimately limited by the rate of background collisions, and the precise loss rate depends on the trap depth. Because the differential scattering cross section (for elastic collisions) is highly forward peaked, there are copious glancing angle collisions which impart a very small amount of energy. The consequence is that the loss rate varies substantially with trap depth even for very shallow traps [1]. We present a comparison of this new technique with an established method for MOT trap depth measurements relying on measurements of trap loss induced by optical excitation to a purely repulsive molecular state [2]. The excitation produces particle pairs of a well defined energy whose escape probability provides a measure of the trap depth. [1] Fagnan, Wang, Zhu, Djuricanin,Klappauf, Booth, and Madison, ``Observation of quantum diffractive collisions using shallow atomic traps,'' Phys. Rev. A 80, 022712 (2009). [2] Hoffmann, Bali, and Walker, ``Trap-depth measurements using ultracold collision,'' Phys. Rev. A 54, R1030 (1996). [Preview Abstract] |
|
M1.00169: Enhancement of Rb fine-structure transfer in He and Ar due to three-body collisions Jerry Sell, Brian Patterson, Tim Genda, Ben Naumann, Randy Knize, Alina Gearba Using ultrafast laser excitation and time-correlated single- photon counting techniques we have measured the collisional mixing rates between the rubidium $5^{2}P$ fine-structure levels in the presence of He and Ar inert gases. The mixing rates and collisional cross sections are determined from the time-dependence of the fluorescence observed from collisional transfer. A nonlinear dependence of the mixing rate with $^{4} $He density is observed. This nonlinearity corresponds to Rb fine-structure transfer primarily due to binary collisions with $^{4}$He at densities of $\leq$ 10$^{19}$ cm$^{-3}$, while at greater densities three-body collisions become significant. These interactions can be between bound, quasibound, and free atoms which we discuss. Recent measurements of Rb-Ar fine- structure transfer will also be presented. [Preview Abstract] |
|
M1.00170: Treatment of anomalous long range derivative couplings in atom-atom collisions Bernard Zygelman In the multi-channel Born-Oppenheimer approximation the system wavefunction is expanded in a basis of adiabatic states. In such a description, non-adiabatic derivative couplings (or gauge potentials) may arise and which do not vanish in the asymptotic region. Traditionally, electron translation factors are introduced in the multi-channel expansion to eliminate such couplings. Here we present an alternative method that involves a series of gauge transformations. We apply and illustrate this technique in the H-H system where one of the collision partners is in the n=2 excited state. In addition, a fully solvable model is introduced that illustrates the physical basis for these transformations. [Preview Abstract] |
|
M1.00171: Polarization and Hyperfine Transitions of Metastable $^{129}$Xe in Discharge Cells Tian Xia, Steven Morgan, Yuan-Yu Jau, William Happer The polarization and relaxation rates of metastable $^{129}$Xe atoms are measured with magnetic resonance spectroscopy, at both microwave frequencies, where $\Delta F = 1$ transitions are induced between the sublevels, and at radiofrequencies, corresponding to $\Delta F = 0$ transitions. The nuclear spin polarization of the resonant velocity group is measured to be $22\pm2\%$. However, the relaxation rate of spin polarization is much larger than the velocity changing rate, the narrow line pumping laser produces spin polarization only for atoms with resonant velocity. The relaxation of metastable xenon atoms is dominated by depolarizing collisions with ground state atoms, with lesser contributions from metastability exchange collisions. We also measure the pressure broadening coefficient of the relaxation rate by varying the temperature of the cryogenic part of the cell. [Preview Abstract] |
|
M1.00172: Disalignment of Ne$^{\ast }$(2p$_{10 }$[J=1]) atoms due to He(1s$^{2})$ atom collisions in glow discharges at 294 K Cristian Bahrim, Vaibhav Khadilkar, Hiraku Matsukuma, Masahiro Hasuo Our experimental disalignment rate of the Ne$^{\ast }$(2p$_{10})$ atoms induced by He atom collisions in a gaseous mixture at 294 K using a laser-induced fluorescence spectroscopy method is (3.8 $\pm $ 0.3) x 10$^{-17}$ m$^{3}$s$^{-1}$. This value is only 4.6{\%} lower than our calculation of 4.3 x 10$^{-17}$ m$^{3}$s$^{-1}$ based on a quantum close-coupling many-channel method and the model potential proposed in [1]. In order to check the accuracy of our theoretical model, we calculate the energy-averaged cross section for destruction of alignment of the Ne$^{\ast }$(2p$_{10})$ atoms induced by He, and compare with measurements extracted from Hanle signals [2] at 315 $\pm $ 15 K. The experimental data of (3.20 $\pm $ 0.32) x 10$^{-20}$ m$^{2}$ [2] is in agreement with our calculations of 3.25 x 10$^{-20}$ m$^{2}$ at 300 K and 3.50 x 10$^{-20}$ m$^{2}$ at 330 K. These results are about one order of magnitude smaller than for the Ne$^{\ast }$(2p$_{5}$ [J=1]) atoms [3] at the same temperature because of a weaker electrostatic interaction between He and Ne$^{\ast }$(2p$_{10})$ atoms than with Ne$^{\ast }$(2p$_{5})$ [1]. [1] Bahrim C and Khadilkar V V 2009 \textit{Phys. Rev. A} \textbf{79} 042715. [2] Carrington C G and Corney A 1971 \textit{J. Phys. B }\textbf{4} 849-868. [3] Matsukuma H, Bahrim C and Hasuo M 2009 \textit{J. Plasma Fusion Res. SERIES } \textbf{8} 169-173. [Preview Abstract] |
|
M1.00173: Spin flipping collisions of hydrogen atoms Bernard Zygelman We present a unified multichannel approach to calculate electron spin exchange and spin flipping transition cross sections for collisions of H with H, H with T, and T with T. We use the theory to calculate the hyperfine quenching cross sections for collision energies that range from 1 mK to thermal temperatures. We show that spin flipping transitions are induced by the splitting of the $b^{3}\Sigma_{u}$ Born-Oppenheimer potential via the long-range magnetic interactions among electrons. We find that the spin flipping cross sections in the tritium dimer are about a magnitude larger than that predicted by mass scaling the H-H cross sections. For the former, we show that the spin exchange cross sections are several magnitudes larger, at cold temperatures, than that of the hydrogen system. We compare the results of the multichannel approach with those obtained using approximate methods such as the degenerate internal state approximation, the elastic and Born approximations and discuss their respective range of validity. [Preview Abstract] |
|
M1.00174: Collisional Transfer of Population and Orientation in NaK C.M. Wolfe, S. Ashman, J. Huennekens, B. Beser, J. Bai, A.M. Lyyra We report current work to study transfer of population and orientation in collisions of NaK molecules with argon and potassium atoms using polarization labeling (PL) and laser- induced fluorescence (LIF) spectroscopy. In the PL experiment, a circularly polarized pump laser excites a specific NaK $A^{1}\Sigma^{+}$($v'$=16, $J'$) $\leftarrow$ $X^{1}\Sigma^{+}$($v''$=0, $J'\pm1$) transition, creating an orientation (non-uniform $M_{J'}$ level distribution) in both levels. The linearly polarized probe laser is scanned over various $3^{1}\Pi$($v$, $J'\pm$1) $\leftarrow$ $A^{1}\Sigma^{+}$($v'$=16, $J'$) transitions. The probe laser passes through a crossed linear polarizer before detection, and signal is recorded if the probe laser polarization has been modified by the vapor (which occurs when it comes into resonance with an oriented level). Using both spectroscopic methods, analysis of weak collisional satellite lines adjacent to these directly populated lines, as a function of argon buffer gas pressure and cell temperature, allows us to discern separately the effects collisions with argon atoms and potassium atoms have on the population and orientation of the molecule. In addition, code has been written which provides a theoretical analysis of the process, through a solution of the density matrix equations of motion for the system. [Preview Abstract] |
|
M1.00175: Extreme Potential Energy Surface Sensitivity for Rotational Quenching of Water via Hydrogen Atom Impact Benhui Yang, Phillip Stancil Quantitative determinations of inelastic cross sections and rate coefficients for H$_2$O-H collisions are of interest for astrophysical models, while the water-H interaction is crucial for molecular dynamics simulations of hydrogen atom collisions on crystalline and amorphous ices. In this work, rotational energy transfer of H$_2$O due to H collisions was studied using an explicit quantum close-coupling approach for collision energies between 10$^{-6}$ and 1000 cm$^{-1}$ with para-H$_2$O initially in levels 1$_{1,1}$ and 2$_{2,0}$, and ortho-H$_2$O in levels 1$_{1,0}$ and 2$_{2,1}$. Total quenching cross sections and rate coefficients are obtained on two different potential energy surfaces typically adopted in molecular dynamics simulations. The quenching cross sections are found to differ significantly over the full range of considered energies. Elastic cross also show large discrepancies in the cold to ultracold regimes, but agree for collisions energies greater than 10 cm$^{-1}$, where agreement is also found with relative total scattering experiments. [Preview Abstract] |
|
M1.00176: Inelastic collisions of excited lithium molecules Mark Rosenberry, Ramesh Marhatta, Brian Stewart Energy transfer and reactions during molecular collisions are fundamental processes in astronomy and chemistry. The H$_{2}$ + H system has been well studied, and theoretical calculations are now becoming feasible for an excited lithium dimer colliding with a ground state lithium atom, increasing interest in corresponding experimental measurements. Our laboratory observes laser-induced fluorescence spectra from lithium vapor in a heat pipe oven. Our recent switch from a modest diode laser to a pulsed dye laser gives us new access to a variety of highly excited molecular states. Here we report our progress in measuring absolute level-to-level rate constants and collision-induced dissociation for molecular states of this system. [Preview Abstract] |
|
M1.00177: Alkali-Hybrid Spin Exchage Optical Pumping Polarized He-3 Targets for Electron Scattering Jaideep Singh, Peter Dolph, Karen Mooney, Vladimir Nelyubin, Al Tobias, Gordon Cates Polarized He-3 has long been proven to be extremely useful for exploring the structure of the neutron in electron-scattering experiments. Using spin-exchange optical pumping (SEOP), the He-3 polarization of these high-density (10 amagats) two-chamber target cells now regularly approaches 70\%. This remarkable performance has been achieved by taking advantage of both alkali-hybrid SEOP and high-power spectrally-narrowed diode lasers. We'll share what we've learned (1) about applying these new technologies, (2) about the factors that are limiting the He-3 polarization in these target cells, and (3) from comparisons of numerical simulations with empirical results. [Preview Abstract] |
|
M1.00178: POST-DEADLINE ABSTRACTS II |
|
M1.00179: Self-Excitation and Feedback Cooling of an Isolated Proton J. DiSciacca, N. Guise, G. Gabrielse Using techniques similar to the electron g-2 experiment, a one-proton self-excited oscillator (SEO) is realized. The SEO frequency resolution is at the high precision needed for the direct observation of a single-proton spin-flip transition. Such spin-flip spectroscopy could lead to a million-fold improved comparison of the proton and antiproton magnetic moments. Feedback cooling is realized for the first time with a proton and is used to vary the proton's temperature. This temperature is investigated with sideband cooling, as each application of sideband cooling typically changes the frequency by an amount much greater than the SEO resolution. Understanding this and employing the tools of feedback cooling along with the SEO open a path towards observing a single-proton spin-flip. [Preview Abstract] |
|
M1.00180: Stabilization of the p-wave superfluid state in an optical lattice Yang-hao Chan, Yong-jian Han, Wei Yi, Andrew Daley, Sebastian Diehl, Peter Zoller, Luming Duan It is hard to stabilize the $p$-wave superfluid state of cold atomic gas in free space due to inelastic collisional losses. We consider the $p$-wave Feshbach resonance in an optical lattice, and show that it is possible to have a stable $p$-wave superfluid state where the multi-atom collisional loss is suppressed through the quantum Zeno effect. We derive the effective Hamiltonian for this system, and calculate its phase diagram in a one-dimensional optical lattice. The results show rich phase transitions between the $p$-wave superfluid state and different types of insulator states induced either by interaction or by dissipation. [Preview Abstract] |
|
M1.00181: Sub-Fourier characteristics of a $\delta$-kicked rotor resonance Ishan Talukdar, Rajendra Shrestha, Gil Summy We experimentally investigate the sub-Fourier behavior of a $\delta$-kicked rotor resonance by performing an overlap measurement on a Bose-Einstein condensate (BEC) exposed to a periodically pulsed standing wave. The width of the fidelity resonance peak centered at the Talbot time and zero initial momentum exhibits an inverse cube pulse number dependent scaling compared to an inverse squared mean energy measured around the same resonance. A theoretical analysis shows that the width of resonances situated around the zero of an accelerating potential depends on the inverse cube of the pulse number which we verify experimentally. Such a sub-Fourier effect can find potential applications in high resolution gravity measurements. [Preview Abstract] |
|
M1.00182: Time-resolving intra-atomic two-electron collision dynamics Agapi Emmanouilidou We present a completely new idea of how to time-resolve the dynamics of two electrons as they escape to the continuum [1]. Our study is a theoretical one in the framework of classical and semiclassical physics. However, it is at the same time a numerical experiment taking into account realistic laser pulses. To our knowledge, this is the first time an attosecond streak camera for two electrons is formulated. The current state of the art is the attosecond streak camera with one continuum electron. As Free Electron Lasers develop our two electron streak camera will be extended to a variety of processes concerned with deep core electron dynamics. In addition, we expect that our two-electron streak camera will be applied to time-resolve many electron dynamics in atomic and molecular systems, problems which are at the forefront of Attosecond Science. \\[4pt] [1] A. Emmanouilidou, A. Staudte, P. Corkum (March 2010, submitted) [Preview Abstract] |
|
M1.00183: Rydberg Atom Lattices R.M.W. van Bijnen, E.J.D. Vredenbregt, K.A.H. van Leeuwen, S.J.J.M.F. Kokkelmans Ultracold atomic gases are used extensively to realize textbook examples of condensed matter phenomena. Typically, such experiments deal with neutral atoms interacting via short-range VdW potentials much weaker than the Coulomb interactions between electrons in solids. In contrast, we study highly excited Rydberg atoms arranged on a self-assembled lattice, representing a more accurate dilute model system for e.g. metallic conductors. Here, the interaction strengths approach Coulombic potentials, while retaining the controllability characteristical of cold atom experiments. Rydberg lattices can also cross over to the plasma regime with a quantumdegenerate electron gas by increasing the Rydberg excitation, making such systems a scientific playground for studying various fundamental phenomena. We plan an experimental and theoretical investigation of such self-assembled Rydberg lattices, following a recent proposal by T. Pohl et al. Using a tailored excitation scheme, the correlated crystal state is built up from a disordered atomic gas. We give a theoretical treatment of this scheme and the Rydberg crystal ground states, and discuss its feasibility. [Preview Abstract] |
|
M1.00184: QND Measurements in a Resonant Cavity-QED System Zilong Chen, Justin G. Bohnet, Jiayan (Phoenix) Dai, James K. Thompson We demonstrate QND measurements on an ensemble of $10^6$ $^{87}$Rb atoms. Quantum state-dependent populations are determined at the projection noise level by measurements of the collective Vacuum Rabi Splitting for the resonantly coupled atom-cavity system. The splitting is measured by simultaneously scanning the frequency of two probes across the two transmission resonances and phase coherently detecting the full IQ response of the reflected electric fields. Measurement back-action imposes AC Stark shifts on the atoms, resulting in a reduction of the Ramsey fringe contrast due to inhomogeneity in the probe-atom coupling. We show that the spin-echo sequences that will be needed to achieve atomic spin-squeezing on the Rb clock transition also strongly suppress these AC stark shifts. The remaining probe-induced decoherence is close to the fundamental limit imposed by free space scattering of the probe photons. [Preview Abstract] |
|
M1.00185: Adiabatic magnetoassociation of KRb Feshbach molecules Ruth Shewmon, Tyler Cumby, John Perreault, Deborah Jin We study the creation of Fermionic $^{40}$K$^{87}$Rb Feshbach molecules via magnetoassociation. Two types of behavior can be accessed by varying the magnetic field sweep rate. In the nonadiabatic limit where few molecules are created, pair formation is governed by Landau-Zener physics. This intuitive two-body picture breaks down at the other extreme, where adiabatic molecule creation efficiency saturates below unity. A better understanding of this efficiency is useful for experiments where Feshbach molecules are a first step, such as the creation of ground state polar molecules. [Preview Abstract] |
|
M1.00186: Collisional disorientation cross section in the J=1/2 cesium atoms Dave S. Fisher, Sarah Lauber, Robert Misconin, Sean Baumgartner, Burcin S. Bayram Measurements of collisional depolarization cross sections play important role to gain valuable information about the interaction between neutral and rare-gas atoms. A key element to understand collision dynamics is the detail analysis of the polarization of the emitted photons. We have experimentally investigated collisional cross section of the excited $J$=1/2 cesium atoms, by collisions with the ground level argon atoms from a circular polarization spectra. Orientation in the $J$=1/2 level was optically induced by a circularly polarized light with a positive helicity. A two-photon double-resonance $6s\,^2S_{1/2}$$\rightarrow$$6p\,^2P_{1/2}$$\rightarrow10s\,^2S_{1/2}$ condition was achieved using nanosecond pulse dye lasers, and an intensity of the cascade fluorescence was monitored in the presence of argon atoms ranging from 5 mbar to 133 mbar. We present collisional disorientation cross section which was extracted from the circular polarization spectra. [Preview Abstract] |
|
M1.00187: Fiber optics in surface ion traps for scalable quantum information processing Yves Colombe, Aaron VanDevender, Jason Amini, Dietrich Leibfried, Christian Ospelkaus, John Bollinger, David Wineland Fiber optics can provide a more scalable and resource efficient means of delivering light to and collecting fluorescence from a trapped ion than bulk optics. We demonstrate trapping of a $^ {24}$Mg$^+$ ion in a gold-on-quartz surface-electrode Paul trap with an integrated high numerical-aperture multi-mode fiber located 50 $\mu$m below the electrode surface, and observe fluorescence photons through the fiber with a collection numerical aperture of 0.37. The trap features multiple RF electrodes whose potentials can be adjusted to vary the height of the pseudopotential zero from 30 to 50 $\mu$m above the electrode surface (80 to 100 $\mu$m from the fiber). This demonstrates the ability to trap and position ions near dielectrics, an important step toward trapping ions in fiber optic microcavities. [Preview Abstract] |
|
M1.00188: Time-Dependent Three-Body Reactive Scattering in Hyperspherical Coordinates Jeffrey Crawford, Gregory Parker A time-dependent wave packet method for extracting state-to-state reactive S matrix elements is presented using hyperspherical coordinates. This method expresses the wave packet in the adiabatically adjusting, principal axes hyperspherical (APH) coordinates during propagation, since they treat all arrangement channels equivalently. This allows efficient conversion from mass-scaled Jacobi reactant channel coordinates to APH coordinates and from APH coordinates to Delves' product channel coordinates. The final state analysis is carried out by projecting the product channel eigenfunctions onto the propagated wave packet along a fixed asymptotic hyperradius at each time step. The S matrix elements are proportional to the Fourier transform of the projection coefficients. Comparisons with other results are given. Future work to include collision-induced dissociation and recombination is discussed. [Preview Abstract] |
|
M1.00189: Momentum Imaging of Electron Wave Packet Interference Aihua Liu, Feng He, Uwe Thumm The recent experiment by Gopal, {{\emph{et al.}}}[\emph{Phys. Rev. Lett.} \textbf{103}, 053001 (2009) ] detects intriguing interference patterns in the single ionization of helium by few-cycle, phase-stabilized IR laser pulses, which Gopal, {\emph{et al.}} interpret in terms of the coherent emission of distinct photoelectron wave packets within one IR cycle. By numerically solving the time-dependent Schr\"{o}dinger equation for the photoionization of helium within a single active electron model, we find interference fringes in the photoelectron momentum distribution that cannot be explained as above-threshold ionization peaks. We are in the process of analyzing these oscillations in the momentum-differential electron yield in terms of interfering photoelectron wave packets. [Preview Abstract] |
|
M1.00190: Nondipole Photoemission from Chiral Enantiomers of Camphor K.P. Bowen, W.C. Stolte, J.A. Young, I.N. Demchenko, R. Guillemin, O. Hemmers, M.N. Piancastelli, D.W. Lindle K-shell photoemission from the carbonyl carbon in the chiral molecule camphor has been studied in the region just above the core-shell ionization threshold. Differences between angular distributions of emitted photoelectrons from the two enantiomers are attributed to the influence of chirality combined with nondipole effects in the photoemission process, despite the fact the measurements were taken using \textit{linearly polarized} x-rays. The results suggest the possibility of a new form of linear dichroism. [Preview Abstract] |
|
M1.00191: Efimov Physics in a $^6$Li Gas E.L. Hazlett, J.R. Williams, R.W. Stites, Y. Zhang, K.M. O'Hara, J.H. Huckans We have established the existence of ground- and first-excited Efimov trimers in a system of three distinguishable $^6$Li fermions. The presence of the trimers is indicated by resonantly enhanced three-body recombination which occurs when the trimer binding energy intersects the three-atom scattering threshold. We find the three-body recombination rate, which varies by over eight orders of magnitude in our experiments, to be in good agreement with predictions based on the zero-range approximation. Furthermore, the relative location of the three- body recombination resonances are in agreement with a discrete universal scaling factor of 22.7 despite the fact that the scattering lengths cross through a non-univeral regime between the resonances. These results demonstrate that the Efimov effect occurs in a system of three distinguishable fermions with the same universal scaling factor that occurs in a system of identical bosons. Finally, we will report on our progress toward direct production of Efimov trimers by radio-frequency photoassociation. [Preview Abstract] |
|
M1.00192: A Fully Self-Consistent Mean-Field Study of Population Imbalanced Fermionic Gases In Anisotropic Traps H. Lu, L. Baksmaty, C. Bolech, H. Pu Relying on a fully self-consistent numerical solver for Bogoliubov de Gennes (BdG) equations, we study the population imbalanced Femionic gases in anisotropic traps with realistic system size (up to $10^{5}$ atoms). We find that for a large enough sample in a highly elongated trap, there are typically three types of solutions which are almost degenerate and have the ff. properties: (i) There is a solution very similar to the local density approximation (LDA) which is consistently the lowest in energy.(ii) However one of the other two solutions, connected by a smooth transition, and which are more consistent with experiment at high aspect ratio, supports a state very similar to the long sought FFLO (Fulde Ferrel Larkin Ovchinnikov) state. We submit that these solutions are relevant false vacua because, given high energy barriers and near degeneracy of the obtained solutions, the actual states observed in an experiment could be a strong function of the experimental procedure. Darpa OLE grant, ARO Grant no.W911NF-07-1-0464,Welch foundation (C-1669, C-1681) and NSF. [Preview Abstract] |
|
M1.00193: Progress towards observation of coherent backscattering from two microscopic clusters of trapped atoms Pasad Kulatunga We report on the progress towards observing coherent back-scattering from two ``sphere '' clusters of trapped ultra-cold $^{85}$Rb atoms. The two clusters of atoms are composed of two microscopic dipole traps, each consisting of few hundred atoms. Each trap will be approximately 5 $\mu$m in waist and are individually and dynamically configurable. The Coherent back-scattered signal is observed in an angular width of the order $1/kd$ where $k$ is the wavenumber and $d$ is the cluster (trap) separation. Ideally the back scattered peak should be a factor 2 greater than the back ground, any deviation from this is an indication of near-field effects. [Preview Abstract] |
|
M1.00194: Ultralong-range Rydberg Molecules: Investigation of a Novel Binding Mechanism Bj\"orn Butscher, Vera Bendkowsky, Johannes Nipper, Jonathan Balewski, James P. Shaffer, Robert L\"ow, Tilman Pfau For highly excited Rydberg atoms, the scattering of the Rydberg electron from a nearby polarizable ground state atom can generate an attractive mean-field potential which is able to bind the ground state atom to the Rydberg atom within the Rydberg electron wave function at binding energies ranging from a few MHz to hundreds of MHz[1]. We present spectroscopic data on the observation of various bound states including the vibrational ground and excited states of rubidium dimers Rb(5S)-Rb(nS) as well as those of trimer states. Furthermore, we show calculations that reproduce the observed binding energies remarkably well and reveal that some of the excited states are purely bound by quantum reflection at a shape resonance for p-wave scattering [2]. To further characterize the coherent excitation of the molecular states, we performed echo experiments. \\[0pt] [1] V. Bendkowsky, B. Butscher, J. Nipper, J. P. Shaffer, R. L\"{o}w, T. Pfau, \textit{Nature }\textbf{\textit{458}}\textit{, 1005 (2009)}; [2] V. Bendkowsky, B. Butscher, J. Nipper, J. Balewski, J. P. Shaffer, R. L\"{o}w, T. Pfau, W. Li, J. Stanojevic, T. Pohl,and J. M. Rost, \textit{arXiv:0912.4058 (2009)} [Preview Abstract] |
|
M1.00195: Sub-nanoscale Resolution for Atom Localization, Lithography and Microscopy via Coherent Population Trapping Kishor T. Kapale, Girish S. Agarwal We present a coherent population trapping based scheme to attain sub-nanoscale resolution for atom localization, microscopy and lithography. Our method uses three-level atoms coupled to amplitude modulated probe field and spatially dependent drive field. The modulation of the probe field allows us to tap into the steep dispersion normally associated with electromagnetically induced transparency and offers an avenue to attain sub-nanometer resolution using just optical fields. We illustrate application of the techniques to the area of microscopy and lithography and show how multilevel schemes offer the possibility of improving resolution further. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700