Bulletin of the American Physical Society
47th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 61, Number 8
Monday–Friday, May 23–27, 2016; Providence, Rhode Island
Session K1: Poster Session II (4:00pm-6:00pm)Poster
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Room: Exhibit Hall C |
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K1.00001: ATOMIC AND MOLECULAR STRUCTURE IN STATIC FIELDS |
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K1.00002: Numerical calculations of photoassociation of cold $^{85}$Rb$_{2}$ molecules to the 1_{g}(5P_{1/2})$ State Thomas Bergeman Data obtained at the University of Connecticut by Jianbing Qi, Dajun Wang, Ye Huang, H. K. Pechkis, E. E. Eyler, P. Gould and W. C. Stwalley in 2003 have been only partially analyzed and assigned. In [1], transitions observed by Qi et al. to the $0_{u}^{+}$ state were presented. Ref. [2] analyzed transitions of $^{87}$Rb$_{2}$ to the ${1_{g}(P_{1/2})$ state, simplified by double spin polarization, observed in the D. Heinzen Laboratory. Transitions to $0_{g}^{-}$ and $1_{g}$ levels without double spin polarization are more problematical. This is a preliminary report, based on data obtained by Qi et al. with a dense array of spectral lines, having certain signal:noise limitations. \\ 1. T. Bergeman {\it et al.}, J. Phys. B {\bf 38} S813 (2006). \\ 2. C.-C. Tsai, T. Bergeman, E. Tiesinga, P. Julienne and D. Heinzen, Phys. Rev. A {\bf 88}, 052509 (2013). [Preview Abstract] |
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K1.00003: Rydberg EIT in High Magnetic Field Lu Ma, David Anderson, Stephanie Miller, Georg Raithel We present progress towards an all-optical approach for measurements of strong magnetic fields using electromagnetically induced transparency (EIT) with Rydberg atoms in an atomic vapor. Rydberg EIT spectroscopy is a promising technique for the development of atom-based, calibration- and drift-free technology for high magnetic field sensing. In this effort, Rydberg EIT is employed to spectroscopically investigate the response of Rydberg atoms exposed to strong magnetic fields, in which Rydberg atoms are in the strong-field regime. In our setup, two neodymium block magnets are used to generate fields of about 0.8 Tesla, which strongly perturb the atoms. Information on the field strength and direction is obtained by a comparison of experimental spectra with calculated spectral maps. Investigations of magnetic-field inhomogeneities and other decoherence sources will be discussed. [Preview Abstract] |
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K1.00004: ELECTRON-MOLECULE COLLISIONS |
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K1.00005: The role of fullerene shell upon stuffed atom polarization potential Miron Amusia, Larissa Chernysheva We have demonstrated that the polarization of the fullerene shell considerably alters the polarization potential of an atom, stuffed inside a fullerene. This essentially affects the electron elastic scattering phases as well as corresponding cross-sections. We illustrate the general trend by concrete examples of electron scattering upon endohedrals that are formed when Ne and Ar atom are stuffed inside fullerene C60. To obtain the presented results, we have suggested a simplified approach that permits to incorporate the effect of fullerenes polarizability into the endohedrals$_{\mathrm{\thinspace }}$polarization potential. By applying this approach, we obtained numeric results that show strong variations in shape and magnitudes of scattering phases and cross-sections due to effect of fullerene polarization upon the endohedral polarization potential. Using concrete examples we have demonstrated that the elastic scattering of electrons upon endohedrals is an entirely quantum mechanical process, where addition of even a single atom can qualitatively alter the multi-particle cross-section. [Preview Abstract] |
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K1.00006: Metastable Detection Using Cold Solid$_{\mathrm{\thinspace }}$Matrices William McConkey, Wladek Kedzierski, Fatimah Alsaiari Metastable particles produced in the interaction of electrons of carefully controlled energy with thermal gaseous target beams in a crossed beam set-up have been studied in the energy range from threshold to 300 eV. The e-beam is pulsed and the metastables produced drift to a solid nitrogen or rare gas detector held at 10 K. Here they form excimers which immediately radiate. The resultant photons are detected using a photomultiplier-filter combination. Time-of-flight techniques are used to separate these photons from prompt photons produced in the initial electron collision. With N$_{\mathrm{2}}$ as both target and detection matrix, the excimer emission is strongest in the green but still significant in the red spectral region. Excitation functions will be presented together with threshold measurements. These help to identify the metastable states being observed and the excitation mechanisms which are responsible. [Preview Abstract] |
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K1.00007: Ionizing Collisions of Electrons with Radical Species OH, H$_{\mathrm{2}}$O$_{\mathrm{2}}$ and HO$_{\mathrm{2}}$; Theoretical Calculations K N Joshipura, S H Pandya, B G Vaishnav, U R Patel In this paper we present our calculated total ionization cross sections (TICS) of electron impact on radical targets OH, H$_{\mathrm{2}}$O$_{\mathrm{2}}$ and HO$_{\mathrm{2}}$ at energies from threshold to 2000 eV. Reactive species such as these pose difficulties in measurements of electron scattering cross sections. No measured data have been reported in this regard except an isolated TICS measurement on OH radical, and hence the present work on the title radicals hold significance. These radical species are present in an environment in which water molecules undergo dissociation (neutral or ionic) in interactions with photons or electrons. The embedding environments could be quite diverse, ranging from our atmosphere to membranes of living cells. Ionization of OH, H$_{\mathrm{2}}$O$_{\mathrm{2}}$ or HO$_{\mathrm{2}}$ can give rise to further chemistry in the relevant bulk medium. Therefore, it is appropriate and meaningful to examine electron impact ionization of these radicals in comparison with that of water molecules, for which accurate da are available. For the OH target single-centre scattering calculations are performed by starting with a 4-term complex potential, that describes simultaneous elastic \textit{plus} inelastic scattering. TICS are obtained from the total inelastic cross sections in the \textit{complex scattering potential - ionization contribution }formalism$, $a well established method. For H$_{\mathrm{2}}$O$_{\mathrm{2}}$ and HO$_{\mathrm{2}}$ targets, we employ the additivity rule with overlap or screening corrections. Detailed results will be presented in the Conference. [Preview Abstract] |
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K1.00008: Electron Impact Ionization of SO$_{\mathrm{x}}$, NO$_{\mathrm{x}}$ and H$_{\mathrm{2}}$SO$_{\mathrm{4}}$ - The Aerosol Relevance B G VAISHNAV, U R PATEL, K N JOSHIPURA, S H PANDYA This paper reports our theoretical studies on electron impact ionization of reactive molecules SO$_{\mathrm{x}}$, NO$_{\mathrm{x}}$ (x $=$1-3) and H$_{\mathrm{2}}$SO$_{\mathrm{4}}$, at incident energies from threshold to 2000 eV. Motivation for this work derives from the relevance of these molecules in connection with atmospheric aerosols analysis through mass spectrometric studies and quantification of mass concentrations amongst the aerosol species. The ionization efficiency of a molecule is directly proportional to ionization cross section, which represents the efficiency on a per-molecule basis. Study of electron impact ionization cross sections of molecules, like H$_{\mathrm{2}}$SO$_{\mathrm{4}}$, versus number of electrons in the molecule can lead to information about mass concentrations of aerosol species. We have employed in this work, the well-known spherical complex potential formalism (SCOP), which provides total elastic as well as inelastic cross sections, wherein the latter includes ionization cross sections. We have developed a method to extract ionization cross section from calculated inelastic cross section by introducing a ratio function, in a semi-empirical formalism known as CSP-\textit{ic} method. For SO$_{\mathrm{x}}$ and NO$_{\mathrm{x}}$ targets single-centre scattering calculations are performed, while for H$_{\mathrm{2}}$SO$_{\mathrm{4}}$, the additivity rule augmented with overlap or screening corrections, has been employed. The calculated cross sections are examined as functions of incident electron energy along with comparisons (theoretical or experimental) as available. [Preview Abstract] |
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K1.00009: Studying dissociative electron attachment through formation of heavy-Rydberg ion-pair states* Michael Kelley, Sitti Buathong, F. Barry Dunning Following dissociative electron transfer in collisions between Rydberg atoms and electron-attaching targets, it is possible for the resulting pair of ions to remain electrostatically bound, forming heavy-Rydberg ion-pair states. Precise measurement of the velocity distributions of such ion-pair states provides information concerning the dissociation dynamics of the excited intermediates initially created by electron transfer. Here, electric-field-induced dissociation is used to detect the product ion pairs and observe their velocity distributions. These distributions are analyzed with the aid of a Monte Carlo collision code that models the electron transfer. Measurements with a number of different target species show that through this analysis, dissociation energetics, the branching ratios into different dissociation products, and the lifetimes of the excited intermediates can be examined. *Research supported by the Robert A. Welch Foundation. [Preview Abstract] |
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K1.00010: Electron and Positron$^{\mathrm{\thinspace }}$Scattering with a Few Alkyne Molecules - Theoretical Cross sections U R Patel, K N Joshipura, H N Kothari Electron molecule scattering processes play an important role in the understanding of the electron driven physiochemical phenomena in diverse environments such as biological media, planetary atmospheres, interstellar clouds and plasmas. In modeling and simulating effects induced by electrons traversing through matter, the relevant cross section data are required as an input. An alternative probe, positron has also been used for the similar study of atoms, molecules and matter in bulk. Interaction of positrons with atoms and molecules differs from electron interactions due to opposite sign of charge and absence of exchange potential. In the present paper, our aim is to apply an identical theoretical method$^{\mathrm{1,2}}$ to electrons as well as positrons interacting with alkyne molecules like acetylene (HC$\equiv $CH), 1- Butyne (HC$\equiv $C-CH$_{\mathrm{2}}$CH$_{\mathrm{3}})$ and Propyne (HC$\equiv $C-CH$_{\mathrm{3}})$. We have carried out calculations of total scattering cross sections by starting with complex potential approach followed by the solution of the Schrodinger equation using numerical method. Ionization cross sections are deduced as in$^{\mathrm{1,2}}$. Comparisons have been made with available theoretical and experimental results for both electron (e$^{\mathrm{-}})$ and positron (e$^{\mathrm{+}})$. The study will be extended to alkanes and alkenes. $^{\mathrm{1}}$U R Patel, K N Joshipura, H N Kothari and S H Pandya \textit{J. Chem. Phys. }\textbf{\textit{140}} \quad 044302 (2014) $^{\mathrm{2}}$H N Kothari and K N Joshipura \textit{Pramana- J. Phys.} \textbf{79 }435(2012) [Preview Abstract] |
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K1.00011: Elastic Electron Scattering from o-, m- and p- Xylene. Murtadha Khakoo, Ahmad Sakaamini, Sabaha Khakoo, Leigh Hargreaves, Diego Pastega, Marcio Bettega Low energy experimental and theoretical differential cross sections for elastic scattering of low energy electrons from all isomers of xylene are presented. The theory is the Schwinger Multi-Channel Method with Born correction and polarization effects included. Electron energies are from 1eV to 30 eV and scattering angles from 10$^{\mathrm{o}}$ to 130$^{\mathrm{o}}$. [Preview Abstract] |
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K1.00012: Low energy electron impact vibrational excitation of acetylene. Sigma Patra, Leigh Hargreaves, Murtadha Khakoo Experimental differential cross sections for the vibration excitation of the four fundamental modes of acetylene at low incident electron energies from 1eV to 20eV and scattering angles of 10$^{\mathrm{o}}$ to 130$^{\mathrm{o}}$ will be presented. The results will be compared to results available in the literature. [Preview Abstract] |
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K1.00013: Electron impact vibrational excitation of methyl chloride. Ahmad Sakaamini, Leigh Hargreaves, Murtadha Khakoo Low energy differential cross sections and excitation functions for vibrational excitation of CH$_{\mathrm{3}}$Cl are presented for five vibrational features in the electron energy loss spectrum of this molecule. Electron energies range from 1eV to 15 eV and scattering angles from 10$^{\mathrm{o}}$ to 125$^{\mathrm{o}}$. Results will be compared to existing data for CH$_{\mathrm{3}}$Cl in the literature. [Preview Abstract] |
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K1.00014: Bond Formation and Bond Scission Dynamics in Polyatomic Molecules Revealed by Momentum Imaging Experiments and Electron Scattering Calculations. Daniel Slaughter, Cynthia Trevisan, Marvin Weyland, Alexander Dorn, Nicolas Douguet, Ann Orel, Hidehito Adaniya, Bill McCurdy, Ali Belkacem, Tom Rescigno We present combined experimental and theoretical studies of dissociative electron attachment (DEA) dynamics in methane and ammonia. DEA in each of these systems proceeds through electronic Feshbach resonances, where a valence electron is excited and captured with the incident electron in the lowest unoccupied orbital. In methane, one triply-degenerate resonance undergoes Jahn-Teller splitting through molecular distortions, leading to four observed final states, each having a 2-body and a 3-body dissociation with anionic products H$^{\mathrm{-}}$ and CH$_{\mathrm{2}}^{\mathrm{-}}$ and neutrals CH$_{\mathrm{3}}$, CH$_{\mathrm{2}}$, H$_{\mathrm{2}}$ or H. In ammonia, one resonance leads to H$^{\mathrm{-}} \quad +$ NH$_{\mathrm{2}}$ and NH$_{\mathrm{2}}^{\mathrm{-}} \quad +$ H, the latter resulting from non-adiabatic charge transfer. A higher energy resonance leads directly to H$^{\mathrm{-}} \quad +$ NH$_{\mathrm{2}}$* and indirectly to NH$_{\mathrm{2}}^{\mathrm{-}} \quad +$ H. We examine the dynamics of the transient anion in each of these processes. [Preview Abstract] |
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K1.00015: Electron-impact ionization of molecular hydrogen at 38 eV incident energy James Colgan, Xueguang Ren, Alexander Dorn, M. S. Pindzola We report on recent measurements of the triple differential cross sections from electron-impact ionization of molecular hydrogen at an incident energy of 38 eV. Results are reported for various orientations of the target molecule, as well as various scattering angles and energy sharings of the outgoing electrons. The measurements are compared with calculations performed using a time-dependent close-coupling approach. Reasonable agreement is found between theory and measurement. We also compare and contrast our results to those obtained at higher incident electron energies [1], which were reported recently. [1] X. Ren, T. Pfl\"uger, S. Xu, J. Colgan, M. S. Pindzola, J. Ullrich, and A. Dorn, Phys. Rev. Letts. {\bf 109}, 123202 (2012). [Preview Abstract] |
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K1.00016: Theoretical Studies of Dissociative Recombination of Electrons with SH$^+$ Ions D. O. Kashinski, O. E. Di Nallo, A. P. Hickman, J. Zs. Mezei, F. Colboc, I. F. Schneider, K. Chakrabarti, D. Talbi We are investigating the dissociative recombination (DR) of electrons with the molecular ion SH$^+$, i.e. $e^- + \mathrm{SH}^+ \rightarrow \mathrm{S + H}$. SH$^+$ is found in the interstellar medium (ISM), and little is known concerning its chemistry. Understanding the role of DR of electrons with SH$^+$ will lead to more accurate astrophysical models. Large active-space multi-reference configuration interaction (MRCI) electronic structure calculations were performed using the GAMESS code to obtain ground and excited $^2\Pi$ state potential energy curves (PECs) for several values of SH separation. Core-excited Rydberg states have proven to be of huge importance. The block diagonalization method was used to disentangle interacting states and form a diabatic representation of the PECs. Currently we are performing dynamics calculations using Multichannel Quantum Defect Theory (MQDT) to obtain DR rates. The status of the work will be presented at the conference. [Preview Abstract] |
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K1.00017: Dynamics of Dissociative Electron Attachment to Uracil and Furane Samantha Fonseca dos Santos, Nicolas Douguet, Ann Orel, Thomas Rescigno We present the results of a theoretical study of dissociative electron attachment (DEA) to Uracil and Furan. In both cases we will present calculated angular distributions based on analysis of the entrance amplitudes obtained from the results of complex Kohn scattering calculations. For uracil, we will compare our results with available experimentally measured angular distributions obtained using the COLTRIMS method. [Preview Abstract] |
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K1.00018: Dissociative recombination of N$_2$H$^+$: 1D, 2D and 3D cross sections Samantha Fonseca dos Santos, Asa Larson, Ann Orel We have studied the low-energy indirect dissociative recombination mechanism of this system, and now we now extend those studies to higher energy where the direct dissociative recombinaiton mechanism becomes important. We carried out electron scattering calculations using the Complex Kohn Variational Method as a function of the three internal degrees of freedom to obtain the resonance energy surfaces and autoionization widths. We then use this data as input to form the Hamiltonian relevant to the nuclear dynamics. The multidimensional wave equation is solved using the Multi-Configuration Time-Dependent Hartree (MCTDH) approach. We compute the relative dissociative electron recombination (DR) cross sections and compare to available experiment. [Preview Abstract] |
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K1.00019: Energy and Angular Dependence of Dissociative Electron Attachment in CF$_4$ D. Reedy, A. L. Landers, A. Nemer, A. Edmonds, G. Laurent, M. Fogle We have observed the process of dissociative electron attachment on the tetrafluoromethane $(CF_4)$ molecule. Different preferential attachment angles have been observed for both the $F^{-} + CF_3$ and $CF_3^{-} + F$ channels. We have also measured the kinetic energy release in the dissociation of the molecule for both channels with electron energies spanning the respective DEA resonances. Our results, obtained using Cold Target Recoil Ion Momentum Spectroscopy (COLTRIMS), contrast with recent experiments on the same system using different experimental methods. [Preview Abstract] |
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K1.00020: LONG RANGE INTERACTIONS |
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K1.00021: Blockade involving high-$n$, $n\sim300$, strontium Rydberg atoms Shuhei Yoshida, Joachim Burgd\"orfer, Xinyue Zhang, F.Barry Dunning The blockade of high-$n$ strontium $n ^1F_3$ Rydberg states contained in a hot atomic beam is investigated both theoretically and experimentally. One difficulty in such experiments is that, once created, Rydberg atoms move out of the excitation volume reducing blockade effects. While the effects of such motion are apparent, the data provide strong evidence of blockade, consistent with theoretical predictions. Because of their relatively high angular momentum $(L=3)$, a pair of $n ^1F_3$ Rydberg atoms have many degenerate states whose degeneracy is removed by Rydberg-Rydberg interactions yielding a high density of states near the target energy. To evaluate the effect of blockade not only the energy shifts but also the modification of the oscillator strengths for excitation have to be taken into account. The $n$-scaling of the interactions and the importance of high-order multipoles will also be discussed. [Preview Abstract] |
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K1.00022: Fully converged iterative method for coupled channel problems Di Shu, I. Simbotin, R. C\^ot\'e We implemented a numerical method using a distorted-wave perturbative approach for coupled-channel scattering problems. Our new method provides a way to avoid costly computations for the propagation of the full solutions in coupled-channel problems to large distances for slowly vanishing couplings. Thus, instead of dealing with large matrices, all computations are performed in a channel by channel fashion. The distorted wavefunction for each channel is initialized with the appropriate solution (which includes the diagonal element of the coupling potential matrix). We then solve single-channel inhomogeneous radial equations which contain the (off-diagonal) couplings as a perturbation, and we iterate until desired accuracy is achieved. We tested for stability by continuing to iterate even after convergence has been achieved, e.g., for a total of 75 iterations. [Preview Abstract] |
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K1.00023: Rovibrationally Inelastic Collisions of Ultracold Lithium Dimer William Jasmine, Brian Stewart We have calculated cross sections for rovibrationally inelastic collisions of Li$_2 \ A \ (1) ^1 \Sigma_u^+$ colliding with neon and xenon on {\it ab initio} potentials. We find that the inelastic cross section can be very large and increasing at low collision velocity. This behavior is very well modeled as a Langevin process. The total inelastic cross section is a sizable fraction of the total capture cross section, typically about a third. For Li$_2$ - Xe, the total inelastic rate constants are several thousand square angstroms, and level-to-level rate constants are several hundred square angstroms at collision speeds below 1000 cm/s, implying that such collisions might be observable in photoassociated lithium dimer. [Preview Abstract] |
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K1.00024: Towards Many-Body Quantum Engineering in a Near-Concentric Optical Cavity Emily Davis, Gregory Bentsen, Monika Schleier-Smith Light-mediated interactions between atoms coupled to an optical cavity offer a powerful approach to engineering Hamiltonians giving rise to many-body entanglement. The interactions are non-local, and both their strength and sign can be dynamically controlled. We present an experiment optimized for generating coherent and controllable light-mediated interactions by trapping atoms in the waist of a near-concentric cavity. The unique near-concentric geometry provides strong atom-light coupling and furthermore allows high spatial resolution for local addressing and imaging from the side of the cavity. The latter capability will enable entanglement of atomic sub-ensembles and detection of spatial correlations. We report here on the completed construction and characterization of the near-concentric cavity, as well as progress towards many-particle quantum control. [Preview Abstract] |
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K1.00025: PHOTONIZATION, PHOTODETACHMENT AND PHOTODISSOCIATION Abstract APS TBD [Preview Abstract] |
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K1.00026: Double Photoionization of Beryllium atoms using Effective Charge approximation Haripada Saha We plan to report the results of our investigation on double photoionization K-shell electrons from Beryllium atoms. We will present the results of triple differential cross sections at excess energy of 20 eV using our recently extended MCHF method [1]. We will use multiconfiguration Hartree Fock method to calculate the wave functions for the initial state. The final state wave functions will be obtained in the angle depended Effective Charge approximation [2-4] which accounts for electron correlation between the two final state continuum electrons. We will discuss the effect of core correlation and the valence shell electrons in the triple differential cross section. The results will be compared with the available accurate theoretical calculations and experimental findings. [1] Hari P. Saha, Phys. Rev. A 87, 042703 (2013). [2] M.R.H. Rudge, Rev. Mod. Phys. 40, 564 (1968). [3] D. Proulox and R. Shakeshaft,, Phys. Rev A 48, R875 (1993). [4]; M. Pont and R. Shakeshaft, Phys. Rev. A51, R2676 (1995). [Preview Abstract] |
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K1.00027: Multiphoton ionization of Uracil Eladio Prieto, Denhi Martinez, Alfonso Guerrero, Ignacio Alvarez, Carmen Cisneros Multiphoton ionization and dissociation of Uracil using a Reflectron time of flight spectrometer was performed along with radiation from the second harmonic of a Nd:YAG laser. Uracil is one of the four nitrogen bases that belong to RNA. The last years special interest has been concentrated on the study of the effects under UV radiation in nucleic acids$^{\mathrm{1}}$ and also in the role that this molecule could have played in the origin and development of life on our planet$^{\mathrm{2}}$. The MPI mass spectra show that the presence and intensity of the resulting ions strongly depend on the density power. The identification of the ions in the mass spectra is presented. The results are compared with those obtained in other laboratories under different experimental conditions and some of them show partial agreement$^{\mathrm{3}}$. [Preview Abstract] |
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K1.00028: Generalized local frame transformation theory for Rydberg atoms in external fields Panagiotis Giannakeas, Francis Robicheaux, Chris H. Greene In this work a rigorous theoretical framework is developed generalizing the local frame transformation theory (GLFT) and it is applied to the photoionization spectra of Rydberg atoms in an external electric field. The resulting development is compared with previous theoretical treatments, including the first version of local frame transformation theory, developed initially by Fano and Harmin. Our revised version of the theory yields non-trivial corrections because we now take into account the full Hilbert space on the energy shell without adopting truncations utilized by the original Fano-Harmin theory. The semi-analytical calculations from GLFT approach are compared with ab initio numerical simulations yielding errors of few tens of MHz whereas the errors in the original Fano-Harmin theory are one or two orders of magnitude larger. Our analysis provides a systematic pathway to precisely describe the corresponding photoabsorption spectra that should be accurate enough to meet modern experimental standards. [Preview Abstract] |
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K1.00029: Inter-Coulombic decay (ICD) of endofullerene inner-vacancies in coherence with the Auger decay Maia Magrakvelidze, Ruma De, Mohammad Javani, Mohamed Madjet, Steven T. Manson, Himadri Chakraborty For an endohedrally confined atom in a fullerene, an innershell vacancy created either in the atom or the fullerene can decay through the continuum of an outer electron hybridized between the systems. Such decays, which can be viewed as coherent superpositions of the single-center Auger and two-center inter-Coulombic (ICD) amplitudes, are found to govern leading decay mechanisms in endofullerenes [1]. Resonances calculated by the method of time-dependent local density approximation (TDLDA) [2] in the photoionization of noble gas endofullerenes show details of the underlying processes [3]. These resonances are found to be significantly stronger than both regular ICD and Auger resonances, which make them well amenable for experimental detection. [1] Javani et al., PRA \textbf{89}, 063420 (2014); [2] Madjet \textit{et al.,} PRA \textbf{81}, 013202 (2010); [3] Magrakvelidze \textit{et al.}, \underline {arXiv:1512.03377}~[physics.atm-clus] [Preview Abstract] |
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K1.00030: Coherence of inter-Coulombic (ICD) and electron transfer mediated (ETMD) decay in endofullerenes Ruma De, Maia Magrakvelidze, Mohamed Madjet, Steven T. Manson, Himadri Chakraborty For the photoionization of noble gas endofullerenes, the decay of fullerene innershell vacancies through the continuum of a subvalent electron in the confined atom \textit{via} the inter-Coulombic decay (ICD) pathway is calculated in the time-dependent local density approximation (TDLDA) scheme [1]. Excitations to atom-fullerene hybrid states indicate coherence between ICD and electron-transfer mediated decay (ETMD) [2]. This coherence requires that both the fullerene and the trapped atom have dipole-allowed final states, continuum and quasi-discrete, of the same symmetry. This should be the dominant above-threshold decay process for a variety of confined systems, and the strength of these resonances is such that they should be accessible for study by photoelectron spectroscopy. [1] Madjet \textit{et al.,} PRA \textbf{81}, 013202 (2010); [2] De \textit{et al.}, arXiv:1512.07291~[physics.atm-clus] [Preview Abstract] |
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K1.00031: Spin-Orbit Activated Confinement Resonances David Keating, Steven Manson, Pranawa Deshmukh At high enough Z relativistic effects become important contributors to even the qualitative nature of atomic properties. This is likely to be true for confined atoms as well. One relativistic effect of interest is the spin-orbit activated interchannel coupling of a pair of spin-orbit doublet channels. This interaction is possible owing to the spin-orbit interaction breaking the degenerancy among the electrons of a subshell [1] allowing, for example, the 5p3/2 and 5p1/2 subshells of mercury (Z$=$80) and the 6p3/2 and 6p1/2 of radon (Z$=$86), to interact. To explore the effect confinement has on spin-orbit activated interchannel coupling, a theoretical study of the 5p subshell of mercury and the 6p subshell of radon both confined in a C60 cage has been performed using the relativistic-random-phase approximation (RRPA) methodology [2]. The effects of the C60 potential modeled by a static spherical well which is reasonable in the energy region well above the C60 plasmons [3]. It is found in the photoionization cross sections of the 5p3/2 of confined mercury and the 6p3/2 of confined radon an extra confinement resonance due to spin-orbit activated interchannel coupling with the respective np1/2 photoionization channels. [1] M. Ya. Amusia, et al, Phys. Rev. Lett 88, 9 (2002); [2] W. R. Johnson and C. D. Lin, Phys. Rev. A 20, 964 (1979); [3] V. K. Dolmatov, Adv. Quantum. Chem. 58, 13 (2009) [Preview Abstract] |
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K1.00032: TIME-RESOLVED ELECTRON DYNAMICS AND ATTOSECOND SPECTROSCOPY |
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K1.00033: Time-dependent local density approximation study of attosecond time delays in the photoionization of xenon. Maia Magrakvelidze, Mohamed Madjet, Himadri Chakraborty We investigate Wigner-Smith (WS) time delays of the photoionization from various subshells of xenon using the time-dependent local density approximation (TDLDA) [1] with the Leeuwen and Baerends exchange-correlation functional. At the 4d giant dipole resonance region as well as near all the Cooper minimum anti-resonances in 5p, 5s and 4d photoemissions, effects of electron correlations uniquely determine the shapes of the emission quantum phase. The Wigner-Smith time delay derived from this phase indicates significant variations as a function of energy. The results qualitatively support our TDLDA predictions at the fullerene plasmon region [2] and at 3p Cooper minimum in argon [3], and should encourage attosecond measurements of Xe photoemission via two-photon interferometric techniques, such as RABITT. [1] M. E. Madjet et al., PRA 81, 013202 (2010); [2] T. Barillot et al., PRA 91, 033413 (2015); [3] M. Magrakvelidze et al.,PRA 91, 063415 (2015). [Preview Abstract] |
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K1.00034: Electron correlation effects on photoionization time delay in atomic Ar and Xe A. Ganesan, S. Saha, P. C. Decshmukh, S. T. Manson, A. S. Kheifets Time delay studies in photoionization processes [1] have stimulated much interest as they provide valuable dynamical information about electron correlation and relativistic effects. In a recent work [2] on Wigner time delay [3] in the photoionization of noble gas atoms, it was found that correlations resulting from interchannel coupling involving shells with different principal quantum numbers have significant effects on 2s and 2p photoionization of Ne, 3s photoionization of Ar, and 3d photoionization of Kr. In the present work, photoionization time delay in inner and outer subshells of the noble gases Ar and Xe are examined by including electron correlations using different many body techniques: (i) the relativistic-random-phase approximation (RRPA) [4], (ii) RRPA with \textit{relaxation}, to include relaxation effects of the residual ion [5] and (iii) the relativistic multiconfiguration Tamm-Dancoff (RMCTD) approximation [6]. The (sometimes substantial) effects of the inclusion of non-RPA correlations on the photoionization Wigner time delay are reported. Work supported by DOE, Office of Chemical Sciences and DST (India). [1] R. Pazourek, S. Nagele and J. Burgd\"{o}rfer, Rev. Mod. Phys. \textbf{87}, 765 (2015) and references therein; [2] A.S. Kheifets \textit{et al} Phys. Rev. A \textbf{92}, 063422 (2015); [3] E.P. Wigner, Phys. Rev. \textbf{98}, 145 (1955); [4] W. R. Johnson and C. D. Lin, Phys. Rev. A \textbf{20}, 964 (1979); [5] V. Radojevic, M. Kutzner and H. P. Kelly, Phys. Rev. A\textbf{ 40} 727 (1989); [6] V.Radojevic and W. R. Johnson, Phys. Rev. A \textbf{31}, 2991 (1985). [Preview Abstract] |
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K1.00035: Angular dependence of Wigner time delay: Relativistic Effects A. Mandal, P. C. Deshmukh, S. T. Manson, A. S. Kkeifets Laser assisted photoionization time delay mainly consists of two parts: Wigner time delay, and time delay in continuum-continuum transition [1]. Wigner time delay results from the energy derivative of the phase of the photoionization amplitude (matrix element). In general, the photoionization time delay is not the same in all directions relative to the incident photon polarization [2], although when a single transition dominates the amplitude, the resultant time delay is essentially isotropic. The relativistic-random-phase approximation [3] is employed to determine the Wigner time delay in photoionization from the outer np subshells of the noble gas atoms, Ne through Xe. The time delay is found to significantly depend on angle, as well as energy. The angular dependence of the time delay is found to be quite sensitive to atomic dynamics and relativistic effects, and exhibit strong energy and angular variation in the neighborhood of Cooper minima [4]. Work supported by DOE, Office of Chemical Sciences and DST (India). [1] R. Pazourek, S. Nagele and J. Burgd\"{o}rfer, Rev. Mod. Phys. \textbf{87}, 765 (2015) and references therein; [2] J. W\"{a}tzel, A. S. Moskalenko, Y. Pavlyukh and J. Berakdar, J. Phys. B \textbf{48}, 025602 (2015); [3] W. R.Johnson and C. D. Lin., Phys. Rev. A\textbf{ 20}, 964 (1979); [4] J. W. Cooper, Phys. Rev., \textbf{128}, 681 (1962). [Preview Abstract] |
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K1.00036: TIME RESOLVED MOLECULAR DYNAMICS AND FEMTOCHEMISTRY |
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K1.00037: Femtosecond Heterodyne Transient Grating Spectroscopic Studies of Intramolecular Charge Transfer Character of Peridinin and Peridinin Analogs Michael Bishop, Soroush Khosravi, Razib Obaid, Hope Whitelock, Ann Marie Carroll, Amy LaFountain, Harry Frank, Warren Beck, George Gibson, Nora Berrah The peridinin chlorophyll-a protein is a light harvesting complex found in several species of dinoflagellates. Peridinin absorbs strongly in the mid-visible spectral region and, despite the lack of a strong permanent dipole moment in its lowest energy excited state, is able to transfer excitation energy quickly and efficiently to chlorophyll-a. It is believed that the high efficiency arises from the development of intramolecular charge-transfer (ICT) character upon photoexcitation. Recently, heterodyne transient grating spectroscopy has been used to study the ultrafast (\textless 50 fs) dynamics of $\beta $ carotene and peridinin. The studies show evidence for a structurally displaced intermediate in both cases and strong ICT character in the case of peridinin, but up to now the work has not provided appropriate control experiments. The present experiments examine peridinin and two peridinin analogs, S1-peridinin and S2-peridinin. S1-peridinin is reported to have greatly diminished ICT character, and S2-peridinin is reported to have little-or-no ICT character. Heterodyne transient grating data will be presented and provide a more unambiguous characterization spectral and kinetic properties associated with the peridinin ICT state. [Preview Abstract] |
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K1.00038: Role of electronic structure in ionization and fragmentation of endohedral fullerenes Ho$_{\mathrm{3}}$N@C$_{\mathrm{80}}$ in an intense femtosecond laser field Hui Xiong, Li Fang, Timur Osipov, Emily Sistruk, Thomas Wolf, Benoit Mignolet, Francoise Remacle, Markus Gühr, Nora Berrah The ionization and fragmentation of gas phase endohedral fullerene Ho$_{\mathrm{3}}$N@C$_{\mathrm{80}}^{\mathrm{\thinspace }}$was investigated using ultrashort 800 nm laser pulses with an ion velocity map imaging (VMI) spectrometer. The power law's dependence I$^{\mathrm{n}}$ on laser intensity of the singly, doubly, and triply charged Ho$_{\mathrm{3}}$N@C$_{\mathrm{80}}$ molecule and Ho$^{\mathrm{+}}$ ion fragments have been experimentally determined. Theoretical calculation indicates that the superatom molecular orbitals (SAMOs) electronic states in Ho$_{\mathrm{3}}$N@C$_{\mathrm{80}}$ can be populated through direct multiphoton excitation. The ionization power law essentially reflects the photoexcitation step to the SAMOs. In addition to the molecular nuclear frame heating by electron-vibrational coupling, we observe a rapid heating process, which could be an `avalanche' process, produced via semi-free electrons impacting the molecular nuclear frame at high laser intensity. [Preview Abstract] |
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K1.00039: Development and Implementation of an Ultrafast Vacuum-UV (8eV) Light Source for use in UV-VUV Pump Probe Experiments of Neutral Excited State Dynamics YUSONG LIU, Spencer Horton, Spiridoula Matsika, Thomas Weinacht Probing neutral excited state dynamics in polyatomic molecules with ultrafast laser systems enables us to study phenomena such as internal conversion, isomerization, intersystem crossing, and dissociation. Using the third harmonic (260nm) and the fifth harmonic (156nm) of our laser system we have developed an apparatus to perform pump-probe experiments for the study neutral excited state dynamics in various polyatomic molecules. The fifth harmonic of our laser system is generated through the four-wave-mixing process of $\overrightarrow k_{5\omega } =2\overrightarrow k_{3\omega } -\overrightarrow k_{\omega } $ performed with a non-collinear geometry in an argon gas cell. In several polyatomic molecular systems of interest a photon with 8eV of energy gives us the unique ability to ionize from essentially anywhere along the excited state potential, but does not produce any ionization yield from the ground state. This enables us to measure excited state lifetimes without the photon energy becoming too low to ionize while the nuclear wave-packet is traveling on the excited state potential. We also have the advantage of working in the perturbative weak-field ionization regime. These experiments can also be directly compare to strong-field ionization experiments conducted with a UV-pump and an IR-probe conducted on the same molecules. [Preview Abstract] |
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K1.00040: Ultrafast nuclear dynamics in halomethanes studied with time-resolved Coulomb explosion imaging and channel-selective Fourier spectroscopy Y. Malakar, B. Kaderiya, W.L. Pearson, F. Ziaee, Kanaka Raju P., M. Zohrabi, K. Jensen, J. Rajput, I. Ben-Itzhak, D. Rolles, A. Rudenko Halomethanes have recently attracted considerable attention since they often serve as prototype systems for laser-controlled chemistry (e.g., selective bond breaking or concerted elimination reactions), and are important molecules in atmospheric chemistry. Here we combine a femtosecond laser pump-probe setup with coincident 3D ion momentum imaging apparatus to study strong-field induced nuclear dynamics in methane and several of its halogenated derivatives (CH$_{3}$I, CH$_{2}$I$_{2}$, CH$_{2}$ICl). We apply a time-resolved Coulomb explosion imaging technique to map the nuclear motion on both, bound and continuum potential surfaces, disentangle different fragmentation pathways and, for halogenated molecules, observe clear signatures of vibrational wave packets in neutral or ionized states. Channel-selective and kinetic-energy resolved Fourier analysis of these data allows for unique identification of different electronic states and vibrational modes responsible for a particular structure. [Preview Abstract] |
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K1.00041: STRONG FIELD PHYSICS |
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K1.00042: Photon-electron-ion momentum transfer in high intensityIR laser pulse ionization Andre D Bandrauk, Szczefan Chelkowski, Paul Corkum Photon momentum sharing between electrons and parent ions in high intensityIR multiphoton ionization requires going beyond the traditional perturbative dipole approximation[1].Using numerical solutions of the 2-D TDSE(Time dependent Schroedinger equation) for one electron atom models[2],we show that the radiation pressure on photoelectrons is sensitive to the ionization mechanism,either direct or by recollision.A complex electron-ion response is obtained due to the interplay between the Lorentz force and Coulomb attraction of the ion.The influence of the photon momentum sharing is shown to be discernible in IR high intensity atomic and/or molecular holographic patterns thus suggesting a new research subject in IR strong field physics. [1]S Chelkowski,AD Bandrauk,PB Corkum, Phys Rev Lett 113,263005(2014) [2]S Chelkowski,AD Bandrauk,PB Corkum,Phys Rev A 92,R051401(2015) [Preview Abstract] |
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K1.00043: Contributions of inner valence molecular orbitals and multiphoton resonances to high harmonic generation: A TDDFT study Xi Chu, Gerrit Groenenboom Using a TDDFT method, we calculated the high harmonic generation (HHG) spectra of N$_2$ in 800 nm and 1300 nm intense lasers. The calculations reproduce the experimentally observed minimum near 40 eV and the shift of the minimum due to interference of different molecular orbitals. They also support the proposed shape resonance near 30 eV. The TDDFT method allows us to analyze the involvement of different electronic configurations in the HHG process. We identified a significant role of Rydberg states and autoionizing states in enhancing HHG. This finding is consistent with studies of photoelectron spectra in a similar energy range. Moreover, we discover a significant contribution of the $2\sigma_g$ orbital above 40 eV, demonstrating the complexity of electronic structure information contained in molecular HHG. At high energy not only the HOMO and HOMO-1 are important, as suggested by earlier studies, but the HOMO-3 contributes substantially as well. [Preview Abstract] |
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K1.00044: Mechanism of Anomalous Ellipticity Dependence of Near-threshold Harmonics in H$_{2}^{+}$ kobra nasiri avanaki, Dmitry A. Telnov, Shih-I Chu We have studied the mechanism of anomalous dependence of near-threshold harmonics in H$_{2}^{+}$ on ellipticity of driving field with the carrier wavelength 780~nm. The numerical procedure is based on accurate solution of the time-dependent Schr\"odinger equation in prolate spheroidal coordinates with the help of generalized pseudospectral method. Our analysis reveals that the origin of this phenomenon is mainly in the near-resonant excitation of $\pi_{u}$ molecular orbitals in H$_{2}^{+}$. For the lowest affected harmonic, the maximum in the ellipticity dependence of the radiation energy is exclusively due to excitation of the $1\pi_{u}$ state; however, for higher near-threshold harmonics, higher-lying excited $\pi_{u}$ states are playing significant role as well. The closer the harmonic to the threshold, the larger number of excited states make considerable contributions. All these contributions interfere, resulting in the anomalous ellipticity dependence with a maximum at some non-zero value of the ellipticity parameter. In the vicinity of this value, the harmonics with the anomalous dependence are linearly polarized along the minor axis of the polarization ellipse of the driving field and may show strong elliptical polarization as well. [Preview Abstract] |
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K1.00045: Electron Dynamics in Intense Laser Fields: A Bohmian Mechanics Study Hossein Z. Jooya, Dmitry A. Telnov, Shih-I Chu We study the electron quantum dynamics of atomic hydrogen under intense near infrared laser fields by means of the De Broglie–Bohm’s framework of Bohmian mechanics. This method is used to study the mechanism of the multiple plateau generation and the cut-off extension, as the main characteristic features of high order harmonic generation spectrum. Electron multiple recollision dynamics under intense mid-infrared laser fields is also investigated. In this case, the resulting patterns in the high-order harmonic generation and the above-threshold ionization spectra are analyzed by comprehensive picture provided by Bohmian mechanics. The time evolution of individual trajectories is closely studied to address some of the major structural features of the photoelectron angular distributions. [Preview Abstract] |
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K1.00046: Enhancement of VUV and EUV generation by field-controlled resonance structures of diatomic molecules John Heslar, Dmitry A. Telnov, Shih-I Chu Below- and near-threshold harmonic generation provides a potential approach to achieve a high conversion efficiency of vacuum-ultraviolet and extreme-ultraviolet sources for the advancement of spectroscopy. Here we perform an \textit{all-electron} time-dependent density functional theory (TDDFT) study for the nonperturbative treatment of below- and near-threshold harmonic generation of CO and N$_{\mathrm{2\thinspace }}$diatomic molecules subject to short near-infrared laser pulses and aligned parallel to the laser field polarization. We find that with the use of different driving laser pulse shapes we can control and enhance harmonic generation through the excited state resonance structures. Our analysis reveals several novel features where the HHG signal is enhanced, boosting the conversion efficiency on the microscopic level. Depending on the pulse shape, the enhancement can reach 5 to 7 orders of magnitude as compared to the reference sine-squared laser pulse of the same duration. [Preview Abstract] |
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K1.00047: Reconstruction of crystal band structure from the power spectrum of strong-field generated high harmonics Chang-Ming Wang, Tak-San Ho, Shih-I Chu The study of high harmonic generation in solid driven by intense laser fields is a subject of much current interest. Recently we introduce a new optimization method to directly reconstruct the band structure of the crystal from the power spectrum of strong-field generated high harmonics. Without loss of generality, the reconstruction is formulated for a one-dimensional single band model as a minimization problem and solved by a derivative-free unconstrained optimization algorithm-NEWUOA. The method can be readily generalized to treat multi-band problems. Numerical simulations are presented to demonstrate the applicability of the method, and the reconstructed band structure is found to be in excellent agreement with the exact one. It is also shown that our optimization method remains robust and efficient even starting from the poorly guessed band structure. [Preview Abstract] |
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K1.00048: Photodetachment dynamics in a strong single-cycle terahertz pulse Baochun Yang, Francis Robicheaux We present theory and calculations for the photodetachment dynamics of negative ions driven by a single-cycle terahertz pulse. The photoelectron can follow two or more classical trajectories to arrive at a detector simultaneously, allowing the electron waves to interfere quantum mechanically. For negative hydrogen and fluorine ions, both the in-phase and antiphase interference oscillations are observed in the temporal electron flux recorded at a large distance (0.5m). As the terahertz pulse gets strong enough, an oscillatory photodetachment rate can be observed, which arises from the quantum interferences near the source region caused by the returning electron waves following three types of closed classical orbits. Our semiclassical formulas are proved to be quantitatively accurate by comparing with exact quantum simulations. The presented theory could also be generalized for other similar systems where the electron experiences an interaction with an applied electric-field driving pulse. [Preview Abstract] |
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K1.00049: The interaction of excited atoms and few-cycle laser pulses James Calvert, Han Xu, Adam Palmer, Dane Laban, Igor Litvinyuk, David Kielpinksi, Robert Sang, Rohan Glover, Xiao-Min Tong, Valeriy Dolmatov, Anatoli Kheifets, Klaus Bartschat We present the observations of the ionisation of neon in a metastable atomic state utilising a strong-field few\-cycle laser pulse [1,2]. We compare the observations to theoretical predictions based on the Ammosov-Delone-Krainov (ADK) theory [3] and a solution to the time-dependent Schr\"{o}dinger equation (TDSE) [4]. The TDSE provides better agreement with the experimental data than the ADK theory. We optically pump the target atomic species and demonstrate that the ionisation rate depends on the spin state of the target atoms and provide physically transparent interpretation of such a spin dependence in the frameworks of the spin-polarised Hartree-Fock and random-phase approximations [5]. [1] J. E. Calvert {\em et al.}, arXiv:1601.03786, 2016, Sci. Rep. submitted [2] I. A. Ivanov, Sci. Rep. 19002 (2016) [3] M. V. Ammosov {\em et al.}, Sov. Phys. JETP {\b 64}, 425 (1986). [4] X. M. Tong {\em et al.}, Phys. Rev. A {\b 74}, 031405(R) (2006). [5] M. Y. Amus'ya {\em et al.}, Sov. Phys. . JETP {\b 58}, 67 (1983). [Preview Abstract] |
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K1.00050: SCIENCE WITH XUV AND X RAY FREE-ELECTRON LASERS |
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K1.00051: Multi-photon two-color ionization of atoms and ions by femtosecond pulses. Nicolas Douguet, Joel Venzke, Klaus Bartschat, Alexei N. Grum-Grzhimailo, Elena Gryzlova, Ekaterina Staroselskaya We consider several processes related to two-color ionization induced by femtosecond pulses. Using the first and second harmonics of an XUV pulse, one can produce two-pathway interferences, which directly influence the photoelectron angular distribution. We discuss the process with linearly as well as circularly polarized light of various mutual orientations and helicities. Furthermore, combining the XUV light with an optical laser, one can generate sidebands around the main photoelectron line and study a variety of asymmetries in photoelectron emission and their dependencies on the absolute and relative intensities, time delay, and polarization of the light. Calculations for atomic hydrogen, He$^+$(1s) generated by an initial XUV pulse, and Ne(2p) were performed by directly solving the time-dependent Schr\"odinger equation as well as employing second-order nonstationary perturbation theory. Our predictions serve as guidelines for experiments at various X-ray Free-Electron Laser facilities, such as LCLS, FERMI, FLASH, and the European XFEL [1,2]. \par\noindent [1] K. Prince {\it et al}., Nature Photonics (2016), in press \par\noindent [2] K. Prince, G. Sansone, and M. Meyer (2016), private communication [Preview Abstract] |
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K1.00052: Atomistic Simulations of High-intensity XFEL Pulses on Diffractive Imaging of Nano-sized System Dynamics Phay Ho, Christopher Knight, Christoph Bostedt, Linda Young, Miklos Tegze, Gyula Faigel We have developed a large-scale atomistic computational method based on a combined Monte Carlo and Molecular Dynamics (MC/MD) method to simulate XFEL-induced radiation damage dynamics of complex materials. The MD algorithm is used to propagate the trajectories of electrons, ions and atoms forward in time and the quantum nature of interactions with an XFEL pulse is accounted for by a MC method to calculate probabilities of electronic transitions. Our code has good scalability with MPI/OpenMP parallelization, and it has been run on Mira, a petascale system at the Argonne Leardership Computing Facility, with particle number \textgreater 50 million. Using this code, we have examined the impact of high-intensity 8-keV XFEL pulses on the x-ray diffraction patterns of argon clusters. The obtained patterns show strong pulse parameter dependence, providing evidence of significant lattice rearrangement and diffuse scattering. Real-space electronic reconstruction was performed using phase retrieval methods. We found that the structure of the argon cluster can be recovered with atomic resolution even in the presence of considerable radiation damage. [Preview Abstract] |
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K1.00053: NONLINEAR OPTICS |
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K1.00054: Frequency Characteristics of Parametric Four-Wave Mixing Erik Brekke, Sam Potier We have investigated the frequency characteristics of the coherent 420 nm beam generated via parametric four-wave mixing. A single, high-power 778 nm laser is directed through a high-density rubidium cell with a detuning of 1 THz from the intermediate state, generating fields at 420 nm and 5.23 $\mu $m through four-wave mixing. The frequency of the 420 nm light has been found to shift as the excitation laser is tuned, with a measured frequency shift ratio of 1.87 corresponding with the selection of a different velocity class at each excitation frequency. The 420 nm light has been tuned over a range of 1 GHz. Further investigation is underway to increase the efficiency of the process using optical pumping and a build-up cavity. This parametric four-wave mixing process has potential application as a tunable photon source at novel wavelengths. [Preview Abstract] |
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K1.00055: Nonlinear Optics with Tapered Fibers and Magneto-Optically Trapped Rubidium Bethany Little, Chris Mullarkey, John Howell, Nick Vamivakas, Qiang Lin Tapered optical fibers of sub-wavelength diameter present a promising means of integrating the light-atom interaction into larger scale devices. We present work on a tapered fiber system loaded by a magneto optical trap of Rubidium atoms, in which a combination of red and blue detuned beams create a one-dimensional lattice trap along the fiber. The same fiber is used for interacting with the atoms in the trap via the evanescent fields of light propagating along the fiber. Light storage has been demonstrated in a similar system with Cesium \footnote{Sayrin, Clausen, Albrecht, Schneeweiss, and Rauschenbeutel, Optica {\bf 2},353-356 (2015)}, and we believe that much nonlinear optics remains to be explored in this regime. We also plan to see how these nonlinear effects can be enhanced with the addition of a micro-resonator such as the ones in \footnote{Lu, Lee, Rogers, and Lin, Optics Express {\bf 25}, 30826-30832 (2014)} [Preview Abstract] |
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K1.00056: Coherent manipulation of absorption by intense fields in four level ladder system Pardeep Kumar, Shubhrangshu Dasgupta Nonlinear optical processes attributed to the dependence of the susceptibility of the medium on the input fluence can be remarkably manipulated by the quantum interference and coherence. One of these processes, the optical bistability (OB), that refers to the possibilities of two stable outputs for the same input fields, can also be modified by quantum coherence. Further, the nonlinear dependence of the absorption on the power of the input light gives rise to interesting processes like saturable absorption (SA) and reverse saturable absorption (RSA). While the SA corresponds to the decrease in the absorption coefficient with the increase of intensity of input light, the RSA corresponds to otherwise, that finds applications in optical limiting. We show, using a four-level Ladder system, how a control field manipulates these processes for an intense probe field applied in the excited state transition. The nonlinear absorption increases whereas the threshold of OB decreases in presence of a control field. We further delineates how the control field and the decay rates modifies SA and RSA. The control of these processes find applications in optical switching, optical limiting and optical communications. [Preview Abstract] |
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K1.00057: Characterization of Ultrafast Laser Pulses using a Low-dispersion Frequency Resolved Optical Grating Spectrometer Hope Whitelock, Michael Bishop, Soroush Khosravi, Razib Obaid, Nora Berrah A low dispersion frequency-resolved optical gating (FROG) spectrometer was designed to characterize ultrashort (\textless 50 femtosecond) laser pulses from a commercial regenerative amplifier, optical parametric amplifier, and a home-built non-colinear optical parametric amplifier. This instrument splits a laser pulse into two replicas with a 90:10 intensity ratio using a thin pellicle beam-splitter and then recombines the pulses in a birefringent medium. The instrument detects a wavelength-sensitive change in polarization of the weak probe pulse in the presence of the stronger pump pulse inside the birefringent medium. Scanning the time delay between the two pulses and acquiring spectra allows for characterization of the frequency and time content of ultrafast laser pulses, that is needed for interpretation of experimental results obtained from these ultrafast laser systems. [Preview Abstract] |
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K1.00058: Laser-cooled cesium atoms confined in a fiber-guided magic-wavelength dipole trap Taehyun Yoon, Christopher Haapamaki, Jeremy Flannery, Golam Bappi, Rubayet Al Maruf, Omar Alshehri, Michal Bajcsy Strong light-matter interactions crucial for the achievement of optical nonlinearities with small photon numbers can be implemented by confining both photons and an atomic ensemble inside a hollow-core optical waveguide. We have developed an experimental setup trapping cesium atoms in a magneto-optical trap (MOT) and loading them into a hollow-core photonic crystal fiber (HCPCF) where they are transversely confined by a red-detuned optical dipole trap that is also guided by the fiber. This dipole trap is realized at cesium's 'magic wavelength' (935.6nm), which results in a state-insensitive trap and suppression of the radially varying AC-Stark shift for the confined atomic cloud. This was not possible with rubidium atoms used the previous experiments in this platform\footnote{M. Bajcsy et al., PRL 102, 203902 (2009)} since rubidium does not have a convenient magic wavelength for the red-detuned dipole trap. We report our procedure to load and probe the laser-cooled atoms inside the HCPCF and discuss the outlooks of this system for implementing nonlinear optics with single photons. We also describe our progress on integrating cavities into the the HCPCF that could potentially allow transforming the fiber into a cQED system in the strong coupling regime. [Preview Abstract] |
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K1.00059: Collimated Blue and Infrared Beams Generated by Two-Photon Excitation in Rubidium Vapor Alina Gearba, Jerry Sell, Robert Olesen, Randy Knize Utilizing nonlinear optical processes in Rb vapor we describe the generation of optical fields at 420 nm, 1.32 $\mu$m, and 1.37 $\mu$m. Input laser beams at 780 nm and 776 nm enter a heated Rb vapor cell collinear and circularly polarized. Rubidium atoms are excited to the $5D_{5/2}$ state, with blue light generated by four-wave mixing through the $6P_{3/2} \rightarrow 5S_{1/2}$ states, while infrared beams at 1.37 $\mu$m and 1.32 $\mu$m are generated by cascading decays through the $6S_{1/2} \rightarrow 5P_{3/2}$ and $6S_{1/2} \rightarrow 5P_{1/2}$ states, respectively. While the blue beam emission from four-wave mixing has been studied in detail, the mechanisms responsible for generating the infrared beams are still under investigation. We will present our results for the conditions which give rise to infrared beam generation by two-photon excitation in rubidium vapor. [Preview Abstract] |
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K1.00060: Optical Parametric Amplification via Difference Frequency Wayne Huang, Herman Batelaan, Marlan Scully Conventionally, broadband frequency conversion is achieved through spontaneous parametric down conversion. Such a process requires a pump source with frequencies higher than the targeted frequencies. This presents the limitation for light generation in the ultraviolet regime. Here, we present a different approach for optical parametric amplification using a difference-frequency pump. The prerequisite for optical amplification is complex-valued nonlinear susceptibility, which can only be realized in non-Hermitian optical systems. Such an effect may be used for realizing all-optical table-top XUV lasers. We will also discuss our first demonstration of this novel effect in a wave system using coupled acoustic Fabry-Perot cavities. [Preview Abstract] |
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K1.00061: Compact spectrometer for precision studies of multimode behavior in an extended-cavity diode laser Timothy Roach, Josian Golemi, Thomas Krueger We have built a compact, inexpensive, high-precision spectrometer and used it to investigate the tuning behavior of a grating stabilized extended-cavity diode laser (ECDL). A common ECDL design uses a laser chip with an uncoated (partially reflecting) front facet, and the laser output exhibits a complicated pattern of mode hops as the frequency is tuned, in some cases even showing chaotic dynamics. Our grating spectrometer (based on a design by White {\&} Scholten) monitors a span of 4000GHz (8nm at 780nm) with a linewidth of 3GHz, which with line-splitting gives a precision of 0.02GHz in determining the frequency of a laser mode. We have studied multimode operation of the ECDL, tracking two or three simultaneous chip cavity modes (spacing \textasciitilde 30GHz) during tuning via current or piezo control of the external cavity. Simultaneous output on adjacent external cavity modes (spacing \textasciitilde 5GHz) is monitored by measuring an increase in the spectral linewidth. Computer-control of the spectrometer (for line-fitting and averaging) and of the ECDL (electronic tuning) allows rapid collection of spectral data sets, which we will use to test mathematical simulation models of the non-linear laser cavity interactions. [Preview Abstract] |
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K1.00062: Development of a high-frequency electronic integrator for photon-number resolving detectors Kristina Meier, Michael Wayne, Paul Kwiat Efficient photon-number-resolving single-photon detectors are a critical resource for optical quantum information processing, e.g., for realizing deterministic single-photon production. Previously, we have developed Visible Light Photon Counters (VLPCs) that can detect single photons with high quantum efficiency. The detector configuration allows photons to initiate multiple electron avalanches simultaneously, creating a signal with a charge proportional to the number of photons detected. One current obstacle is the extraction of the total charge of each pulse at frequencies ranging from 200 MHz to 20 GHz. The charge of each pulse is proportional to the area under the input signal and so we are currently developing an electronic integrator that, with appropriate signal amplification, will produce an output signal of pulses with heights equal to the integral of the VLPC pulse, thereby fully realizing the photon-number resolving capabilities of these detectors. Finally, we are also studying the use of optical annealing to reduce the detector's dark counts. [Preview Abstract] |
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K1.00063: Current work on developing more convenient single frequency blue and UV lasers using second harmonic generation. Ali Khademian, David Shiner We have reported 81.5{\%} efficiency in converting \textasciitilde 600 mW of input IR to 486 nm output using a periodically poled Lithium Tantalate (PPSLT) crystal. A resonant IR enhancement cavity was used and conversion efficiency was high enough that impedance matching was possible with a 10{\%} input coupler. The cavity had a total parasitic loss of 0.63{\%}. Improving these results by identifying and minimizing various sources of loss can make this approach more widely applicable: for instance in the efficient conversion of input powers as low as a few mW or in the efficient conversion of wavelengths down to perhaps 300 nm. To this end we investigate the sources of our cavity loss. We find a 0.25{\%} loss from polarization misalignment caused by the crystal. Also a 0.15{\%} loss due to reflection from the periodically poled boundaries was measured. This refection also causes feedback to the IR source, leading to instability and mode hoping. We report on results using new PPSLT crystals with slightly tilted periodically poled slabs designed to eliminate the reflection loss mechanism and the feedback. We report on the polarization stability of these crystals, which have undergone a more careful annealing process. We have developed a sensitive technique to measure the total scattering and absorption loss within the crystals. Significantly, measurements on previous crystals indicated these losses to be negligible. We discuss this work and update the overall conversion efficiency. [Preview Abstract] |
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K1.00064: ATOM AND MATTER OPTICS |
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K1.00065: Characterising the topological superradiant state J S Pan, X J Liu, W Zhang, X Z Qiu, W Yi Coherently driven atomic gases inside optical cavities hold great promises in generating rich dynamics and exotic states of matter. Recently, it has been shown that a novel topological superradiant state exists in a two-component degenerate Fermi gas coupled to a cavity, where local order parameters coexist with global topological invariants. In this work, we characterise in detail various properties of this exotic state, focusing on the feedback interactions between the atoms and the cavity field. In particular, we demonstrate that the cavity-induced inter-band couplings play a crucial role in inducing the topological phase transition between the conventional and the topological superradiant state. Furthermore, we analyse how the closing and reopening of the atomic bulk gap across the topological phase boundary leaves interesting signatures in the cavity field. We also discuss the robustness of the topological superradiant state by investigating the steady-state phase diagram under various circumstances. Our work provides many valuable insights into the unique atom-cavity hybrid system under study, and is helpful for future experimental exploration of the topological superradiant state. [Preview Abstract] |
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K1.00066: Three-photon coherence of Rydberg atomic states Hyo Min Kwak, Taek Jeong, Yoon-seok Lee, Han Seb Moon We investigated three-photon coherence effects of the Rydberg state in a four-level ladder-type atomic system for the 5S$_{\mathrm{1/2}}$ (F$=$3) -- 5P$_{\mathrm{3/2\thinspace }}$(F'$=$4) -- 50D$_{\mathrm{5/2}}$ -- 51P$_{\mathrm{3/2}}$ transition of $^{\mathrm{85}}$Rb atoms. By adding a resonant electric field of microwave (MW) at electromagnetically induced transparency (EIT) in Rydberg state scheme, we observed experimentally that splitting of EIT signal appears under the condition of three-photon resonance in the Doppler-broadened atomic system. Discriminating the two- and three-photon coherence terms from the calculated spectrum in a simple four-level ladder-type Doppler-broadened atomic system, we found that the physical origin of splitting of EIT was three-photon coherence effect, but not three-photon quantum interference phenomena such as three-photon electromagnetically induced absorption (TPEIA). [Preview Abstract] |
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K1.00067: Time-Resolved Luminescence Nanothermometry with Nitrogen-Vacancy Centers in Nanodiamonds Pei-Chang Tsai, Oliver Y. Chen, Yan-Kai Tzeng, Hsiou-Yuan Liu, Hsiang Hsu, Shaio-Chih Huang, Jeson Chen, Fu-Ghoul Yee, Huan-Cheng Chang, Ming-Shien Chang Measuring thermal properties with nanoscale spatial resolution either at or far from equilibrium is gaining importance in many scientific and engineering applications. Although negatively charged nitrogen-vacancy (NV$^{\mathrm{-}})$ centers in diamond have recently emerged as promising nanometric temperature sensors, most previous measurements were performed under steady state conditions. Here we employ a three-point sampling method which not only enables real-time detection of temperature changes over ±100 K with a sensitivity of 2 K/(Hz)$^{\mathrm{1/2}}$, but also allows the study of nanometer scale heat transfer with a temporal resolution of better than 1 $\mu $s with the use of a pump-probe-type experiment. In addition to temperature sensing, we further show that nanodiamonds conjugated with gold nanorods, as optically-activated dual-functional nanoheaters and nanothermometers, are useful for highly localized hyperthermia treatment. We experimentally demonstrated time-resolved fluorescence nanothermometry, and the validity of the measurements was verified with finite-element numerical simulations. The approaches provided here will be useful for probing dynamical thermal properties on nanodevices in operation. [Preview Abstract] |
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K1.00068: Radiation Guiding In a Dense, Elongated Cold-Atom Cloud Andira Ramos, Yun-Jhih Chen, Jamie MacLennan, Georg Raithel Radiation guiding through a dense, elongated cold-atom cloud in a deep optical lattice created by an in-vacuum cavity has been experimentally observed [1]. When atoms are loaded into the optical lattice, a cylindrically symmetric depletion zone surrounding the lattice location is created. This variation in atomic density gives rise to a position-dependent index of refraction which allows for a probe beam properly coupled into the atomic cloud to be guided through it. For a Hermite-Gaussian mode (HG$_{00})$, this mini fiber exhibits a transmission pattern consisting of a central feature and multiple concentric rings around it, with higher cavity modes also being accessible in the current experimental setup. Simulations that look to properly model these features are presented. This form of radiation guiding can be useful for Rydberg polariton and EIT experiments, where the atomic fiber would guide one or more trains of single-photon pulses, depending on the cavity mode [2]. [1] Yun-Jhih Chen, Stefan Zigo, and Raithel, G. "Atom trapping and spectroscopy in cavity-generated optical potentials." PRA 89, 063409 (2014). [2] T. Peyronel, O. Firstenberg, Q. Y. Liang, S. Hoerberth,A. V. Gorshkov, T. Pohl, M. D. Lukin, and V. Vuletic, Nature 488, 57 (2012). [Preview Abstract] |
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K1.00069: Measuring the Gouy Phase of Matter Waves using Singular Atom Optics with Spinor BECs Justin T. Schultz, Azure Hansen, Joseph D. Murphree, Maitreyi Jayaseelan, Nicholas P. Bigelow The Gouy phase is a propagation-dependent geometric phase found in confined waves as they propagate through a focus. Although it has been observed and studied extensively both in scalar and vector optical beams as well as in electron vortex beams, it has not yet been directly observed in ultracold matter waves. The Schr\"{o}dinger equation has the same form as the paraxial wave equation from electromagnetism; expansion of a BEC upon release from a trap has the same mathematical form as a beam propagating away from a focus. We employ and extend this analogy between coherent optical beams and coherent matter waves to include spin angular momentum (polarization), which enables us measure the matter wave Gouy phase using coreless vortex spin textures in spinor BECs. Because the Gouy phase is dependent on the orbital angular momentum of the wave, the vortex and core states acquire different Gouy phase shifts. Parameters that are sensitive to the relative phase such as two-dimensional maps of the Stokes parameters rotate during evolution due to this phase difference. Using atom-optic polarimetry we can access the evolution of the atomic Stokes parameters and observe this rotation. [Preview Abstract] |
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K1.00070: An orbital angular momentum spectrometer for electrons Tyler Harvey, Vincenzo Grillo, Benjamin McMorran With the advent of techniques for preparation of free-electron and neutron orbital angular momentum (OAM) states, a basic follow-up question emerges: how do we measure the orbital angular momentum state distribution in matter waves? Control of both the energy and helicity of light has produced a range of spectroscopic applications, including molecular fingerprinting and magnetization mapping. Realization of an analogous dual energy-OAM spectroscopy with matter waves demands control of both initial and final energy and orbital angular momentum states: unlike for photons, final state post-selection is necessary for particles that cannot be annihilated. We propose a magnetic field-based mechanism for quantum non-demolition measurement of electron OAM. We show that OAM-dependent lensing is produced by an operator of form $U=\exp\left(i\frac{L_z\rho^2}{\hbar b^2}\right)$ where $\rho=\sqrt{x^2+y^2}$ is the radial position operator, $L_z$ is the orbital angular momentum operator along $z$, and $b$ is the OAM dispersion length. We can physically realize this operator as a term in the time evolution of an electron in magnetic round lens. We discuss prospects and practical challenges for implementation of a lensing orbital angular momentum measurement. [Preview Abstract] |
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K1.00071: STOPPING AND SLOWING LIGHT |
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K1.00072: Controllable high bandwidth storage of optical information in a Bose-Einstein Condensate Maitreyi Jayaseelan, Justin T. Schultz, Joseph D. Murphree, Azure Hansen, Nicholas P. Bigelow The storage and retrieval of optical information has been of interest for a variety of applications including quantum information processing, quantum networks and quantum memories. Several schemes have been investigated and realized with weak, narrowband pulses, including techniques using EIT in solid state systems and both hot and cold atomic vapors. In contrast, we investigate the storage and manipulation of strong, high bandwidth pulses in a Bose-Einstein Condensate (BEC) of ultracold $^{87}$Rb atoms. As a storage medium for optical pulses, BECs offer long storage times and preserve the coherence properties of the input information, suppressing unwanted thermal decoherence effects. We present numerical simulations of nanosecond pulses addressing a three-level lambda system on the D2 line of $^{87}$Rb. The signal pulse is stored as a localized spin excitation in the condensate and can be moved or retrieved by reapplication of successive control pulses. The relative Rabi frequencies and areas of the pulses and the local atomic density in the condensate determine the storage location and readout of the signal pulse. Extending this scheme to use beams with a variety of spatial modes such as Hermite- and Laguerre-Gaussian modes offers an expanded alphabet for information storage. [Preview Abstract] |
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K1.00073: Controllable Dispersion in an Optical Laser Gyroscope Owen Wolfe, ShuangLi Du, Simon Rochester, Dmitry Budker, Irina Novikova, Eugeniy Mikhailov Optical gyroscopes use Sagnac interferometry to make precise measurements of angular velocity. Increased gyroscope sensitivity will allow for more accurate control of aerospace systems and allow for more precise measurements of the Earth's rotation. Severalfold improvements to optical gyroscope sensitivity were predicted for fast light regimes ($n_g < 1$). We evaluated the feasibility of these improvements in the N-bar dual pump scheme in ${}^{87}$Rb vapor. We were able to modify the stimulated gyroscope response via tuning the experimental parameters. Gyroscope sensitivity was shown to be dependent on several parameters including pump power, pump detunning, and vapor density. [Preview Abstract] |
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K1.00074: Zeeman Electromagnetically Induced Transparency with crossed pump and probe beams: Small angle dependence Kaleb Campbell, Somaya Madkhaly, Dillon de Medeiros, Samir Bali Progress toward undergraduate oriented experiments on image storage in room-temperature atomic vapor using Electromagnetically Induced Transparency is described. Using a scanning longitudinal magnetic field technique we diagnose and suppress stray magnetic fields and polarization impurity. Following Carvalho et al. \textit{Phys. Rev. A} \textbf{70}, 063818 (2004) we consider the pump-probe angular dependence of the EIT signal but at much smaller angles of less than a milliradian. [Preview Abstract] |
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K1.00075: QUANTUM GATES |
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K1.00076: A Scalable Microfabricated Ion Trap for Quantum Information Processing Peter Maunz, Raymond Haltli, Andrew Hollowell, Daniel Lobser, Jonathan Mizrahi, John Rembetski, Paul Resnick, Jonathan D. Sterk, Daniel L. Stick, Matthew G. Blain Trapped Ion Quantum Information Processing (QIP) relies on complex microfabricated trap structures to enable scaling of the number of quantum bits\footnote{D. Kielpinski, C. Monroe, and D. J. Wineland, \textbf{Nature} 417, 709 (2002)}. Building on previous demonstrations of surface-electrode ion traps\footnote{S. Seidelin, et al., \textbf{Phys. Rev. Lett.} 96, 253003 (2006), D. Stick, et al., \textbf{arXiv:}1008.0990 (2010), D. L. Moehring, et al., \textbf{New Journal of Physics} 13, 075018 (2011).}, we have designed and characterized the Sandia high-optical-access (HOA-2) microfabricated ion trap. This trap features high optical access, high trap frequencies, low heating rates, and negligible charging of dielectric trap components. We have observed trap lifetimes of more than 100h, measured trap heating rates for ytterbium of less than 40quanta/s, and demonstrated shuttling of ions from a slotted to an above surface region and through a Y-junction. Furthermore, we summarize demonstrations of high-fidelity single and two-qubit gates realized in this trap. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000. [Preview Abstract] |
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K1.00077: Rydberg ensemble based CNOT$^{\mathrm{N}}$ gates using STIRAP Tanvi Gujarati, Luming Duan Schemes for implementation of CNOT gates in atomic ensembles are important for realization of quantum computing. We present here a theoretical scheme of a CNOT$^{\mathrm{N}}$ gate with an ensemble of three-level atoms in the lambda configuration and a single two-level control atom. We work in the regime of Rydberg blockade for the ensemble atoms due to excitation of the Rydberg control atom. It is shown that using STIRAP, atoms from one ground state of the ensemble can be adiabatically transferred to the other ground state, depending on the state of the control atom. A thorough analysis of adiabatic conditions for this scheme and the influence of the radiative decay is provided. We show that the CNOT$^{\mathrm{N}}$ process is immune to the decay rate of the excited level in ensemble atoms. [Preview Abstract] |
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K1.00078: Dual species entanglement of Rb and Cs qubits with Rydberg blockade for crosstalk free qubit measurements Kevin Baker, Zhaoning Yu, Matthew Ebert, Yuan Sun, Mark Saffman One of the outstanding challenges facing neutral atom qubit approaches to quantum computation is suppression of crosstalk between proximal qubits due to scattered light that is generated during optical pumping and measurement operations. We have recently proposed a dual species approach to solving this challenge whereby computational qubits encoded in Cs atoms are entangled with Rb atoms via an interspecies Rydberg interaction[1]. The quantum state of a Cs atom can then be readout by measuring the state of a Rb atom. The difference in resonant wavelengths of the two species effectively suppresses crosstalk. We will present progress towards experimental demonstration of dual species entanglement using Rb and Cs atoms cotrapped in a single beam optical trap. [1] I. I. Beterov and M. Saffman, Phys. Rev. A {\bf 92}, 042710 (2015). [Preview Abstract] |
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K1.00079: QUANTUM COMPUTATION AND SIMULATION |
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K1.00080: Towards a scalable quantum computation platform with solid-state spins in low temperature Wengang Zhang Nitrogen-vacancy (NV) center can be treated as an "ion" trapped in the diamond lattice. An electron spin triplet ground state (S$=$1) of NV center can be polarized, coherently manipulated and detected. Together with hyperfine-coupled proximal Carbon-13 and Nitrogen-14 (15) nuclear spins, NV center acts as a promising platform for large scale quantum computation platform at room temperature. By cooling down the diamond to liquid-helium temperature (4K), phonons can be largely suppressed, giving us much longer spin relaxation time (T1) and coherence time (T2) compared with room temperature, and a possibility to readout electron spin state in a single shot. Here we report our progress in building up a prototype for a scalable diamond based quantum computer. [Preview Abstract] |
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K1.00081: W-State Characterization and Progress Toward Non-Destructive State-Selective Measurements with an EMCCD Camera in Rb Matthew Ebert, Minho Kwon, Mark Saffman, Thad Walker We present a method for differentiating k-partite W-State entanglement from other singly-excited states, under the assumption that there are less than two excitations, valid for Rydberg blockade experiments. We use this method to demonstrate ~9 atom W-State entanglement generation via Rydberg blockade with two separate state rotations: a Jx Microwave rotation experiment and a Jz Ramsey fringe experiment. We also report progress towards a non-destructive state-selective readout with an EMCCD camera, which could increase experimental data rates significantly. [Preview Abstract] |
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K1.00082: Experimental implementation of Grover's search algorithm with neutral atom qubits Yuan Sun, Martin Lichtman, Kevin Baker, Mark Saffman Grover's algorithm for searching an unsorted data base provides a provable speedup over the best possible classical search and is therefore a test bed for demonstrating the power of quantum computation. The algorithm has been demonstrated with NMR, trapped ion, photonic, and superconducting hardware, but only with two qubits encoding a four element database. We report on progress towards experimental demonstration of Grover's algorithm using two and three neutral atom qubits encoding a database with up to eight elements. Our approach uses a Rydberg blockade C$_k$NOT gate for efficient implementation of the Grover iterations[1]. Quantum Monte Carlo simulations of the algorithm performance[2] that account for gate errors and decoherence rates are compared with experimental results. [1] K. M\o{}lmer, L. Isenhower, and M. Saffman, J. Phys. B {\bf 44}, 184016 (2011). [2] D. Petrosyan, M. Saffman, and K. M\o{}lmer, arXiv: 1512.05588. [Preview Abstract] |
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K1.00083: An architecture for quantum computation with magnetically trapped Holmium atoms Mark Saffman, James Hostetter, Donald Booth, Jeffrey Collett Outstanding challenges for scalable neutral atom quantum computation include correction of atom loss due to collisions with untrapped background gas, reduction of crosstalk during state preparation and measurement due to scattering of near resonant light, and the need to improve quantum gate fidelity. We present a scalable architecture based on loading single Holmium atoms into an array of Ioffe-Pritchard traps. The traps are formed by grids of superconducting wires giving a trap array with 40 $\mu\rm m$ period, suitable for entanglement via long range Rydberg gates. The states $|F=5,M=5\rangle$ and $|F=7,M=7\rangle$ provide a magic trapping condition at a low field of 3.5 G for long coherence time qubit encoding. The $F=11$ level will be used for state preparation and measurement. The availability of different states for encoding, gate operations, and measurement, spectroscopically isolates the different operations and will prevent crosstalk to neighboring qubits. Operation in a cryogenic environment with ultra low pressure will increase atom lifetime and Rydberg gate fidelity by reduction of blackbody induced Rydberg decay. We will present a complete description of the architecture including estimates of achievable performance metrics. [Preview Abstract] |
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K1.00084: Experimental Demonstration of Quantum Imaging by Coherent Enhancement Robert McConnell, Colin Bruzewicz, Guang Hao Low, Theodore Yoder, John Chiaverini, Jeremy Sage, Isaac Chuang Classical (incoherent) imaging requires scattering many photons from a target to be imaged and provides resolution which improves statistically with the square root of the number of scattered photons, and hence with the square root of interrogation time. In contrast, quantum imaging by coherent enhancement [1] utilizes coherent excitation of the target to provide imaging resolution which improves linearly with time, achieving the Heisenberg limit for scaling. We present experimental progress towards the realization of quantum-enhanced imaging in a trapped-ion system. A narrow-linewidth laser drives a long-coherence-time transition in a confined $^{88}$Sr$^{+}$ ion; precise phase control over the excitation sequence allows an optimally narrow and unambiguous excitation of the ion as a function of laser intensity which results in very precise localization of the target within the profile of the addressing beam. This technique may have applications in radar imaging, where long-wavelength radiation is used to penetrate clouds or other obstructions but where large diffraction-limited spot size ordinarily limits resolution. \newline [1]. G. H. Low, T. J. Yoder, and I. L. Chuang, PRL \textbf{114}, 100801 (2015). [Preview Abstract] |
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K1.00085: Trilinear hamiltonian with trapped ions and its applications Shiqian Ding, Gleb Maslennikov, Roland Hablutzel, Dzmitry Matsukevich The model of three harmonic oscillators coupled by the trilinear Hamiltonian of the form $a^{\dagger} b c + a b^{\dagger} c^{\dagger}$ can describe wide range of physical processes. We experimentally realize such interaction between three modes of motion in the system of 3 trapped Yb ions. We discuss several application of this coupling, including implementation of the quantum absorption refrigerator, simulation of the interaction between light and atoms described by a Tavis-Cummings model, simulation of the non-degenerate parametric down conversion process in the fully quantum regime and studies of a simple model of Hawking radiation. [Preview Abstract] |
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K1.00086: Bang-Bang shortcut to adiabaticity in trapped ion quantum simulators Bryce Yoshimura, Shankar Balasubramanian, Shuyang Han, James Freericks An experimental simulation can prepare a nontrivial ground state via an adiabatic process, however due to experimental constraints this process becomes more and more difficult as the number of ions increase. Instead, we model the bang-bang optimization protocol as a shortcut to adiabaticity in the ground-state preparation of an ion-trap-based quantum simulator. This well known technique in the quantum control community is simple to implement and can be applied without prior knowledge of the Hamiltonian. We apply the bang-bang optimization protocol to the transverse-field Ising model as simulated in a linear Paul trap. We compare our results to a transverse magnetic field that exponential decays and the locally adiabatic approach. The bang-bang protocol produces a significantly higher ground-state probability than the exponential ramp. Although the bang-bang protocol produces a somewhat lower ground-state probability than the locally adiabatic approach, the implementation of the bang-bang protocol is far more simple than the locally adiabatic approach. [Preview Abstract] |
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K1.00087: Towards Non-Equilibrium Dynamics with Trapped Ions Ariel Silbert, Sierra Jubin, Charlie Doret Atomic systems are superbly suited to the study of non-equilibrium dynamics. These systems' exquisite isolation from environmental perturbations leads to long relaxation times that enable exploration of far-from-equilibrium phenomena. One example of particular relevance to experiments in trapped ion quantum information processing, metrology, and precision spectroscopy is the approach to thermal equilibrium of sympathetically cooled linear ion chains. Suitable manipulation of experimental parameters permits exploration of the quantum-to-classical crossover between ballistic transport and diffusive, Fourier's Law conduction, a topic of interest not only to the trapped ion community but also for the development of microelectronic devices and other nanoscale structures. We present progress towards trapping chains of multiple co-trapped calcium isotopes geared towards measuring thermal equilibration and discuss plans for future experiments in non-equilibrium statistical mechanics. [Preview Abstract] |
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K1.00088: Progress in sorting individual atoms in 3D Tsung-Yao Wu, Aishwarya Kumar, Yang Wang, David Weiss An exactly unity filled optical lattice is a desirable initial state for a neutral atom quantum computer. We have previously proposed an efficient way to compact a partially filled lattice into a perfectly filled one, [Phys. Rev. A \textbf{70}, 040302(R) (2004)], by combining site-resolved imaging, site-selective qubit rotations and state-selective motion steps. We have previously demonstrated site-resolved imaging and site-selective rotations in our system of cesium atoms in a 40{\%} filled 5x5x5 3D lattice. [Phys. Rev. Lett. \textbf{115}, 043003 (2015)] We have now demonstrated the final element, state-selective motion steps in 3D produced by rotating the polarizations of one of the lattice beams in each pair. We will present our progress in putting all the elements together to reach perfect unity filling. [Preview Abstract] |
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K1.00089: Toward Visible-Wavelength Multi-Species Trapped-Ion Quantum Logic Colin Bruzewicz, Robert McConnell, William Loh, Jeremy Sage, John Chiaverini Large-scale quantum information processing and quantum networking using trapped ions will likely require multiple atomic species to allow for sympathetic cooling of ion vibrational modes, quantum state measurement without decoherence of unmeasured qubits, and interfacing with flying qubits. Inter-species quantum logic and quantum state transfer are key components of these tasks, particularly in the cases of quantum-error-correction syndrome extraction or remote entanglement generation using sympathetic ions. Multi-species logic and manipulation in a large processor will require control light of several wavelengths delivered to many ion-trap array sites in parallel, a challenge at short wavelengths. We report on progress toward sympathetic cooling and intra- and inter-species logic using Sr$^{+}$ and Ca$^{+}$ ions in surface-electrode trap arrays. These species admit optical control fields that can be routed using photonic waveguides straightforwardly integrated into the trap-array structure as their relevant transitions are accessible using visible and near-infra-red light. [Preview Abstract] |
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K1.00090: Integrated Technologies for Large-Scale Trapped-Ion Quantum Information Processing C. Sorace-Agaskar, S. Bramhavar, D. Kharas, K.K. Mehta, W. Loh, R. Panock, C.D. Bruzewicz, R. McConnell, R.J. Ram, J.M. Sage, J. Chiaverini Atomic ions trapped and controlled using electromagnetic fields hold great promise for practical quantum information processing due to their inherent coherence properties and controllability. However, to realize this promise, the ability to maintain and manipulate large-scale systems is required. We present progress toward the development of, and proof-of-principle demonstrations and characterization of, several technologies that can be integrated with ion-trap arrays on-chip to enable such scaling to practically useful sizes. Of particular use are integrated photonic elements for routing and focusing light throughout a chip without the need for free-space optics. The integration of CMOS electronics and photo-detectors for on-chip control and readout, and methods for monolithic fabrication and wafer-scale integration to incorporate these capabilities into tile-able 2D ion-trap array cells, are also explored. [Preview Abstract] |
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K1.00091: Quantum information experiments with 2D arrays of hundreds of trapped ions Kevin Gilmore, Justin Bohnet, Brian Sawyer, Joseph Britton, Michael Wall, Michael Foss-Feig, Ana Maria Rey, John Bollinger We summarize recent experimental work with 2D arrays of hundreds of trapped $^9$Be$^+$ ions stored in a Penning trap. Penning traps utilize static magnetic and electric fields to confine ions, and enable the trapping and laser cooling of ion crystals larger than typically possible in RF ion traps. We work with single-plane ion crystals where the ions form a triangular lattice through minimization of their Coulomb potential energy. The crystals rotate, and we present numerical studies that determine optimal operating parameters for producing low temperature, stable 2-dimensional crystals with Doppler laser cooling and a rotating wall potential. Our qubit is the electron spin-flip transition in the ground state of $^9$Be$^+$ and is sensitive to magnetic field fluctuations. Through mitigation of part-per-billion, vibration-induced magnetic field fluctuations we demonstrate T2 coherence times longer than 50 ms. We engineer long-range Ising interactions with spin-dependent optical dipole forces, and summarize recent measurements that characterize the entanglement generated through single-axis twisting. Supported by: JILA-NSF-PFC-1125844, NSF-PHY-1521080, ARO, AFOSR, AFOSR-MURI. [Preview Abstract] |
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K1.00092: QUANTUM NETWORKS AND PROTOCOLS |
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K1.00093: Entropy of entanglement in continuous frequency space of the biphoton state from multiplexed cold atomic ensembles Hsiang-Hua Jen We consider a scheme of multiplexed cold atomic ensembles that generate a frequency-entangled biphoton state with controllable entropy of entanglement. The biphoton state consists of a telecommunication photon (signal) immediately followed by an infrared one (idler) via four-wave mixing with two classical pump fields. Multiplexing the atomic ensembles with frequency and phase-shifted signal and idler emissions, we can manipulate and control the spectral property of the biphoton state. Mapping out the entropy of entanglement in the scheme provides the optimal configuration for entanglement resources. This paves the way for efficient long-distance quantum communication and for potentially useful multimode structures in quantum information processing. [Preview Abstract] |
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K1.00094: Ultra-low-loss optical fiber cavities for applications in quantum information processing Manuel Uphoff, Manuel Brekenfeld, Dominik Niemietz, Stephan Ritter, Gerhard Rempe Single atoms strongly coupled to optical cavities are well suited as light-matter interfaces at the single photon level. The strength of the coupling is inversely proportional to the square root of the mode volume of the cavity, which depends on the radius of curvature of the mirrors. We report on the fabrication of near-spherical surfaces with small radii of curvature on the end facets of optical fibers using a CO$_2$ laser at 9.3 $\mu$m wavelength. The surfaces are coated with a commercial, highly reflective, dielectric coating. Cavities built from two of these fibers show a finesse of up to 190000. Due to the small radii of curvature and the high finesse of these cavities, deviations from the paraxial approximation become relevant. This results in a frequency splitting of polarization eigenmodes depending on the eccentricity of the mirrors. Our analytic model that explains this effect is in excellent agreement with our measurements. This allows for the control of the frequency splitting by the geometry of the mirror surfaces. Our results confirm the great prospects of laser-machined cavities for experiments in quantum information processing. The possibility of implementing a quantum repeater node based on our cavity technologies will also be discussed. [Preview Abstract] |
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K1.00095: Comparison between Two Practical Methods of Light Source Monitoring in Quantum Key Distribution Gan Wang, Ziyang Chen, Bingjie Xu, Zhengyu Li, Xiang Peng, Hong Guo The practical security of a quantum key distribution (QKD) is a critical issue due to the loopholes opened by the imperfections of practical devices. The untrusted source problem is a fundamental issue that exists in almost every protocol, including the loss-tolerant protocol and the measurement-device-independent protocol. Two practical light source monitoring methods were proposed, i.e., two-threshold detector scheme and photon-number-resolving (PNR) detector scheme. In this work, we test the fluctuation level of different gain-switched pulsed lasers, i.e., the ratio between the standard deviation and the mean of the pulse energy (noted as $\gamma )$ changes from 1{\%} to 7{\%}. Moreover, we propose an improved practical PNR detector scheme, and discuss in what circumstances one should use which light source monitoring method, i.e., generally speaking when the fluctuation is large the PNR detector method performs better. This provides an instruction of selecting proper monitoring module for different practical systems. [Preview Abstract] |
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K1.00096: Long-distance quantum networks using ultra-cold atoms Neal Solmeyer, Xiao Li, Qudsia Quraishi The generation of entanglement between distantly located quantum memories via frequency converted single photons could enable many applications in quantum networking, including quantum teleportation, distributed quantum computing and potentially distributed precision timing. A quantum network with three or more nodes has yet to be demonstrated and moreover hybrid networks leverage advantages of different platforms. With an existing memory at the Army Research Laboratory (ARL), based on weak Raman scattering in a Rb magneto-optical trap, we are building a second node at the Joint Quantum Institute (JQI), connected to ARL by a 13 km optical fiber. The second node will be a higher photon-rate node based on Rydberg excitations of a Rb ensemble in an optical dipole trap (N. Solmeyer et. al., arXiv:1511.00025) and the first node will be upgraded to a Rydberg system soon. In the near term, we plan to generate entanglement between the second and a third node, based on a similar experimental setup, 100 m away at the JQI. For the ARL-JQI link we are presently working on quantum frequency conversion from IR photons to telecom wavelengths. Separately, we are pursuing frequency conversion from 493 nm photons to 780 nm to be used in a hybrid quantum network between ions and neutral atoms. [Preview Abstract] |
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K1.00097: Memory assisted free space quantum communication. Bertus Jordaan, Mehdi Namazi, Connor Goham, Reihaneh Shahrokhshahi, Giuseppe Vallone, Paolo Villoresi, Eden Figueroa A quantum memory assisted node between different quantum channels has the capability to modify and synchronize its output, allowing for easy connectivity, and advanced cryptography protocols. We present the experimental progress towards the storage of single photon level pulses carrying random polarization qubits into a dual rail room temperature quantum memory (RTQM) after $\sim $ 20m of free space propagation. The RTQM coherently stores the input pulses through electromagnetically induced transparency (EIT) of a warm $^{\mathrm{87}}$Rb vapor and filters the output by polarization elements and temperature-controlled etalon resonators. This allows the characterization of error rates for each polarization basis and the testing of the synchronization ability of the quantum memory. This work presents a steppingstone towards quantum key distribution and quantum repeater networks. [Preview Abstract] |
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K1.00098: Hybrid ion chains inside an optical cavity Zichao Zhou, James Siverns, Qudsia Quraishi Trapped ions remain a leading candidate for the implementation of large-scale quantum networks. These networks require nodes that can store and process quantum information as well as communicate with each other though photonic flying qubits. We propose to use hybrid ion chains of barium, for communication, and ytterbium, for quantum information processing. We report on progress in setting up a hybrid ion chain in a versatile four-blade trap using high numerical aperture collection optics. Although the visible photons produced from barium ions are more favorable as they are not suitable for long distance fiber communication. With this in mind, we intend to implement frequency conversion to overcome this issue. Also, with the view toward increasing the flying-qubit production rate, we propose a cavity-based system to enhance interactions between the ions and photons. The cavity axis is to be placed along the axial direction of the trap allowing a chain of multiple ions to interact with the cavity at the same time. With this configuration the atom-photon coupling strength can be improved by sqrt(N), where N is the number of ions. Experiments will focus on exploring the dynamics of hybrid ion chain, dual species quantum information processing, two-colour entanglement and phase gates assisted by the ion-cavity coupling are to be explored. [Preview Abstract] |
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K1.00099: COLD ATOMS, MOLECULES AND PLASMAS |
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K1.00100: Renormalization shielding effect on the electron-impact ionization process in dense partially ionized plasmas Young-Dae Jung The influence of renormalization shielding on the electron-impact ionization process is investigated in dense partially ionized plasmas. The effective projectile-target interaction Hamiltonian and the semiclassical trajectory method are employed to obtain the transition amplitude as well as the ionization probability as functions of the impact parameter, the collision energy, and the renormalization parameter. It is found that the renormalization shielding effect suppresses the transition amplitude for the electron-impact ionization process in dense partially ionized plasmas. It is also found that the renormalization effect suppresses the differential ionization cross section in the peak impact parameter region. In addition, it is found that the influence of renormalization shielding on the ionization cross section decreases with an increase of the relative collision energy. The variations of the renormalization shielding effects on the electron-impact ionization cross section are also discussed. [Preview Abstract] |
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K1.00101: Non-thermal Dupree diffusivity and shielding effects on atomic collisions in Lorentzian turbulent plasmas Myoung-Jae Lee, Young-Dae Jung The influence of non-thermal Dupree turbulence and the plasma shielding on the electron-ion collision is investigated in Lorentzian turbulent plasmas. The second-order eikonal analysis and the effective interaction potential including the Lorentzian far-field term are employed to obtain the eikonal scattering phase shift and the eikonal collision cross section as functions of the diffusion coefficient, impact parameter, collision energy, Debye length and spectral index of the astrophysical Lorentzian plasma. It is shown that the non-thermal effect suppresses the eikonal scattering phase shift. However, it enhances the eikonal collision cross section in astrophysical non-thermal turbulent plasmas. The effect of non-thermal turbulence on the eikonal atomic collision cross section is weakened with increasing collision energy. The variation of the atomic cross section due to the non-thermal Dupree turbulence is also discussed. [Preview Abstract] |
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K1.00102: Cryogenic Linear Ion Trap for Large-Scale Quantum Simulations Guido Pagano, Paul Hess, Harvey Kaplan, Eric Birckelbaw, Micah Hernanez, Aaron Lee, Jake Smith, Jiehang Zhang, Christopher Monroe Ions confined in RF Paul traps are a useful tool for quantum simulation of long-range spin-spin interaction models. As the system size increases, classical simulation methods become incapable of modeling the exponentially growing Hilbert space, necessitating quantum simulation for precise predictions. Current experiments are limited to less than 30 qubits due to collisions with background gas that regularly destroys the ion crystal. We present progress toward the construction of a cryogenic ion trap apparatus, which uses differential cryopumping to reduce vacuum pressure to a level where collisions do not occur. This should allow robust trapping of about 100 ions/qubits in a single chain with long lifetimes. Such a long chain will provide a platform to investigate simultaneously cooling of various vibrational modes and will enable quantum simulations that outperform their classical counterpart. Our apparatus will provide a powerful test-bed to investigate a large variety of Hamiltonians, including spin 1 and spin 1/2 systems with Ising or XY interactions. [Preview Abstract] |
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K1.00103: Efimov studies of an ultracold cloud of $^{39}$K atoms in microgravity: Numerical modelling and experimental design Maren Mossman, Peter Engels, Jose D'Incao, Deborah Jin, Eric Cornell Ultracold atomic gases at or near quantum degeneracy provide a powerful tool for the investigation of few-body physics. A particularly intriguing few-body phenomenon is the existence of Efimov trimer states at large interatomic scattering lengths. These trimers are predicted to exhibit universal geometric scaling relations, but in practice the situation is complicated e.g. by finite-range and finite-temperature effects. While some Efimov trimers have already been experimentally observed by several groups in ground-based experiments, NASA’s Cold Atom Laboratory (CAL) onboard the ISS will greatly enhance the experimentally accessible regimes by providing ultracold clouds of $^{39}$K atoms with temperatures at or below 1~nK, low densities, and long observation times. We present results of numerical modelling and simulations that lay out Efimov experiments capitalizing on the particular strengths of CAL. [Preview Abstract] |
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K1.00104: Degenerate Bose-Fermi mixtures of rubidium and ytterbium Jiraphat Tiamsuphat, Varun Vaidya, Steven Rolston, James Porto We report the realization of a quantum degenerate mixture of bosonic $^{\mathrm{87}}$Rb and fermionic $^{\mathrm{171}}$Yb atoms in a hybrid optical dipole trap with a tunable, species-dependent trapping potential. $^{\mathrm{87}}$Rb is shown to be a viable refrigerant for the non-interacting $^{\mathrm{171}}$Yb atoms, cooling up to 2.4$\times $10$^{\mathrm{5}}$ Yb atoms to a temperature of T/T$_{\mathrm{F}}=$0.16(2) while simultaneously forming a $^{\mathrm{87}}$Rb Bose-Einstein condensate of 3.5$\times $10$^{\mathrm{5}}$ atoms. Furthermore we demonstrate our ability to independently tailor the potentials for each species, which paves the way for studying impurities immersed in a Bose gas. [Preview Abstract] |
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K1.00105: Characterization of Launched Atoms Leading to Observations of Cold Rydberg Atoms in the Field of a Charged Wire Anne Goodsell, Emma Erwin We are preparing to accelerate and decelerate cold Rydberg atoms in the field of a charged wire. We cool and launch rubidium atoms and observe the distribution of atoms up to 16 mm above the trap location. We report a transverse speed less than 1/10 of the longitudinal launch speed. For Rydberg-atom observations, the cold cloud will be illuminated in mid-flight to promote atoms into the desired Rydberg state (e.g. $n$ = 33-40). With a three-photon sequence we will access $nf$ states and the nearby manifolds with linear Stark shifts. We observed the first two steps of this process using counter-propagating beams of 780 nm and 776 nm in a Rb cell. For cold Rydberg atoms, we will compare states that are strongly accelerated to states that are strongly decelerated by the field around the charged-wire target. We calculate that the displacement during the Rydberg lifetime (e.g. $n$ = 35, $\tau$ = 30 $\mu$s) will be 200-300 $\mu$m farther for extreme attracted states. Detection will occur by spatially-dependent field ionization. Observations of atoms with zero angular momentum around the wire can be extended to atoms with nonzero angular momentum and also to study dynamics of Rydberg atoms with a quadratic Stark shift, building on previous work with ground-state atoms. [Preview Abstract] |
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K1.00106: Experiments in Planar Multipole Ion Traps Rob Clark, Timothy Burke, Dylan Green We present the design and demonstration of multipole ion traps based on concentric rings. We have developed both surface-electrode and layered planar trap designs which enable one to null the quadratic term in the electric potential to a high degree. Experiments demonstrating frequency upconversion of an applied signal demonstrate the nonlinear dynamics present in the trap. Applications include quantum chaos, ultracold chemistry, and, potentially, mass spectrometry. [Preview Abstract] |
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K1.00107: Study of Cold Potassium Atom - Calcium Ion Reactions Kisra Egodapitiya, Shu Gang, Robert Clark, Kenneth Brown We report on our progress towards constructing a hybrid system for studying reactions between cold Potassium (K) atoms and cold Calcium (Ca$^{\mathrm{+}})^{\mathrm{\thinspace }}$ions. Ca$^{\mathrm{+\thinspace }}$ions will be trapped and Doppler-cooled inside a linear quadrupole ion trap. Cold K atoms will be created inside a magneto optical trap, such that the ion and the atoms are in an overlapping volume. Trapping and re-pumping beams for the Potassium MOT are derived from the same laser with wavelength 766 nm using two acousto optic modulators. The reaction products will be detected using a time-of- flight mass spectrometer that is designed to detect radially ejected ions. The main objective of this experiment is to study the rate coefficients, and identification of reaction channels between cold K atoms and Ca$^{\mathrm{+\thinspace }}$ions. Subsequently this setup will be used to study reactions between cold K atoms and sympathetically cooled molecular ions such as CaO$^{\mathrm{+}}$, and to study internal state quenching of molecular ions. [Preview Abstract] |
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K1.00108: BOSE-EINSTEIN CONDENSATES |
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K1.00109: ABSTRACT WITHDRAWN |
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K1.00110: Quench dynamics of a Bose gas under synthetic spin-orbit coupling Tian-Shu Deng, Wei Zhang, Wei Yi, Guang-Can Guo We study the quench dynamics of a Bose-Einstein condensate under a Raman-asssited synthetic spin-orbit coupling. To model the dynamical process, we adopt a self-consistent Bogoliubov approach, which is equivalent to applying the time-dependent Bogoliubov-de-Gennes equations. We investigate the dynamics of the condensate fraction as well as the momentum distribution of the Bose gas following a sudden change of system parameters. Typically, the system evolves into a steady state in the long-time limit, which features a stationary condensate fraction and an oscillating momentum distribution. The condensate fraction of the steady state depends on the quench parameter. We investigate how different quench parameters such as the inter- and intra-species interactions and the spin-orbit-coupling parameters affect the condensate fraction in the steady state. Furthermore, we find that the oscillatory momentum distribution in the long-time limit can be described by a generalized Gibbs ensemble with two branches of momentum-dependent Gibbs temperatures. Our study is relevant to the experimental investigation of dynamical processes in a spin-orbit coupled Bose-Einstein condensate. [Preview Abstract] |
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K1.00111: Measurement of the mobility edge for 3D Anderson localization Giulia Semeghini, Manuele Landini, Patricia Castilho, Sanjukta Roy, Giacomo Spagnolli, Andreas Trenkwalder, Marco Fattori, Massimo Inguscio, Giovanni Modugno An outstanding problem of Anderson localization (AL) in 3D systems is the determination of the mobility edge, i.e. the energy threshold that separates localized and extended states. In our experiment we use a Bose-Einstein condensate of $^{39}$K atoms and study its transport properties in a disordered optical potential. By tuning the inter-particle interactions to zero via magnetic Feshbach resonances, we study the single-particle phenomenon of AL. A novel technique to measure and control the atomic energy distribution allows us to measure for the first time the position of the localization threshold as a function of the disorder strength [G. Semeghini et al., \textit{Nature Physics} \textbf {11}, 554-559 (2015)]. We also study how the addition of finite repulsive or attractive interactions breaks the localized regime and triggers subdiffusive expansion of the atoms. In the future, similar experiments might also probe the existence of many-body localization in 3D. [Preview Abstract] |
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K1.00112: Non-equilibrium dynamics in driven Bose-Einstein condensates Lei Feng, Logan W. Clark, Li-Chung Ha, Cheng Chin We report recent progress on the study of non-equilibrium dynamics in Bose-Einstein condensates using the shaken optical lattice or optically controlled Feshbach resonances. In the shaken lattice at sufficient shaking amplitude we observe a quantum phase transition from ordinary condensates to pseudo-spinor 1/2 condensates containing discrete domains with effective ferromagnetic interactions. We study the temporal and spatial Kibble-Zurek scaling laws for the dependence of this domain structure on the quench rate across the transition. Furthermore, we observe long-range density correlations within the ferromagnetic condensate. With optically controlled Feshbach resonances we demonstrate control of the interaction strength between atoms at timescales as short as ten nanoseconds and length scales smaller than the condensate. We find that making interactions attractive within only one region of the gas induces localized collapse of the condensate. [Preview Abstract] |
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K1.00113: Progress toward observation of quantum interference of currents in an Atom SQUID Changhyun Ryu, E. Carlo Samson, Malcolm Boshier Quantum interference of currents was first observed in a superconducting loop with two Josephson junctions, leading to the name “SQUID” for this device. This interference effect has been used to develop extremely sensitive magnetometers. The Atom SQUID, an analogous device based on ultracold atoms, has been developed recently to study SQUID physics in a device offering a better understanding of the underlying microscopic dynamics. Although many exciting experiments have been done with Atom SQUIDs, the quantum interference of currents has not yet been observed. In analogy with the SQUID magnetometer, it should be possible to use the quantum interference effect in an Atom SQUID to measure rotation, which may lead to the development of a sensitive gyroscope. In a previous experiment, we showed Josephson effects with an atom SQUID by observing the change from the dc Josephson regime to the ac Josephson regime by measurement of the critical atom number for this transition. Quantum interference should cause this critical atom number to vary with rotation rate. We have simulated this system with the Gross-Pitaevski Equation and found the expected oscillatory change of the critical atom number. We will present this simulation result and report the current status of our experiment to [Preview Abstract] |
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K1.00114: Recent experiments with ring Bose-Einstein condensates S. Eckel, A. Kumar, N.W. Anderson, G.K. Campbell Here, we present three recent results of our experiments with ring-shaped $^{23}$Na Bose-Einstein condensates. First, we present results of the effect of temperature on the decay of persistent currents in the presence of a local, stationary perturbation, or weak link. When the weak link rotates, it can drive transitions between quantized persistent current states in the ring, that form hysteresis loops whose size depends strongly on temperature. We find that that our data does not fit with a simple model of thermal activation. Second, we present a new method to measure the quantized persistent current state of the ring in a minimally-destructive way. This technique uses phonons as probes of the background flow through the Doppler effect. Finally, we present a set of experiments designed to reproduce the horizon problem in the early universe. Supersonic expansion of the ring creates causally-disconnected regions of BEC whose phase evolves at different rates. When the expansion stops and these regions are allowed to recombine, they form topological excitations. These excitations can be predicted using a simple theory that shows excellent agreement with the data. [Preview Abstract] |
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K1.00115: Realization of an Er 2D MOT for a Na+Er mixture experiment Neil Anderson, Swarnav Banik, Monica Gutierrez, Avinash Kumar, Stephen Eckel, Gretchen Campbell We have realized a dual-species sodium and erbium 2D MOT. This compact source allows us to rapidly switch between loading either species into 3D MOTs in a main chamber. We have characterized the flux from this source and the resulting loading rates into the 3D MOTs . This new source opens possibilities of studying lanthanide-alkali collisions and Feshbach spectra, possibly opening new pathways to realizing interesting quantum many body systems. [Preview Abstract] |
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K1.00116: Studies of the Efimov Effect in $^7$Li D. Luo, J. H. V. Nguyen, R. G. Hulet Ultracold atomic gases provide an ideal environment to study few body physics in the universal regime. Passive techniques, such as monitoring loss of the atomic sample while varying the hold time allows us to explore properties such as the scaling behavior of Efimov trimers. In our experiment, we explore how the Efimov states are affected by non-zero temperature. We measure the three-body loss rate for a $^7$Li atom gas at different scattering lengths and extract the location and width of an Efimov recombination minimum for various temperatures. Alternatively, we may perform more active experiments such as creating dimers using RF-field modulation as a probe of molecular binding energies. We use RF-association to form Feshbach dimers and Efimov trimers, and find a strong enhancement of the dimer formation rate at the atom-dimer resonance, which could be explained by an avalanche mechanism. In the past the enhancement in the three-body recombination rate at the same location had also been observed\footnote{S.E. Pollack, D. Dries, \& R.G. Hulet, Science, 326, 1683 (2009)}, and attributed to the avalanche. We explore the link between these findings with a side-by-side comparison of the dimer-formation rate and the three-body loss rate. [Preview Abstract] |
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K1.00117: Bose polarons: Dynamical decay and RF signatures John Corson, John Bohn Interactions of a single impurity with a quantum many-body environment are known to alter the character of the impurity, thereby forming a ``quasiparticle''. The condensed matter tradition often identifies quasiparticles as poles of a Green function in the complex plane, a notion whose sophistication sometimes obscures the underlying physics. The problem of a single quantum impurity in a Bose condensate, or Bose polaron, is an illustrative example where the meaning of the impurity Green function, and hence the quasiparticle itself, becomes especially transparent. Using direct diagonalization in a truncated Hilbert space, we examine the dynamical evolution and quasiparticle decay of the repulsive Bose polaron. This approach also allows us to simulate RF spectroscopy across a Feshbach resonance and outside the linear regime, as well as account for motional and thermal effects in a harmonic trap. [Preview Abstract] |
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K1.00118: Theoretical studies of Efimov states and dynamics in quenched unitary Bose gases Jose P D'Incao, Jia Wang, Cathy Klauss, Xin Xie, Deborah S Jin, Eric A Cornell We study the three-body physics relevant for quenched unitary Bose gas experiments [1] in order to determine the role of Efimov states on the dynamics of the atomic and molecular populations. Initially, the interatomic interactions are quenched from weak to infinitely strong. After some dwelling time, the interactions are slowly ramped back to some final weak value where a mixture of atoms, dimers, and Efimov trimers can exist and whose populations depend strongly on the dwell time. We model the problem using the adiabatic hyperspherical representation for three atoms assuming a local interaction model in which a harmonic potential mimics finite density effects. We also developed a novel Slow Variable Discretization (SVD) method to accurately determine the time evolution of the system, overcoming the difficulty of implementing diabatization schemes to minimize unwanted effects due to sharp-avoid crossings. This method also allows us to account for three-body losses during the time evolution. This research is supported by the U. S. National Science Foundation. [1] P. Makotyn, C. E. Klauss, D. L. Goldberger, E. A. Cornell, and D. S. Jin, Nat. Phys. 10, 116119 (2014). [Preview Abstract] |
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K1.00119: Progress toward studies of bubble-geometry Bose-Einstein condensates in microgravity with a ground-based prototype of NASA CAL Nathan Lundblad, Thomas Jarvis, Daniel Paseltiner, Courtney Lannert We have proposed using NASA's Cold Atom Laboratory (CAL, launching to the International Space Station in 2017) to generate bubble-geometry Bose-Einstein condensates through radiofrequency dressing of an atom-chip magnetic trap. This geometry has not been truly realized terrestrially due to the perturbing influence of gravity, making it an ideal candidate for microgravity investigation aboard CAL. We report progress in the construction of a functional prototype of the orbital BEC apparatus: a compact atom-chip machine loaded by a 2D+MOT source, conventional 3D MOT, quadrupole trap, and transfer coil. We also present preliminary modeling of the dressed trap uniformity, which will crucially inform the geometric closure of the BEC shell surface as atom number, bubble radius, and bubble aspect ratio are varied. Finally, we discuss plans for experimental sequences to be run aboard CAL guided by intuition from ground-based prototype operation. [Preview Abstract] |
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K1.00120: Simple Single-Shot Field Reconstruction on the 10 micro-Gauss Level Arturo Pazmino, Ludwig Krinner, Michael Stewart, Dominik Schneble Accurate knowledge of the magnetic field is imperative in many physical systems for the determination of their energies and timescales. In ultracold atomic clouds, precise control of magnetic-field induced Zeeman splittings of hyperfine transitions can be challenging due to spatially constricted geometries subject to slowly drifting, spatially inhomogeneous fields. Here we present a technical note on the precise reconstruction of magnetic fields, on the $\sim 10\mu$G level, at the position of a trapped atomic cloud, using only atomic population to determine the magnetic field in a single-shot measurement. [Preview Abstract] |
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K1.00121: Progress Towards a Quantum Degenerate Mixture with Extreme Mass Imbalance B. J. DeSalvo, Jacob Johansen, Cheng Chin We report experimental progress towards a quantum degenerate Bose-Fermi mixture of $^{133}$Cs and $^{6}$Li . Beyond providing the largest mass imbalance of any bi-alkali mixture, this system exhibits multiple interspecies Feshbach resonances allowing wide tuning of the interaction strength and Efimov resonances potentially inducing three-body interactions. The use of a dual-color optical dipole trap in our experiment overcomes the large differential gravitational sag due to the mass imbalance and facilitates mixing the species nano-Kelvin temperatures allowing precision studies of interspecies interactions. Turning from few-body physics to many-body, we will present our efforts to reach simultaneous quantum degeneracy as well as discuss prospects of high resolution imaging of both species. [Preview Abstract] |
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K1.00122: DEGENERATE FERMI GASES |
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K1.00123: Progress towards a rapid production of a two-species mixture of quantum degenerate Bose and Fermi gases Haoxiang Yang, Liyuan Qiu, Tian Tian, XiangHao Mu, Yingmei Liu, Luming Duan We present the design and construction of a novel apparatus to rapidly generate a mixture of quantum degenerate $^{\mathrm{6}}$Li Fermi and $^{\mathrm{23}}$Na Bose gases. Sodium and lithium atoms are collected in a two-species magnetic-optical trap and cooled to around 40 microKelvin through a three-step polarization gradient cooling process. The cold dense atomic clouds are then transferred to a tightly-focused crossed optical trap. Sodium Bose-Einstein condensates are generated from evaporation and rethermalization via a simple all-optical approach, while a quantum degenerate $^{\mathrm{6}}$Li Fermi gas is produced through interspecies sympathetic cooling. We also discuss how to optimize the efficiency of sympathetic cooling in the $^{\mathrm{23}}$Na-$^{\mathrm{6}}$Li system. [Preview Abstract] |
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K1.00124: Towards quantum simulation with two-electron $^{173}Yb$ fermions in an optical lattice Bo Song, Yueyang Zou, Chengdong He, Elnur Haciyev, Geyue Cai, Wing Kin Chan, Wei Huang, Gyu-Boong Jo Recent development of cooling and manipulating Ytterbium atoms opens a new avenue to investigate unprecedented atomic systems with SU(N) spin symmetry and orbital degrees of freedom. The available metastable states and narrow-line optical transitions of Ytterbium atoms allow for the versatile control of the system. Here, we first describe our apparatus for producing ultracold Ytterbium-173 quantum gases in an optical lattice. A gas of $3\times 10^4$ Ytterbium-173 atoms is routinely produced at $T/T_F \sim 0.3$, and loaded into an optical lattice potential. Then we report our recent progress on the spin orbital (SO) coupling interaction realized in optical lattice. As a novel quantum simulator, cold Ytterbium atoms with SO coupling provide a platform to explore the intriguing topological physics. [Preview Abstract] |
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K1.00125: Three-component Fulde-Ferrell super uids in a two- dimensional Fermi gas with spin-orbit coupling Fang Qin, Fan Wu, Wei Zhang, Wei Yi, Guang-Can Guo We investigate the pairing physics of a three-component spin-orbit coupled (SOC) Fermi gas in two spatial dimensions. The three atomic hyperfine states of the system are coupled by the recently realized synthetic SOC, which mixes different hyperfine states into helicity branches in a momentum-dependent manner. As a consequence, the interplay of SOC and the hyperfine-state dependent interactions leads to the emergence of Fulde-Ferrell (FF) pairing states with finite center-of-mass (COM) momenta even in the absence of the Fermi-surface asymmetry that is usually mandatory to stabilize an SOC-induced FF state. We show that, for different combinations of spin-dependent interactions, the ground state of the system can either be the conventional BCS pairing state with zero COM momentum or be the FF pairing states. Of particular interest here is the existence of a three-component FF pairing state in which every two out of the three components form FF pairing. We map out the phase diagram of the system and characterize the properties of the three-component FF state, such as the order parameters, the gapless contours and the momentum distributions. Based on these results, we discuss possible experimental detection schemes for the interesting pairing states in the system. [Preview Abstract] |
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K1.00126: Polarized Ytterbium with orbital Feshbach resonance Su Wang, Zhengwei Zhou Orbital Feshbash resonance make progress for Feshbach resonance on alkaline earth atoms. It urge us to control the interaction of alkaline earth atoms using magnetic field without optical heating. In this work, we research the polarized Ytterbium gases with orbital Feshbach resonance. The gases have normal, superfuild, breach pair double, breach pair open phases in BEC region. It only have normal, and superfuild phases in BCS region. We also plot the particle number fixed phase diagrams. The gases have the phase separation region and normal phase region. [Preview Abstract] |
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K1.00127: Feshbach enhanced $s$-wave scattering of fermions: direct observation with optimized absorption imaging Dina Genkina, Lauren Aycock, Benjamin Stuhl, Hsin-I Lu, Ross Williams, Ian Spielman We directly measured the normalized~$s$-wave scattering cross-section of ultracold~$^{\mathrm{40}}$K atoms across a magnetic-field Feshbach resonance by colliding pairs of degenerate Fermi gases (DFGs) and imaging the scattered atoms. We extracted the scattered fraction for a range of bias magnetic fields, and measured the resonance location to be~$B$~$_{\mathrm{0}}$~$=$~20.206(15) mT with width $\Delta $~$=$~1.0(5) mT. To optimize the signal-to-noise ratio (SNR) of atom number in scattering images, we developed techniques to interpret absorption images in a regime where recoil induced detuning corrections are significant. These imaging techniques are generally applicable to experiments with lighter alkalis that would benefit from maximizing SNR on atom number counting at the expense of spatial imaging resolution. [Preview Abstract] |
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K1.00128: Strongly interacting ultracold quantum gases of fermionic ytterbium-173 Moritz H\"ofer, Luis Riegger, Chrisitian Hofrichter, Diogo Rio Fernandes, Simon F\"olling, Immanuel Bloch In contrast to the more common alkali atoms, alkaline-earth-like ytterbium features a strong decoupling between the nuclear and the electronic spin degree of freedom and possesses a metastable excited state. The decoupling gives rise to an extended SU($N$)-symmetry with $N\leq6$ for ytterbium-173. This enables us to study the SU($N$)-symmetric Fermi-Hubbard model in a three-dimensional optical lattice. We prepare a low-temperature SU($N$)-symmetric Mott insulator and characterize the Mott crossover. High local resolution allows us to extract the equation of state for a large range of interactions. In a second experiment, we investigate the scattering properties between the $^1$S$_0$ ground state and $^3$P$_0$ metastable state, where the interactions cannot be tuned with standard magnetic Feshbach resonances as in alkalis. We report on the discovery of a new orbital interaction-induced Feshbach resonance in ytterbium-173, permitting tunable interactions between these two states. [Preview Abstract] |
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K1.00129: Mapping out spin and particle conductances of a single-mode channel with tunable interactions Martin Lebrat, Sebastian Krinner, Charles Grenier, Dominik Husmann, Samuel H\"ausler, Shuta Nakajima, Jean-Philippe Brantut, Tilman Esslinger We study particle and spin transport in a single-mode quantum point contact, shaped by light potentials onto a charge neutral, quantum degenerate gas of $^6$Li fermions with tunable interactions. The spin and particle conductances are measured as a function of chemical potential or confinement, covering weak attraction, where quantized conductance is observed, to the strongly interacting superfluid regime. Spin conductance exhibits a broad maximum when varying the chemical potential at moderate interactions, which signals the emergence of superfluidity. In contrast, the particle conductance is unexpectedly enhanced even before the gas is expected to turn into a superfluid: it shows conductance plateaus at non-universal values continuously increasing from 1/h to 4/h, as the interaction strength is increased from weak to intermediate. For strong interactions, the particle conductance plateaus disappear and the spin conductance gets suppressed, confirming the spin-insulating character of a superfluid. Our observations document the breakdown of universal conductance quantization as many-body correlations appear. This anomalous quantization is incompatible with a Fermi liquid description, shedding new light on the nature of the strongly attractive Fermi gas in the normal phase. [Preview Abstract] |
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K1.00130: Progress towards alkaline-earth fermions in a 1D uniform potential Benjamin J. Reschovsky, Daniel S. Barker, Neal C. Pisenti, Gretchen K. Campbell We present our progress towards realizing a 1D uniform "box trap" potential for degenerate fermionic alkaline-earth atoms in order to study highly symmetric SU(N) spin models. Our experiment first generates a degenerate gas of $^{87}$Sr atoms via evaporation in a crossed dipole trap. Next, we plan to load the atoms into an array of 1D box traps formed by a red-detuned 2D optical lattice and blue-detuned end-caps. The end-caps are generated by direct imaging of a digital micromirror device (DMD), which gives us dynamic control of the potential. We report initial characterization of the blue traps and heating rate measurements. [Preview Abstract] |
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K1.00131: Combining Yb and Li: Rapid Quantum Degenerate Gas Production and Interacting Mixtures Alaina Green, Richard Roy, Ryan Bowler, Subhadeep Gupta We detail a readily adaptable method for optimizing evaporative cooling efficiency in optical dipole traps (ODTs), reducing the production time of quantum degenerate gases. Utilizing the time-averaged 'painting' potential of a rapidly moving laser beam, we dynamically shape the trap over the course of evaporation to produce $^{174}$Yb Bose-Einstein condensates of (0.5-1.0) $\times$ 10$^5$ atoms in (1.6-1.8) seconds.\footnote{R. Roy, A. Green, R. Bowler, and S.Gupta. \textit{Rapid cooling to quantum degeneracy in dynamically shaped atom traps.} arXiv:1601.05103} We also report on interaction studies in the quantum degenerate Bose-Fermi $^{174}$Yb-$^6$Li mixture in the BEC-BCS crossover. Additionally, we present work on photoassociation spectroscopy on $^6$Li-Yb mixtures and the production of YbLi* molecules in a dual magneto-optical trap, a first step toward coherent production of ultracold $^{2}\Sigma$ molecules. [Preview Abstract] |
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K1.00132: Strongly Interacting Homogeneous Fermi Gases Biswaroop Mukherjee, Parth Patel, Zhenjie Yan, Julian Struck, Martin Zwierlein We present a homogeneous box potential for strongly interacting Fermi gases. The local density approximation (LDA) allows measurements on traditional inhomogeneous traps to observe a continuous distribution of Fermi gases in a single shot, but also suffer from a broadened response due to line-of-sight averaging over varying densities. We trap ultracold Fermionic ($^6$Li) in an optical homogeneous potential and characterize its flatness through in-situ tomography. A hybrid approach combining a cylindrical optical potential with a harmonic magnetic trap allows us to exploit the LDA and measure local RF spectra without requiring significant image reconstruction. We extract various quantities from the RF spectra such as the Tan's contact, and discuss further measurements of homogeneous Fermi systems under spin imbalance and finite temperature. [Preview Abstract] |
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K1.00133: VORTICES AND EXCITATIONS IN DEGERATE QUANTUM GASES |
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K1.00134: Universal nonequilibrium physics with spinor Bose condensates in the strongly coupled regime Hil F. H. Cheung, Yogesh Sharad Patil, Airlia Shaffer, Huiyao Y. Chen, Mukund Vengalattore A rich tapestry of magnetically ordered phases and topological defects arise in spinor condensates due to the interplay between their spin and charge degrees of freedom. While studies in such spinor condensates have been limited to regimes of weak spin-charge coupling [1], a range of novel phases and unexplored nonequilibrium phenomena arise in strongly interacting spinor gases. We identify the $^7$Li F=1 spinor gas as an experimental candidate with strong spin dependent interactions and describe its spinor phase diagram. We address the stability of its various topological defects and the role of these defects in its nonequilibrium dynamics, a topic of intense study in presence of strong interactions. We explore the universal scalings in the dynamics of these non-equilibrium states and attempt to generically understand if such nonequilibrium behavior can be described by generalized Gibbs ensembles. \\[4pt] [1] R. Barnett, A. Polkovnikov, and M. Vengalattore, Phys. Rev. A 84, 023606 (2011) [Preview Abstract] |
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K1.00135: Simple point vortex model for the relaxation of 2D superfluid turbulence in a Bose-Einstein condensate Joon Hyun Kim, Woo Jin Kwon, Yong-il Shin In a recent experiment [Phys. Rev. A 92, 051601(R) (2015)], it was found that the dissipative evolution of a corotating vortex pair in a trapped Bose-Einstein condensate is well described by a point vortex model with longitudinal friction on the vortex motion and the thermal friction coefficient was determined as a function of sample temperature. In this poster, we present a numerical study on the relaxation of 2D superfluid turbulence based on the dissipative point vortex model. We consider a homogeneous system in a cylindrical trap having randomly distributed vortices and implement the vortex-antivortex pair annihilation by removing a pair when its separation becomes smaller than a certain threshold value. We characterize the relaxation of the turbulent vortex states with the decay time required for the vortex number to be reduced to a quarter of initial number. We find the vortex decay time is inversely proportional to the thermal friction coefficient. In particular, we observe the decay times obtained from this work show good quantitative agreement with the experimental results in [Phys. Rev. A 90, 063627 (2014)], indicating that in spite of its simplicity, the point vortex model reasonably captures the physics in the relaxation dynamics of the real system. [Preview Abstract] |
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K1.00136: Knot Solitons in Spinor Bose-Einstein Condensates David Hall, Michael Ray, Konstantin Tiurev, Emmi Ruokokoski, Andrei Horia Gheorghe, Mikko M\"ott\"onen Knots are familiar entities that appear at a captivating nexus of art, technology, mathematics and science. Following a lengthy period of theoretical investigation and development, they have recently attracted great experimental interest in classical contexts ranging from knotted DNA and nanostructures to vortex knots in fluids. We demonstrate here the controlled creation and detection of knot solitons in the quantum-mechanical order parameter of a spinor Bose--Einstein condensate. Images of the superfluid reveal the circular shape of the soliton core and its associated linked rings. Our observations of the knot soliton establish an experimental foundation for future studies of their stability, dynamics and applications within quantum systems. [Preview Abstract] |
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K1.00137: Raman $q$-plates for Singular Atom Optics Justin T. Schultz, Azure Hansen, Joseph D. Murphree, Maitreyi Jayaseelan, Nicholas P. Bigelow We use a coherent two-photon Raman interaction as the atom-optic equivalent of a birefringent optical $q$-plate to facilitate spin-to-orbital angular momentum conversion in a pseudo-spin-1/2 BEC. A $q$-plate is a waveplate with a fixed retardance but a spatially varying fast axis orientation angle. We derive the time evolution operator for the system and compare it to a Jones matrix for an optical waveplate to show that in our Raman $q$-plate, the equivalent orientation of the fast axis is described by the relative phase of the Raman beams and the retardance is determined by the pulse area. The charge of the Raman $q$-plate is determined by the orbital angular momentum of the Raman beams, and the beams contain umbilic $C$-point polarization singularities which are imprinted into the condensate as spin singularities: lemons, stars, spirals, and saddles. By tuning the optical beam parameters, we can create a full-Bloch BEC, which is a coreless vortex that contains every possible superposition of two spin states, that is, it covers the Bloch sphere. [Preview Abstract] |
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K1.00138: Vortex formation in spin-orbit coupled Bose condensates Taras Hrushevskyi, Anindya Rastogi, Erhan Saglamyurek, Lindsay LeBlanc Using recently developed Raman-beam techniques, artificial spin-orbit coupling can be realized in an ultracold gas. Here, we study the formation of vortices in a BEC subjected to a spatially-dependent spin-orbit coupling that, in some regimes, acts to provide oppositely directed artificial magnetic fields for two different spin states [1,2]. We numerically investigate the formation of these vortices to understand the interplay between trap configuration, spin-orbit coupling parameter, and interactions (both spin-dependent and -independent). Finally, we discuss our progress towards the experimental realization of this system in our laboratory using an ultracold gas of $^{87}$Rb atoms in a new apparatus. [1] C. Wang, et al. Phys. Rev. Lett. 105, 160403 (2010). [2] J. Radi\’c, et al. Phys. Rev. A 84, 063604 (2011). [Preview Abstract] |
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K1.00139: ULTRACOLD COLLISIONS AND PHOTOASSOCIATION PROCESS |
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K1.00140: Geometric phase effects in ultracold chemistry Jisha Hazra, Balakrishnan Naduvalath, Brian K. Kendrick In molecules, the geometric phase, also known as Berry's phase, originates from the adiabatic transport of the electronic wavefunction when the nuclei follow a closed path encircling a conical intersection between two electronic potential energy surfaces. It is demonstrated that the inclusion of the geometric phase has an important effect on ultracold chemical reaction rates. The effect appears in rotationally and vibrationally resolved integral cross sections as well as cross sections summed over all product quantum states. It arises from interference between scattering amplitudes of two reaction pathways: a direct path and a looping path that encircle the conical intersection between the two lowest adiabatic electronic potential energy surfaces. Illustrative results are presented for the O+OH$\to$H+O$_2$ reaction and for hydrogen exchange in H+H$_2$ and D+HD reactions. It is also qualitatively demonstrated that the geometric phase effect can be modulated by applying an external electric field allowing the possibility of quantum control of chemical reactions in the ultracold regime. [Preview Abstract] |
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K1.00141: Photoassociative Spectroscopy of Ultracold Argon and Krypton M.K. Omar, W.D. Williams, C.I. Sukenik We report on photoassociative spectroscopy experiments performed separately on ultracold $^{40}$Ar and ultracold $^{84}$Kr with the spectroscopy laser tuned around the trapping transition for each species ($ns{[3/2]}_2 \rightarrow np{[5/2]}_3$ where $n=4$ for argon and $n=5$ for krypton). Previous studies in argon observed several discrete features in the spectrum that have now been positively identified as arising from otherwise undetectable frequency sidebands on the spectroscopy laser and not from molecular structure. Spectra have been taken over a range of laser intensities and show a broad (several GHz) signature of single photon photo-association, but with no individual vibrational levels resolved. We will discuss our results and compare our spectra to those obtained in ultracold, noble gas photoassociative spectroscopy experiments conducted by other groups in recent years. [Preview Abstract] |
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K1.00142: Pulse Controlled Frequency-Chirped Laser Light at Large Detuning for Use in Atomic, Molecular, and Optical Physics Experiments Brian Kaufman, Tracy Paltoo, Tanner Grogan, Matthew Wright We have developed a laser system that generates a moderate frequency chirp (1 GHz in 4 ns) at a large controllable detuning (\textasciitilde 7 GHz) using an electro-optical phase modulator in an injection-lock laser system.~ This system can effectively pulse the laser on timescales less than 3 ns by turning on and off the injection lock.~ This system can also create arbitrary frequency chirp shapes on the laser on the tens of nanosecond time scales with a cutoff frequency of 200 MHz.~ As a test of the laser system, we have explored excitation of a room-temperature atomic Rb gas with frequency-chirped light.~ We have found that our experimental results agree with the solution to the Optical Bloch equations for the same parameters. [Preview Abstract] |
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K1.00143: Photoassociation spectroscopy of $^{174}$Yb Bose-Einstein Condensate using the $^1$S$_0 \leftrightarrow ^3$P$_1$ transition Jongchul Mun, Jeongwon Lee, Jae Hoon Lee, Min-seok Kim, Yong-il Shin We studied the photoassociation spectrum of $^{174}$Yb Bose-Einstein condensate (BEC) using an optical Feshbach resonance near the intercombination transition (${}^1$S${}_0 - {}^3$P$_1$, 578 nm). The optical length $l_{opt}$, which characterize the interaction strength of optical Feshbach resonances, of four least-bound molecular levels ($\nu ’=-1 \sim -4$) were precisely determined by measuring the two-body loss rate at various optical powers. We also found the parameter $\eta=\Gamma_{spon}/\Gamma_{mol}$, which characterizes the enhancement of molecular loss, to be $>1$ as in the previous studies[1,2]. Our BEC apparatus and experimental scheme are also introduced in this presentation. \\ $ $ [1] Phys. Rev. Lett. 107, 073202 (2011) \\ $ $ [2] Phys. Rev. Lett. 110, 123201 (2013) [Preview Abstract] |
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K1.00144: Ultracold Three-body Elastic Scattering in the Adiabatic Hyperspherical Representation Victor Colussi, Jose D'Incao, Chris Greene, Murray Holland In the past few years, advances in ultracold quantum gases together with the ability to control interatomic interactions have opened up important questions related to three-body contributions to collective phenomena observables. In order to theoretically understand such contributions one needs to explore the three-body elastic scattering problem, which is fundamentally different than its two-body counterpart. The main difficulty is in the necessity to determine contributions to three-body scattering that originate from multiple scattering events where two atoms interact while the third spectates [1]. These contributions must be subtracted out in order to determine scattering events that are truly of a three-body nature, i.e., collision events in which all three atoms participate. Here, we study this problem in the adiabatic hyperspherical representation and identify how unwanted two-body scattering events manifest in this picture. This opens up ways to develop a simple procedure capable of extracting truly three-body contributions to elastic scattering. [1] R. D. Amado and M. H. Rubin, Phys. Rev. 25, 194 (1970). [Preview Abstract] |
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K1.00145: Observation of Deeply-Bound $^{85}$Rb$_{2}$ Vibrational Levels Using Feshbach Optimized Photoassociation Sean Krzyzewski, Tom Akin, James Dizikes, Michael Morrison, Eric Abraham We demonstrate Feshbach optimized photoassociation (FOPA) into the $0_{g}^{-} (5$S$_{1/2}+5$P$_{1/2}$) state in $^{85}$Rb$_{2}$. FOPA uses the enhancement of the amplitude of the initial atomic scattering wave function due to a Feshbach resonance to increase the molecular formation rate from photoassociation. We observe three vibrational levels, $v=127$, 140, and 150, with previously unmeasured binding energies of 256, 154, and 96 cm$^{-1}$. We measure the frequency, central magnetic field position, and magnetic field width of each Feshbach resonance. Our findings experimentally confirm that this technique can measure vibrational levels lower than those accessible to traditional photoassociative spectroscopy. We present theory concerning the polarization dependence of FOPA for this system, and discuss implications of using this system to measure the time-variation of the electron/proton mass ratio. [Preview Abstract] |
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K1.00146: Strong Photoassociation in Ultracold Fermions Li Jing, Alan Jamison, Timur Rvachov, Sepher Ebadi, Hyungmok Son, Yijun Jiang, Martin Zwierlein, Wolfgang Ketterle Despite many studies there are still open questions about strong photoassociation in ultracold gases. Photoassociation occurs only at short range and thus can be used as a tool to probe and control the two-body correlation function in an interacting many-body system and to engineer Hamiltonians using dissipation. We propose the possibility to slow down decoherence by photoassociation through the quantum Zeno effect. This can realized by shining strong photoassociation light on the superposition of the lowest two hyperfine states of Lithium 6. [Preview Abstract] |
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K1.00147: LASER COOLING AND TRAPPING |
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K1.00148: Simulation of Bichromatic Force Cooling Xiang Hua, Christopher Corder, Harold Metcalf Laser cooling without spontaneous emission as implemented by the bichromatic force (BF) remains a controversial topic. We have done a numerical simulation of the BF on He using the 2$^3$S $\leftrightarrow$ 3$^3$P transition at $\lambda$ = 389 nm in order to support the interpretation of previously reported measurements\footnote{C. Corder et al., Phys Rev. Lett. {\bf 114,} 043002 (2015).}$^,$\footnote{C. Corder et al., J. Opt. Soc. Am. B {\bf 32}, B75 (2015).}. Our experiments and the simulation reported here use a time scale comparable to the excited state lifetime$^{2,3}$ so that spontaneous emission cannot contribute significantly. The average velocity change is 30 - 40 times larger than the recoil velocity but the measurements of both phase space and velocity space compression are limited by the longitudinal velocity spread of the atomic beam to $\sim\,$2.$^{2,3}$ The simulation clearly shows this spreading. The code passed several preliminary tests using single-frequency traveling and standing waves, and then it was run with the appropriate bichromatic light fields. Its output agrees very well with the measurements and, most importantly, shows that significant laser cooling is indeed possible on a time scale comparable to that of a single absorption-spontaneous cycle. [Preview Abstract] |
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K1.00149: Progress towards isotope-dependent trapping of strontium Roger Ding, Francisco Camargo, Joseph D. Whalen, Germano Woehl Jr., F. Barry Dunning, Thomas C. Killian Independently controllable trapping potentials for different atomic elements, isotopes, and states are useful for forming quantum degenerate gases through sympathetic cooling, for quantum computing architectures\footnote{Anderlini et al., Nature 448, 452-456 (2007)}, and for fundamental studies in many-body physics\footnote{Mandel et al., Phys. Rev. Lett. 91, 010407 (2003)}. In strontium, the large isotope shifts ($\sim100$ MHz) relative to the narrow \textsuperscript{1}S\textsubscript{0}-\textsuperscript{3}P\textsubscript{1} intercombination line (7.5 kHz) offers the possibility of creating multi-isotope optical traps in which the potentials are optimized for each individual species, such as \textsuperscript{86}Sr with \textsuperscript{87}Sr or \textsuperscript{86}Sr with \textsuperscript{88}Sr, allowing for efficient evaporative cooling. We will present results for confinement of \textsuperscript{84}Sr when a dimple is created using far-detuned 689 nm light ($\Gamma/\Delta \sim 10^{-5}$) within a large-volume 1064 nm dipole trap ($\Gamma/\Delta \sim 10^{-7}$). The 689 nm dimple will be used to develop a trap for efficient creation of \textsuperscript{88}Sr Bose-Einstein condensates, overcoming the slow evaporation currently required. [Preview Abstract] |
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K1.00150: Proposal for a hybrid 2D MOT/molasses configuration for potassium-41 W. A. Peterson, J. P. Wrubel We report a proposed design for a compact 2D MOT-optical molasses hybrid for potassium-41 atoms. Adding electromagnets to a previously-reported permanent-magnet based 2D MOT [G. Lamporesi et al$.$, Rev. Sci. Instrum. 84, 063102 (2013)], we show it is possible to flatten the magnetic field at the trap's center, creating a region suitable for molasses. The remaining magnetic field at the fringes of the molasses provides a restoring force sufficient to keep the atoms trapped. This technique should reduce the rate of atom escape from the molasses and allow cooling times substantially longer than in a standard, un-trapped molasses. [Preview Abstract] |
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K1.00151: Critically evaluated theoretical energies, lifetimes, static and dynamic polarizabilities, and magic wavelengths in cesium Marianna Safronova, U. I. Safronova, Charles W. Clark Systematic study of Cs atomic properties is carried out using a high-precision relativistic all-order method. Excitation energies of the $ns$, $np$, $nd$, and $nf$ (n $\leq$ 12) states in neutral cesium are evaluated. Reduced matrix elements, transition rates, and lifetimes are determined for the levels up to $n$ = 8. Recommended values and estimates of their uncertainties are provided for a large number of electric-dipole transitions. Electric-dipole ($6s-np$, $n$ = 6-26)and electric-quadrupole ($6s-ndj$ , $n$ = 5-26) matrix elements are calculated to obtain the ground state E1 and E2 static polarizabilities. Scalar polarizabilities of the $ns, np, and nd$ states, and tensor polarizabilities of the $np_{3/2}$ and $nd_j$ excited states of Cs are evaluated. These calculations provide recommended values critically evaluated for their accuracy for a number of Cs atomic properties useful for a variety of applications. Using first-principles calculations, we identify magic wavelengths $\lambda$ for the $6s-7p_{1/2}$ and $6s-7p_{3/2}$ transitions in Cs. The $ns$ and $np_j$ atomic levels have the same ac Stark shifts at the corresponding magic wavelength, which facilitates state-insensitive optical cooling and trapping. [Preview Abstract] |
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K1.00152: Freezing motion-induced dephasing for single spin-state stored in atomic ensemble Yan Jiang, Rui Jun, Xiao-Hui Bao, Jian-Wei Pan Atomic-ensemble quantum memories are well considered as a promising approach of long-distance quantum communication and computation for strong light-matter interaction. While the storage lifetime is limited by the motion-induced dephasing. Spin-echo technique, increasing wavelength of spin-wave, as well as optical lattice are used commonly to overcome this dephasing process. However, these techniques either need extremely high fidelity of echo pulse or put high restriction on filter and experimental complexity. In this poster, we demonstrate a convenient technique to freeze the motion-induced dephasing without population inversion and can be used in large storage angles. Combined with ``clock states'', the lifetime is extended by one order of magnitude to the limit of the thermal expansion. What's more, high non-classical correlation above 20 has been achieved to guarantee the memory in quantum regime.By making the advance from passive engineering to coherent manipulation of single spin-wave states, our work enriches the experimental toolbox of harnessing atomic ensembles for high-performance quantum memories, especially for holographic quantum memories where many spin-waves with different wave-vectors are used. [Preview Abstract] |
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K1.00153: Optimized modulation parameters for a two-dimensional magneto-optical trap for cold fermionic potassium atoms Jae Hoon Lee, Jongchul Mun We study optimized parameters for a high flux atomic beam source for \textsuperscript{40}K fermionic atoms from a frequency modulated two-dimensional magneto-optical trap (2D MOT). The laser cooling beam frequencies of the 2D MOT were effectively broadened via elecro-optical modulators at $10 MHz$ with modulation depths $\beta $ ranging up to 7, depending on the laser intensity. A two-color pushing laser beam was also implemented for an asymmetrically directed atomic beam source. All laser parameters of the 2D MOT beams along with the magnetic field gradient were scanned for optimal atomic flux. With the added modulation, we were able to obtain ~4 times enhancement of the atomic flux which was limited by the applied laser power. [Preview Abstract] |
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K1.00154: Phase Stability and the Velocity Dependence of the ARP Force John Elgin, Brian Arnold, Taichi Inaki, Yifan Fang, Harold Metcalf Adiabatic Rapid Passage (ARP) has been shown to produce optical forces much stronger than the usual radiative force.\footnote{X. Miao, Phys. Rev. A 75, 011402 (2007).} Recent work\footnote{J. Elgin, {\it Study of the Velocity Dependence of the Adiabatic Rapid Passage (ARP) Optical Force in Helium.} Ph.D Thesis, Stony Brook University, 2015.} has found that the ARP force is very sensitive to the phase of the optical field. Thus, the use of two free running, oppositely detuned lasers is not the ideal way to achieve an accurate measurement of the velocity dependence by mimicking the Doppler shift. We believe that phase locking the two lasers to a third, master laser will address these phase concerns, thereby allowing a proper measure of the velocity dependence. We have implemented this in our experiment and will present the results obtained from this change. We will also compare these results to those obtained using independent lasers and comment on the implications. [Preview Abstract] |
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K1.00155: An open-source laser electronics suite Neal C. Pisenti, Benjamin J. Reschovsky, Daniel S. Barker, Alessandro Restelli, Gretchen K. Campbell We present an integrated set of open-source electronics for controlling external-cavity diode lasers and other instruments in the laboratory. The complete package includes a low-noise circuit for driving high-voltage piezoelectric actuators, an ultra-stable current controller based on the design of~[1], and a high-performance, multi-channel temperature controller capable of driving thermo-electric coolers or resistive heaters. Each circuit (with the exception of the temperature controller) is designed to fit in a Eurocard rack equipped with a low-noise linear power supply capable of driving up to 5~A at $\pm$~15~V. A custom backplane allows signals to be shared between modules, and a digital communication bus makes the entire rack addressable by external control software over TCP/IP. The modular architecture makes it easy for additional circuits to be designed and integrated with existing electronics, providing a low-cost, customizable alternative to commercial systems without sacrificing performance. [1]~Erickson, C.J., \textit{et. al.} Rev. Sci. Instrum. 79, 073107 (2008). [Preview Abstract] |
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K1.00156: Progress in Laser Cooling of Antihydrogen C. Hamley, G. Gabrielse, M. George, B. Glowacz, D. Grzonka, E. Hessels, N. Jones, S.A. Lee, K. Marable, M. Marshall, C. Meisenhelder, T. Morrison, W. Oelert, C. Rasor, S.R. Ronald, T. Sefzick, T. Skinner, C. Storry, E. Tardiff, M. Weel, D. Yost, M. Zielinski Precision spectroscopy of antihydrogen promises to be one of the most stringent tests to date of CPT symmetry. Multiple groups at CERN's Antiproton Decelerator facility are endeavoring to perform precision spectroscopy on the 1S-2S two photon transition in antihydrogen for comparison to hydrogen precision measurements. For trapped antihydrogen the necessary overlapped Penning and Ioffe-Pritchard traps have a large bias and gradient contributing to significant spread due to Zeeman shifts as the antihydrogen orbits in the magnetic trap. The ATRAP collaboration is working on laser cooling of antihydrogen on the 121 nm Lyman alpha line (1S-2P) in order to reduce this spread for more precise 1S-2S spectroscopy. Here we report on the ATRAP collaboration's progress in laser cooling of antihydrogen. [Preview Abstract] |
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K1.00157: A 2D MOT design optimized for dual-species $^6$Li-$^7$Li experiments Yanping Cai, Jesse Evans, Kevin Wright We have built a 2D MOT optimized for simultaneous capture and cooling of $^6$Li and $^7$Li. The design includes a vapor source located very close to the capture region, which reduces depletion of the low-velocity part of the oven flux. The source is angled so that the most probable longitudinal velocity of captured atoms is near optimal for transferring to a 3D MOT, even without a push beam. Because $^6$Li D2 repump light can impede capture and cooling of $^7$Li, we have characterized the system performance with $^6$Li repumped on both the D1 and D2 transitions. This design provides ample cold atom flux to load a dual-species 3D MOT for quantum degenerate gas experiments. [Preview Abstract] |
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K1.00158: Proposal for laser cooling of rare-earth ions Olivier Dulieu, Ye Hong, Jean-Fran\ccois Wyart, Maxence Lepers The efficiency of laser cooling relies on the existence of an almost closed optical-transition cycle in the energy spectrum of the considered species. In this respect, rare-earth elements exhibit many transitions which are likely to induce noticeable leaks from the cooling cycle. In this work, to determine whether laser cooling of singly ionized erbium Er$^+$ is feasible, we have performed accurate electronic-structure calculations of energies and spontaneous-emission Einstein coefficients of Er$^+$, using a combination of ab initio and least-squares-fitting techniques. We identify five weak closed transitions suitable for laser cooling, the broadest of which is in the kilohertz range. For the strongest transitions, by simulating the cascade dynamics of spontaneous emission, we show that repumping is necessary, and we discuss possible repumping schemes.We expect our detailed study on Er$^+$ to give good insight into the laser cooling of neighboring ions such as Dy$^+$. [Preview Abstract] |
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K1.00159: Enhanced apparatus for AC Zeeman experiments with ultracold potassium Andrew Rotunno, ShuangLi Du, Charles Fancher, Andrew Pyle, Seth Aubin Ultracold atomic potassium is an excellent candidate for studies of the AC Zeeman force, due to small hyperfine splittings. These experiments require a sufficient sample of potassium near an atom chip supporting RF currents, and an RF source which can make rapid phase-continuous frequency sweeps for fast manipulation of spin states. We present progress on the construction of laser amplifier system for improved laser cooling and trapping of potassium, development of a frequency-agile RF source, and research on RF-capable atom chips. The laser amplifier system consists of two tapered amplifiers for producing 0.4 W of 767 nm light, with a goal of collecting 10$^{\mathrm{7}}$ potassium atoms at 100 $\mu $K, which will then be cooled sympathetically with ultracold rubidium. We have constructed a direct digital synthesizer (DDS) to produce 1-400 MHz with Hz-level linewidth and noise level below -60dBc, and the ability to produce fast 100$\mu $s frequency sweeps. We are investigating atom chip designs for supporting large RF currents. Immediate applications include AC Zeeman potentials and traps for atom interferometry, and quantum many-body physics. [Preview Abstract] |
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K1.00160: Diode laser frequency stabilization using a low cost, low finesse Fabry-Perot cavity Hannah Hastings, Noura B. Jaber, Georgia Piatt, Vincent C. Gregoric, Thomas J. Carroll, Michael W. Noel Our lab employs low cost, low finesse Fabry-Perot cavities to stabilize the frequency of diode lasers used in ultra-cold Rydberg atom experiments. To characterize the stability of this technique, we perform a self-heterodyne linewidth measurement. For comparison, we also measure the linewidth when using a saturated absorption spectrometer to provide frequency stability. [Preview Abstract] |
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K1.00161: Direct frequency comb two-photon laser cooling and trapping Xueping Long, Andrew Jayich, Wesley C. Campbell Generating and manipulating high energy photons for spectroscopy on electric dipole transitions of atoms and molecules with deeply bound valence electrons is difficult. Further, laser cooling of such species is even more challenging for lack of laser power. A possible solution is to drive two-photon transitions [1]. This may alleviate the photon energy problem and open the door to cold, trapped samples of highly desirable species with tightly bound electrons. We perform a proof of principle experiment with rubidium by driving a two-photon transition with an optical frequency comb. We perform optical cooling and extend this technique to trapping, where we are able to make a magneto-optical trap in one dimension. This work is supported by the National Science Foundation CAREER program.\\ \\[1] D. Kielpinski, Phys. Rev. A 73, 063407 (2006) [Preview Abstract] |
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K1.00162: Thermal levitation of 10 um size particles in low vacuum Long Fung Frankie Fung, Nicholas Kowalski, Colin Parker, Cheng Chin We report on experimental methods for trapping 10 micron-sized ice, glass, ceramic and polyethylene particles with thermophoresis in medium vacuum, at pressures between 5 Torr and 25 Torr. Under appropriate conditions particles can launch and levitate robustly for up to an hour. We describe the experimental setup used to produce the temperature gradient necessary for the levitation, as well as our procedure for generating and introducing ice into the experimental setup. In addition to analyzing the conditions necessary for levitation, and the dependence of levitation on the experimental parameters, we report on the behavior of particles during levitation and ejection, including position and stability, under different pressures and temperatures. We also note a significant discrepancy between theory and data, suggesting the presence of other levitating forces. [Preview Abstract] |
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K1.00163: Optical Bichromatic Force on CaF Molecules L. Aldridge, S.E. Galica, D. Sheets, E.E. Eyler The optical bichromatic force (BCF) is a coherent optical force which can be much stronger than saturated radiative forces. BCF has been experimentally demonstrated in atomic systems and has recently drawn attention as an option for deflecting or decelerating neutral molecular beams. We have devised a realistic numerical model for calcium monofluoride (CaF), including the full 16-level hyperfine structure of two rovibrational states and magnetic-field destabilization of coherent dark states. We show that BCF illumination of this system produces a force two orders of magnitude stronger than that achieved by radiative forces, and we find that the required parameters are experimentally realistic and are robust against small variations. A simplified simulation scheme that saves computational time at little expense to accuracy is also presented. Experimental tests on the $B\leftrightarrow X$ transition in CaF are underway in our laboratory, starting with transverse deflection of a supersonic molecular beam. In collaboration with the group of John Doyle, we are also looking into BCF on the triatomic SrOH molecule. [Preview Abstract] |
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K1.00164: Progress towards ultracold gases in arbitrary 2D potentials Theodore Corcovilos We describe our progress in building an apparatus for investigating degenerate quantum gases of potassium in arbitrary two-dimensional optical potentials. The optical potentials are created by holographic projection of an image created using a MEMS mirror array. Systems we would like to study with this experiment are quantum simulations of bosons and fermions at crystal heterojunctions and systems with well defined boundaries, including topological edge states. [Preview Abstract] |
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K1.00165: Towards Stimulated-Force Slowing of SrF Molecules Eustace Edwards, Daniel McCarron, David DeMille In recent years, the techniques of laser slowing, cooling, and trapping have been applied to diatomic molecules. However, when applied to molecules the scattering force is reduced relative to the familiar case of atoms, due to additional states in the optical cycle (associated with rovibrational branching). Various schemes can circumvent this problem by applying optical forces without the need for spontaneous emission. This project examines the use of such methods (such as the bichromatic force, optical Stark deceleration, etc.) to slow a beam of diatomic molecules. Since the change in velocity due to these stimulated forces increases with the laser intensity and the interaction time, a tunable, high energy, long pulse laser has been developed. This poster will present the current progress of the project. [Preview Abstract] |
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K1.00166: ATOMIC MAGNETOMETERS AND SENSORS |
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K1.00167: Radio-frequency Electrometry Using Rydberg Atoms in Vapor Cells: Towards the Shot Noise Limit Santosh Kumar, Haoquan Fan, Akbar Jahangiri, Harald Kuebler, James P. Shaffer Rydberg atoms are a promising candidate for radio frequency (RF) electric field sensing. Our method uses electromagnetically induced transparency with Rydberg atoms in vapor cells to read out the effect that the RF electric field has on the Rydberg atoms. The method has the potential for high sensitivity (pV cm$^{\mathrm{-1}}$ Hz$^{\mathrm{-1/2}})$ and can be self-calibrated. Some of the main factors limiting the sensitivity of RF electric field sensing from reaching the shot noise limit are the residual Doppler effect and the sensitivity of the optical read-out using the probe laser. We present progress on overcoming the residual Doppler effect by using a new multi-photon scheme and reaching the shot noise detection limit using frequency modulated spectroscopy. Our experiments also show promise for studying quantum optical effects such as superradiance in vapor cells using Rydberg atoms. [Preview Abstract] |
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K1.00168: Magnetic-field-assisted atomic polarization spectroscopy of $^{\mathrm{4}}$He Sheng Li, Haidong Wang, Teng Wu, Xiang Peng, Hong Guo Atomic polarization spectroscopy (PS) is a high resolution sub-Doppler atomic spectroscopic technique with free modulation. It is always desirable to obtain a PS signal with zero background as it can provide a more preferable laser frequency stabilization performance. There are many factors that can affect the PS signal background, i.e., the laser power, the laser polarization and the magnetic field. Here, we demonstrate a method for observing and analyzing the effects on the PS signal of $^{\mathrm{4}}$He under different magnetic fields. At the beginning, under nearly zero magnetic field, the large asymmetrical PS signal background has been observed and cannot be eliminated by only optically adjusting. Then, we find that the PS signal profile can be changed and controlled by varying the magnetic field with transverse or longitudinal direction and different intensity. The optimized PS signal with symmetrical dispersive profile and zero background is obtained when the magnetic field is chosen and controlled in the transverse direction and more than 20000nT intensity. Similar phenomenon cannot be observed under the longitudinal magnetic field. A theoretical model is also presented, which explains and agrees well with our experimental results. [Preview Abstract] |
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K1.00169: Scanning Cryogenic Magnetometry with a Bose-Einstein Condensate Joshua Straquadine, Fan Yang, Benjamin Lev Microscopy techniques co-opted from nonlinear optics and high energy physics have complemented solid-state probes in elucidating exotic order manifest in condensed matter systems. We present a novel scanning magnetometer which adds the techniques of ultracold atomic physics to the condensed matter toolbox. Our device, the Scanning Quantum CRyogenic Atom Microscope (SQCRAMscope) uses a one-dimensional Bose-Einstein condensate of $^{87}$Rb to image magnetic and electric fields near surfaces between room and cryogenic temperatures, and allows for rapid sample changes while retaining UHV compatibility for atomic experiments. We present our characterization of the spatial resolution and magnetic field sensitivity of the device, and discuss the advantages and applications of this magnetometry technique. In particular, we will discuss our plans for performing local transport measurements in technologically relevant materials such as Fe-based superconductors and topological insulators. [Preview Abstract] |
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K1.00170: Measuring Microwaves via Absorption and Dispersion in Rydberg Atoms Daniel Stack, Paul Kunz, David Meyer, Neal Solmeyer Weak microwave frequency electromagnetic fields can be difficult to detect and fully characterize with traditional methods. However it is possible to transduce the measurement of these fields from the microwave domain to the optical domain via resonant transitions between Rydberg levels in atomic vapors using electromagnetically-induced transparency and the Autler-Townes effect. This technique allows for sensitive measurements of the microwave field amplitude, polarization, and spatial waveform (via the position of the probe and coupling laser beams) as compared to measurements performed with dipole antennas. We are able to obtain these quantities by monitoring the properties of a probe laser beam as it passes through a rubidium vapor cell. Previous experiments using Rydberg spectroscopy have typically relied on measuring the absorption of the probe laser as it passed through the atomic system. We report on progress to use the polarization rotation of the probe as it passes through the atoms in a static magnetic field, which corresponds to the real part of the susceptibility of the atomic medium, for measuring the characteristics of a microwave frequency signal. This effect is known as Nonlinear Magneto Optical Rotation (NMOR) and has been used for sensitive magnetometry. [Preview Abstract] |
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K1.00171: Nanoscale NMR and NQR with Nitrogen Vacancy Centers Elana Urbach, Igor Lovchinsky, Javier Sanchez-Yamagishi, Soonwon Choi, Alexei Bylinskii, Bo Dwyer, Trond Andersen, Alex Sushkov, Hongkun Park, Mikhail Lukin Nuclear quadrupole resonance (NQR) is a powerful tool which is used to detect quadrupolar interaction in nuclear spins with I > 1/2. Conventional NQR and NMR technology, however, rely on measuring magnetic fields from a macroscopic number of spins. Extending NMR and NQR techniques to the nanoscale could allow us to learn structural information about interesting materials and biomolecules. We present recent progress on using Nitrogen-Vacancy (NV) centers in diamond to perform room temperature nanoscale NMR and NQR spectroscopy on small numbers of nuclear spins in hexagonal boron nitride. [Preview Abstract] |
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K1.00172: Towards an NV Diamond Based Pressure Imager Timothy Milbourne, John Barry, Matthew Turner, Huiliang Zhang, Keigo Arai, Ronald Walsworth The ability to image applied pressures is of great interest for various biological and physical applications. Using an array of wires printed on a thin layer of polydimethylsiloxane (PDMS), nitrogen-vacancy (NV) center-based magnetic field imaging techniques may be used to realize a combination of high sensitivity and spatial resolution not offered by current sensing technologies. Here we present the first steps toward such a NV-based pressure imager. [Preview Abstract] |
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K1.00173: Dual Species NMR Oscillator Joshua Weber, Anna Korver, Daniel Thrasher, Thad Walker We present progress towards a dual species nuclear magnetic oscillator using synchronous spin exchange optical pumping. By applying the bias field as a sequence of alkali 2$\pi$ pulses, we generate alkali polarization transverse to the bias field. The alkali polarization is then modulated at the noble gas resonance so that through spin exchange collisions the noble gas becomes polarized. This novel method of NMR suppresses the alkali field frequency shift by at least a factor of 2500 as compared to longitudinal NMR. We will present details of the apparatus and measurements of dual species co-magnetometry using this method. Research supported by the NSF and Northrop-Grumman Corp. [Preview Abstract] |
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K1.00174: Advances in Rock Magnetometry Enabled by Nitrogen-Vacancy Magnetic Imaging David Glenn, Pauli Kehayias, Roger Fu, Eduardo Lima, Benjamin Weiss, Ronald Walsworth Magnetic imaging using nitrogen-vacancy (NV) centers in diamond allows qualitatively new questions to be addressed in the field of paleomagnetism. The NV-diamond magnetic microscope provides sensitive magnetic imaging with resolution of approximately 1 micron at room temperature, enabling spatially heterogenous magnetic sources in rock samples to be resolved at this scale for the first time. We describe new work using NV-based techniques to isolate magnetic grains in ancient terrestrial minerals (zircons), as well as ongoing investigations of several meteorite samples with interesting magnetic properties. Finally, we demonstrate the possibility of making spatially-resolved hysteresis measurements in-situ, providing a new tool for the characterization of magnetic grain sizes and composition at the micron scale. [Preview Abstract] |
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K1.00175: Development of an NV-diamond magnetometer for application in neuroscience John Barry, Jennifer Schloss, Matthew Turner, David Glenn, Ron Walsworth Magnetic field imaging based on optically detected magnetic resonances (ODMR) in NV-diamond offers an unmatched combination of sensitivity, resolution and field-of-view. For certain biological applications NV-diamond imaging is particularly useful; in contrast to traditional fluorescent markers, NV-diamond imaging is label-free and does not suffer from bleaching. In addition, the solid-state nature of NV-diamond imaging allows for various fast modulation techniques to be employed to increase the signal-to-noise ratio. Here we present results demonstrating the magnetic detection of action potentials from single neurons in multiple types of invertebrate organisms. Furthermore, we lay out a path forward for imaging of the magnetic field associated with neuronal activity with the goal of application to mammalian neurons. [Preview Abstract] |
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K1.00176: Applications of Nanoscale NMR Using Ensembles of NV Centers in Diamond Dominik Bucher, David Glenn, Ronald Walsworth Ensembles of nitrogen vacancy (NV) centers in diamond are now the frontier modality for nuclear magnetic resonance (NMR) signals at length-scales of microns to Angstroms. Promising applications including NMR and nuclear ~quadrupole resonance (NQR) spectroscopy in sub-nanoliter volumes, studies of diffusion and transport in small samples of biological tissue, and magnetic resonance imaging (MRI) of individual biological cells and molecules. Here, we describe recent progress toward such applications.~ [Preview Abstract] |
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K1.00177: Advances in nano-NMR using nitrogen vacancy centers in diamond Mark Ku, Emma Rosenfeld, Trevor David Rhone, Dominik Bucher, Huiliang Zhang, Ronald Walsworth We present recent progress in the development of new techniques for nanoscale NMR using nitrogen vacancy (NV) centers in diamond. Resonant transfer of polarization from an NV center to the nuclear spin bath using a dressed-state scheme (spin lock) enables identification of target nuclear spins without the spurious harmonics present in dynamical decoupling measurements. Furthermore, developments in diamond nano-beams containing shallow NVs provide a means to perform nanoscale NMR studies of solid-state systems. These advances - giving rise to a selective, sensitive and nanoscale probe - create new avenues for NMR studies of condensed matter and biological systems at the nanoscale. [Preview Abstract] |
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K1.00178: Atomic Sensors using Nonlinear Magneto-Optical Rotation in the Strongly Saturated Regime Paul Kunz, David Meyer, Qudsia Quraishi, Fredrik Fatemi We report on two separate atomic sensor experiments that rely on narrow spectral features associated with nonlinear magneto-optical rotation (NMOR). The first experiment uses a cold cloud of rubidium to investigate a ``twist'' feature nested within the standard dispersive-shaped NMOR curve. Though similar features have been observed previously in warm vapor, in this case the mechanism responsible is different. Here it is due to the combination of Zeeman and AC Stark shifts leading to complex evolutions of the atomic angular momentum, namely alignment-to-orientation conversion (AOC). This twist can be used as a rapid measure of transverse magnetic fields since its width scales linearly with the magnitude of the magnetic field directed along the optical polarization. We demonstrate applications of this feature both as a measure of background DC magnetic fields and also magnetic field gradients imaged with a CCD camera. Separately, in the second experiment we have begun investigations of NMOR in Rydberg levels for the purpose of measuring microwave electric field amplitudes. This has the potential to significantly enhance the signal-to-noise ratio over previous absorption-based techniques. [Preview Abstract] |
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K1.00179: A $^{3}$He-$^{129}$Xe co-magnetometer with $^{87}$Rb magnetometry Mark Limes, Dong Sheng, Mike Romalis We report progress on a $^{3}$He-$^{129}$Xe co-magnetometer detected with a $^{87}$Rb magnetometer. The noble-gas co-magnetometer is insensitive to any long-term bias field drifts, but the presence of hot Rb can cause instability in the ratio of $^{3}$He-$^{129}$Xe precession frequencies. We use a sequence of Rb $\pi$ pulses to suppress the instability due to Rb-noble gas interactions by a factor of $10^4$ along all three spatial axes. For detection, our $^{87}$Rb magnetometer operates using single-axis $^{87}$Rb $\pi$ pulses with $\sigma_+/\sigma_-$ pumping---this technique decouples the $^{87}$Rb magnetometer from bias fields, and allows for SERF operation. We are presently investigating systematic effects due to combinations of several imperfections, such as longitudinal noble gas polarization, imperfect $^{87}$Rb $\pi$ pulses, and $^{87}$Rb pump light shifts. Thus far, our $^{87}$Rb magnetometer has a sensitivity of 40 fT/$\sqrt{\text{Hz}}$, and our $^{3}$He-$^{129}$Xe co-magnetometer has achieved a single-shot precession frequency ratio error of 20 nHz and a long-term bias drift of 8 nHz at 7 h. We are developing the co-magnetometer for use as an NMR gyro, and to search for possible spin-gravity interactions. [Preview Abstract] |
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K1.00180: Spin Mass Interaction Limiting Experiment (SMILE) Junyi Lee, Michael Romalis We present preliminary results of an upcoming experiment to limit possible anomalous spin mass interactions. Such interactions arise naturally if light pseudoscalar bosons like the axion exist and a bound on such interactions places constraints on the couplings of the axion, which is of particular interest both as a solution to the strong CP problem in QCD and as a dark matter candidate. In this experiment, we measure the couplings of the axion using a $^3$He-K co-magnetometer by modulating the positions of two 200kg source masses that produces an energy shift in the atoms proportional to the axion's coupling constants. Astroyphysical observations\footnote{G. Raffelt, Phys. Rev. D \textbf{86}, 015001 (2012).} currently exceed the best laboratory limits\footnote{A. N. Youdin, D. Krause, Jr., K. Jagannathan, and L. R. Hunter, Phys. Rev. Lett. \textbf{77}, 11 (1996).} of light axions' couplings to nucleons by two order of magnitudes but we expect, for the first time in a laboratory experiment, to surpass those astrophysical bounds. Construction of the experiment has been completed and we present here some preliminary results and discuss possible systematic effects. Supported by NSF PHY-1404325. [Preview Abstract] |
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K1.00181: ABSTRACT WITHDRAWN |
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K1.00182: Vector light shift averaging in paraffin-coated alkali vapor cells Elena Zhivun, Arne Wickenbrock, Julia Sudyka, Brian Patton, Szymon Pustelny, Dmitry Budker Light shifts are an important source of noise and systematics in optically pumped magnetometers. We demonstrate that the long spin coherence time in paraffin-coated cells leads to spatial averaging of the light shifts over the entire cell volume. This renders the averaged light shift independent, under certain approximations, of the light-intensity distribution within the sensor cell. These results and the underlying mechanism can be extended to other spatially varying phenomena in anti-relaxation-coated cells with long coherence times. [Preview Abstract] |
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K1.00183: Using NV centers to probe magnetization dynamics in normal metal/magnetic insulator hybrid system at the nanoscale Huiliang Zhang, Mark J.H. Ku, Minyong Han, Francesco Casola, Toeno van der Sar, Amir Yacoby, Ronald L. Walsworth Understanding magnetization dynamics induced by electric current is of great interest for both fundamental and practical reasons. Great endeavor has been dedicated to spin--orbit torques (SOT) in metallic structures, while quantitative study of analogous phenomena in magnetic insulators remains challenging where transport measurements are not feasible. Recently we have developed techniques using nitrogen vacancy (NV) centers in diamond to probe few-nanometre-scale correlated-electron magnetic excitations (i.e., spin waves). Here we demonstrate how this powerful tool can be implemented to study magnetization dynamics inside ferromagnetic insulator, Yttrium iron garnet (YIG) with spin injection from electrical current through normal metal (Platinum in our case). Particularly our work will focus on NV magnetic detection, imaging, and spectroscopy of coherent auto-oscillations in Pt/YIG microdisc. Magnetic fluctuations and local temperature measurements, both with nearby NV centers, will also be interesting topics relevant to SOT physics in Pt/YIG hybrid system. [Preview Abstract] |
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K1.00184: Optimization of NV-Diamond for Ensemble Sensing Applications Linh Pham, Scott Alsid, Paola Cappellaro, Danielle Braje The nitrogen-vacancy (NV) center in diamond is a promising spin system for a number of quantum sensing applications; in recent years, NV centers have been employed to measure temperature, electric field, and magnetic field. In bulk diamond sensors, which take advantage of probing an ensemble of NV centers for improved measurement sensitivity, the sensitivity may be further enhanced by increasing the concentration of NV centers through electron irradiation and annealing. We study the effects of a range of electron irradiation dosages and annealing recipes on the conversion of native substitutional nitrogen defects to negatively-charged NV centers and on NV spin coherence properties such as T2* and T2, in order to optimize NV properties in bulk diamond for a range of quantum sensing applications. [Preview Abstract] |
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K1.00185: ELECTRIC-DIPOLE SEARCHES AND TESTS OF FUNDAMENTAL SYMMETRIES |
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K1.00186: Efficient transfer of francium atoms Seth Aubin, John Behr, Alexander Gorelov, Matt Pearson, Michael Tandecki, Robert Collister, Gerald Gwinner, Kyle Shiells, Eduardo Gomez, Luis Orozco, Jiehang Zhang, Yanting Zhao We report on the progress of the FrPNC collaboration towards Parity Non Conservation Measurements (PNC) using francium atoms at the TRIUMF accelerator. We demonstrate efficient transfer (higher than 40{\%}) to the science vacuum chamber where the PNC measurements will be performed. The transfer uses a downward resonant push beam from the high-efficiency capture magneto optical trap (MOT) towards the science chamber where the atoms are recaptured in a second MOT. The transfer is very robust with respect to variations in the parameters (laser power, detuning, alignment, etc.). We accumulate a growing number of atoms at each transfer pulse (limited by the lifetime of the MOT) since the push beam does not eliminate the atoms already trapped in the science MOT. The number of atoms in the science MOT is on track to meet the requirements for competitive PNC measurements when high francium rates (previously demonstrated) are delivered to our apparatus. The catcher/neutralizer for the ion beam has been tested reliably to 100,000 heating/motion cycles. We present initial tests on the direct microwave excitation of the ground hyperfine transition at 45 GHz. [Preview Abstract] |
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K1.00187: Electron EDM measurement in a beam of ThO: Demonstrated and planned upgrades Zack Lasner, Vitaly Andreev, Daniel Ang, Jacob Baron, David DeMille, John Doyle, Gerald Gabrielse, Nicholas Hutzler, Brendon O'Leary, Cristian Panda, Elizabeth Petrik, Christian Weber, Adam West, Grey Wilburn The permanent electric dipole moment (EDM) $d$ of a particle with spin $S$ is characterized by a linear interaction $H\propto d\,\vec{S}\cdot \vec{E}$ with an electric field $\vec{E}$. This Hamiltonian is inherently $P$- and $T$-odd, making it a powerful probe of fundamental physics. To date, no EDM of a fundamental particle has been observed, but limits placed for several particles have significantly constrained theories beyond the Standard Model in the TeV range. In 2014, the ACME collaboration set a new upper limit on the electron EDM (eEDM) of $|d|<1\times10^{-28}\, e\cdot$cm by means of a spin-precession measurement in a beam of thorium monoxide (ThO) [1]. We present our measurement scheme and demonstrated apparatus upgrades designed to suppress known systematic errors and achieve an order of magnitude greater statistical sensitivity in a next-generation measurement of the eEDM. In addition, we describe upgrades currently in development to improve our statistical sensitivity beyond next-generation levels. [1] Baron $\textit{et al.}$, Science $\textbf{343}$ (2014), 269-272 [Preview Abstract] |
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K1.00188: Twelve-fold increase in the number of usable ThO molecules for the ACME electron electric dipole measurement through STIRAP C. D. Panda, B. R. O'Leary, Z. Lasner, E. S. Petrik, A. D. West, D. DeMille, J. M. Doyle, G. Gabrielse The ACME Collaboration recently reported an order of magnitude improved limit on the electric dipole moment of the electron (eEDM) (ACME collaboration, Science \textbf{343} (2014), 269$-$272), setting more stringent constraints on many time reversal (T) violating extensions to the Standard Model. The experiment was performed using spin precession measurements in a molecular beam of thorium oxide. We report here on a new method of preparing the coherent spin superposition state that serves as the initial state of the spin precession measurement using STImulated Raman Adiabatic Passage (STIRAP). We demonstrate a transfer efficiency of $75\%$, giving a twelve-fold increase in signal. We discuss the particularities of implementing STIRAP in the ACME measurement and the methods we have used to overcome various challenges. [Preview Abstract] |
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K1.00189: Spectroscopy of TaN in Support of Fundamental Physics Richard Mawhorter, David Sharfi, Yongrak Kim, Damian Kokkin, Jacob Bouchard, Timothy Steimle Tantalum nitride, TaN, has been recently identified as a leading candidate for extending the study of T, P-odd effects in the nuclear realm to include proton, neutron, and quark electric dipole moments (EDM) and beyond. This is primarily due to enhancements in the interaction of electrons with the nuclear magnetic quadrupole moment (MQM) and the resulting parity-violating effects. Study of the dispersed laser induced fluorescence resulting from the excitation of the 17570.80 ($\Omega =$0$^{\mathrm{+}})$, 18427.38 ($\Omega =$0$^{\mathrm{+}})$, 19216.80 ($\Omega =$1), and 19396.78 ($\Omega =$1) bands above the $X^{\mathrm{1}}\Sigma ^{\mathrm{+}}$ (v$=$0) ground state of TaN near 569 nm, 543 nm, 520 nm, and 515 nm has enabled a determination of the branching ratios and transition dipole moments of all 4 states. Radiative lifetimes of 454(32) ns, 479(12) ns, 333(4) ns, and 480(17) ns respectively were measured from an analysis of the fluorescence decay curves, and potential optical pumping approaches for both populating and detecting the parity-violation sensitive $^{\mathrm{3}}\Delta_{\mathrm{1}}$ state are proposed. Further experiments using CW laser excitation have enabled the observation of the hyperfine structure of several bands in the gateway 18427.38 ($\Omega =$0$^{\mathrm{+}})$ to $X^{\mathrm{1}}\Sigma ^{\mathrm{+}}$ (v$=$0) transition, and analysis of these complex spectra is underway. [Preview Abstract] |
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K1.00190: Second generation measurement of the electric dipole moment of the electron using trapped ThF$^+$ ions Kia Boon Ng, Yan Zhou, Daniel Gresh, William Cairncross, Matthew Grau, Yiqi Ni, Jun Ye, Eric Cornell ThF$^+$ has been chosen as the candidate for a second generation measurement of the electric dipole moment of the electron (eEDM). Compared to the current HfF$^+$ eEDM experiment, ThF$^+$ has several advantages: (i) the eEDM--sensitive state ($^3\Delta_1$) is the ground state, which facilitates a long coherence time\footnote{D. N. Gresh, K. C. Cossel, Y. Zhou, J. Ye, E. A. Cornell, Journal of Molecular Spectroscopy, 319 (2016), 1-9}; (ii) its effective electric field (38 GV/cm) is 50\% larger than that of HfF$^+$, which promises a direct increase of the eEDM sensitivity\footnote{T. Fleig, M. K. Nayak, Physical Review A 88 (2013) 032514}; and (iii) the ionization energy of neutral ThF is lower than its dissociation energy, which introduces greater flexibility in rotational state--selective photoionization via core--nonpenetrating Rydberg states\footnote{Z. J. Jakubek, R. W. Field, Journal of Molecular Spectroscopy 205 (2001) 197–220.}. Here, we present progress of our experimental setup, preliminary spectroscopic data of multi--photon ionization, and discussions of new features in ion trapping, state preparation and population readout. [Preview Abstract] |
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K1.00191: A new precision measurement of the electron's electric dipole moment using trapped ions William Cairncross, Kevin C Cossel, Matt Grau, Daniel N Gresh, Kia Boon Ng, Yiqi Ni, Yan Zhou, Eric A Cornell, Jun Ye A precision measurement of the permanent electric dipole moment of the electron (eEDM) can be used to place constraints on extensions to the Standard Model. The most sensitive measurements of the eEDM to date have used neutral atomic or molecular beams, and thus are all susceptible to similar classes of systematic errors. Here we present a competitive measurement of the eEDM in a radically different experimental scheme: a thermal cloud of HfF$^{+}$ ions confined in an RF trap. The long coherence times achieved in the RF trap and the large effective electric field of a molecular system provide high sensitivity to an eEDM, while our new experimental platform permits studies of a different class of systematic errors. We will present our experimental setup, known sources of systematic error and our efforts to suppress them, and the results of our recent eEDM measurement. [Preview Abstract] |
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K1.00192: A cold, slow beam of TlF molecules for an improved probe for the nuclear Schiff moment Daniel McCarron, Eustace Edwards, Matthew Steinecker, Stephen Peck, Larry Hunter, David DeMille We present a new experimental effort to search for the nuclear Schiff moment (SM) using thallium fluoride (TlF) molecules. Our approach capitalizes on the strong internal electric field present in a polarized molecule to amplify the effect of the SM. We project a 25-fold improvement over the current state of the art sensitivity to certain underlying mechanisms such as the CP-violating QCD $\theta $-parameter [1]. Our recent measurements indicate that optical cycling is possible on the $X^{\mathrm{1}}\Sigma ^{\mathrm{+}}\to B^{\mathrm{3}}\Pi_{\mathrm{1}}$ electronic transition of TlF [2]. Here a single laser will enable 100 photons to be scattered before an excited vibrational level is populated. This is sufficient for unit-efficiency fluorescence detection, rotational cooling, and state preparation. With a single repump laser, \textasciitilde 10$^{\mathrm{4}}$ photons could be scattered, sufficient for transverse laser cooling that could substantially increase the brightness of the molecular beam. We report on the production of a cold and slow beam of TlF molecules from a cryogenic buffer gas beam source and present flux measurements for a range of TlF vaporization techniques. We also present our progress towards understanding the hyperfine structure in the $B^{\mathrm{3}}\Pi_{\mathrm{1}}$ state and its role in optical cycling. [1] B. Graner, Y. Chen, E. G. Lindahl, and B.R. Heckel, Reduced limit on the Permanent Electric Dipole Moment of $^{\mathrm{199}}$Hg, arXiv:1601.04339. [2] L. R. Hunter, S. K. Peck, A. S. Greenspon, S. Saad Alam, and D. DeMille, Prospects for laser cooling TlF, \textit{Phys. Rev. A}, \textbf{85}, 012511 (2012). [Preview Abstract] |
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K1.00193: Controlling the formation of excited neutral D$^{*}$ fragments of D$_2$ using intense ultrashort laser pulses Peyman Feizollah, Ben Berry, T. Severt, Bethany Jochim, M. Zohrabi, Kanaka Raju P., Jyoti Rajput, K.D. Carnes, B.D. Esry, I. Ben-Itzhak Excited neutral D$^{*}$ fragments ($n\gg$1) are produced by the interaction of strong-field laser pulses with D$_2$ molecules. In this work, we focus on the formation of low kinetic energy release (KER) D$^{*}$ fragments, which are relatively unstudied, using NIR (800-nm) and UV (400-nm) laser pulses. The KER spectrum is found to be very sensitive to the laser parameters, including laser chirp. By changing the chirp of the UV laser pulses, two separate low-KER peaks are generated instead of a single peak. Moreover, the ratio between these peaks can be controlled with the chirp. Similarly, by chirping the NIR pulses, the low-KER peak is attenuated and shifted to lower energy. [Preview Abstract] |
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K1.00194: Three imaging methods for lattice-trapped ultracold gases Liyuan Qiu, Haoxiang Yang, Tian Tian, Xianghao Mu, Yingmei Liu, Luming Duan An optical lattice is a versatile technique to control the mobility of atoms and enhance interatomic interactions. A Bose-Einstein condensate confined in optical lattices has attracted much attention for its abilities to simulate condensed matter models. We have developed and compared three different methods for detecting lattice-trapped sodium Bose-Einstein condensates. Our study shows that the in-situ imaging implemented with a digital micro-mirror device can provide a few interesting advantages. These detecting methods may be applicable to other optically trappable atomic species and molecules. [Preview Abstract] |
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K1.00195: Fetal MCG with Atomic Magnetometer Array Zack DeLand, Michael D. Bulatowicz, Ibrahim A. Sulai, Colin P. Wahl, Ronald T. Wakai, Thad G. Walker We present results on the development of $^8^7Rb$ atomic magnetometers for the detection of a fetal magnetocardiogram (fMCG). Operating in the spin-exchange relaxation free (SERF) regime, the magnetometers' sensitivities are reported at the $\sim $ 1fT/ $\sqrt{\mbox{Hz}$ level. Environmental common-mode noise, including the field from the maternal heart, can be suppressed by operating the magnetometers in a gradiometric configuration. We report on schemes from implementing such gradiometers along with recent fMCG measurements. This work is supported by the National Institutes of Health. [Preview Abstract] |
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K1.00196: Investigating Enhanced Multiple Ionization Near Conical Intersections in C2H2$+$ Greg McCracken, Chelsea Liekhus-Schmaltz, Andreas Kaldun, Phil Bucksbaum Nonadiabatic behavior near conical intersections (CIs) leads to strong nonradiative mixing between different electronic states in polyatomic molecules. Recently, evidence was shown that strong field multiple ionization was significantly enhanced near the CI driving the isomerization of CHD [1]. An interesting question is if it is a general feature that conical intersections enhance ionization rates. In this talk, we investigate the possibility of enhanced multiple ionization near the CI between the $A $and $X $states of the C2H2 cation, which is involved in the isomerization pathway to vinylidene. The cation is prepared in the $A $state nonlinearly using 50 fs pulses at 266 nm. The evolution of the nuclear wavepacket through the CI is then probed by a strong ultrafast pulse at 800 nm. Using a newly designed system to reconstruct the momenta of all ion fragments from a single Coulomb explosion event, we are able to see any enhancement of highly charged channels over doubly charged ones from events that are probed near the CI. [1] V.S. Petrovich et. al, J. Chem. Phys. 139, 184309 (2013) [Preview Abstract] |
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K1.00197: Characterizing spin-charge separation in ultracold atoms confined to 1D1 C.Y. Shih One dimensional systems of fermions are predicted by Luttinger liquid theory to have different dispersion relations for spin and charge exci- tations. Evidence of spin-charge separation has been seen in quantum wire tunneling experiments 23. However, independent measurements for spin and charge dispersion were not accessible. Ultracold atoms, how- ever, provide highly tunable system to directly observe this phenomenon using Bragg spectroscopy4 in a 2-D optical lattice. By measuring the momentum transfer from a Raman transition while varying the relative detuning of the two-photon transition, we can measure the dispersion relation ?(k). The two “spin” states are different hyperfine levels of the atom, and by appropriate choice of detuning, it may be possible to independently measure the spin and charge modes. By exploiting the tunability of interactions via a Feshbach resonance, we have measured the Bragg spectrum for the charge mode. [Preview Abstract] |
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K1.00198: Ab initio wave function propagation of bosonic ensembles in elongated traps Valentin Bolsinger, Sven Kr\"onke, Peter Schmelcher We use the ab initio, numerically exact, Multi-Layer - Multi-Configurational Time Dependent Hartree method for Bosons [1] to simulate correlated bosonic many body system in higher spatial dimensions. This method is based on time-dependent, variational optimized, multi-particle basis. We use the fact that in elongated traps strong spatial correlations are suppressed due to the energz scales in the longitudinal and transversal direction and obtain a linear scaling in the number of grid points in contrast to other methods, using a product grid, with cubic scaling. As an illustrative example, we study perturbed dipole-oscillations for a bosonic many body system in an elongated harmonic trap. The perturbation is created by a Gaussian hump at the trap center. We study time-dependent beyond mean-field effects in many-particle systems in the cross-over from one to three dimensions and focus on transversal excitations created by the hump and its influence of longitudinal propagation. [Preview Abstract] |
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K1.00199: Modeling of PT-systems based on Optical Parametric Amplification and Stimulated Raman Scattering Alexey Sukhinin, Natalia Litchinitser Most of the research on PT-materials has been performed with the premise that the gain of the system is based on the amplitude-independent or linear amplification mechanisms. In this talk, I will discuss the theoretical model that includes nonlinear optical effects such as Optical Parametric Amplification and Stimulated Raman Scattering to realize larger optical gain. This setup could lead to a build-up of the next generation of PT-materials. [Preview Abstract] |
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