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Sample records for 2d optical lattice

  1. Quasiparticle Spectrum of 2-d Dirac Vortices in Optical Lattices

    NASA Astrophysics Data System (ADS)

    Haddad, Laith

    2009-10-01

    Bose-Einstein condensates in a honeycomb optical lattice are described by a nonlinear Dirac equaton (NLDE) in the long wavelength, mean field limit [1]. The upper and lower two-spinor equations decouple and superficially resemble the equations of previously studied NLDE's such as the Soler model for extended fermions. Although much work has been done on NLDE's, the bulk of the literature deals with models with Poincare invariant nonlinearites. In contrast our equations break Poincare symmetry providing an opportunity to study phenomenological models in cosmology and particle physics where this symmetry is not manifest. We obtain and classify localized solutions to our equations for both repulsive and attractive contact interactions. We also derive analogs of the Bogoliubov-de Gennes equations for the lattice and use these to study the stability and low energy spectrum of our solutions showing the existence of stable exotic structures such as vortices with fractional statistics.[4pt] [1] L. H. Haddad and L. D. Carr, ``The Nonlinear Dirac Equation in Bose-Einstein Condensates: Foundation and Symmetries,'' Physica D: Nonlinear Phenomena, v. 238, p. 1413 (2009). http://arxiv.org/pdf/0803.3039v1

  2. 2D Superexchange-mediated magnetization dynamics in an optical lattice

    NASA Astrophysics Data System (ADS)

    Goldschmidt, Elizabeth; Brown, Roger; Wyllie, Robert; Koller, Silvio; Foss-Feig, Michael; Porto, Trey

    2015-05-01

    The interplay of magnetic exchange interactions and tunneling underlies many complex quantum phenomena observed in real materials. We study nonequilibrium magnetization dynamics in an extended 2D system by loading effective spin-1/2 bosons into a spin-dependent optical lattice, and we use the lattice to separately control the resonance conditions for tunneling and superexchange. After preparing a nonequilibrium antiferromagnetically ordered state, we observe relaxation dynamics governed by two well-separated rates, which scale with the underlying Hamiltonian parameters associated with superexchange and tunneling. Remarkably, with tunneling off-resonantly suppressed, we are able to observe superexchange-dominated dynamics over two orders of magnitude in magnetic coupling strength, despite the presence of vacancies. In this regime, the measured timescales are in agreement with simple theoretical estimates, but the detailed dynamics of this 2D, strongly-correlated, and far-from-equilibrium quantum system remain out of reach of current computational techniques. Now at Georgia Tech Research Institute.

  3. Interferometric Approach to Measuring Band Topology in 2D Optical Lattices

    NASA Astrophysics Data System (ADS)

    Abanin, Dmitry A.; Kitagawa, Takuya; Bloch, Immanuel; Demler, Eugene

    2013-04-01

    Recently, optical lattices with nonzero Berry’s phases of Bloch bands have been realized. New approaches for measuring Berry’s phases and topological properties of bands with experimental tools appropriate for ultracold atoms need to be developed. In this Letter, we propose an interferometric method for measuring Berry’s phases of two-dimensional Bloch bands. The key idea is to use a combination of Ramsey interference and Bloch oscillations to measure Zak phases, i.e., Berry’s phases for closed trajectories corresponding to reciprocal lattice vectors. We demonstrate that this technique can be used to measure the Berry curvature of Bloch bands, the π Berry’s phase of Dirac points, and the first Chern number of topological bands. We discuss several experimentally feasible realizations of this technique, which make it robust against low-frequency magnetic noise.

  4. Hubbard Model study of Off Diagonally Confined fermions in a 2D Optical Lattice

    NASA Astrophysics Data System (ADS)

    Cone, Dave; Chiesa, Simone; Scalettar, Richard; Batrouni, George

    2010-03-01

    We report Quantum Monte Carlo simulations of a Hubbard Hamiltonian which incorporates a proposed new method for confining atoms in an optical lattice employing an inhomogeneous array of hopping matrix elements which trap atoms by going to zero at the lattice edges. This has been termed ``Off Diagonal Confinement (ODC)'' [1] to distinguish it from the more conventional use of a parabolic trap coupling to (diagonal) density operators. It has the advantage of producing systems which, while still being inhomogeneous, are entirely in the Mott phase, and allow simulations which are free of the sign problem at low temperatures. We analyze the effects of using ODC traps on the local density, density fluctuation, spin, and pairing correlation functions. Finally, we will discuss the advantages and importance of this new confinement technique for modeling correlated systems. Research supported by the Department of Energy, Office of Science SCIDAC program, DOE-DE-FC0206ER25793. [1] V.G. Rousseau et al., arXiv:0909.3543

  5. Nano-spatial parameters from 3D to 2D lattice dimensionality by organic variant in [ZnCl4]- [R]+ hybrid materials: Structure, architecture-lattice dimensionality, microscopy, optical Eg and PL correlations

    NASA Astrophysics Data System (ADS)

    Kumar, Ajit; Verma, Sanjay K.; Alvi, P. A.; Jasrotia, Dinesh

    2016-04-01

    The nanospatial morphological features of [ZnCl]- [C5H4NCH3]+ hybrid derivative depicts 28 nm granular size and 3D spreader shape packing pattern as analyzed by FESEM and single crystal XRD structural studies. The organic moiety connect the inorganic components through N-H+…Cl- hydrogen bond to form a hybrid composite, the replacement of organic derivatives from 2-methylpyridine to 2-Amino-5-choloropyridine results the increase in granular size from 28nm to 60nm and unit cell packing pattern from 3D-2D lattice dimensionality along ac plane. The change in optical energy direct band gap value from 3.01eV for [ZnCl]- [C5H4NCH3]+ (HM1) to 3.42eV for [ZnCl]- [C5H5ClN2]+ (HM2) indicates the role of organic moiety in optical properties of hybrid materials. The photoluminescence emission spectra is observed in the wavelength range of 370 to 600 nm with maximum peak intensity of 9.66a.u. at 438 nm for (HM1) and 370 to 600 nm with max peak intensity of 9.91 a.u. at 442 nm for (HM2), indicating that the emission spectra lies in visible range. PL excitation spectra depicts the maximum excitation intensity [9.8] at 245.5 nm for (HM1) and its value of 9.9 a.u. at 294 nm, specify the excitation spectra lies in UV range. Photoluminescence excitation spectra is observed in the wavelength range of 280 to 350 nm with maximum peak intensity of 9.4 a.u. at 285.5 nm and 9.9 a.u. at 294 and 297 nm, indicating excitation in the UV spectrum. Single crystal growth process and detailed physiochemical characterization such as XRD, FESEM image analysis photoluminescence property reveals the structure stability with non-covalent interactions, lattice dimensionality (3D-2D) correlations interweaving into the design of inorganic-organic hybrid materials.

  6. Beam-Plasma Instabilities in a 2D Yukawa Lattice

    SciTech Connect

    Kyrkos, S.; Kalman, G. J.; Rosenberg, M.

    2009-06-05

    We consider a 2D Yukawa lattice of grains, with a beam of other charged grains moving in the lattice plane. In contrast to Vlasov plasmas, where the electrostatic instability excited by the beam is only longitudinal, here both longitudinal and transverse instabilities of the lattice phonons can develop. We determine and compare the transverse and longitudinal growth rates. The growth rate spectrum in wave number space exhibits remarkable gaps where no instability can develop. Depending on the system parameters, the transverse instability can be selectively excited.

  7. 2D Lattices of Ferromagnetic Nanoparticles as Supermagnetics

    DTIC Science & Technology

    1999-06-18

    Supermagnetics DISTRIBUTION: Approved for public release, distribution unlimited Availability: Hard copy only. This paper is part of the following report: TITLE...Technology" OAN.01 i St Petersburg, Russia, June 14-18, 1999 © 1999 loffe Institute 2D lattices of ferromagnetic nanoparticles as supermagnetics A. A...temperature the system became ordered due to the dipole interaction of particles. Such a state of the system was defined as supermagnetic [ ]. The critical

  8. Substrate-assisted 2D DNA lattices and algorithmic lattices from single-stranded tiles.

    PubMed

    Kim, Junghoon; Ha, Tai Hwan; Park, Sung Ha

    2015-08-07

    We present a simple route to circumvent kinetic traps which affect many types of DNA nanostructures in their self-assembly process. Using this method, a new 2D DNA lattice made up of short, single-stranded tile (SST) motifs was created. Previously, the growth of SST DNA assemblies was restricted to 1D (tubes and ribbons) or finite-sized 2D (molecular canvases). By utilizing the substrate-assisted growth method, sets of SSTs were designed as unit cells to self-assemble into periodic and aperiodic 2D lattices which continuously grow both along and orthogonal to the helical axis. Notably, large-scale (∼1 μm(2)) fully periodic 2D lattices were fabricated using a minimum of just 2 strand species. Furthermore, the ability to create 2D lattices from a few motifs enables certain rules to be encoded into these SSTs to carry out algorithmic self-assembly. A set of these motifs was designed to execute simple 1-input 1-output COPY and NOT algorithms, the space-time manifestations which were aperiodic 2D algorithmic SST lattices. The methodology presented here can be straightforwardly applied to other motifs which fall into this type of kinetic trap to create novel DNA crystals.

  9. Interplay between Anderson and Stark Localization in 2D Lattices

    SciTech Connect

    Kolovsky, A. R.

    2008-11-07

    This Letter studies the dynamics of a quantum particle in 2D lattices with on-site disorder in the presence of a static field. It is shown that the particle is localized along the field direction, while in the orthogonal direction to the field it shows diffusive dynamics for algebraically large times. For weak disorder an analytical expression for the diffusion coefficient is obtained by mapping the problem to a band random matrix. This expression is confirmed by numerical simulations of the particle's dynamics, which also indicate the existence of a universal equation for the diffusion coefficient, valid for an arbitrary disorder strength.

  10. Subwavelength Lattice Optics by Evolutionary Design

    PubMed Central

    2015-01-01

    This paper describes a new class of structured optical materials—lattice opto-materials—that can manipulate the flow of visible light into a wide range of three-dimensional profiles using evolutionary design principles. Lattice opto-materials are based on the discretization of a surface into a two-dimensional (2D) subwavelength lattice whose individual lattice sites can be controlled to achieve a programmed optical response. To access a desired optical property, we designed a lattice evolutionary algorithm that includes and optimizes contributions from every element in the lattice. Lattice opto-materials can exhibit simple properties, such as on- and off-axis focusing, and can also concentrate light into multiple, discrete spots. We expanded the unit cell shapes of the lattice to achieve distinct, polarization-dependent optical responses from the same 2D patterned substrate. Finally, these lattice opto-materials can also be combined into architectures that resemble a new type of compound flat lens. PMID:25380062

  11. Optical Lattice Clocks

    NASA Astrophysics Data System (ADS)

    Oates, Chris

    2012-06-01

    Since they were first proposed in 2003 [1], optical lattice clocks have become one of the leading technologies for the next generation of atomic clocks, which will be used for advanced timing applications and in tests of fundamental physics [2]. These clocks are based on stabilized lasers whose frequency is ultimately referenced to an ultra-narrow neutral atom transition (natural linewidths << 1 Hz). To suppress the effects of atomic motion/recoil, the atoms in the sample (˜10^4 atoms) are confined tightly in the potential wells of an optical standing wave (lattice). The wavelength of the lattice light is tuned to its ``magic'' value so as to yield a vanishing net AC Stark shift for the clock transition. As a result lattice clocks have demonstrated the capability of generating high stability clock signals with small absolute uncertainties (˜ 1 part in 10^16). In this presentation I will first give an overview of the field, which now includes three different atomic species. I will then use experiments with Yb performed in our laboratory to illustrate the key features of a lattice clock. Our research has included the development of state-of-the-art optical cavities enabling ultra-high-resolution optical spectroscopy (1 Hz linewidth). Together with the large atom number in the optical lattice, we are able to achieve very low clock instability (< 0.3 Hz in 1 s) [3]. Furthermore, I will show results from some of our recent investigations of key shifts for the Yb lattice clock, including high precision measurements of ultracold atom-atom interactions in the lattice and the dc Stark effect for the Yb clock transition (necessary for the evaluation of blackbody radiation shifts). [4pt] [1] H. Katori, M. Takamoto, V. G. Pal'chikov, and V. D. Ovsiannikov, Phys. Rev. Lett. 91, 173005 (2003). [0pt] [2] Andrei Derevianko and Hidetoshi Katori, Rev. Mod. Phys. 83, 331 (2011). [0pt] [3] Y. Y. Jiang, A. D. Ludlow, N. D. Lemke, R. W. Fox, J. A. Sherman, L.-S. Ma, and C. W. Oates

  12. Cold atoms in a rotating optical lattice

    NASA Astrophysics Data System (ADS)

    Foot, Christopher J.

    2009-05-01

    We have demonstrated a novel experimental arrangement which can rotate a two-dimensional optical lattice at frequencies up to several kilohertz. Our arrangement also allows the periodicity of the optical lattice to be varied dynamically, producing a 2D ``accordion lattice'' [1]. The angles of the laser beams are controlled by acousto-optic deflectors and this allows smooth changes with little heating of the trapped cold (rubidium) atoms. We have loaded a BEC into lattices with periodicities ranging from 1.8μm to 18μm, observing the collapse and revival of the diffraction orders of the condensate over a large range of lattice parameters as recently reported by a group in NIST [2]. We have also imaged atoms in situ in a 2D lattice over a range of lattice periodicities. Ultracold atoms in a rotating lattice can be used for the direct quantum simulation of strongly correlated systems under large effective magnetic fields, i.e. the Hamiltonian of the atoms in the rotating frame resembles that of a charged particle in a strong magnetic field. In the future, we plan to use this to investigate a range of phenomena such as the analogue of the fractional quantum Hall effect. [4pt] [1] R. A. Williams, J. D. Pillet, S. Al-Assam, B. Fletcher, M. Shotter, and C. J. Foot, ``Dynamic optical lattices: two-dimensional rotating and accordion lattices for ultracold atoms,'' Opt. Express 16, 16977-16983 (2008) [0pt] [2] J. H. Huckans, I. B. Spielman, B. Laburthe Tolra, W. D. Phillips, and J. V. Porto, Quantum and Classical Dynamics of a BEC in a Large-Period Optical Lattice, arXiv:0901.1386v1

  13. Optical diffraction by ordered 2D arrays of silica microspheres

    NASA Astrophysics Data System (ADS)

    Shcherbakov, A. A.; Shavdina, O.; Tishchenko, A. V.; Veillas, C.; Verrier, I.; Dellea, O.; Jourlin, Y.

    2017-03-01

    The article presents experimental and theoretical studies of angular dependent diffraction properties of 2D monolayer arrays of silica microspheres. High-quality large area defect-free monolayers of 1 μm diameter silica microspheres were deposited by the Langmuir-Blodgett technique under an accurate optical control. Measured angular dependencies of zeroth and one of the first order diffraction efficiencies produced by deposited samples were simulated by the rigorous Generalized Source Method taking into account particle size dispersion and lattice nonideality.

  14. Quantum Lattice Algorithms for 2D and 3D Magnetohydrodynamics

    DTIC Science & Technology

    2007-11-01

    Vahala (William & Mary) on both quantum and entropic lattice algorithms for the solution of nonlinear physics problems. Because of the extreme...for CAP-Phase II on the 9000 core on the SGI-Altix at ASC. 15. SUBJECT TERMS Nonlinear Physics; Quantum Lattice Algorithms; Entropic Lattice...solution of nonlinear physics problems. Because of the extreme scalability of the algorithms that we have been developing, we were chosen for CAP

  15. Lattice Boltzmann Equation On a 2D Rectangular Grid

    NASA Technical Reports Server (NTRS)

    Bouzidi, MHamed; DHumieres, Dominique; Lallemand, Pierre; Luo, Li-Shi; Bushnell, Dennis M. (Technical Monitor)

    2002-01-01

    We construct a multi-relaxation lattice Boltzmann model on a two-dimensional rectangular grid. The model is partly inspired by a previous work of Koelman to construct a lattice BGK model on a two-dimensional rectangular grid. The linearized dispersion equation is analyzed to obtain the constraints on the isotropy of the transport coefficients and Galilean invariance for various wave propagations in the model. The linear stability of the model is also studied. The model is numerically tested for three cases: (a) a vortex moving with a constant velocity on a mesh periodic boundary conditions; (b) Poiseuille flow with an arbitrasy inclined angle with respect to the lattice orientation: and (c) a cylinder &symmetrically placed in a channel. The numerical results of these tests are compared with either analytic solutions or the results obtained by other methods. Satisfactory results are obtained for the numerical simulations.

  16. Optical Abelian lattice gauge theories

    SciTech Connect

    Tagliacozzo, L.; Celi, A.; Zamora, A.; Lewenstein, M.

    2013-03-15

    We discuss a general framework for the realization of a family of Abelian lattice gauge theories, i.e., link models or gauge magnets, in optical lattices. We analyze the properties of these models that make them suitable for quantum simulations. Within this class, we study in detail the phases of a U(1)-invariant lattice gauge theory in 2+1 dimensions, originally proposed by P. Orland. By using exact diagonalization, we extract the low-energy states for small lattices, up to 4 Multiplication-Sign 4. We confirm that the model has two phases, with the confined entangled one characterized by strings wrapping around the whole lattice. We explain how to study larger lattices by using either tensor network techniques or digital quantum simulations with Rydberg atoms loaded in optical lattices, where we discuss in detail a protocol for the preparation of the ground-state. We propose two key experimental tests that can be used as smoking gun of the proper implementation of a gauge theory in optical lattices. These tests consist in verifying the absence of spontaneous (gauge) symmetry breaking of the ground-state and the presence of charge confinement. We also comment on the relation between standard compact U(1) lattice gauge theory and the model considered in this paper. - Highlights: Black-Right-Pointing-Pointer We study the quantum simulation of dynamical gauge theories in optical lattices. Black-Right-Pointing-Pointer We focus on digital simulation of abelian lattice gauge theory. Black-Right-Pointing-Pointer We rediscover and discuss the puzzling phase diagram of gauge magnets. Black-Right-Pointing-Pointer We detail the protocol for time evolution and ground-state preparation in any phase. Black-Right-Pointing-Pointer We provide two experimental tests to validate gauge theory quantum simulators.

  17. 2D optical beam splitter using diffractive optical elements (DOE)

    NASA Astrophysics Data System (ADS)

    Wen, Fung J.; Chung, Po S.

    2006-09-01

    A novel approach for optical beam distribution into a 2-dimensional (2-D) packaged fiber arrays using 2-D Dammann gratings is investigated. This paper focuses on the design and fabrication of the diffractive optical element (DOE) and investigates the coupling efficiencies of the beamlets into a packaged V-grooved 2x2 fibre array. We report for the first time experimental results of a 2-D optical signal distribution into a packaged 2x2 fibre array using Dammann grating. This grating may be applicable to the FTTH network as it can support sufficient channels with good output uniformity together with low polarization dependent loss (PDL) and acceptable insertion loss. Using an appropriate optimization algorithm (the steepest descent algorithm in this case), the optimum profile for the gratings can be calculated. The gratings are then fabricated on ITO glass using electron-beam lithography. The overall performance of the design shows an output uniformity of around 0.14 dB and an insertion loss of about 12.63 dB, including the DOE, focusing lens and the packaged fiber array.

  18. Quantum spin Hall phase in 2D trigonal lattice

    PubMed Central

    Wang, Z. F.; Jin, Kyung-Hwan; Liu, Feng

    2016-01-01

    The quantum spin Hall (QSH) phase is an exotic phenomena in condensed-matter physics. Here we show that a minimal basis of three orbitals (s, px, py) is required to produce a QSH phase via nearest-neighbour hopping in a two-dimensional trigonal lattice. Tight-binding model analyses and calculations show that the QSH phase arises from a spin–orbit coupling (SOC)-induced s–p band inversion or p–p bandgap opening at Brillouin zone centre (Γ point), whose topological phase diagram is mapped out in the parameter space of orbital energy and SOC. Remarkably, based on first-principles calculations, this exact model of QSH phase is shown to be realizable in an experimental system of Au/GaAs(111) surface with an SOC gap of ∼73 meV, facilitating the possible room-temperature measurement. Our results will extend the search for substrate supported QSH materials to new lattice and orbital types. PMID:27599580

  19. Mirror effects and optical meta-surfaces in 2d atomic arrays

    NASA Astrophysics Data System (ADS)

    Shahmoon, Ephraim; Wild, Dominik; Lukin, Mikhail; Yelin, Susanne

    2016-05-01

    Strong optical response of natural and artificial (meta-) materials typically relies on the fact that the lattice constant that separates their constituent particles (atoms or electromagnetic resonators, respectively) is much smaller than the optical wavelength. Here we consider a single layer of a 2d atom array with a lattice constant on the order of an optical wavelength, which can be thought of as a highly dilute 2d metamaterial (meta-surface). Our theoretical analysis shows how strong scattering of resonant incoming light off the array can be controlled by choosing its lattice constant, e.g. allowing the array to operate as a perfect mirror or a retro-reflector for most incident angles of the incoming light. We discuss the prospects for quantum metasurfaces, i.e. the ability to shape the output quantum state of light by controlling the atomic states, and the possible generality of our results as a universal wave phenomena.

  20. New optical 2D modulator jacketed in rotational plastic optics

    NASA Astrophysics Data System (ADS)

    Heinol, Horst G.; Xu, Z.; Schwarte, Rudolf; Loffeld, Otmar

    1995-12-01

    Optical and therefore nontactile 3D-measurement techniques are of increasing interest in industrial automation, especially in quality control and guidance of automotive vehicles. In connection with these demands, a new type of optical modulator jacketed in rotational plastic optics is introduced in the paper. Furthermore first results obtained by simulation studies will be presented. A simple nevertheless effective way of obtaining 3D information is to illuminate the whole 3D object or scene simultaneously with rf-modulated light. This can be well achieved by using the suggested optical modulator that incorporates the properties of a high aperture and minimum aberration in the 3D-imaging process. The mentioned modulator makes use of the effect of Frustrated Total Reflection (FTR). To exploit this FTR effect in an optical 2D mixer, the gap width between media of higher dense has to be modulated by an rf-voltage applied to a piezo crystal as an rf-controlled tuning medium. Considering the limited modulation bandwidth due to the parasitic capacity of the piezo crystal, the geometrical dimension of the modulator must be made as small as possible. Therefore the spot of the light is collimated at the focal point of the jacketing rotational ellipsoid. The integrated component made of plastic optics and piezo crystal plays a substantial role for the optical modulation and imaging. Some simulation results of this optical device show that the inherent non-linearity of the FTR modulator may be neglected in practical applications, thus yielding a high modulation depth. Furthermore, a 3D-image system adopting this plastic-made optics is also depicted in the paper, which is robust and handy for several industrial applications.

  1. Multi-resonant optical parametric oscillator based on 2D-PPLT nonlinear photonic crystal.

    PubMed

    Lazoul, Mohamed; Boudrioua, Azzedine; Simohamed, Lotfy-Mokhtar; Peng, Lung-Han

    2015-04-15

    The aim of this work is to achieve an optical parametric oscillator based on two-dimensional periodically poled lithium tantalate (2D-PPLT) crystals that are designed to allow multiple reciprocal lattice-vector contribution to the quasi-phase matching scheme. We are particularly interested in the effect of the multi-wavelength parametric generation performed by the 2D nonlinear photonic crystal to achieve a multi-resonant optical parametric oscillator. The performances are studied in terms of generation efficiency and multi-wavelength generation.

  2. 2D Materials for Optical Modulation: Challenges and Opportunities.

    PubMed

    Yu, Shaoliang; Wu, Xiaoqin; Wang, Yipei; Guo, Xin; Tong, Limin

    2017-02-21

    Owing to their atomic layer thickness, strong light-material interaction, high nonlinearity, broadband optical response, fast relaxation, controllable optoelectronic properties, and high compatibility with other photonic structures, 2D materials, including graphene, transition metal dichalcogenides and black phosphorus, have been attracting increasing attention for photonic applications. By tuning the carrier density via electrical or optical means that modifies their physical properties (e.g., Fermi level or nonlinear absorption), optical response of the 2D materials can be instantly changed, making them versatile nanostructures for optical modulation. Here, up-to-date 2D material-based optical modulation in three categories is reviewed: free-space, fiber-based, and on-chip configurations. By analysing cons and pros of different modulation approaches from material and mechanism aspects, the challenges faced by using these materials for device applications are presented. In addition, thermal effects (e.g., laser induced damage) in 2D materials, which are critical to practical applications, are also discussed. Finally, the outlook for future opportunities of these 2D materials for optical modulation is given.

  3. 2D mapping of texture and lattice parameters of dental enamel.

    PubMed

    Al-Jawad, Maisoon; Steuwer, Axel; Kilcoyne, Susan H; Shore, Roger C; Cywinski, Robert; Wood, David J

    2007-06-01

    We have used synchrotron X-ray diffraction to study the texture and the change in lattice parameter as a function of position in a cross section of human dental enamel. Our study is the first to map changes in preferred orientation and lattice parameter as a function of position within enamel across a whole tooth section with such high resolution. Synchrotron X-ray diffraction with a micro-focused beam spot was used to collect two-dimensional (2D) diffraction images at 150 microm spatial resolution over the entire tooth crown. Contour maps of the texture and lattice parameter distribution of the hydroxyapatite phase were produced from Rietveld refinement of diffraction patterns generated by azimuthally sectioning and integrating the 2D images. The 002 Debye ring showed the largest variation in intensity. This variation is indicative of preferred orientation. Areas of high crystallite alignment on the tooth cusps match the expected biting surfaces. Additionally we found a large variation in lattice parameter when travelling from the enamel surface to the enamel-dentine junction. We believe this to be due to a change in the chemical composition within the tooth. The results provide a new insight on the texture and lattice parameter profiles within enamel.

  4. Influence of lattice defects on the ferromagnetic resonance behaviour of 2D magnonic crystals

    PubMed Central

    Manzin, Alessandra; Barrera, Gabriele; Celegato, Federica; Coïsson, Marco; Tiberto, Paola

    2016-01-01

    This paper studies, from a modelling point of view, the influence of randomly distributed lattice defects (non-patterned areas and variable hole size) on the ferromagnetic resonance behaviour and spin wave mode profiles of 2D magnonic crystals based on Ni80Fe20 antidot arrays with hexagonal lattice. A reference sample is first defined via the comparison of experimental and simulated hysteresis loops and magnetoresistive curves of patterned films, prepared by self-assembly of polystyrene nanospheres. Second, a parametric analysis of the dynamic response is performed, investigating how edge, quasi-uniform and localized modes are affected by alterations of the lattice geometry and bias field amplitude. Finally, some results about the possible use of magnetic antidot arrays in frequency-based sensors for magnetic bead detection are presented, highlighting the need for an accurate control of microstructural features. PMID:26911336

  5. 2D Magneto-Optical Trapping of Diatomic Molecules

    NASA Astrophysics Data System (ADS)

    Hummon, Matthew T.; Yeo, Mark; Stuhl, Benjamin K.; Collopy, Alejandra L.; Xia, Yong; Ye, Jun

    2013-04-01

    We demonstrate one- and two-dimensional transverse laser cooling and magneto-optical trapping of the polar molecule yttrium (II) oxide (YO). In a 1D magneto-optical trap (MOT), we characterize the magneto-optical trapping force and decrease the transverse temperature by an order of magnitude, from 25 to 2 mK, limited by interaction time. In a 2D MOT, we enhance the intensity of the YO beam and reduce the transverse temperature in both transverse directions. The approach demonstrated here can be applied to many molecular species and can also be extended to 3D.

  6. Lattice-induced nonadiabatic frequency shifts in optical lattice clocks

    SciTech Connect

    Beloy, K.

    2010-09-15

    We consider the frequency shift in optical lattice clocks which arises from the coupling of the electronic motion to the atomic motion within the lattice. For the simplest of three-dimensional lattice geometries this coupling is shown to affect only clocks based on blue-detuned lattices. We have estimated the size of this shift for the prospective strontium lattice clock operating at the 390-nm blue-detuned magic wavelength. The resulting fractional frequency shift is found to be on the order of 10{sup -18} and is largely overshadowed by the electric quadrupole shift. For lattice clocks based on more complex geometries or other atomic systems, this shift could potentially be a limiting factor in clock accuracy.

  7. Realizing Parafermions in Optical Lattices

    NASA Astrophysics Data System (ADS)

    Liu, Fangli; Gorshkov, Alexey

    2016-05-01

    Parafermions, which are the fractional versions of Majorana fermions, possess more exotic braiding statistics than Majorana fermions and are therefore more powerful from the point of view of topological quantum computing. We propose a scheme to realize parafermionic zero modes in optical lattices, without the use of superconductive paring. With the help of laser assisted tunneling and on-site interactions, two layers of ultracold atoms in distinct hyperfine states can be engineered to host +/- 1 / m fractional quantum Hall states. We then introduce a finite-extent potential barrier that pierces both layers - this gives rise to two counter-propagating edge states that sit on top of each other. Finally, laser induced coupling is used to introduce backscattering between the two edge states and to gap them out. We show that the resulting defects give rise to the topological degeneracy associated with parafermions. We also discuss methods for preparation and detection.

  8. 2D lattice model of a lipid bilayer: Microscopic derivation and thermodynamic exploration

    NASA Astrophysics Data System (ADS)

    Hakobyan, Davit; Heuer, Andreas

    2017-02-01

    Based on all-atom Molecular Dynamics (MD) simulations of a lipid bilayer we present a systematic mapping on a 2D lattice model. Keeping the lipid type and the chain order parameter as key variables we derive a free energy functional, containing the enthalpic interaction of adjacent lipids as well as the tail entropy. The functional form of both functions is explicitly determined for saturated and polyunsaturated lipids. By studying the lattice model via Monte Carlo simulations it is possible to reproduce the temperature dependence of the distribution of order parameters of the pure lipids, including the prediction of the gel transition. Furthermore, application to a mixture of saturated and polyunsaturated lipids yields the correct phase separation behavior at lower temperatures with a simulation time reduced by approximately 7 orders of magnitude as compared to the corresponding MD simulations. Even the time-dependence of the de-mixing is reproduced on a semi-quantitative level. Due to the generality of the approach we envisage a large number of further applications, ranging from modeling larger sets of lipids, sterols, and solvent proteins to predicting nucleation barriers for the melting of lipids. Particularly, from the properties of the 2D lattice model one can directly read off the enthalpy and entropy change of the 1,2-dipalmitoyl-sn-glycero-3-phosphocholine gel-to-liquid transition in excellent agreement with experimental and MD results.

  9. 2D photonic crystals on the Archimedean lattices (tribute to Johannes Kepler (1571 1630))

    NASA Astrophysics Data System (ADS)

    Gajić, R.; class="cross-out">D. Jovanović,

    2008-03-01

    Results of our research on 2D Archemedean lattice photonic crystals are presented. This involves the calculations of the band structures, band-gap maps, equifrequency contours and FDTD simulations of electromagnetic propagation through the structures as well as an experimental verification of negative refraction at microwaves. The band-gap dependence on dielectric contrast is established both for dielectric rods in air and air-holes in dielectric materials. A special emphasis is placed on possibilities of negative refraction and left-handedness in these structures. Together with the familiar Archimedean lattices like square, triangular, honeycomb and Kagome' ones, we consider also, the less known, (3 2, 4, 3, 4) (ladybug) and (3, 4, 6, 4) (honeycomb-ring) structures.

  10. Self-Assembly of Cubes into 2D Hexagonal and Honeycomb Lattices by Hexapolar Capillary Interactions

    NASA Astrophysics Data System (ADS)

    Soligno, Giuseppe; Dijkstra, Marjolein; van Roij, René

    2016-06-01

    Particles adsorbed at a fluid-fluid interface induce capillary deformations that determine their orientations and generate mutual capillary interactions which drive them to assemble into 2D ordered structures. We numerically calculate, by energy minimization, the capillary deformations induced by adsorbed cubes for various Young's contact angles. First, we show that capillarity is crucial not only for quantitative, but also for qualitative predictions of equilibrium configurations of a single cube. For a Young's contact angle close to 90°, we show that a single-adsorbed cube generates a hexapolar interface deformation with three rises and three depressions. Thanks to the threefold symmetry of this hexapole, strongly directional capillary interactions drive the cubes to self-assemble into hexagonal or graphenelike honeycomb lattices. By a simple free-energy model, we predict a density-temperature phase diagram in which both the honeycomb and hexagonal lattice phases are present as stable states.

  11. Anyonic braiding in optical lattices

    PubMed Central

    Zhang, Chuanwei; Scarola, V. W.; Tewari, Sumanta; Das Sarma, S.

    2007-01-01

    Topological quantum states of matter, both Abelian and non-Abelian, are characterized by excitations whose wavefunctions undergo nontrivial statistical transformations as one excitation is moved (braided) around another. Topological quantum computation proposes to use the topological protection and the braiding statistics of a non-Abelian topological state to perform quantum computation. The enormous technological prospect of topological quantum computation provides new motivation for experimentally observing a topological state. Here, we explicitly work out a realistic experimental scheme to create and braid the Abelian topological excitations in the Kitaev model built on a tunable robust system, a cold atom optical lattice. We also demonstrate how to detect the key feature of these excitations: their braiding statistics. Observation of this statistics would directly establish the existence of anyons, quantum particles that are neither fermions nor bosons. In addition to establishing topological matter, the experimental scheme we develop here can also be adapted to a non-Abelian topological state, supported by the same Kitaev model but in a different parameter regime, to eventually build topologically protected quantum gates. PMID:18000038

  12. Analysis of the antiferromagnetic phase transitions of the 2D Kondo lattice

    NASA Astrophysics Data System (ADS)

    Jones, Barbara

    2010-03-01

    The Kondo lattice continues to present an interesting and relevant challenge, with its interactions between Kondo, RKKY, and coherent order. We present our study[1] of the antiferromagnetic quantum phase transitions of a 2D Kondo-Heisenberg square lattice. Starting from the nonlinear sigma model as a model of antiferromagnetism, we carry out a renormalization group analysis of the competing Kondo-RKKY interaction to one-loop order in an ɛ-expansion. We find a new quantum critical point (QCP) strongly affected by Kondo fluctuations. Near this QCP, there is a breakdown of hydrodynamic behavior, and the spin waves are logarithmically frozen out. The renormalization group results allow us to propose a new phase diagram near the antiferromagnetic fixed point of this 2D Kondo lattice model. The T=0 phase diagram contains four phases separated by a tetracritical point, the new QCP. For small spin fluctuations, we find a stable local magnetic moment antiferromagnet. For stronger coupling, region II is a metallic quantum disordered paramagnet. We find in region III a paramagnetic phase driven by Kondo interactions, with possible ground states of a heavy fermion liquid or a Kondo driven spin-liquid. The fourth phase is a spiral phase, or a large-Fermi-surface antiferromagnetic phase. We will describe these phases in more detail, including possible experimental confirmation of the spiral phase. The existence of the tetracritical point found here would be expected to affect the phase diagram at finite temperatures as well. In addition, It is hoped that these results, and particularly the Kondo interaction paramagnetic phase, will serve to bridge to solutions starting from the opposite limit, of a Kondo effect leading to a heavy fermion ground state. Work in collaboration with T. Tzen Ong. [4pt] [1] T. Ong and B. A. Jones, Phys. Rev. Lett. 103, 066405 (2009).

  13. Optical physics: Magnetic appeal in strained lattice

    NASA Astrophysics Data System (ADS)

    Lepetit, Thomas

    2013-02-01

    Using strain to induce a pseudomagnetic field in a photonic lattice at optical frequencies might bring improvements to fields such as photonic crystal fibres, supercontinuum generation and frequency combs.

  14. Colloquium: Physics of optical lattice clocks

    SciTech Connect

    Derevianko, Andrei; Katori, Hidetoshi

    2011-04-01

    Recently invented and demonstrated optical lattice clocks hold great promise for improving the precision of modern time keeping. These clocks aim at the 10{sup -18} fractional accuracy, which translates into a clock that would neither lose nor gain a fraction of a second over an estimated age of the Universe. In these clocks, millions of atoms are trapped and interrogated simultaneously, dramatically improving clock stability. Here the principles of operation of these clocks are discussed and, in particular, a novel concept of magic trapping of atoms in optical lattices. Recently proposed microwave lattice clocks are also highlights and several applications that employ the optical lattice clocks as a platform for precision measurements and quantum information processing.

  15. Colloquium: Physics of optical lattice clocks

    NASA Astrophysics Data System (ADS)

    Derevianko, Andrei; Katori, Hidetoshi

    2011-04-01

    Recently invented and demonstrated optical lattice clocks hold great promise for improving the precision of modern time keeping. These clocks aim at the 10-18 fractional accuracy, which translates into a clock that would neither lose nor gain a fraction of a second over an estimated age of the Universe. In these clocks, millions of atoms are trapped and interrogated simultaneously, dramatically improving clock stability. Here the principles of operation of these clocks are discussed and, in particular, a novel concept of magic trapping of atoms in optical lattices. Recently proposed microwave lattice clocks are also highlights and several applications that employ the optical lattice clocks as a platform for precision measurements and quantum information processing.

  16. DESIGN OF THE RCMS LATTICE OPTICS.

    SciTech Connect

    CARDONA,J.; KEWISCH,J.; PEGGS,S.

    2002-06-02

    THE RAPID CYCLING MEDICAL SYNCHROTRON (RCMS) IS DESIGNED TO BE A VERY LIGHT AND INEXPENSIVE ACCELERATOR. THIS IS POSSIBLE DUE TO THE SMALL BEAM SIZE THAT HAS BEEN CHOSEN EARLY DURING THE DESIGN STAGE. THIS CHOICE HAS IMPLICATIONS IN THE DESIGN OF THE LATTICE OPTICS. IN THIS PAPER, WE PRESENT AN OVERVIEW OF THE RCMS OPTICS LATTICE, THE KIND OF MAGNETS TO BE USED AND ALSO A DESCRIPTION OF A SPECIAL OPTIC MODULE THAT MATCHES THE ROTATING GANTRY WITH THE REST OF THE FIXED ACCELERATOR. TECHNIQUESDEVELOPED TO WIN ADDITIONAL SPACE BETWEEN QUADRUPOLES WITHOUT DISTRUBING BETA FUNCTIONS ARE ALSO PRESENTED.

  17. Fermionic Optical Lattices: A Computational Study

    DTIC Science & Technology

    2014-10-22

    Army Research Office P.O. Box 12211 Research Triangle Park, NC 27709-2211 optical lattices, degenerate quantum gases , quantum control, correlation...with a different wavelength. We systematically determine the real - and momentum-space properties of these states. The crossover from 3D to two...fermions in square lattices. The phases are systematically characterized by the symmetry of the order parameter and the real - and momentum-space

  18. The optical potential on the lattice

    SciTech Connect

    Agadjanov, Dimitri; Doring, Michael; Mai, Maxim; MeiBner, Ulf -G.; Rusetsky, Akaki

    2016-06-08

    The extraction of hadron-hadron scattering parameters from lattice data by using the Luscher approach becomes increasingly complicated in the presence of inelastic channels. We propose a method for the direct extraction of the complex hadron-hadron optical potential on the lattice, which does not require the use of the multi-channel Luscher formalism. Furthermore, this method is applicable without modifications if some inelastic channels contain three or more particles.

  19. Cold bosons in noisy optical lattices

    NASA Astrophysics Data System (ADS)

    Schachenmayer, Johannes; Pichler, Hannes; Zoller, Peter; Daley, Andrew

    2012-02-01

    Cold atoms in optical lattices open the possibility to experimentally study strongly interacting many-body quantum systems with controllable parameters. A key challenge to prepare interesting quantum states in these systems is to achieve sufficiently low temperatures. At these temperatures a deep theoretical understanding of possible heating processes and how they affect the characteristics of the quantum state becomes essential. In every realistic experiment there exist many sources of noise that cause phase and amplitude fluctuations in the standing laser waves that form the optical lattice potential. This classical noise can lead to heating and a significant change of the quantum state. We study the stochastic many-body non-equilibrium dynamics of bosons in an optical lattice and determine how the state changes depending on the characteristics of the noise. We do this by solving time-dependent stochastic many-body Schr"odinger equations, both analytically and numerically.

  20. Creation of quantum-degenerate gases of ytterbium in a compact 2D-/3D-magneto-optical trap setup

    SciTech Connect

    Doerscher, Soeren; Thobe, Alexander; Hundt, Bastian; Kochanke, Andre; Le Targat, Rodolphe; Windpassinger, Patrick; Becker, Christoph; Sengstock, Klaus

    2013-04-15

    We report on the first experimental setup based on a 2D-/3D-magneto-optical trap (MOT) scheme to create both Bose-Einstein condensates and degenerate Fermi gases of several ytterbium isotopes. Our setup does not require a Zeeman slower and offers the flexibility to simultaneously produce ultracold samples of other atomic species. Furthermore, the extraordinary optical access favors future experiments in optical lattices. A 2D-MOT on the strong {sup 1}S{sub 0}{yields}{sup 1}P{sub 1} transition captures ytterbium directly from a dispenser of atoms and loads a 3D-MOT on the narrow {sup 1}S{sub 0}{yields}{sup 3}P{sub 1} intercombination transition. Subsequently, atoms are transferred to a crossed optical dipole trap and cooled evaporatively to quantum degeneracy.

  1. Optical Lattice Gases of Interacting Fermions

    DTIC Science & Technology

    2015-12-02

    theoretical research supported by this grant focused on discovering new phases of quantum matter for ultracold fermionic atoms or molecules confined in optical...Communications, including a review paper on the orbital physics of cold atoms in optical lattices [1] and a book chapter on topological insulators of cold... atoms [14]. A few significant results are highlighted below. 1. Novel phases of cold atoms on higher orbital bands. The research team discovered

  2. Enhancement of long-range correlations in a 2D vortex lattice by an incommensurate 1D disorder potential

    NASA Astrophysics Data System (ADS)

    Guillamon, I.; Vieira, S.; Suderow, H.; Cordoba, R.; Sese, J.; de Teresa, J. M.; Ibarra, R.

    In two dimensional (2D) systems, theory has proposed that random disorder destroys long range correlations driving a transition to a glassy state. Here, I will discuss new insights into this issue obtained through the direct visualization of the critical behaviour of a 2D superconducting vortex lattice formed in a thin film with a smooth 1D thickness modulation. Using scanning tunneling microscopy at 0.1K, we have tracked the modification in the 2D vortex arrangements induced by the 1D thickness modulation while increasing the vortex density by three orders of magnitude. Upon increasing the field, we observed a two-step order-disorder transition in the 2D vortex lattice mediated by the appearance of dislocations and disclinations and accompanied by an increase in the local vortex density fluctuations. Through a detailed analysis of correlation functions, we find that the transition is driven by the incommensurate 1D thickness modulation. We calculate the critical points and exponents and find that they are well above theoretical expectation for random disorder. Our results show that long range 1D correlations in random potentials enhance the stability range of the ordered phase in a 2D vortex lattice. Work supported by Spanish MINECO, CIG Marie Curie Grant, Axa Research Fund and FBBVA.

  3. Ultra-Cold Atoms on Optical Lattices

    ERIC Educational Resources Information Center

    Ghosh, Parag

    2009-01-01

    The field of ultra-cold atoms, since the achievement of Bose-Einstein Condensation (Anderson et al., 1995; Davis et al., 1995; Bradley et al., 1995), have seen an immensely growing interest over the past decade. With the creation of optical lattices, new possibilities of studying some of the widely used models in condensed matter have opened up.…

  4. Atomic Current across an Optical Lattice

    SciTech Connect

    Ponomarev, Alexey V.; Kolovsky, Andrey R.; Madronero, Javier; Buchleitner, Andreas

    2006-02-10

    We devise a microscopic model for the emergence of a collision-induced, fermionic atomic current across a tilted optical lattice. Tuning the--experimentally controllable--parameters of the microscopic dynamics allows us to switch from Ohmic to negative differential conductance.

  5. FDTD analysis of 2D triangular-lattice photonic crystals with arbitrary-shape inclusions based on unit cell transformation

    NASA Astrophysics Data System (ADS)

    Ma, Zetao; Ogusu, Kazuhiko

    2009-04-01

    A finite-difference time-domain method based on Yee's orthogonal cell is utilized to calculate the band structures of 2D triangular-lattice-based photonic crystals through a simple modification to properly shifting the boundaries of the original unit cell. A strategy is proposed for transforming the triangular unit cell into an orthogonal one, which can be used to calculate the band structures of 2D PhCs with various shapes of inclusions, such as triangular, quadrangular, and hexagonal shapes, to overcome the shortage of plane-wave expansion method for circular one. The band structures of 2D triangular-lattice-based PhCs with hexagonal air-holes are calculated and discussed for different values of its radius and rotation angle. The obtained results provide an insight to manipulate the band structures of PhCs.

  6. Controlling polar molecules in optical lattices

    SciTech Connect

    Kotochigova, S.; Tiesinga, E.

    2006-04-15

    We theoretically investigate the interaction of polar molecules with optical lattices and microwave fields. We demonstrate the existence of frequency windows in the optical domain where the complex internal structure of the molecule does not influence the trapping potential of the lattice. In such frequency windows the Franck-Condon factors are so small that near-resonant interaction of vibrational levels of the molecule with the lattice fields have a negligible contribution to the polarizability, and light-induced decoherences are kept to a minimum. In addition, we show that microwave fields can induce a tunable dipole-dipole interaction between ground-state rotationally symmetric (J=0) molecules. A combination of a carefully chosen lattice frequency and microwave-controlled interaction between molecules will enable trapping of polar molecules in a lattice and possibly realize molecular quantum logic gates. Our results are based on ab initio relativistic electronic structure calculations of the polar KRb and RbCs molecules combined with calculations of their rovibrational motion.

  7. Micropolar dissipative models for the analysis of 2D dispersive waves in periodic lattices

    NASA Astrophysics Data System (ADS)

    Reda, H.; Ganghoffer, J. F.; Lakiss, H.

    2017-03-01

    The computation of the dispersion relations for dissipative periodic lattices having the attributes of metamaterials is an actual research topic raising the interest of researchers in the field of acoustics and wave propagation phenomena. We analyze in this contribution the impact of wave damping on the dispersion features of periodic lattices, which are modeled as beam-lattices. The band diagram structure and damping ratio are computed for different repetitive lattices, based on the homogenized continuum response of the initially discrete lattice architecture, modeled as Kelvin-Voigt viscoelastic beams. Three of these lattices (reentrant hexagonal, chiral diamond, hexachiral lattice) are auxetic metamaterials, since they show negative Poisson's ratio. The effective viscoelastic anisotropic continuum behavior of the lattices is first computed in terms of the homogenized stiffness and viscosity matrices, based on the discrete homogenization technique. The dynamical equations of motion are obtained for an equivalent homogenized micropolar continuum evaluated based on the homogenized properties, and the dispersion relation and damping ratio are obtained by inserting an harmonic plane waves Ansatz into these equations. The comparison of the acoustic properties obtained in the low frequency range for the four considered lattices shows that auxetic lattices attenuate waves at lower frequencies compared to the classical hexagonal lattice. The diamond chiral lattice shows the best attenuation properties of harmonic waves over the entire Brillouin zone, and the hexachiral lattice presents better acoustic properties than the reentrant hexagonal lattice. The range of validity of the effective continuum obtained by the discrete homogenization has been assessed by comparing the frequency band structure of this continuum with that obtained by a Floquet-Bloch analysis.

  8. Ultracold Quantum Gases in Hexagonal Optical Lattices

    NASA Astrophysics Data System (ADS)

    Sengstock, Klaus

    2010-03-01

    Hexagonal structures occur in a vast variety of systems, ranging from honeycombs of bees in life sciences to carbon nanotubes in material sciences. The latter, in particular its unfolded two-dimensional layer -- Graphene -- has rapidly grown to one of the most discussed topics in condensed-matter physics. Not only does it show proximity to various carbon-based materials but also exceptional properties owing to its unusual energy spectrum. In quantum optics, ultracold quantum gases confined in periodic light fields have shown to be very general and versatile instruments to mimic solid state systems. However, so far nearly all experiments were performed in cubic lattice geometries only. Here we report on the first experimental realization of ultracold quantum gases in a state-dependent, two-dimensional, Graphene-like optical lattice with hexagonal symmetry. The lattice is realized via a spin-dependent optical lattice structure with alternating σ^+ and σ^- -sites and thus constitutes a so called `magnetic'-lattice with `antiferromagnetic'-structure. Atoms with different spin orientation can be loaded to specific lattice sites or -- depending on the parameters -- to the whole lattice. As a consequence e.g. superpositions of a superfluid spin component with a different spin component in the Mott-insulating phase can be realized as well as spin-dependent transport properties, disorder etc. After preparing an antiferromagnetically ordered state we e.g. measure sustainable changes of the transport properties of the atoms. This manifests in a significant reduction of the tunneling as compared to a single-component system. We attribute this observation to a partial tunneling blockade for one spin component induced by population in another spin component localized at alternating lattice sites. Within a Gutzwiller-Ansatz we calculate the phase diagrams for the mixed spin-states and find very good agreement with our experimental results. Moreover, by state-resolved recording

  9. Fibonacci optical lattices for tunable quantum quasicrystals

    NASA Astrophysics Data System (ADS)

    Singh, K.; Saha, K.; Parameswaran, S. A.; Weld, D. M.

    2015-12-01

    We describe a quasiperiodic optical lattice, created by a physical realization of the abstract cut-and-project construction underlying all quasicrystals. The resulting potential is a generalization of the Fibonacci tiling. Calculation of the energies and wave functions of ultracold atoms loaded into such a lattice demonstrate a multifractal energy spectrum, a singular continuous momentum-space structure, and the existence of controllable edge states. These results open the door to cold atom quantum simulation experiments in tunable or dynamic quasicrystalline potentials, including topological pumping of edge states and phasonic spectroscopy.

  10. Optical Multiplications With Single Element 2-D Acousto-Optic Laser Beam Deflector

    NASA Astrophysics Data System (ADS)

    Soos, Jolanta I.; Leepa, Douglas C.; Rosemeier, Ronald G.

    1989-05-01

    With the current need for developing very fast computers in comparison to conventional digital chip based systems, the future for optical based signal processing is very bright. Attention has turned to a different application of optics utilizing mathematical operations, in which case operations are numerical, sometimes discrete, and often algebraic in nature. Interest has been so vigorous that many view it as a small revolution in optics, whereby optical signal processing is beginning to encompass what is frequently described as optical computing. The term is fully intended to imply a close comparison with the operations performed by scientific digital canputers. This paper will describe the applications of single element 2-D acousto-optic deflectors for optical multiplication systems.

  11. Twisted complex superfluids in optical lattices

    PubMed Central

    Jürgensen, Ole; Sengstock, Klaus; Lühmann, Dirk-Sören

    2015-01-01

    We show that correlated pair tunneling drives a phase transition to a twisted superfluid with a complex order parameter. This unconventional superfluid phase spontaneously breaks the time-reversal symmetry and is characterized by a twisting of the complex phase angle between adjacent lattice sites. We discuss the entire phase diagram of the extended Bose—Hubbard model for a honeycomb optical lattice showing a multitude of quantum phases including twisted superfluids, pair superfluids, supersolids and twisted supersolids. Furthermore, we show that the nearest-neighbor interactions lead to a spontaneous breaking of the inversion symmetry of the lattice and give rise to dimerized density-wave insulators, where particles are delocalized on dimers. For two components, we find twisted superfluid phases with strong correlations between the species already for surprisingly small pair-tunneling amplitudes. Interestingly, this ground state shows an infinite degeneracy ranging continuously from a supersolid to a twisted superfluid. PMID:26345721

  12. Twisted complex superfluids in optical lattices.

    PubMed

    Jürgensen, Ole; Sengstock, Klaus; Lühmann, Dirk-Sören

    2015-09-08

    We show that correlated pair tunneling drives a phase transition to a twisted superfluid with a complex order parameter. This unconventional superfluid phase spontaneously breaks the time-reversal symmetry and is characterized by a twisting of the complex phase angle between adjacent lattice sites. We discuss the entire phase diagram of the extended Bose-Hubbard model for a honeycomb optical lattice showing a multitude of quantum phases including twisted superfluids, pair superfluids, supersolids and twisted supersolids. Furthermore, we show that the nearest-neighbor interactions lead to a spontaneous breaking of the inversion symmetry of the lattice and give rise to dimerized density-wave insulators, where particles are delocalized on dimers. For two components, we find twisted superfluid phases with strong correlations between the species already for surprisingly small pair-tunneling amplitudes. Interestingly, this ground state shows an infinite degeneracy ranging continuously from a supersolid to a twisted superfluid.

  13. Fast dynamics for atoms in optical lattices.

    PubMed

    Łącki, Mateusz; Zakrzewski, Jakub

    2013-02-08

    Cold atoms in optical lattices allow for accurate studies of many body dynamics. Rapid time-dependent modifications of optical lattice potentials may result in significant excitations in atomic systems. The dynamics in such a case is frequently quite incompletely described by standard applications of tight-binding models (such as, e.g., Bose-Hubbard model or its extensions) that typically neglect the effect of the dynamics on the transformation between the real space and the tight-binding basis. We illustrate the importance of a proper quantum mechanical description using a multiband extended Bose-Hubbard model with time-dependent Wannier functions. We apply it to situations directly related to experiments.

  14. The NIM Sr Optical Lattice Clock

    NASA Astrophysics Data System (ADS)

    Lin, Y.; Wang, Q.; Li, Y.; Meng, F.; Lin, B.; Zang, E.; Sun, Z.; Fang, F.; Li, T.; Fang, Z.

    2016-06-01

    A 87Sr optical lattice clock is built at the National Institute of Metrology (NIM) of China. The atoms undergo two stages of laser cooling before being loaded into a horizontal optical lattice at the magic wavelength of 813 nm. After being interrogated by a narrow linewidth 698 nm clock laser pulse, the normalized excitation rate is measured to get the frequency error, which is then used to lock the clock laser to the ultra-narrow 1S0-3P0 clock transition. The total systematic uncertainty of the clock is evaluated to be 2.3 × 10-16, and the absolute frequency of the clock is measured to be 429 228 004 229 873.7(1.4) Hz with reference to the NIM5 cesium fountain.

  15. Acousto-Optic Processing of 2-D Signals Using Temporal and Spatial Integration.

    DTIC Science & Technology

    1986-04-29

    AD-AI?3 411 ACOUSTO - OPTIC PROCESSING OF 2-D SIGNALS USING TEMPORAL 1/ AND SPATIAL INTEGR..(U) CRLIFORNIA INST OF TECH PASADENA DEPT OF ELECTRICAL...LECTE 3 FINAL REORT4 Submitted to: Al FORCE OFFICE OF SCIENTIFIC RESEARCH Grant Number AFOSR-82-0128 :A of % ACOUSTO - OPTIC PROCISSING OF 2-D SIGNALS...Psaltis, Applied Optics, Vol. 21, No. 3, 1 February 1982. (3) " Acousto - Optic /CCD Image Processor, Demetri Psaltis, Eung Gi Paek and Santosh Venkatesh

  16. Spin-1/2 Optical Lattice Clock

    NASA Astrophysics Data System (ADS)

    Lemke, N. D.; Ludlow, A. D.; Barber, Z. W.; Fortier, T. M.; Diddams, S. A.; Jiang, Y.; Jefferts, S. R.; Heavner, T. P.; Parker, T. E.; Oates, C. W.

    2009-08-01

    We experimentally investigate an optical clock based on Yb171 (I=1/2) atoms confined in an optical lattice. We have evaluated all known frequency shifts to the clock transition, including a density-dependent collision shift, with a fractional uncertainty of 3.4×10-16, limited principally by uncertainty in the blackbody radiation Stark shift. We measured the absolute clock transition frequency relative to the NIST-F1 Cs fountain clock and find the frequency to be 518 295 836 590 865.2(0.7) Hz.

  17. On the sign problem in 2D lattice super Yang-Mills

    NASA Astrophysics Data System (ADS)

    Catterall, Simon; Galvez, Richard; Joseph, Anosh; Mehta, Dhagash

    2012-01-01

    In recent years a new class of supersymmetric lattice theories have been proposed which retain one or more exact supersymmetries for non-zero lattice spacing. Recently there has been some controversy in the literature concerning whether these theories suffer from a sign problem. In this paper we address this issue by conducting simulations of the mathcal{N} = (2, 2) and mathcal{N} = (8, 8) supersymmetric Yang-Mills theories in two dimensions for the U(N ) theories with N = 2, 3, 4, using the new twisted lattice formulations. Our results provide evidence that these theories do not suffer from a sign problem in the continuum limit. These results thus boost confidence that the new lattice formulations can be used successfully to explore non-perturbative aspects of four-dimensional mathcal{N} = 4 supersymmetric Yang-Mills theory.

  18. 2-D Acousto-Optic Signal Processors for Simultaneous Spectrum Analysis and Direction Finding

    DTIC Science & Technology

    1990-11-01

    National Dfense Defence nationale 2-D ACOUSTO - OPTIC SIGNAL PROCESSORS FOR SIMULTANEOUS SPECTRUM ANALYSIS 00 AND DIRECTION FINDING (U) by NM Jim P.Y...Wr pdft .1w I0~1111191 3 05089 National DIfense Defence nationale 2-D ACOUSTO - OPTIC SIGNAL PROCESSORS FOR SIMULTANEOUS SPECTRUM ANALYSIS AND DIRECTION...Processing, J.T. Tippet et al., Eds., Chapter 38, pp. 715-748, MIT Press, Cambridge 1965. [6] A.E. Spezio," Acousto - optics for Electronic Warfare

  19. Hofstadter butterfly in the Falicov-Kimball model on some finite 2D lattices

    NASA Astrophysics Data System (ADS)

    Pradhan, Subhasree

    2016-12-01

    Spinless, interacting electrons on a finite size triangular lattice moving in an extremely strong perpendicular magnetic field are studied in comparison to a square lattice. Using a Falicov-Kimball model, the effects of Coulomb correlation, magnetic field and finite system size on their energy spectrum are observed. Exact diagonalization and Monte Carlo simulation methods (based on a modified Metropolis algorithm) have been employed to examine the recursive structure of the Hofstadter spectrum in the presence of several electronic correlation strengths for different system sizes. It is possible to introduce a gap in the density of states even in the absence of electron correlation, which is anticipated as a metal to insulator transition driven by an orbital magnetic field. With further inclusion of the interaction, the gap in the spectrum is modified and in some cases the correlation is found to suppress extra states manifested by the finite size effects. At a certain flux, the opened gap due to magnetic field is reduced by the Coulomb interaction. An orbital current is calculated for both the square and the triangular lattice with and without electron correlation. In the non-interacting limit, the bulk current shows several patterns, while the edge current shows oscillations with magnetic flux. The oscillations persist in the interacting limit for the square lattice, but not for the triangular lattice.

  20. Hofstadter butterfly in the Falicov-Kimball model on some finite 2D lattices.

    PubMed

    Pradhan, Subhasree

    2016-12-21

    Spinless, interacting electrons on a finite size triangular lattice moving in an extremely strong perpendicular magnetic field are studied in comparison to a square lattice. Using a Falicov-Kimball model, the effects of Coulomb correlation, magnetic field and finite system size on their energy spectrum are observed. Exact diagonalization and Monte Carlo simulation methods (based on a modified Metropolis algorithm) have been employed to examine the recursive structure of the Hofstadter spectrum in the presence of several electronic correlation strengths for different system sizes. It is possible to introduce a gap in the density of states even in the absence of electron correlation, which is anticipated as a metal to insulator transition driven by an orbital magnetic field. With further inclusion of the interaction, the gap in the spectrum is modified and in some cases the correlation is found to suppress extra states manifested by the finite size effects. At a certain flux, the opened gap due to magnetic field is reduced by the Coulomb interaction. An orbital current is calculated for both the square and the triangular lattice with and without electron correlation. In the non-interacting limit, the bulk current shows several patterns, while the edge current shows oscillations with magnetic flux. The oscillations persist in the interacting limit for the square lattice, but not for the triangular lattice.

  1. New optimization problems arising in modelling of 2D-crystal lattices

    NASA Astrophysics Data System (ADS)

    Evtushenko, Yury; Lurie, Sergey; Posypkin, Mikhail

    2016-10-01

    The paper considers the problem of finding the structure of a fragment of two-dimensional crystal lattice with the minimal energy. Atoms in a lattice reside on parallel lines (layers). The interatomic distances are the same within one layer but can differ for distinct layers. The energy of the piece of material is computed using so-called potential functions. We used Lennard-Jones, Morse and Tersoff potentials. The proposed formulation can serve as a scalable complex non-smooth optimization test. The paper evaluates various optimization techniques for the problem under consideration, compares their performances and draws the conclusion about the best choice of optimization methods for the problem under test. As a result we were able to locate minima meaningful from the physical point of view, e.g. reproducing graphene lattice.

  2. Quantum theory of cold bosonic atoms in optical lattices

    SciTech Connect

    Tilahun, Dagim; Duine, R. A.; MacDonald, A. H.

    2011-09-15

    Ultracold atoms in optical lattices undergo a quantum phase transition from a superfluid to a Mott insulator as the lattice potential depth is increased. We describe an approximate theory of interacting bosons in optical lattices which provides a qualitative description of both superfluid and insulator states. The theory is based on a change of variables in which the boson coherent state amplitude is replaced by an effective potential which promotes phase coherence between different number states on each lattice site. It is illustrated here by applying it to uniform and fully frustrated lattice cases but is simple enough that it can be applied to spatially inhomogeneous lattice systems.

  3. Quantum Entanglement in Optical Lattice Systems

    DTIC Science & Technology

    2015-02-18

    superfluidity, Physical Review A (02 2013) Yinyin Qian, Ming Gong, Chuanwei Zhang. Many-body Landau -Zener transition in cold-atom double-well...in a Trapped Bose-Einstein Condensate, arXiv:1111.4778v1 (11 2011) Yinyin Qian, Ming Gong, Chuanwei Zhang. Many-body Landau -Zener Transition in...PhysRevA.87.023611 5. Y. Qian, M. Gong, and C. Zhang, Many-body Landau -Zener Transition in Cold Atom Double Well Optical Lattices, Physical Review A 87

  4. Solids and Supersolids of Three-Body Interacting Polar Molecules on an Optical Lattice

    SciTech Connect

    Schmidt, Kai P.; Dorier, Julien; Laeuchli, Andreas M.

    2008-10-10

    We study the physics of cold polar molecules loaded into an optical lattice in the regime of strong three-body interactions, as put forward recently by Buechler et al.[Nature Phys. 3, 726 (2007)]. To this end, quantum Monte Carlo simulations, exact diagonalization, and a semiclassical approach are used to explore hard-core bosons on the 2D square lattice which interact solely by long-ranged three-body terms. The resulting phase diagram shows a sequence of solid and supersolid phases. Our findings are directly relevant for future experimental implementations and open a new route towards the discovery of a lattice supersolid phase in experiment.

  5. The puzzle of apparent linear lattice artifacts in the 2d non-linear σ-model and Symanzik's solution

    NASA Astrophysics Data System (ADS)

    Balog, Janos; Niedermayer, Ferenc; Weisz, Peter

    2010-01-01

    Lattice artifacts in the 2d O( n) non-linear σ-model are expected to be of the form O(a), and hence it was (when first observed) disturbing that some quantities in the O(3) model with various actions show parametrically stronger cutoff dependence, apparently O(a), up to very large correlation lengths. In a previous letter Balog et al. (2009) [1] we described the solution to this puzzle. Based on the conventional framework of Symanzik's effective action, we showed that there are logarithmic corrections to the O(a) artifacts which are especially large ( lna) for n=3 and that such artifacts are consistent with the data. In this paper we supply the technical details of this computation. Results of Monte Carlo simulations using various lattice actions for O(3) and O(4) are also presented.

  6. Observation of Stueckelberg oscillations in accelerated optical lattices

    SciTech Connect

    Zenesini, A.; Ciampini, D.; Arimondo, E.; Morsch, O.

    2010-12-15

    We report the experimental observation of Stueckelberg oscillations of matter waves in optical lattices. Extending previous work on Landau-Zener tunneling of Bose-Einstein condensates in optical lattices, we study the effects of the accumulated phase between two successive crossings of the Brillouin zone edge. Our results agree well with a simple model for multiple Landau-Zener tunneling events taking into account the band structure of the optical lattice.

  7. Phases of a two-dimensional bose gas in an optical lattice.

    PubMed

    Jiménez-García, K; Compton, R L; Lin, Y-J; Phillips, W D; Porto, J V; Spielman, I B

    2010-09-10

    Ultracold atoms in optical lattices realize simple condensed matter models. We create an ensemble of ≈60 harmonically trapped 2D Bose-Hubbard systems from a 87Rb Bose-Einstein condensate in an optical lattice and use a magnetic resonance imaging approach to select a few 2D systems for study, thereby eliminating ensemble averaging. Our identification of the transition from superfluid to Mott insulator, as a function of both atom density and lattice depth, is in excellent agreement with a universal state diagram [M. Rigol, Phys. Rev. A 79 053605 (2009)] suitable for our trapped system. In agreement with theory, our data suggest a failure of the local density approximation in the transition region.

  8. A low maintenance Sr optical lattice clock

    NASA Astrophysics Data System (ADS)

    Hill, I. R.; Hobson, R.; Bowden, W.; Bridge, E. M.; Donnellan, S.; Curtis, E. A.; Gill, P.

    2016-06-01

    We describe the Sr optical lattice clock apparatus at NPL with particular emphasis on techniques used to increase reliability and minimise the human requirement in its operation. Central to this is a clock-referenced transfer cavity scheme for the stabilisation of cooling and trapping lasers. We highlight several measures to increase the reliability of the clock with a view towards the realisation of an optical time-scale. The clock contributed 502 hours of data over a 25 day period (84% uptime) in a recent measurement campaign with several uninterrupted periods of more than 48 hours. An instability of 2 x 10-17 was reached after 105 s of averaging in an interleaved self-comparison of the clock.

  9. Lattice Boltzmann methods for some 2-D nonlinear diffusion equations:Computational results

    SciTech Connect

    Elton, B.H.; Rodrigue, G.H. . Dept. of Applied Science Lawrence Livermore National Lab., CA ); Levermore, C.D. . Dept. of Mathematics)

    1990-01-01

    In this paper we examine two lattice Boltzmann methods (that are a derivative of lattice gas methods) for computing solutions to two two-dimensional nonlinear diffusion equations of the form {partial derivative}/{partial derivative}t u = v ({partial derivative}/{partial derivative}x D(u){partial derivative}/{partial derivative}x u + {partial derivative}/{partial derivative}y D(u){partial derivative}/{partial derivative}y u), where u = u({rvec x},t), {rvec x} {element of} R{sup 2}, v is a constant, and D(u) is a nonlinear term that arises from a Chapman-Enskog asymptotic expansion. In particular, we provide computational evidence supporting recent results showing that the methods are second order convergent (in the L{sub 1}-norm), conservative, conditionally monotone finite difference methods. Solutions computed via the lattice Boltzmann methods are compared with those computed by other explicit, second order, conservative, monotone finite difference methods. Results are reported for both the L{sub 1}- and L{sub {infinity}}-norms.

  10. Nuclear spin effects in optical lattice clocks

    SciTech Connect

    Boyd, Martin M.; Zelevinsky, Tanya; Ludlow, Andrew D.; Blatt, Sebastian; Zanon-Willette, Thomas; Foreman, Seth M.; Ye Jun

    2007-08-15

    We present a detailed experimental and theoretical study of the effect of nuclear spin on the performance of optical lattice clocks. With a state-mixing theory including spin-orbit and hyperfine interactions, we describe the origin of the {sup 1}S{sub 0}-{sup 3}P{sub 0} clock transition and the differential g factor between the two clock states for alkaline-earth-metal(-like) atoms, using {sup 87}Sr as an example. Clock frequency shifts due to magnetic and optical fields are discussed with an emphasis on those relating to nuclear structure. An experimental determination of the differential g factor in {sup 87}Sr is performed and is in good agreement with theory. The magnitude of the tensor light shift on the clock states is also explored experimentally. State specific measurements with controlled nuclear spin polarization are discussed as a method to reduce the nuclear spin-related systematic effects to below 10{sup -17} in lattice clocks.

  11. Acousto-Optic Processing of 2-D Signals Using Temporal and Spatial Integration.

    DTIC Science & Technology

    1983-05-31

    Documents includes data on: Architectures; Coherence Properties of Pulsed Laser Diodes; Acousto - optic device data; Dynamic Range Issues; Image correlation; Synthetic aperture radar; 2-D Fourier transform; and Moments.

  12. Effect of impurities on the vortex lattice in Bose-Einstein condensates on optical lattice

    NASA Astrophysics Data System (ADS)

    Mithun, T.; Porsezian, K.; Dey, Bishwajyoti

    2015-06-01

    We numerically solve the Gross-Pitaeveskii equation to study the Bose-Einstein condensate in the rotating harmonical tarp and co-rotating optical lattice. The effect of a pinning site or impurity shows that it is able to move the vortex lattice center to either left or right depending on the position of the impurity. Also, it is observed that the impurity at the random positions can destroy the vortex lattice and the resulting disordered lattice has more energy.

  13. ``SAFFMAN-TAYLOR'' Finger in 2d Parallel Viscous: BGK Lattice Gas Simulations

    NASA Astrophysics Data System (ADS)

    Salin, Dominique; Rakotomalala, Nicole; Watzky, Philippe

    1996-11-01

    We study the displacement of miscible fluids between two parallel plates for different values of the Peclet number Pe and of the viscosity ratio M. The full Navier-Stokes problem is addressed. We use the BGK lattice gas method, which is well suited for miscible fluids and allows to introduce molecular diffusion at the microscopic scale of the lattice. This numerical experiment leads to a symmetric concentration profile about the middle of the gap between the plates. At Pe numbers of the order of 1, mixing involves diffusion and advection in the flow direction. At large Pe, the fluids do not mix and an interface between them can be defined. Moreover, above M ~ 10, the interface becomes a well defined finger, the reduced width of which tends to λ_∞=0.56 at large values of M. Assuming that miscible fluids at high Pe numbers are similar to immiscible fluids at high capillary numbers, we find the analytical shape of the finger, using an extrapolation of the Reinelt-Saffman calculations for a Stokes immiscible flow. Surprisingly, the result is that our finger can be deduced from the celebrated Saffman-Taylor' s one, obtained in a potential flow, by a streching in the flow direction by a numerical factor of 2.125.

  14. Modeling Selective Local Interactions with Memory: Motion on a 2D Lattice.

    PubMed

    Weinberg, Daniel; Levy, Doron

    2014-06-15

    We consider a system of particles that simultaneously move on a two-dimensional periodic lattice at discrete times steps. Particles remember their last direction of movement and may either choose to continue moving in this direction, remain stationary, or move toward one of their neighbors. The form of motion is chosen based on predetermined stationary probabilities. Simulations of this model reveal a connection between these probabilities and the emerging patterns and size of aggregates. In addition, we develop a reaction diffusion master equation from which we derive a system of ODEs describing the dynamics of the particles on the lattice. Simulations demonstrate that solutions of the ODEs may replicate the aggregation patterns produced by the stochastic particle model. We investigate conditions on the parameters that influence the locations at which particles prefer to aggregate. This work is a two-dimensional generalization of [Galante & Levy, Physica D, http://dx.doi.org/10.1016/j.physd.2012.10.010], in which the corresponding one-dimensional problem was studied.

  15. Colloidal sorting in dynamic optical lattices

    NASA Astrophysics Data System (ADS)

    Smith, Ryan L.; Spalding, G. C.; Dholakia, K.; MacDonald, M. P.

    2007-08-01

    Passive microfluidic sorting techniques based upon the interaction of particles with an optically defined potential energy landscape have possible advantages over active sorting techniques such as microfluorescence activated cell sorting (FACS), including ease of integration into lab-on-a-chip systems, reconfigurability, and scalability. Rather than analysing and deflecting a single-file stream of particles one by one, a passive approach intrinsically aimed at parallel processing may, ultimately, offer greater potential for high throughput. However attempts to sort many particles simultaneously in high density suspensions are inevitably limited by particle particle interactions, which lead to a reduction in the efficiency of the sorting. In this paper we describe two different approaches aimed at reducing colloidal traffic flow problems. We find that continuous translation of the sorting lattice helps to reduce nearest neighbour particle spacing, providing promise for efficiency improvements in future high throughput applications, and that a flashing lattice yields a reduction in unwanted pile-up and spillover effects which otherwise limit the efficiency of sorting.

  16. Kondo lattice on the edge of a 2D topological insulator

    NASA Astrophysics Data System (ADS)

    Maciejko, Joseph

    2012-02-01

    Much attention has been devoted recently to the experimental and theoretical study of the effect of magnetic impurities on the stability of the gapless boundary modes of topological insulators. When the quantum dynamics of the impurities is considered, those boundary modes constitute novel types of fermionic baths which may affect the nature of possible impurity phases and phase transitions. We study a regular one-dimensional array of quantum magnetic impurities interacting with the helical edge liquid of a two-dimensional time-reversal invariant topological insulator. Exact solutions at the special Toulouse and Luther-Emery points as well as a renormalization group analysis àla Anderson-Yuval allow us to construct a phase diagram in the space of Kondo coupling, electron-electron interaction strength, and electron density. We point out similarities and differences with the Kondo lattice in a ordinary one-dimensional electron gas.

  17. A hydrodynamically-consistent MRT lattice Boltzmann model on a 2D rectangular grid

    NASA Astrophysics Data System (ADS)

    Peng, Cheng; Min, Haoda; Guo, Zhaoli; Wang, Lian-Ping

    2016-12-01

    A multiple-relaxation time (MRT) lattice Boltzmann (LB) model on a D2Q9 rectangular grid is designed theoretically and validated numerically in the present work. By introducing stress components into the equilibrium moments, this MRT-LB model restores the isotropy of diffusive momentum transport at the macroscopic level (or in the continuum limit), leading to moment equations that are fully consistent with the Navier-Stokes equations. The model is derived by an inverse design process which is described in detail. Except one moment associated with the energy square, all other eight equilibrium moments can be theoretically and uniquely determined. The model is then carefully validated using both the two-dimensional decaying Taylor-Green vortex flow and lid-driven cavity flow, with different grid aspect ratios. The corresponding results from an earlier model (Bouzidi et al. (2001) [28]) are also presented for comparison. The results of Bouzidi et al.'s model show problems associated with anisotropy of viscosity coefficients, while the present model exhibits full isotropy and is accurate and stable.

  18. Adiabatic and Hamiltonian computing on a 2D lattice with simple two-qubit interactions

    NASA Astrophysics Data System (ADS)

    Lloyd, Seth; Terhal, Barbara M.

    2016-02-01

    We show how to perform universal Hamiltonian and adiabatic computing using a time-independent Hamiltonian on a 2D grid describing a system of hopping particles which string together and interact to perform the computation. In this construction, the movement of one particle is controlled by the presence or absence of other particles, an effective quantum field effect transistor that allows the construction of controlled-NOT and controlled-rotation gates. The construction translates into a model for universal quantum computation with time-independent two-qubit ZZ and XX+YY interactions on an (almost) planar grid. The effective Hamiltonian is arrived at by a single use of first-order perturbation theory avoiding the use of perturbation gadgets. The dynamics and spectral properties of the effective Hamiltonian can be fully determined as it corresponds to a particular realization of a mapping between a quantum circuit and a Hamiltonian called the space-time circuit-to-Hamiltonian construction. Because of the simple interactions required, and because no higher-order perturbation gadgets are employed, our construction is potentially realizable using superconducting or other solid-state qubits.

  19. Topologically induced swarming phase transition on a 2D percolated lattice

    NASA Astrophysics Data System (ADS)

    Quint, David A.; Gopinathan, Ajay

    2015-07-01

    The emergence of collective motion, or swarming, in groups of moving individuals who orient themselves using only information from their neighbors is a very general phenomenon that occurs at multiple spatio-temporal scales. Swarms that occur in natural environments typically have to contend with spatial disorder such as obstacles that can hinder an individual’s motion or can disrupt communication with neighbors. We study swarming agents, possessing both aligning and mutually avoiding repulsive interactions, in a 2D percolated network representing a topologically disordered environment. We numerically find a phase transition from a collectively moving swarm to a disordered gas-like state above a critical value of the topological or environmental disorder. For agents that utilize only alignment interactions, we find that the swarming transition does not exist in the large system size limit, while the addition of a mutually repulsive interaction can restore the existence of the transition at a finite critical value of disorder. We find there is a finite range of topological disorder where swarming can occur and that this range can be maximized by an optimal amount of mutual repulsion.

  20. A hierarchical lattice spring model to simulate the mechanics of 2-D materials-based composites

    NASA Astrophysics Data System (ADS)

    Brely, Lucas; Bosia, Federico; Pugno, Nicola

    2015-07-01

    In the field of engineering materials, strength and toughness are typically two mutually exclusive properties. Structural biological materials such as bone, tendon or dentin have resolved this conflict and show unprecedented damage tolerance, toughness and strength levels. The common feature of these materials is their hierarchical heterogeneous structure, which contributes to increased energy dissipation before failure occurring at different scale levels. These structural properties are the key to exceptional bioinspired material mechanical properties, in particular for nanocomposites. Here, we develop a numerical model in order to simulate the mechanisms involved in damage progression and energy dissipation at different size scales in nano- and macro-composites, which depend both on the heterogeneity of the material and on the type of hierarchical structure. Both these aspects have been incorporated into a 2-dimensional model based on a Lattice Spring Model, accounting for geometrical nonlinearities and including statistically-based fracture phenomena. The model has been validated by comparing numerical results to continuum and fracture mechanics results as well as finite elements simulations, and then employed to study how structural aspects impact on hierarchical composite material properties. Results obtained with the numerical code highlight the dependence of stress distributions on matrix properties and reinforcement dispersion, geometry and properties, and how failure of sacrificial elements is directly involved in the damage tolerance of the material. Thanks to the rapidly developing field of nanocomposite manufacture, it is already possible to artificially create materials with multi-scale hierarchical reinforcements. The developed code could be a valuable support in the design and optimization of these advanced materials, drawing inspiration and going beyond biological materials with exceptional mechanical properties.

  1. Lattice gaugefixing and other optics in lattice gauge theory

    SciTech Connect

    Yee, Ken.

    1992-06-01

    We present results from four projects. In the first, quark and gluon propagators and effective masses and {Delta}I = 1/2 Rule operator matching coefficients are computed numerically in gaugefixed lattice QCD. In the second, the same quantities are evaluated analytically in the strong coupling, N {yields} {infinity} limit. In the third project, the Schwinger model is studied in covariant gauges, where we show that the effective electron mass varies with the gauge parameter and that longitudinal gaugefixing ambiguities affect operator product expansion coefficients (analogous to {Delta}I = 1/2 Rule matching coefficients) determined by matching gauge variant matrix elements. However, we find that matching coefficients even if shifted by the unphysical modes are {xi} invariant. In the fourth project, we show that the strong coupling parallelogram lattice Schwinger model as a different thermodynamic limit than the weak coupling continuum limit. As a function of lattice skewness angle these models span the {Delta} = {minus}1 critical line of 6-vertex models which, in turn, have been identified as c = 1 conformal field theories.

  2. Engineering the electronic and magnetic properties of d(0) 2D dichalcogenide materials through vacancy doping and lattice strains.

    PubMed

    Ao, L; Pham, A; Xiao, H Y; Zu, X T; Li, S

    2016-03-14

    We have systematically investigated the effects of different vacancy defects in 2D d(0) materials SnS2 and ZrS2 using first principles calculations. The theoretical results show that the single cation vacancy and the vacancy complex like V-SnS6 can induce large magnetic moments (3-4 μB) in these single layer materials. Other defects, such as V-SnS3, V-S, V-ZrS3 and V-ZrS6, can result in n-type conductivity. In addition, the ab initio studies also reveal that the magnetic and conductive properties from the cation vacancy and the defect complex V-SnS6 can be modified using the compressive/tensile strain of the in-plane lattices. Specifically, the V-Zr doped ZrS2 monolayer can be tuned from a ferromagnetic semiconductor to a metallic/half-metallic material with decreasing/increasing magnetic moments depending on the external compressive/tensile strains. On the other hand, the semiconducting and magnetic properties of V-Sn doped SnS2 is preserved under different lattice compression and tension. For the defect complex like V-SnS6, only the lattice compression can tune the magnetic moments in SnS2. As a result, by manipulating the fabrication parameters, the magnetic and conductive properties of SnS2 and ZrS2 can be tuned without the need for chemical doping.

  3. Strongly Interacting Fermions in Optical Lattices

    NASA Astrophysics Data System (ADS)

    Koetsier, A. O.

    2009-07-01

    presented here concerns fermionic atoms in periodic potential formed by interfering laser beams. Indeed, the standing light wave created by the interfering beams gives rise to a lattice potential because of the Stark effect which couples the electronic energy levels of the atoms to the spatially undulating electric field. Furthermore, fermionic atoms can be prepared in two different hyperfine states corresponding to the the spin-up and spin-down quantum states, and as such mimic electrons moving in the lattice structure of solids. This system is well described by the famous Hubbard model which we introduce in chapter 2 and, under certain conditions, undergoes a phase transition into the Néel state which believed to be a precursor to superconductivity in certain high-temperature superconductors. In chapter 3, we calculate precisely how the Néel state may be achieved in an ultracold fermionic atom gas. When the number of spin-up and spin-down atoms is unequal the system becomes spin-canted and exhibits both ferro- and antiferromagnetic characteristics, as we show in chapter 4. We also find there are topological excitations present in the quantum spin texture known as merons which have never unambiguously been observed before. In order to form a Bose-Einstein condensate, fermionic atoms must first form pairs, and can do so in two contrasting ways. The relationship between these two qualitatively di erent forms of pairing is described in chapter 5, and we examine how these two types of pairs transform into one another in an optical lattice in chapter 6. Finally, chapter 7 is a detailed eld-theoretic study of pairing as it occurs in an ultracold Bose gas. There, we find there is an intriguing bosonic analogy of the two forms of fermion pairing and explore the properties of these pairs.

  4. Estimating strong correlations in optical lattices

    NASA Astrophysics Data System (ADS)

    Gertis, J.; Friesdorf, M.; Riofrío, C. A.; Eisert, J.

    2016-11-01

    Ultracold atoms in optical lattices provide one of the most promising platforms for analog quantum simulations of complex quantum many-body systems. Large-size systems can now routinely be reached and are already used to probe a large variety of different physical situations, ranging from quantum phase transitions to artificial gauge theories. At the same time, measurement techniques are still limited and full tomography for these systems seems out of reach. Motivated by this observation, we present a method to directly detect and quantify to what extent a quantum state deviates from a local Gaussian description, based on available noise correlation measurements from in situ and time-of-flight measurements. This is an indicator of the significance of strong correlations in ground and thermal states, as Gaussian states are precisely the ground and thermal states of noninteracting models. We connect our findings, augmented by numerical tensor network simulations, to notions of equilibration, disordered systems, and the suppression of transport in Anderson insulators.

  5. Topological defect formation in 1D and 2D spin chains realized by network of optical parametric oscillators

    NASA Astrophysics Data System (ADS)

    Hamerly, Ryan; Inaba, Kensuke; Inagaki, Takahiro; Takesue, Hiroki; Yamamoto, Yoshihisa; Mabuchi, Hideo

    2016-09-01

    A network of optical parametric oscillators (OPOs) is used to simulate classical Ising and XY spin chains. The collective nonlinear dynamics of this network, driven by quantum noise rather than thermal fluctuations, seeks out the Ising/XY ground state as the system transitions from below to above the lasing threshold. We study the behavior of this “Ising machine” for three canonical problems: a 1D ferromagnetic spin chain, a 2D square lattice and problems where next-nearest-neighbor couplings give rise to frustration. If the pump turn-on time is finite, topological defects form (domain walls for the Ising model, winding number and vortices for XY) and their density can be predicted from a numerical model involving a linear “growth stage” and a nonlinear “saturation stage”. These predictions are compared against recent data for a 10,000-spin 1D Ising machine.

  6. Superlubric-pinned Aubry transition of two dimensional monolayers in optical lattices

    NASA Astrophysics Data System (ADS)

    Mandelli, Davide; Vanossi, Andrea; Manini, Nicola; Tosatti, Erio

    Two-dimensional (2D) crystalline colloidal monolayers sliding over a laser-induced optical lattice ``corrugation'' potential emulate friction between ideal crystal surfaces. Static friction is always present when the monolayer and the optical lattices are commensurate, but when they are incommensurate the presence or absence of static friction depends upon the system parameters. In 1D, at the Aubry dynamical phase transition the static friction goes continuously from zero (superlubricity) to finite as the periodic corrugation strength is increased. We look for the Aubry-like transition in the more realistic 2D case of a monolayer in an incommensurate periodic potential using molecular dynamics simulations. Results confirm a clear and sharp 2D superlubric-pinned transition upon increasing corrugation strength. Unlike the 1D Aubry transition which is continuous, the 2D transition is first-order, with a jump of static friction. At the 2D Aubry transition there is no change of symmetry, a sudden rise of the colloid-colloid interaction energy, and a compensating drop of the colloid-corrugation energy. The observability of the superlubric-pinned colloid transition is proposed and discussed. This work has been supported by ERC Advanced Grant N. 320796 MODPHYSFRICT.

  7. Toward a 2-D magneto-optical trap for polar molecules

    NASA Astrophysics Data System (ADS)

    Hummon, Matthew; Stuhl, Benjamin; Yeo, Mark; Collopy, Alejandra; Ye, Jun

    2012-06-01

    The additional structure that arises from the rotational degree of freedom in diatomic molecules makes difficult the adaptation of a traditional atomic magneto-optical trap (MOT) for use with molecules. We describe progress toward development of a 2-D MOT for laser cooled yttrium monoxide molecules based on a resonant LC baseball coil geometry.

  8. Comment on 'Feshbach resonances in an optical lattice'

    SciTech Connect

    Diener, Roberto B.; Ho, T.-L.

    2006-01-15

    We point out some logical inconsistencies in the model proposed in [Phys. Rev. A 71, 043604 (2005)] as well as in the calculations performed on it. The proposed model is not able to describe Feshbach resonances in optical lattices.

  9. Matter-wave localization in a weakly perturbed optical lattice

    SciTech Connect

    Cheng, Yongshan; Adhikari, S. K.

    2011-11-15

    By numerical solution and variational approximation of the Gross-Pitaevskii equation, we studied the localization of a noninteracting and weakly interacting Bose-Einstein condensate in a weakly perturbed optical lattice in one and three dimensions. The perturbation achieved through a weak delocalizing expulsive or a linear potential as well as a weak localizing harmonic potential removes the periodicity of the optical lattice and leads to localization. We also studied some dynamics of the localized state confirming its stability.

  10. Light-induced atomic elevator in optical lattices

    NASA Astrophysics Data System (ADS)

    Prants, S. V.

    2016-12-01

    It is shown how an atomic elevator that can elevate falling cold atoms in a vertical optical lattice can be created. The effect appears near resonance owing to the nonlinear interaction between the electronic and mechanical degrees of freedom of an atom, which is responsible for its random walk in rigid optical lattices without any modulation and additional action. Numerical experiments involving spontaneous emission demonstrate that random walk of atoms and light-induced atomic elevator can be observed in a real experiment.

  11. A new class of aperiodic, long-range ordered artificial spin ices based upon Fibonacci distortions of 2D periodic lattices

    NASA Astrophysics Data System (ADS)

    Woods, Justin; Bhat, Vinayak; Farmer, Barry; Sklenar, Joseph; Teipel, Eric; Ketterson, John; Hastings, J. Todd; de Long, Lance

    2015-03-01

    Artificial spin ice (ASI) systems are composed of nanoscale ferromagnetic segments whose shape anisotropy dictates they behave as mesoscopic Ising spins. Most ASI have segments patterned on periodic lattices and a single vertex topology. We have continuously distorted 2D honeycomb and square lattices such that the pattern vertex spacings follow a Fibonacci chain sequence along primitive lattice directions. The Fibonacci distortion is related to the aperiodic translational symmetry of 2D artificial quasicrystals1 that cannot be viewed as continuous distortions of periodic lattices due to their forbidden (e.g., fivefold) rotational symmetries. In contrast, Fibonacci distortions of 2D periodic lattices can be ``turned on'' by control of the ratio of two lattice parameters d1 and d2. Distortions alter film segments such that pattern vertices are no longer equivalent and traditional spin ice rules are no longer strictly valid. We have performed OOMMF simulations of magnetization reversal for samples having different levels of distortion, and found the magnetic reversal to be dramatically slowed by small distortions (d1/d2 ~ 1). Research at Kentucky is supported by U.S. DoE Grant DE-FG02-97ER45653 and NSF Grant EPS-0814194.

  12. Matter-wave propagation in optical lattices: geometrical and flat-band effects

    SciTech Connect

    Metcalf, Mekena; Chern, Gia-Wei; Di Ventra, Massimiliano; Chien, Chih-Chun

    2016-03-17

    Here we report that the geometry of optical lattices can be engineered allowing the study of atomic transport along paths arranged in patterns that are otherwise difficult to probe in the solid state. A question feasible to atomic systems is related to the speed of propagation of matter-waves as a function of the lattice geometry. To address this issue, we have investigated theoretically the quantum transport of non-interacting and weakly-interacting ultracold fermionic atoms in several 2D optical lattice geometries. We find that the triangular lattice has a higher propagation velocity compared to the square lattice, and the cross-linked square lattice has an even faster propagation velocity. The increase results from the mixing of the momentum states which leads to different group velocities in quantum systems. Standard band theory provides an explanation and allows for a systematic way to search and design systems with controllable matter-wave propagation. Moreover, the presence of a flat band such as in a two-leg ladder geometry leads to a dynamical density discontinuity due to its localized atoms. Lastly, we discuss possible realizations of those dynamical phenomena.

  13. Optical design of wavelength selective CPVT system with 3D/2D hybrid concentration

    NASA Astrophysics Data System (ADS)

    Ahmad, N.; Ijiro, T.; Yamada, N.; Kawaguchi, T.; Maemura, T.; Ohashi, H.

    2012-10-01

    Optical design of a concentrating photovoltaic/thermal (CPVT) system is carried out. Using wavelength-selective optics, the system demonstrates 3-D concentration onto a solar cell and 2-D concentration onto a thermal receiver. Characteristics of the two types of concentrator systems are examined with ray-tracing analysis. The first system is a glazed mirror-based concentrator system mounted on a 2-axis pedestal tracker. The size of the secondary optical element is minimized to decrease the cost of the system, and it has a wavelength-selective function for performing 3-D concentration onto a solar cell and 2-D concentration onto a thermal receiver. The second system is a non-glazed beamdown concentrator system containing parabolic mirrors in the lower part. The beam-down selective mirror performs 3-D concentration onto a solar cell placed above the beam-down selective mirror, and 2-D concentration down to a thermal receiver placed at the bottom level. The system is mounted on a two-axis carousel tracker. A parametric study is performed for those systems with different geometrical 2-D/3-D concentration ratios. Wavelength-selective optics such as hot/cold mirrors and spectrum-splitting technologies are taken into account in the analysis. Results show reduced heat load on the solar cell and increased total system efficiency compared to a non-selective CPV system. Requirements for the wavelength-selective properties are elucidated. It is also shown that the hybrid concept with 2-D concentration onto a thermal receiver and 3-D concentration onto a solar cell has an advantageous geometry because of the high total system efficiency and compatibility with the piping arrangement of the thermal receiver.

  14. Impact of bounded noise on the formation and instability of spiral wave in a 2D Lattice of neurons

    PubMed Central

    Yao, Yuangen; Deng, Haiyou; Yi, Ming; Ma, Jun

    2017-01-01

    Spiral waves in the neocortex may provide a spatial framework to organize cortical oscillations, thus help signal communication. However, noise influences spiral wave. Many previous theoretical studies about noise mainly focus on unbounded Gaussian noise, which contradicts that a real physical quantity is always bounded. Furthermore, non-Gaussian noise is also important for dynamical behaviors of excitable media. Nevertheless, there are no results concerning the effect of bounded noise on spiral wave till now. Based on Hodgkin-Huxley neuron model subjected to bounded noise with the form of Asin[ωt + σW(t)], the influences of bounded noise on the formation and instability of spiral wave in a two-dimensional (2D) square lattice of neurons are investigated in detail by separately adjusting the intensity σ, amplitude A, and frequency f of bounded noise. It is found that the increased intensity σ can facilitate the formation of spiral wave while the increased amplitude A tends to destroy spiral wave. Furthermore, frequency of bounded noise has the effect of facilitation or inhibition on pattern synchronization. Interestingly, for the appropriate intensity, amplitude and frequency can separately induce resonance-like phenomenon. PMID:28220877

  15. Impact of bounded noise on the formation and instability of spiral wave in a 2D Lattice of neurons

    NASA Astrophysics Data System (ADS)

    Yao, Yuangen; Deng, Haiyou; Yi, Ming; Ma, Jun

    2017-02-01

    Spiral waves in the neocortex may provide a spatial framework to organize cortical oscillations, thus help signal communication. However, noise influences spiral wave. Many previous theoretical studies about noise mainly focus on unbounded Gaussian noise, which contradicts that a real physical quantity is always bounded. Furthermore, non-Gaussian noise is also important for dynamical behaviors of excitable media. Nevertheless, there are no results concerning the effect of bounded noise on spiral wave till now. Based on Hodgkin-Huxley neuron model subjected to bounded noise with the form of Asin[ωt + σW(t)], the influences of bounded noise on the formation and instability of spiral wave in a two-dimensional (2D) square lattice of neurons are investigated in detail by separately adjusting the intensity σ, amplitude A, and frequency f of bounded noise. It is found that the increased intensity σ can facilitate the formation of spiral wave while the increased amplitude A tends to destroy spiral wave. Furthermore, frequency of bounded noise has the effect of facilitation or inhibition on pattern synchronization. Interestingly, for the appropriate intensity, amplitude and frequency can separately induce resonance-like phenomenon.

  16. Realizing type-II Weyl points in an optical lattice

    NASA Astrophysics Data System (ADS)

    Shastri, Kunal; Yang, Zhaoju; Zhang, Baile

    2017-01-01

    The recent discovery of the Lorentz symmetry-violating "type-II" Weyl semimetal phase has renewed interest in the study of Weyl physics in condensed-matter systems. However, tuning the exceptional properties of this novel state has remained a challenge. Optical lattices, created using standing laser beams, provide a convenient platform to tune tunneling parameters continuously in time. In this paper, we propose a generalized two level system exhibiting type-II Weyl points that can be realized using ultracold atoms in an optical lattice. The system is engineered using a three-dimensional lattice with complex π phase tunneling amplitudes. Various unique properties of the type-II Weyl semimetal such as open Fermi surface, anomalous chirality, and topological Fermi arcs can be probed using the proposed optical lattice scheme.

  17. All-optical XNOR gate based on 2D photonic-crystal ring resonators

    NASA Astrophysics Data System (ADS)

    Moniem, Tamer A.

    2017-02-01

    A novel all-optical XNOR gate is proposed, which combines the nonlinear Kerr effect with photonic-crystal ring resonators (PCRRs). The total size of the proposed optical XNOR gate based on photonic crystals with a square lattice of silicon rods is equal to 35 × 21 μm. The proposed structure has a bandgap in the range from 0.32 to 0.44. To confirm the operation and feasibility of the overall system use is made of analytical and numerical simulation using the dimensional finite difference time domain (FDTD) and plane wave expansion (PWE) methods.

  18. Automatic angle measurement of a 2D object using optical correlator-neural networks hybrid system

    NASA Astrophysics Data System (ADS)

    Manivannan, N.; Neil, M. A. A.

    2011-04-01

    In this paper a novel method is proposed and demonstrated for automatic rotation angle measurement of a 2D object using a hybrid architecture, consisting of a 4f optical correlator with a binary phase only multiplexed matched filter and a single layer neural network. The hybrid set-up can be considered as a two-layer perceptron-like neural network; an optical correlator is the first layer and the standard single layer neural network is the second layer. The training scheme used to train the hybrid architecture is a combination of a Direct Binary Search algorithm, to train the optical correlator, and an Error Back Propagation algorithm, to train the neural network. The aim is to perform the major information processing by the optical correlator with a small additional processing by the neural network stage. This allows the system to be used for real-time applications as optics has the inherent ability to process information in a parallel manner at high speed. The neural network stage gives an extra dimension of freedom so that complicated tasks like automatic rotation angle measurement can be achieved. Results of both computer simulation and experimental set-up are presented for rotation angle measurement of an English alphabetic character as a 2D object. The experimental set-up consists of a real optical correlator using two spatial light modulators for both input and frequency plane representations and a PC based model of a single layer network.

  19. Neutral gas heating via non-resonant optical lattices

    NASA Astrophysics Data System (ADS)

    Cornella, Barry Michael

    The influence of intense optical lattices on atoms or molecules offers a particularly useful method for energy and momentum deposition into a non-resonant gas. In this investigation, a proof-of-concept experiment was conducted to validate high intensity pulsed optical lattices as a means of creating high temperature gases for a myriad of aerospace, basic physics, and nanotechnology applications. Traditional methods for creating these flows have either involved altering the chemical composition of the initial gas sample through combustion or ionization or relied on laser resonant interactions with internal energy modes through laser pyrolysis. Due to its non-resonant nature, the use of optical lattices might be beneficial compared to existing methods since it provides an arbitrary, localized, high temperature gas that is tunable and does not introduce unwanted chemical species or high ionization concentrations. As an intermediate step toward verifying optical lattice gas heating, a coherent Rayleigh-Brillouin scattering (CRBS) study was also performed to verify the presented methodology. CRBS is a gas diagnostic technique used for non-intrusive probing of gas thermodynamic properties. In addition to the experimental investigation, a complementary numerical study was conducted using a direct simulation Monte Carlo approach. The numerical study used a modified version of SMILE to predict the gas phenomena within the strong optical potential fields. The goal of substantiating optical lattice heating was accomplished by detecting the acoustic wave generated from the heated volume. The magnitude of the resulting acoustic wave was shown to vary with the optical lattice phase velocity, peaking on the order of the gas' most probable speed. The trend with lattice velocity is consistent with both theory and the numerical study and eliminates other possible heating mechanisms such as laser-induced ionization or molecular dissociation. Limitations for the investigated heating

  20. Optical CDMA system using 2-D run-length limited code

    NASA Astrophysics Data System (ADS)

    Liu, Maw-Yang; Jiang, Joe-Air

    2010-10-01

    In this paper, time-spreading wavelength-hopping optical CDMA system using 2-D run-length limited code is investigated. The run-length limited code we use here is predicated upon spatial coding scheme, which can improve system performance significantly. In our proposed system, we employ carrier-hopping prime code and its shifted version as signature sequences. Based on the zero auto-correlation sidelobes property of signature sequence, we propose a two-state trellis coding architecture, which utilizes 2-D parallel detection scheme. The proposed scheme is compact and simple that can be applied to more complicated trellis to further enhance system performance. Multiple access interference is the main deterioration factor in optical CDMA system that affects system performance adversely. Aside from the multiple access interference, some of the adverse impacts of system performance are also taken into consideration, which include thermal noise, shot noise, relative intensity noise, and beat noise.

  1. An Optical Lattice Clock with Spin 1/2 Atoms

    DTIC Science & Technology

    2012-01-01

    89 4.4 Vector Stark shift . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90...ytterbium atoms The first proposal for an optical lattice clock called for spectroscopy of a narrow optical tran- sition in ultracold strontium atoms [40...Since then, experimental groups have begun researching not only strontium (Sr) [70, 71, 72, 73, 74], but also ytterbium (Yb) [75, 76, 77, 78, 79] and

  2. Pulse Propagation Effects in Optical 2D Fourier-Transform Spectroscopy: Theory.

    PubMed

    Spencer, Austin P; Li, Hebin; Cundiff, Steven T; Jonas, David M

    2015-04-30

    A solution to Maxwell's equations in the three-dimensional frequency domain is used to calculate rephasing two-dimensional Fourier transform (2DFT) spectra of the D2 line of atomic rubidium vapor in argon buffer gas. Experimental distortions from the spatial propagation of pulses through the sample are simulated in 2DFT spectra calculated for the homogeneous Bloch line shape model. Spectral features that appear at optical densities of up to 3 are investigated. As optical density increases, absorptive and dispersive distortions start with peak shape broadening, progress to peak splitting, and ultimately result in a previously unexplored coherent transient twisting of the split peaks. In contrast to the low optical density limit, where the 2D peak shape for the Bloch model depends only on the total dephasing time, these distortions of the 2D peak shape at finite optical density vary with the waiting time and the excited state lifetime through coherent transient effects. Experiment-specific conditions are explored, demonstrating the effects of varying beam overlap within the sample and of pseudo-time domain filtering. For beam overlap starting at the sample entrance, decreasing the length of beam overlap reduces the line width along the ωτ axis but also reduces signal intensity. A pseudo-time domain filter, where signal prior to the center of the last excitation pulse is excluded from the FID-referenced 2D signal, reduces propagation distortions along the ωt axis. It is demonstrated that 2DFT rephasing spectra cannot take advantage of an excitation-detection transformation that can eliminate propagation distortions in 2DFT relaxation spectra. Finally, the high optical density experimental 2DFT spectrum of rubidium vapor in argon buffer gas [J. Phys. Chem. A 2013, 117, 6279-6287] is quantitatively compared, in line width, in depth of peak splitting, and in coherent transient peak twisting, to a simulation with optical density higher than that reported.

  3. Evolution of the Hofstadter butterfly in a tunable optical lattice

    NASA Astrophysics Data System (ADS)

    Oktel, Mehmet O.; Unal, Nur; Yilmaz, Firat

    Advances in realizing artificial gauge fields on optical lattices promise experimental detection of topologically non-trivial energy spectra. Self-similar fractal energy structures, known as Hofstadter butterflies, depend sensitively on the geometry of the lattice, as well as the applied magnetic field. The recent demonstration of an adjustable lattice geometry [L. Tarruell et al., Nature 483, 302 (2012)] presents a unique opportunity to study this dependence. We calculate the Hofstadter butterflies that can be obtained in such an adjustable lattice and find three qualitatively different regimes. We show that the existence of Dirac points at zero magnetic field does not imply the topological equivalence of spectra at finite field. As the real-space structure evolves from the checkerboard to the honeycomb lattice, two square lattice Hofstadter butterflies merge to form a honeycomb lattice butterfly in a topologically non-trivial way, as it is accomplished by sequential closing of infinitely many gaps. We discuss the evolution of topological properties with underlying lattice geometry by calculating the Chern numbers and comment on the validity of simulating graphene in such an adjustable lattice

  4. Ultracold polar molecules in a 3D optical lattice

    NASA Astrophysics Data System (ADS)

    Yan, Bo

    2015-05-01

    Ultracold polar molecules, with their long-range electric dipolar interactions, offer new opportunities for studying quantum magnetism and many-body physics. KRb molecules loaded into a three-dimensional (3D) optical lattice allow one to study such a spin-lattice system in a stable environment without losses arising from chemical reactions. In the case with strong lattice confinement along two directions and a weak lattice potential along the third, we find the loss rate is suppressed by the quantum Zeno effect. In a deep 3D lattice with no tunneling, we observe evidences for spin exchange interactions. We use Ramsey spectroscopy to investigate the spin dynamics. By choosing the appropriate lattice polarizations and implementing a spin echo sequence, the single particle dephasing is largely suppressed, leaving the dipolar exchange interactions as the dominant contribution to the observed dynamics. This is supported by many-body theoretical calculations. While this initial demonstration was done with low lattice fillings, our current experimental efforts are focused on increasing the lattice filling fraction. This will greatly benefit the study of complex many-body dynamics with long-range interactions, such as transport of excitations in an out-of-equilibrium system and spin-orbit coupling in a lattice.

  5. Lattice-cavity solitons in a degenerate optical parametric oscillator

    SciTech Connect

    Egorov, O. A.; Lederer, F.

    2007-11-15

    We predict the existence of lattice-cavity solitons for a quadratic nonlinear cavity, where the linear losses are compensated for by the optical pump at second harmonic (degenerate optical parametric oscillator), and which is endowed with a one-dimensional photonic lattice. In the limit of strong discreteness (weak coupling) this kind of soliton solution contains as the subclass the quadratic discrete cavity solitons. The nonlinear coupling between the Bloch waves of different photonics bands allows for the formation of a reach variety of localized solutions. In particular, different types of multiband lattice-cavity solitons can be identified. Most types of lattice-cavity solitons do not have counterparts, neither in conventional planar microresonators nor in genuine discrete systems as an array of weakly coupled cavities. We show that these solitons may destabilize as a consequence of the competition between Bloch waves of different photonic bands.

  6. Matter-wave propagation in optical lattices: geometrical and flat-band effects

    DOE PAGES

    Metcalf, Mekena; Chern, Gia-Wei; Di Ventra, Massimiliano; ...

    2016-03-17

    Here we report that the geometry of optical lattices can be engineered allowing the study of atomic transport along paths arranged in patterns that are otherwise difficult to probe in the solid state. A question feasible to atomic systems is related to the speed of propagation of matter-waves as a function of the lattice geometry. To address this issue, we have investigated theoretically the quantum transport of non-interacting and weakly-interacting ultracold fermionic atoms in several 2D optical lattice geometries. We find that the triangular lattice has a higher propagation velocity compared to the square lattice, and the cross-linked square latticemore » has an even faster propagation velocity. The increase results from the mixing of the momentum states which leads to different group velocities in quantum systems. Standard band theory provides an explanation and allows for a systematic way to search and design systems with controllable matter-wave propagation. Moreover, the presence of a flat band such as in a two-leg ladder geometry leads to a dynamical density discontinuity due to its localized atoms. Lastly, we discuss possible realizations of those dynamical phenomena.« less

  7. High-Field Fractional Quantum Hall Effect in Optical Lattices

    SciTech Connect

    Palmer, R.N.; Jaksch, D.

    2006-05-12

    We consider interacting bosonic atoms in an optical lattice subject to a large simulated magnetic field. We develop a model similar to a bilayer fractional quantum Hall system valid near simple rational numbers of magnetic flux quanta per lattice cell. Then we calculate its ground state, magnetic lengths, fractional fillings, and find unexpected sign changes in the Hall current. Finally we study methods for detecting these novel features via shot noise and Hall current measurements.

  8. Unity Occupation of Sites in a 3D Optical Lattice

    NASA Astrophysics Data System (ADS)

    Depue, Marshall T.; McCormick, Colin; Winoto, S. Lukman; Oliver, Steven; Weiss, David S.

    1999-03-01

    An average filling factor of one atom per lattice site has been obtained in a submicron scale far-off-resonance optical lattice (FORL). High site occupation is obtained through a compression sequence that includes laser cooling in a 3D FORL and adiabatic toggling between the 3D FORL and a 1D FORL trap. After the highest filling factor is achieved, laser cooling causes collisional loss from lattice sites with more than one atom. Ultimately 44% of the sites have a single atom cooled to near its vibrational ground state. A theoretical model of site occupation based on Poisson statistics agrees well with the experimental results.

  9. Ultracold two-body dynamics in optical lattices with topological singularities

    NASA Astrophysics Data System (ADS)

    Aghamalyan, Davit; Simoni, Andrea; Launay, Jean-Michel

    2016-05-01

    We study bound levels of two particles trapped in a 2D optical lattice. We use a short-range potential tuned to reproduce typical experimental conditions. Near-threshold bound states are computed using a spectral element discretization approach that guarantees exponential precision in the numerical results. High computational efficiency is attained due to the very sparse nature of the Hamiltonian in this representation. The calculated wavefunction is analyzed both in real and in momentum space. We perform calculations both for standard separable optical potentials and for lattice with topological singularities (Dirac cones) in the band structure. Extension to the calculation of scattering states will be addressed. This work was supported by the Agence Nationale de la Recherche (Contract No. ANR-12-BS04-0020-01).

  10. Controlled wave-packet manipulation with driven optical lattices

    SciTech Connect

    Arlinghaus, Stephan; Holthaus, Martin

    2011-12-15

    Motivated by recent experimental progress achieved with ultracold atoms in kilohertz-driven optical lattices, we provide a theoretical discussion of mechanisms governing the response of a particle in a cosine lattice potential to strong forcing pulses with smooth envelope. Such pulses effectuate adiabatic motion of a wave packet's momentum distribution on quasienergy surfaces created by spatiotemporal Bloch waves. Deviations from adiabaticity can then be deliberately exploited for exerting coherent control and for reaching target states which may not be accessible by other means. As one particular example, we consider an analog of the {pi} pulses known from optical resonance. We also suggest adapting further techniques previously developed for controlling atomic and molecular dynamics by laser pulses to the coherent control of matter waves in shaken optical lattices.

  11. Bloch-Zener oscillations in a tunable optical honeycomb lattice

    SciTech Connect

    Uehlinger, Thomas; Greif, Daniel; Jotzu, Gregor; Esslinger, Tilman; Tarruell, Leticia

    2013-12-04

    Ultracold gases in optical lattices have proved to be a flexible tool to simulate many different phenomena of solid state physics [1, 2]. Recently, optical lattices with complex geometries have been realized [3, 4, 5, 6, 7], paving the way to simulating more realistic systems. The honeycomb structure has recently become accessible in an optical lattice composed of mutually perpendicular laser beams. This lattice structure exhibits topological features in its band structure – the Dirac points. At these points, two energy bands intersect linearly and the particles behave as relativistic Dirac fermions. In optical lattices, Bloch oscillations [8] resolved both in time and in quasi-momentum space can be directly observed. We make use of such Bloch-Zener oscillations to probe the vanishing energy gap at the Dirac points as well as their position in the band structure. In small band gap regions, we observe Landau-Zener tunneling [7, 9] to the second band and the regions of maximum transfer can be identified with the position of the Dirac points.

  12. Quantum simulation of 2D topological physics in a 1D array of optical cavities.

    PubMed

    Luo, Xi-Wang; Zhou, Xingxiang; Li, Chuan-Feng; Xu, Jin-Shi; Guo, Guang-Can; Zhou, Zheng-Wei

    2015-07-06

    Orbital angular momentum of light is a fundamental optical degree of freedom characterized by unlimited number of available angular momentum states. Although this unique property has proved invaluable in diverse recent studies ranging from optical communication to quantum information, it has not been considered useful or even relevant for simulating nontrivial physics problems such as topological phenomena. Contrary to this misconception, we demonstrate the incredible value of orbital angular momentum of light for quantum simulation by showing theoretically how it allows to study a variety of important 2D topological physics in a 1D array of optical cavities. This application for orbital angular momentum of light not only reduces required physical resources but also increases feasible scale of simulation, and thus makes it possible to investigate important topics such as edge-state transport and topological phase transition in a small simulator ready for immediate experimental exploration.

  13. Coupled matter-wave solitons in optical lattices

    SciTech Connect

    Golam Ali, Sk; Talukdar, B.

    2009-06-15

    We make use of a potential model to study the dynamics of two coupled matter-wave or Bose-Einstein condensate (BEC) solitons loaded in optical lattices. With separate attention to linear and nonlinear lattices we find some remarkable differences for response of the system to effects of these lattices. As opposed to the case of linear optical lattice (LOL), the nonlinear lattice (NOL) can be used to control the mutual interaction between the two solitons. For a given lattice wave number k, the effective potentials in which the two solitons move are such that the well (V{sub eff}(NOL)), resulting from the juxtaposition of soliton interaction and nonlinear lattice potential, is deeper than the corresponding well V{sub eff}(LOL). But these effective potentials have opposite k dependence in the sense that the depth of V{sub eff}(LOL) increases as k increases and that of V{sub eff}(NOL) decreases for higher k values. We verify that the effectiveness of optical lattices to regulate the motion of the coupled solitons depends sensitively on the initial locations of the motionless solitons as well as values of the lattice wave number. For both LOL and NOL the two solitons meet each other due to mutual interaction if their initial locations are taken within the potential wells with the difference that the solitons in the NOL approach each other rather rapidly and take roughly half the time to meet as compared with the time needed for such coalescence in the LOL. In the NOL, the soliton profiles can move freely and respond to the lattice periodicity when the separation between their initial locations are as twice as that needed for a similar free movement in the LOL. We observe that, in both cases, slow tuning of the optical lattices by varying k with respect to a time parameter {tau} drags the oscillatory solitons apart to take them to different locations. In our potential model the oscillatory solitons appear to propagate undistorted. But a fully numerical calculation

  14. Coupled matter-wave solitons in optical lattices

    NASA Astrophysics Data System (ADS)

    Golam Ali, Sk; Talukdar, B.

    2009-06-01

    We make use of a potential model to study the dynamics of two coupled matter-wave or Bose-Einstein condensate (BEC) solitons loaded in optical lattices. With separate attention to linear and nonlinear lattices we find some remarkable differences for response of the system to effects of these lattices. As opposed to the case of linear optical lattice (LOL), the nonlinear lattice (NOL) can be used to control the mutual interaction between the two solitons. For a given lattice wave number k, the effective potentials in which the two solitons move are such that the well (Veff(NOL)), resulting from the juxtaposition of soliton interaction and nonlinear lattice potential, is deeper than the corresponding well Veff(LOL). But these effective potentials have opposite k dependence in the sense that the depth of Veff(LOL) increases as k increases and that of Veff(NOL) decreases for higher k values. We verify that the effectiveness of optical lattices to regulate the motion of the coupled solitons depends sensitively on the initial locations of the motionless solitons as well as values of the lattice wave number. For both LOL and NOL the two solitons meet each other due to mutual interaction if their initial locations are taken within the potential wells with the difference that the solitons in the NOL approach each other rather rapidly and take roughly half the time to meet as compared with the time needed for such coalescence in the LOL. In the NOL, the soliton profiles can move freely and respond to the lattice periodicity when the separation between their initial locations are as twice as that needed for a similar free movement in the LOL. We observe that, in both cases, slow tuning of the optical lattices by varying k with respect to a time parameter τ drags the oscillatory solitons apart to take them to different locations. In our potential model the oscillatory solitons appear to propagate undistorted. But a fully numerical calculation indicates that during evolution

  15. Physics of higher orbital bands in optical lattices: a review.

    PubMed

    Li, Xiaopeng; Liu, W Vincent

    2016-11-01

    The orbital degree of freedom plays a fundamental role in understanding the unconventional properties in solid state materials. Experimental progress in quantum atomic gases has demonstrated that high orbitals in optical lattices can be used to construct quantum emulators of exotic models beyond natural crystals, where novel many-body states such as complex Bose-Einstein condensates and topological semimetals emerge. A brief introduction of orbital degrees of freedom in optical lattices is given and a summary of exotic orbital models and resulting many-body phases is provided. Experimental consequences of the novel phases are also discussed.

  16. Physics of higher orbital bands in optical lattices: a review

    NASA Astrophysics Data System (ADS)

    Li, Xiaopeng; Liu, W. Vincent

    2016-11-01

    The orbital degree of freedom plays a fundamental role in understanding the unconventional properties in solid state materials. Experimental progress in quantum atomic gases has demonstrated that high orbitals in optical lattices can be used to construct quantum emulators of exotic models beyond natural crystals, where novel many-body states such as complex Bose-Einstein condensates and topological semimetals emerge. A brief introduction of orbital degrees of freedom in optical lattices is given and a summary of exotic orbital models and resulting many-body phases is provided. Experimental consequences of the novel phases are also discussed.

  17. Stability of matter-wave solitons in optical lattices

    NASA Astrophysics Data System (ADS)

    Ali, Sk. Golam; Roy, S. K.; Talukdar, B.

    2010-08-01

    We consider localized states of both single- and two-component Bose-Einstein condensates (BECs) confined in a potential resulting from the superposition of linear and nonlinear optical lattices and make use of Vakhitov-Kolokolov criterion to investigate the effect of nonlinear lattice on the stability of the soliton solutions in the linear optical lattice (LOL). For the single-component case we show that a weak nonlinear lattice has very little effect on the stability of such solitons while sufficiently strong nonlinear optical lattice (NOL) squeezes them to produce narrow bound states. For two-component condensates we find that when the strength of the NOL (γ1) is less than that of the LOL (V0) a relatively weak intra-atomic interaction (IAI) has little effect on the stability of the component solitons. This is true for both attractive and repulsive IAI. A strong attractive IAI, however, squeezes the BEC solitons while a similar repulsive IAI makes the component solitons wider. For γ1 > V0, only a strong attractive IAI squeezes the BEC solitons but the squeezing effect is less prominent than that found for γ1 < V0. We make useful checks on the results of our semianalytical stability analysis by solving the appropriate Gross-Pitaevskii equations numerically.

  18. A New Family of 2-D Optical Orthogonal Codes and Analysis of Its Performance in Optical CDMA Access Networks

    NASA Astrophysics Data System (ADS)

    Shurong, Sun; Yin, Hongxi; Wang, Ziyu; Xu, Anshi

    2006-04-01

    A new family of two-dimensional optical orthogonal code (2-D OOC), one-coincidence frequency hop code (OCFHC)/OOC, which employs OCFHC and OOC as wavelengthhopping and time-spreading patterns, respectively, is proposed in this paper. In contrary to previously constructed 2-D OOCs, OCFHC/OOC provides more choices on the number of available wavelengths and its cardinality achieves the upper bound in theory without sacrificing good auto-and-cross correlation properties, i.e., the correlation properties of the code is still ideal. Meanwhile, we utilize a new method, called effective normalized throughput, to compare the performance of diverse codes applicable to optical code division multiple access (OCDMA) systems besides conventional measure bit error rate, and the results indicate that our code performs better than obtained OCDMA codes and is truly applicable to OCDMA networks as multiaccess codes and will greatly facilitate the implementation of OCDMA access networks.

  19. Mixtures of bosonic and fermionic atoms in optical lattices

    SciTech Connect

    Albus, Alexander; Illuminati, Fabrizio; Eisert, Jens

    2003-08-01

    We discuss the theory of mixtures of bosonic and fermionic atoms in periodic potentials at zero temperature. We derive a general Bose-Fermi Hubbard Hamiltonian in a one-dimensional optical lattice with a superimposed harmonic trapping potential. We study the conditions for linear stability of the mixture and derive a mean-field criterion for the onset of a bosonic superfluid transition. We investigate the ground-state properties of the mixture in the Gutzwiller formulation of mean-field theory, and present numerical studies of finite systems. The bosonic and fermionic density distributions and the onset of quantum phase transitions to demixing and to a bosonic Mott-insulator are studied as a function of the lattice potential strength. The existence is predicted of a disordered phase for mixtures loaded in very deep lattices. Such a disordered phase possessing many degenerate or quasidegenerate ground states is related to a breaking of the mirror symmetry in the lattice.

  20. Optical and Electronic Properties of 2D Graphitic Carbon-Nitride and Carbon Enriched Alloys

    NASA Astrophysics Data System (ADS)

    Therrien, Joel; Li, Yancen; Schmidt, Daniel; Masaki, Michael; Syed, Abdulmannan

    The two-dimensional form of graphitic carbon-nitride (gCN) has been successfully synthesized using a simple CVD process. In it's pure form, the carbon to nitrogen ratio is 0.75. By adding a carbon bearing gas to the growth environment, the C/N ratio can be increased, ultimately reaching the pure carbon form: graphene. Unlike attempts at making a 2D alloy system out of BCN, the CN system does not suffer from phase segregation and thus forms a homogeneous alloy. The synthesis approach and electronic and optical properties will be presented for the pure gCN and a selection of alloy compositions.

  1. Development of 2-D-MAX-DOAS and retrievals of trace gases and aerosols optical properties

    NASA Astrophysics Data System (ADS)

    Ortega, Ivan

    Air pollution is a major problem worldwide that adversely a_ects human health, impacts ecosystems and climate. In the atmosphere, there are hundreds of important compounds participating in complex atmospheric reactions linked to air quality and climate. Aerosols are relevant because they modify the radiation balance, a_ect clouds, and thus Earth albedo. The amount of aerosol is often characterized by the vertical integral through the entire height of the atmosphere of the logarithm fraction of incident light that is extinguished called Aerosol Optical Depth (AOD). The AOD at 550 nm (AOD550) over land is 0.19 (multi annual global mean), and that over oceans is 0.13. About 43 % of the Earth surface shows AOD550 smaller than 0.1. There is a need for measurement techniques that are optimized to measure aerosol optical properties under low AOD conditions, sample spatial scales that resemble satellite ground-pixels and atmospheric models, and help integrate remote sensing and in-situ observations to obtain optical closure on the effects of aerosols and trace gases in our changing environment. In this work, I present the recent development of the University of Colorado two dimensional (2-D) Multi-AXis Differential Optical Absorption Spectroscopy (2-D-MAX-DOAS) instrument to measure the azimuth and altitude distribution of trace gases and aerosol optical properties simultaneously with a single instrument. The instrument measures solar scattered light from any direction in the sky, including direct sun light in the hyperspectral domain. In Chapter 2, I describe the capabilities of 2-D measurements in the context of retrievals of azimuth distributions of nitrogen dioxide (NO2), formaldehyde (HCHO), and glyoxal (CHOCHO), which are precursors for tropospheric O3 and aerosols. The measurements were carried out during the Multi-Axis DOAS Comparison campaign for Aerosols and Trace gases (MAD-CAT) campaign in Mainz, Germany and show the ability to bridge spatial scales to

  2. Optical lattice polarization effects on magnetically induced optical atomic clock transitions

    SciTech Connect

    Taichenachev, A. V.; Yudin, V. I.; Oates, C. W.

    2007-08-15

    We derive the frequency shift for a forbidden optical transition J=0{yields}J{sup '}=0 caused by the simultaneous actions of an elliptically polarized lattice field and a static magnetic field. We find that a simple configuration of lattice and magnetic fields leads to a cancellation of this shift to first order in lattice intensity and magnetic field. In this geometry, the second-order lattice intensity shift can be minimized as well by use of optimal lattice polarization. Suppression of these shifts could considerably enhance the performance of the next generation of atomic clocks.

  3. Veselago lensing with ultracold atoms in an optical lattice

    NASA Astrophysics Data System (ADS)

    Leder, Martin; Grossert, Christopher; Weitz, Martin

    2014-02-01

    Veselago pointed out that electromagnetic wave theory allows for materials with a negative index of refraction, in which most known optical phenomena would be reversed. A slab of such a material can focus light by negative refraction, an imaging technique strikingly different from conventional positive refractive index optics, where curved surfaces bend the rays to form an image of an object. Here we demonstrate Veselago lensing for matter waves, using ultracold atoms in an optical lattice. A relativistic, that is, photon-like, dispersion relation for rubidium atoms is realized with a bichromatic optical lattice potential. We rely on a Raman π-pulse technique to transfer atoms between two different branches of the dispersion relation, resulting in a focusing that is completely analogous to the effect described by Veselago for light waves. Future prospects of the demonstrated effects include novel sub-de Broglie wavelength imaging applications.

  4. Veselago lensing with ultracold atoms in an optical lattice

    NASA Astrophysics Data System (ADS)

    Leder, Martin; Grossert, Christopher; Weitz, Martin

    2014-05-01

    Veselago pointed out that electromagnetic theory allows for materials with a negative index of refraction, in which most known optical phenomena are reversed. A slab of such a material can focus light by negative refraction, an imaging technique strikingly different from conventional positive refractive index optics, where curved surfaces bend the rays to form an image of an object. Here we demonstrate Veselago lensing for matter waves, using ultracold atoms in an optical lattice. A relativistic, i.e. photon-like, dispersion relation for rubidium atoms is realized with a bichromatic optical lattice potential. A Raman pi-pulse technique serves to transfer atoms between two different branches of the dispersion relation, and the relativistic lensing occurs by a backwards propagation of atomic wavepackets on an energetically mirrored branch of the dispersion relation. We observe negative refraction and Veselago lensing both in a one-dimensional geometry and perform a ray-tracing simulation of a two-dimensional Veselago lens.

  5. Veselago lensing with ultracold atoms in an optical lattice.

    PubMed

    Leder, Martin; Grossert, Christopher; Weitz, Martin

    2014-01-01

    Veselago pointed out that electromagnetic wave theory allows for materials with a negative index of refraction, in which most known optical phenomena would be reversed. A slab of such a material can focus light by negative refraction, an imaging technique strikingly different from conventional positive refractive index optics, where curved surfaces bend the rays to form an image of an object. Here we demonstrate Veselago lensing for matter waves, using ultracold atoms in an optical lattice. A relativistic, that is, photon-like, dispersion relation for rubidium atoms is realized with a bichromatic optical lattice potential. We rely on a Raman π-pulse technique to transfer atoms between two different branches of the dispersion relation, resulting in a focusing that is completely analogous to the effect described by Veselago for light waves. Future prospects of the demonstrated effects include novel sub-de Broglie wavelength imaging applications.

  6. Direct Tunneling Delay Time Measurement in an Optical Lattice

    NASA Astrophysics Data System (ADS)

    Fortun, A.; Cabrera-Gutiérrez, C.; Condon, G.; Michon, E.; Billy, J.; Guéry-Odelin, D.

    2016-07-01

    We report on the measurement of the time required for a wave packet to tunnel through the potential barriers of an optical lattice. The experiment is carried out by loading adiabatically a Bose-Einstein condensate into a 1D optical lattice. A sudden displacement of the lattice by a few tens of nanometers excites the micromotion of the dipole mode. We then directly observe in momentum space the splitting of the wave packet at the turning points and measure the delay between the reflected and the tunneled packets for various initial displacements. Using this atomic beam splitter twice, we realize a chain of coherent micron-size Mach-Zehnder interferometers at the exit of which we get essentially a wave packet with a negative momentum, a result opposite to the prediction of classical physics.

  7. Optical lattice polarization effects on hyperpolarizability of atomic clock transitions.

    PubMed

    Taichenachev, A V; Yudin, V I; Ovsiannikov, V D; Pal'chikov, V G

    2006-10-27

    The light-induced frequency shift due to hyperpolarizability (i.e., terms of second-order in intensity) is studied for a forbidden optical transition, J = 0 --> J = 0. A simple universal dependence on the field ellipticity is obtained. This result allows minimization of the second-order light shift with respect to the field polarization for optical lattices operating at a magic wavelength (at which the first-order shift vanishes). We show the possibility for the existence of a magic elliptical polarization, for which the second-order frequency shift vanishes. The optimal polarization of the lattice field can be either linear, circular, or magic elliptical. The obtained results could improve the accuracy of lattice-based atomic clocks.

  8. Strongly interacting bosons in a disordered optical lattice.

    PubMed

    White, M; Pasienski, M; McKay, D; Zhou, S Q; Ceperley, D; Demarco, B

    2009-02-06

    We experimentally probe the properties of the disordered Bose-Hubbard model using an atomic Bose-Einstein condensate trapped in a 3D disordered optical lattice. Controllable disorder is introduced using a fine-grained optical speckle field with features comparable in size to the lattice spacing along every lattice direction. A precision measurement of the disordering potential is used to compute the single-particle parameters of the system. To constrain theories of the disordered Bose Hubbard model, we have measured the change in condensate fraction as a function of disorder strength for several different ratios of tunneling to interaction energy. We observe disorder-induced, reversible suppression of condensate fraction for superfluid and coexisting superfluid-Mott-insulator phases.

  9. Collisional shifts in optical-lattice atom clocks

    SciTech Connect

    Band, Y. B.; Vardi, A.

    2006-09-15

    We theoretically study the effects of elastic collisions on the determination of frequency standards via Ramsey-fringe spectroscopy in optical-lattice atom clocks. Interparticle interactions of bosonic atoms in multiply occupied lattice sites can cause a linear frequency shift, as well as generate asymmetric Ramsey-fringe patterns and reduce fringe visibility due to interparticle entanglement. We propose a method of reducing these collisional effects in an optical lattice by introducing a phase difference of {pi} between the Ramsey driving fields in adjacent sites. This configuration suppresses site-to-site hopping due to interference of two tunneling pathways, without degrading fringe visibility. Consequently, the probability of double occupancy is reduced, leading to cancellation of collisional shifts.

  10. Spin-orbit coupling in a strontium optical lattice clock

    NASA Astrophysics Data System (ADS)

    Bothwell, Tobias; Bromley, Sarah; Kolkowitz, Shimon; Zhang, Xibo; Wall, Michael; Rey, Ana Maria; Ye, Jun

    2016-05-01

    Synthetic gauge fields are a promising tool for creating complex Hamiltonians with ultracold neutral atoms that may mimic the fractional Quantum Hall effect and other topological states. A promising approach is to use spin-orbit coupling to treat an internal degree of freedom as an effective `synthetic' spatial dimension. Here, this synthetic dimension is comprised by the internal ground and excited states used for high-precision clock spectroscopy in a fermionic strontium optical lattice clock. We report on our progress towards this goal in a system where atoms tunnel through a 1D optical lattice during clock interrogation. We present measurements of the lattice band structure under varying Lamb-Dicke parameters and in a regime where s-wave collisions are expected to contribute density dependent frequency shifts.

  11. Reply to ``Comment on `Feshbach resonances in an optical lattice' ''

    NASA Astrophysics Data System (ADS)

    Dickerscheid, D. B. M.; van Oosten, D.; Stoof, H. T. C.

    2006-01-01

    We show that the Comment by Diener and Ho [Phys. Rev. A 73, 017601 (2006)] is based on the misunderstanding that the Hamiltonian used by Dickerscheid to describe Feshbach resonances in an optical lattice is a microscopic Hamiltonian as opposed to an effective Hamiltonian.

  12. Reply to 'Comment on 'Feshbach resonances in an optical lattice''

    SciTech Connect

    Dickerscheid, D. B. M.; Stoof, H. T. C.; Oosten, D. van

    2006-01-15

    We show that the Comment by Diener and Ho [Phys. Rev. A 73, 017601 (2006)] is based on the misunderstanding that the Hamiltonian used by Dickerscheid et al. to describe Feshbach resonances in an optical lattice is a microscopic Hamiltonian as opposed to an effective Hamiltonian.

  13. Superfluid qubit systems with ring shaped optical lattices.

    PubMed

    Amico, Luigi; Aghamalyan, Davit; Auksztol, Filip; Crepaz, Herbert; Dumke, Rainer; Kwek, Leong Chuan

    2014-03-06

    We study an experimentally feasible qubit system employing neutral atomic currents. Our system is based on bosonic cold atoms trapped in ring-shaped optical lattice potentials. The lattice makes the system strictly one dimensional and it provides the infrastructure to realize a tunable ring-ring interaction. Our implementation combines the low decoherence rates of neutral cold atoms systems, overcoming single site addressing, with the robustness of topologically protected solid state Josephson flux qubits. Characteristic fluctuations in the magnetic fields affecting Josephson junction based flux qubits are expected to be minimized employing neutral atoms as flux carriers. By breaking the Galilean invariance we demonstrate how atomic currents through the lattice provide an implementation of a qubit. This is realized either by artificially creating a phase slip in a single ring, or by tunnel coupling of two homogeneous ring lattices. The single qubit infrastructure is experimentally investigated with tailored optical potentials. Indeed, we have experimentally realized scaled ring-lattice potentials that could host, in principle, n ~ 10 of such ring-qubits, arranged in a stack configuration, along the laser beam propagation axis. An experimentally viable scheme of the two-ring-qubit is discussed, as well. Based on our analysis, we provide protocols to initialize, address, and read-out the qubit.

  14. Doublon dynamics and polar molecule production in an optical lattice.

    PubMed

    Covey, Jacob P; Moses, Steven A; Gärttner, Martin; Safavi-Naini, Arghavan; Miecnikowski, Matthew T; Fu, Zhengkun; Schachenmayer, Johannes; Julienne, Paul S; Rey, Ana Maria; Jin, Deborah S; Ye, Jun

    2016-04-14

    Polar molecules in an optical lattice provide a versatile platform to study quantum many-body dynamics. Here we use such a system to prepare a density distribution where lattice sites are either empty or occupied by a doublon composed of an interacting Bose-Fermi pair. By letting this out-of-equilibrium system evolve from a well-defined, but disordered, initial condition, we observe clear effects on pairing that arise from inter-species interactions, a higher partial-wave Feshbach resonance and excited Bloch-band population. These observations facilitate a detailed understanding of molecule formation in the lattice. Moreover, the interplay of tunnelling and interaction of fermions and bosons provides a controllable platform to study Bose-Fermi Hubbard dynamics. Additionally, we can probe the distribution of the atomic gases in the lattice by measuring the inelastic loss of doublons. These techniques realize tools that are generically applicable to studying the complex dynamics of atomic mixtures in optical lattices.

  15. Superfluid qubit systems with ring shaped optical lattices

    PubMed Central

    Amico, Luigi; Aghamalyan, Davit; Auksztol, Filip; Crepaz, Herbert; Dumke, Rainer; Kwek, Leong Chuan

    2014-01-01

    We study an experimentally feasible qubit system employing neutral atomic currents. Our system is based on bosonic cold atoms trapped in ring-shaped optical lattice potentials. The lattice makes the system strictly one dimensional and it provides the infrastructure to realize a tunable ring-ring interaction. Our implementation combines the low decoherence rates of neutral cold atoms systems, overcoming single site addressing, with the robustness of topologically protected solid state Josephson flux qubits. Characteristic fluctuations in the magnetic fields affecting Josephson junction based flux qubits are expected to be minimized employing neutral atoms as flux carriers. By breaking the Galilean invariance we demonstrate how atomic currents through the lattice provide an implementation of a qubit. This is realized either by artificially creating a phase slip in a single ring, or by tunnel coupling of two homogeneous ring lattices. The single qubit infrastructure is experimentally investigated with tailored optical potentials. Indeed, we have experimentally realized scaled ring-lattice potentials that could host, in principle, n ~ 10 of such ring-qubits, arranged in a stack configuration, along the laser beam propagation axis. An experimentally viable scheme of the two-ring-qubit is discussed, as well. Based on our analysis, we provide protocols to initialize, address, and read-out the qubit. PMID:24599096

  16. Doublon dynamics and polar molecule production in an optical lattice

    PubMed Central

    Covey, Jacob P.; Moses, Steven A.; Gärttner, Martin; Safavi-Naini, Arghavan; Miecnikowski, Matthew T.; Fu, Zhengkun; Schachenmayer, Johannes; Julienne, Paul S.; Rey, Ana Maria; Jin, Deborah S.; Ye, Jun

    2016-01-01

    Polar molecules in an optical lattice provide a versatile platform to study quantum many-body dynamics. Here we use such a system to prepare a density distribution where lattice sites are either empty or occupied by a doublon composed of an interacting Bose-Fermi pair. By letting this out-of-equilibrium system evolve from a well-defined, but disordered, initial condition, we observe clear effects on pairing that arise from inter-species interactions, a higher partial-wave Feshbach resonance and excited Bloch-band population. These observations facilitate a detailed understanding of molecule formation in the lattice. Moreover, the interplay of tunnelling and interaction of fermions and bosons provides a controllable platform to study Bose-Fermi Hubbard dynamics. Additionally, we can probe the distribution of the atomic gases in the lattice by measuring the inelastic loss of doublons. These techniques realize tools that are generically applicable to studying the complex dynamics of atomic mixtures in optical lattices. PMID:27075831

  17. Graphene and graphene-like 2D materials for optical biosensing and bioimaging: a review

    NASA Astrophysics Data System (ADS)

    Zhu, Chengzhou; Du, Dan; Lin, Yuehe

    2015-09-01

    The increasing demands of bioassay and biomedical applications have significantly promoted the rational design and fabrication of a wide range of functional nanomaterials. Coupling these advanced nanomaterials with biomolecule recognition events leads to novel sensing and diagnostic platforms. Because of their unique structures and multifunctionalities, two-dimensional nanomaterials, such as graphene and graphene-like materials (e.g., graphitic carbon nitride, transition metal dichalcogenides, boron nitride, and transition metal oxides), have stimulated great interest in the field of optical biosensors and imaging because of their innovative mechanical, physicochemical and optical properties. Depending on the different applications, the graphene and graphene-like nanomaterials can be tailored to form either fluorescent emitters or efficient fluorescence quenchers, making them powerful platforms for fabricating a series of optical biosensors to sensitively detect various targets including ions, small biomolecules, DNA/RNA and proteins. This review highlights the recent progress in optical biosensors based on graphene and graphene-like 2D materials and their imaging applications. Finally, the opportunities and some critical challenges in this field are also addressed.

  18. Super-resolution microscopy of single atoms in optical lattices

    NASA Astrophysics Data System (ADS)

    Alberti, Andrea; Robens, Carsten; Alt, Wolfgang; Brakhane, Stefan; Karski, Michał; Reimann, René; Widera, Artur; Meschede, Dieter

    2016-05-01

    We report on image processing techniques and experimental procedures to determine the lattice-site positions of single atoms in an optical lattice with high reliability, even for limited acquisition time or optical resolution. Determining the positions of atoms beyond the diffraction limit relies on parametric deconvolution in close analogy to methods employed in super-resolution microscopy. We develop a deconvolution method that makes effective use of the prior knowledge of the optical transfer function, noise properties, and discreteness of the optical lattice. We show that accurate knowledge of the image formation process enables a dramatic improvement on the localization reliability. This allows us to demonstrate super-resolution of the atoms’ position in closely packed ensembles where the separation between particles cannot be directly optically resolved. Furthermore, we demonstrate experimental methods to precisely reconstruct the point spread function with sub-pixel resolution from fluorescence images of single atoms, and we give a mathematical foundation thereof. We also discuss discretized image sampling in pixel detectors and provide a quantitative model of noise sources in electron multiplying CCD cameras. The techniques developed here are not only beneficial to neutral atom experiments, but could also be employed to improve the localization precision of trapped ions for ultra precise force sensing.

  19. Strongly Interacting Atom Lasers in Three-Dimensional Optical Lattices

    SciTech Connect

    Hen, Itay; Rigol, Marcos

    2010-10-29

    We show that the dynamical melting of a Mott insulator in a three-dimensional lattice leads to condensation at nonzero momenta, a phenomenon that can be used to generate strongly interacting atom lasers in optical lattices. For infinite on-site repulsion, the case considered here, the momenta at which bosons condense are determined analytically and found to have a simple dependence on the hopping amplitudes. The occupation of the condensates is shown to scale linearly with the total number of atoms in the initial Mott insulator. Our results are obtained by using a Gutzwiller-type mean-field approach, gauged against exact-diagonalization solutions of small systems.

  20. Experimentally observed field–gas interaction in intense optical lattices

    SciTech Connect

    Graul, Jacob S.; Cornella, Barry M.; Ketsdever, Andrew D.; Lilly, Taylor C.; Shneider, Mikhail N.

    2013-12-09

    When a gas perturbed by a laser interference pattern, an optical lattice, exhibits a periodic modulation of its refractive index, strong Bragg diffraction of the perturbing light can occur. This scattering reduces the field's ability to further manipulate the gas. Experimental observations of Bragg scattering, evidence of a two-way coupling, are compared to the evolution of the light fields calculated by solutions to the wave equation. Comparison indicates momentum deposition as a prime contributor to the shape of the scattering function vs. lattice velocity, a rationale further supported through additional direct simulation Monte Carlo simulation.

  1. Dynamics of matter solitons in weakly modulated optical lattices

    SciTech Connect

    Brazhnyi, V.A.; Konotop, V.V.; Kuzmiak, V.

    2004-10-01

    It is shown that matter solitons can be effectively managed by means of smooth variations of parameters of optical lattices in which the condensate is loaded. The phenomenon is based on the effect of lattice modulations on the carrier wave transporting the soliton and that is why it is well understood in terms of the effective mass approach, where a particular spatial configuration of the band structure is of primary importance. Linear, parabolic, and spatially localized modulations are considered as case examples. It is shown that these defects can originate an accelerating and oscillating motion of matter solitons as well as they can simulate soliton interactions with attractive and repulsive defects.

  2. Effective Dirac dynamics of ultracold atoms in bichromatic optical lattices

    SciTech Connect

    Witthaut, D.; Salger, T.; Kling, S.; Grossert, C.; Weitz, M.

    2011-09-15

    We study the dynamics of ultracold atoms in tailored bichromatic optical lattices. By tuning the lattice parameters, one can readily engineer the band structure and realize a Dirac point, i.e., a true crossing of two Bloch bands. The dynamics in the vicinity of such a crossing is described by the one-dimensional Dirac equation, which is rigorously shown beyond the tight-binding approximation. Within this framework we analyze the effects of an external potential and demonstrate numerically that it is possible to demonstrate Klein tunneling with current experimental setups.

  3. Optical-lattice Hamiltonians for relativistic quantum electrodynamics

    SciTech Connect

    Kapit, Eliot; Mueller, Erich

    2011-03-15

    We show how interpenetrating optical lattices containing Bose-Fermi mixtures can be constructed to emulate the thermodynamics of quantum electrodynamics (QED). We present models of neutral atoms on lattices in 1+1, 2+1, and 3+1 dimensions whose low-energy effective action reduces to that of photons coupled to Dirac fermions of the corresponding dimensionality. We give special attention to (2+1)-dimensional quantum electrodynamics (QED3) and discuss how two of its most interesting features, chiral symmetry breaking and Chern-Simons physics, could be observed experimentally.

  4. Prospects for Optical Clocks with a Blue-Detuned Lattice

    SciTech Connect

    Takamoto, M.; Katori, H.; Marmo, S. I.; Ovsiannikov, V. D.; Pal'chikov, V. G.

    2009-02-13

    We investigated the properties of optical lattice clocks operated with a repulsive light-shift potential. The magic wavelength, where light-shift perturbation for the clock transition cancels, was experimentally determined to be 389.889(9) nm for {sup 87}Sr. The hyperpolarizability effects on the clock transition were investigated theoretically. With minimal trapping field perturbation provided by the blue-detuned lattice, the fractional uncertainty due to the hyperpolarizability effects was found to be 2x10{sup -19} in the relevant clock transition.

  5. Mixtures of Strongly Interacting Bosons in Optical Lattices

    SciTech Connect

    Buonsante, P.; Penna, V.; Giampaolo, S. M.; Illuminati, F.; Vezzani, A.

    2008-06-20

    We investigate the properties of strongly interacting heteronuclear boson-boson mixtures loaded in realistic optical lattices, with particular emphasis on the physics of interfaces. In particular, we numerically reproduce the recent experimental observation that the addition of a small fraction of {sup 41}K induces a significant loss of coherence in {sup 87}Rb, providing a simple explanation. We then investigate the robustness against the inhomogeneity typical of realistic experimental realizations of the glassy quantum emulsions recently predicted to occur in strongly interacting boson-boson mixtures on ideal homogeneous lattices.

  6. Single ions trapped in a one-dimensional optical lattice.

    PubMed

    Enderlein, Martin; Huber, Thomas; Schneider, Christian; Schaetz, Tobias

    2012-12-07

    We report on three-dimensional optical trapping of single ions in a one-dimensional optical lattice formed by two counterpropagating laser beams. We characterize the trapping parameters of the standing-wave using the ion as a sensor stored in a hybrid trap consisting of a radio-frequency (rf), a dc, and the optical potential. When loading ions directly from the rf into the standing-wave trap, we observe a dominant heating rate. Monte Carlo simulations confirm rf-induced parametric excitations within the deep optical lattice as the main source. We demonstrate a way around this effect by an alternative transfer protocol which involves an intermediate step of optical confinement in a single-beam trap avoiding the temporal overlap of the standing-wave and the rf field. Implications arise for hybrid (rf-optical) and pure optical traps as platforms for ultracold chemistry experiments exploring atom-ion collisions or quantum simulation experiments with ions, or combinations of ions and atoms.

  7. Dynamical phase interferometry of cold atoms in optical lattices

    SciTech Connect

    London, Uri; Gat, Omri

    2011-12-15

    We study the propagation of cold-atom wave packets in an interferometer with a Mach-Zehnder topology based on the dynamical phase of Bloch oscillation in a weakly forced optical lattice with a narrow potential barrier that functions as a cold-atom wave-packet splitter. We calculate analytically the atomic wave function, and show that the expected number of atoms in the two outputs of the interferometer oscillates rapidly as a function of the angle between the potential barrier and the forcing direction with period proportional to the external potential difference across a lattice spacing divided by the lattice band energy scale. The interferometer can be used as a high-precision force probe whose principle of operation is different from current interferometers based on the overall position of Bloch oscillating wave packets.

  8. Pinning an ion with an intracavity optical lattice.

    PubMed

    Linnet, Rasmus B; Leroux, Ian D; Marciante, Mathieu; Dantan, Aurélien; Drewsen, Michael

    2012-12-07

    We report one-dimensional pinning of a single ion by an optical lattice. A standing-wave cavity produces the lattice potential along the rf-field-free axis of a linear Paul trap. The ion's localization is detected by measuring its fluorescence when excited by standing-wave fields with the same period, but different spatial phases. The experiments agree with an analytical model of the localization process, which we test against numerical simulations. For the best localization achieved, the ion's average coupling to the cavity field is enhanced from 50% to 81(3)% of its maximum possible value, and we infer that the ion is bound in a lattice well with over 97% probability.

  9. Refractive effects on optical measurement of alveolar volume: a 2-D ray-tracing approach.

    PubMed

    Golabchi, Fatemeh N; Brooks, Dana H; Gouldstone, Andrew; DiMarzio, Charles A

    2011-01-01

    Lung imaging and assessment of alveoli geometry in the lung tissue is of great importance. Optical coherence tomography (OCT) is a real-time imaging technique used for this purpose, based on near-infrared interferometry, that can image several layers of distal alveoli in the lung tissue. The OCT measurements use low coherence interferometry, where light reflections from surfaces in the tissue are used to construct 2D images of the tissue. OCT images provide better depth compared to other optical microscopy techniques such as confocal reflectance and two-photon microscopy. Therefore, it is important to detect and verify optical distortions that happens with OCT, including refractive effect at the tissue-air alveoli wall interface which is not taken into account in the OCT imaging model. In this paper, the refractive effect at the tissue-air interface of the alveoli wall is modeled using exact ray tracing and direct implementation of Snell's law, and differences between alveoli area computed from OCT imaging and those measured by exact ray tracing of the OCT signal are analyzed.

  10. Sorting via injection of particle streams into an optical lattice

    NASA Astrophysics Data System (ADS)

    MacDonald, Michael P.; Neale, Steven L.; Smith, Ryan L.; Spalding, Gabriel C.; Dholakia, Kishan

    2005-08-01

    The growth of research into microfluidics, especially towards micro-Total Analysis Systems (μTAS), is leading to a demand for highly efficient and accurate methods for analyte delivery, sorting, mixing and analysis. Optical techniques, due to their non-invasive, non-contact properties are ideally suited to integration in to microfluidic systems. One of the key abilities in a μTAS device is the ability to sort microscopic matter. When done optically this typically involves fluorescence detection, management of the information detected and subsequent action such as the actuation of an electric field or electro-mechanical valve. We present here a method whereby the detection of a micro-particle's properties is done passively, with simultaneous separation of those particles. To do this particle streams are injected into a three-dimensional crystal-like lattice of optical intensity maxima. A particle's response to the three-dimensional optical potential landscape formed by the lattice depends on its polarisability. This leads to a sensitivity to size, refractive index and shape. More strongly interacting particles are deflected away from the main flow whilst those that interact weakly are washed straight through the lattice without little or no net deflection. We present analysis of both injection and subsequent re-routing/sorting of particle streams, using body-centred tetragonal and three-dimensional "log-pile" optical lattices to separate both inert colloid and blood cells by refractive index or size. Sorting with an efficiency as high as 96% has been achieved with particle deflections in excess of 45 degrees.

  11. Optical Signatures from Magnetic 2-D Electron Gases in High Magnetic Fields to 60 Tesla

    SciTech Connect

    Crooker, S.A.; Kikkawa, J.M.; Awschalom, D.D.; Smorchikova, I.P.; Samarth, N.

    1998-11-08

    We present experiments in the 60 Tesla Long-Pulse magnet at the Los Alamos National High Magnetic Field Lab (NHMFL) focusing on the high-field, low temperature photoluminescence (PL) from modulation-doped ZnSe/Zn(Cd,Mn)Se single quantum wells. High-speed charge-coupled array detectors and the long (2 second) duration of the magnet pulse permit continuous acquisition of optical spectra throughout a single magnet shot. High-field PL studies of the magnetic 2D electron gases at temperatures down to 350mK reveal clear intensity oscillations corresponding to integer quantum Hall filling factors, from which we determine the density of the electron gas. At very high magnetic fields, steps in the PL energy are observed which correspond to the partial unlocking of antiferromagnetically bound pairs of Mn2+ spins.

  12. Optical and electrical study of organic solar cells with a 2D grating anode.

    PubMed

    Sha, Wei E I; Choy, Wallace C H; Wu, Yumao; Chew, Weng Cho

    2012-01-30

    We investigate both optical and electrical properties of organic solar cells (OSCs) incorporating 2D periodic metallic back grating as an anode. Using a unified finite-difference approach, the multiphysics modeling framework for plasmonic OSCs is established to seamlessly connect the photon absorption with carrier transport and collection by solving the Maxwell's equations and semiconductor equations (Poisson, continuity, and drift-diffusion equations). Due to the excited surface plasmon resonance, the significantly nonuniform and extremely high exciton generation rate near the metallic grating are strongly confirmed by our theoretical model. Remarkably, the nonuniform exciton generation indeed does not induce more recombination loss or smaller open-circuit voltage compared to 1D multilayer standard OSC device. The increased open-circuit voltage and reduced recombination loss by the plasmonic OSC are attributed to direct hole collections at the metallic grating anode with a short transport path. The work provides an important multiphysics understanding for plasmonic organic photovoltaics.

  13. Backscattering from a statistically rough 2-D surface: Diffraction corrections to geometrical optics cross sections

    NASA Astrophysics Data System (ADS)

    Fuks, Iosif M.

    2007-12-01

    Diffraction corrections (up to terms ˜1/k2) to the geometric optics backscattering cross sections from a statistically rough 2-D perfectly conducting surface were derived for TE- and TM-polarized electromagnetic waves based on the high-frequency asymptotic expansions of electric and magnetic fields at the surface obtained by Fuks (2004). It was shown that at steep incident angles, where the specular reflections play the main part in scattering, diffraction results can be interpreted as scattering by a fictitious surface, the roughness of which is gentler that the real surface at HH polarization and steeper at VV polarization. The HH/VV polarization ratio (dB), being positive at steep incident angles, gradually decreases as the incident angle increases, and it becomes negative for moderate incident angles.

  14. Resonant and Soliton Transport of Ultracold Atoms on Optical Lattices

    NASA Astrophysics Data System (ADS)

    Rubbo, Chester Philipp

    In this thesis, we present a theoretical study of the dynamics of strongly interacting ultracold atoms in optical lattices. At ultracold temperatures, the dynamics cannot be described classically, but instead, must take into account quantum effects. Here, our focus is on transport and precision measurement. We use exact analysis of few-body systems and mean field analysis. For larger systems, we use a numerical approach called the density matrix renormalization group (DMRG) method which is considered an efficient computational tool for the quantum evolution of 1D systems. After introducing basic concepts, we treat the motional properties of particles in a tilted lattice in a regime where the inter-particle interactions are resonant with the linear potential. In this regime, the dynamics is described by an Ising model with a transverse field which is a basic system to study quantum magnetism and quantum phase transitions. We introduce analytical and numerical methods to draw a simple picture of the dynamics. This helps us to formulate a slinky-like transport scheme that provides full control of the motional direction of particles. After a study of transport on a tilted lattice, we treat the transport of nonlinear waves in strongly interacting systems. These nonlinear waves are called solitons, which are described as local perturbations of a medium that survive after collisions. We identify two species of classical soliton solutions in our system and study their stability under quantum evolution via DMRG. We shift focus from the dynamics related to transport and turn to precision measurements in optical lattice clocks. Here, we investigate one aspect of their limitations which is due to collisions of atoms loaded onto a single site. These collisions introduce a frequency shift in the clock measurement. We provide a microscopic description of the origin of this frequency shift. Our results have motivated improvement in the accuracy and precision of next generation

  15. Wannier functions using a discrete variable representation for optical lattices

    NASA Astrophysics Data System (ADS)

    Paul, Saurabh; Tiesinga, Eite

    2016-09-01

    We propose a numerical method using the discrete variable representation (DVR) for constructing real-valued Wannier functions localized in a unit cell for both symmetric and asymmetric periodic potentials. We apply these results to finding Wannier functions for ultracold atoms trapped in laser-generated optical lattices. Following S. Kivelson [Phys. Rev. B 26, 4269 (1982), 10.1103/PhysRevB.26.4269], for a symmetric lattice with inversion symmetry, we construct Wannier functions as eigenstates of the position operators x ̂, y ̂, and z ̂ restricted to single-particle Bloch functions belonging to one or more bands. To ensure that the Wannier functions are real-valued, we numerically obtain the band structure and real-valued eigenstates using a uniform Fourier grid DVR. We then show, by a comparison of tunneling energies, that the Wannier functions are accurate for both inversion-symmetric and asymmetric potentials to better than 10 significant digits when using double-precision arithmetic. The calculations are performed for an optical lattice with double-wells per unit cell with tunable asymmetry along the x axis and a single sinusoidal potential along the perpendicular directions. Localized functions at the two potential minima within each unit cell are similarly constructed, but using a superposition of single-particle solutions from the two lowest bands. We finally use these localized basis functions to determine the two-body interaction energies in the Bose-Hubbard model and show the dependence of these energies on lattice asymmetry.

  16. Ytterbium optical lattice clock with 10-18 level characterization

    NASA Astrophysics Data System (ADS)

    Phillips, Nathaniel; Sherman, Jeff; Beloy, Kyle; Hinkley, Nathan; Schioppo, Marco; Oates, Chris; Ludlow, Andrew

    2014-05-01

    A recent comparison of two ytterbium-based optical lattice clocks at NIST demonstrated record stability of 1 . 6 parts in 1018 after 25,000s averaging. We report on measurements of the two primary systematic effects that shift the ultra-narrow clock transition, towards a reduction of the clock uncertainty to the 10-18 level. Uncertainty stemming from the blackbody radiation (BBR) shift is largely due to imprecise knowledge of the thermal environment surrounding the atoms. We detail the construction and operation of an in-vacuum, thermally-regulated radiation shield, which permits laser cooling and trapping while enabling an absolute temperature measurement with < 20 mK precision. Additionally, while operation of the optical lattice at the magic wavelength (λm) cancels the scalar Stark shift (since both clock states shift equally), higher-order vector and two-photon hyperpolarizability shifts remain. To evaluate these effects, as well as the polarizability away from λm, we implement a lattice buildup cavity around the atoms. The resulting twenty-fold enhancement of the lattice intensity provides a significant lever arm for precise measurement of these effects.

  17. Superfluid and insulating phases of fermion mixtures in optical lattices.

    PubMed

    Iskin, M; Sá de Melo, C A R

    2007-08-24

    The ground state phase diagram of fermion mixtures in optical lattices is analyzed as a function of interaction strength, fermion filling factor, and tunneling parameters. In addition to standard superfluid, phase-separated or coexisting superfluid -- excess-fermion phases found in homogeneous or harmonically trapped systems, fermions in optical lattices have several insulating phases, including a molecular Bose-Mott insulator (BMI), a Fermi-Pauli (band) insulator (FPI), a phase-separated BMI-FPI mixture or a Bose-Fermi checkerboard (BFC). The molecular BMI phase is the fermion mixture counterpart of the atomic BMI found in atomic Bose systems, the BFC or BMI-FPI phases exist in Bose-Fermi mixtures, and lastly the FPI phase is particular to the Fermi nature of the constituent atoms of the mixture.

  18. Observation of discrete diffraction patterns in an optically induced lattice.

    PubMed

    Sheng, Jiteng; Wang, Jing; Miri, Mohammad-Ali; Christodoulides, Demetrios N; Xiao, Min

    2015-07-27

    We have experimentally observed the discrete diffraction of light in a coherently prepared multi-level atomic medium. This is achieved by launching a probe beam into an optical lattice induced from the interference of two coupling beams. The diffraction pattern can be controlled through the atomic parameters such as two-photon detuning and temperature, as well as orientations of the coupling and probe beams. Clear diffraction patterns occur only near the two-photon resonance.

  19. Driven optical lattices as strong-field simulators

    SciTech Connect

    Arlinghaus, Stephan; Holthaus, Martin

    2010-06-15

    We argue that ultracold atoms in strongly shaken optical lattices can be subjected to conditions similar to those experienced by electrons in laser-irradiated crystalline solids, but without introducing secondary polarization effects. As a consequence, one can induce nonperturbative multiphoton-like resonances due to the mutual penetration of ac-Stark-shifted Bloch bands. These phenomena can be detected with a combination of currently available laboratory techniques.

  20. Ab Initio Study of Ultracold Polar Molecules in Optical Lattices

    DTIC Science & Technology

    2010-01-01

    polar molecules by using optical lattices and microwave fields’’, US-Japan Joint Seminar on Coherent Quantum Systems, Breckenridge, USA, August (2006...corresponds to the dissociation energy of both 40K and 87Rb in the energetically lowest hyperfine state . The levels are grouped by the projection quantum ...vibrational state . The J = 1 to J = 2 transition occurs at a larger photon frequency. For the near-resonance frequencies the polarizabilities in Fig

  1. Damped Bloch oscillations of cold atoms in optical lattices

    SciTech Connect

    Kolovsky, A.R.; Ponomarev, A.V.; Korsch, H.J.

    2002-11-01

    The paper studies Bloch oscillations of cold neutral atoms in the optical lattice. The effect of spontaneous emission on the dynamics of the system is analyzed both analytically and numerically. The spontaneous emission is shown to cause (i) the decay of Bloch oscillations with the decrement given by the rate of spontaneous emission and (ii) the diffusive spreading of the atoms with a diffusion coefficient depending on both the rate of spontaneous emission and the Bloch frequency.

  2. Spin–orbit-coupled fermions in an optical lattice clock

    NASA Astrophysics Data System (ADS)

    Kolkowitz, S.; Bromley, S. L.; Bothwell, T.; Wall, M. L.; Marti, G. E.; Koller, A. P.; Zhang, X.; Rey, A. M.; Ye, J.

    2016-12-01

    Engineered spin–orbit coupling (SOC) in cold-atom systems can enable the study of new synthetic materials and complex condensed matter phenomena. However, spontaneous emission in alkali-atom spin–orbit-coupled systems is hindered by heating, limiting the observation of many-body effects and motivating research into potential alternatives. Here we demonstrate that spin–orbit-coupled fermions can be engineered to occur naturally in a one-dimensional optical lattice clock. In contrast to previous SOC experiments, here the SOC is both generated and probed using a direct ultra-narrow optical clock transition between two electronic orbital states in 87Sr atoms. We use clock spectroscopy to prepare lattice band populations, internal electronic states and quasi-momenta, and to produce spin–orbit-coupled dynamics. The exceptionally long lifetime of the excited clock state (160 seconds) eliminates decoherence and atom loss from spontaneous emission at all relevant experimental timescales, allowing subsequent momentum- and spin-resolved in situ probing of the SOC band structure and eigenstates. We use these capabilities to study Bloch oscillations, spin–momentum locking and Van Hove singularities in the transition density of states. Our results lay the groundwork for using fermionic optical lattice clocks to probe new phases of matter.

  3. Nonlocal optical properties in periodic lattice of graphene layers.

    PubMed

    Chern, Ruey-Lin; Han, Dezhuan

    2014-02-24

    Based on the effective medium model, nonlocal optical properties in periodic lattice of graphene layers with the period much less than the wavelength are investigated. Strong nonlocal effects are found in a broad frequency range for TM polarization, where the effective permittivity tensor exhibits the Lorentzian resonance. The resonance frequency varies with the wave vector and coincides well with the polaritonic mode. Nonlocal features are manifest on the emergence of additional wave and the occurrence of negative refraction. By examining the characters of the eigenmode, the nonlocal optical properties are attributed to the excitation of plasmons on the graphene surfaces.

  4. 2D-Visualization of metabolic activity with planar optical chemical sensors (optodes)

    NASA Astrophysics Data System (ADS)

    Meier, R. J.; Liebsch, G.

    2015-12-01

    Microbia plays an outstandingly important role in many hydrologic compartments, such as e.g. the benthic community in sediments, or biologically active microorganisms in the capillary fringe, in ground water, or soil. Oxygen, pH, and CO2 are key factors and indicators for microbial activity. They can be measured using optical chemical sensors. These sensors record changing fluorescence properties of specific indicator dyes. The signals can be measured in a non-contact mode, even through transparent walls, which is important for many lab-experiments. They can measure in closed (transparent) systems, without sampling or intruding into the sample. They do not consume the analytes while measuring, are fully reversible and able to measure in non-stirred solutions. These sensors can be applied as high precision fiberoptic sensors (for profiling), robust sensor spots, or as planar sensors for 2D visualization (imaging). Imaging enables to detect thousands of measurement spots at the same time and generate 2D analyte maps over a region of interest. It allows for comparing different regions within one recorded image, visualizing spatial analyte gradients, or more important to identify hot spots of metabolic activity. We present ready-to-use portable imaging systems for the analytes oxygen, pH, and CO2. They consist of a detector unit, planar sensor foils and a software for easy data recording and evaluation. Sensors foils for various analytes and measurement ranges enable visualizing metabolic activity or analyte changes in the desired range. Dynamics of metabolic activity can be detected in one shot or over long time periods. We demonstrate the potential of this analytical technique by presenting experiments on benthic disturbance-recovery dynamics in sediments and microbial degradation of organic material in the capillary fringe. We think this technique is a new tool to further understand how microbial and geochemical processes are linked in (not solely) hydrologic

  5. Probing many-body interactions in an optical lattice clock

    SciTech Connect

    Rey, A.M.; Gorshkov, A.V.; Kraus, C.V.; Martin, M.J.; Bishof, M.; Swallows, M.D.; Zhang, X.; Benko, C.; Ye, J.; Lemke, N.D.; Ludlow, A.D.

    2014-01-15

    We present a unifying theoretical framework that describes recently observed many-body effects during the interrogation of an optical lattice clock operated with thousands of fermionic alkaline earth atoms. The framework is based on a many-body master equation that accounts for the interplay between elastic and inelastic p-wave and s-wave interactions, finite temperature effects and excitation inhomogeneity during the quantum dynamics of the interrogated atoms. Solutions of the master equation in different parameter regimes are presented and compared. It is shown that a general solution can be obtained by using the so called Truncated Wigner Approximation which is applied in our case in the context of an open quantum system. We use the developed framework to model the density shift and decay of the fringes observed during Ramsey spectroscopy in the JILA {sup 87}Sr and NIST {sup 171}Yb optical lattice clocks. The developed framework opens a suitable path for dealing with a variety of strongly-correlated and driven open-quantum spin systems. -- Highlights: •Derived a theoretical framework that describes many-body effects in a lattice clock. •Validated the analysis with recent experimental measurements. •Demonstrated the importance of beyond mean field corrections in the dynamics.

  6. Strongly interacting fermions in optical lattices and superlattices

    NASA Astrophysics Data System (ADS)

    Goodman, Timothy S.

    This dissertation summarizes my recent work regarding systems of strongly interacting fermionic atoms in optical lattices. This work addresses the combination of two experimental techniques that have been the subject of much recent research in ultracold atom physics. One is the use of optical lattices, which provide a means to realize diverse interaction configurations within a clean, controllable system. The other is the use of magnetically tunable Feshbach resonances to control the strength of the interatomic interaction. Together, these techniques offer the possibility of an experimental realization of many important model Hamiltonians of condensed matter physics, and may also lead to the discovery of new physics. Recent study of this system has shown that strong interactions near Feshbach resonance will lead to the population of multiple lattice bands, and that collisions between atoms on neighboring sites cannot be neglected. These effects lead to a complicated Hamiltonian, but one which can be simplified to an effective single-band model equivalent to the generalized Hubbard model (GHM), which is an extension of the Hubbard model that includes correlated hopping terms. My main results concern the study of this model. The strong correlations between the particles make it difficult to definitively determine the many body physics of the GHM. As a first approach to understanding the GHM in optical lattices, I focus mainly on cases where the problem is greatly simplified by allowing interactions among only small groups of lattice sites. This restriction can be implemented in experiments using an optical superlattice potential. Our results include a proposed scheme (based on double-well superlattices) to empirically verify that the GHM describes this system and to directly measure the various parameters of this model. Other results include exact solutions on four-site square plaquettes, which demonstrate that d-wave excitations can occur in the low-energy states

  7. Intrinsic Localized Modes in Optical Photonic Lattices and Arrays

    NASA Astrophysics Data System (ADS)

    Christodoulides, Demetrios

    Discretizing light behavior requires optical elements that can confine optical energy at distinct sites. One possible scenario in implementing such arrangements is to store energy within low loss high Q-microcavities and then allow photon exchange between such components in time. This scheme requires high-contrast dielectric elements that became available with the advent of photonic crystal technologies. Another possible avenue where such light discretization can be directly observed and studied is that based on evanescently coupled waveguide arrays. As indicated in several studies, discrete systems open up whole new directions in terms of modifying light transport properties. One such example is that of discrete solitons. By nature, discrete solitons represent self-trapped wavepackets in nonlinear periodic structures and result from the interplay between lattice diffraction (or dispersion) and material nonlinearity. In optics, this class of self-localized states has been successfully observed in both one- and two-dimensional nonlinear waveguide arrays. In recent years such photonic lattices have been implemented or induced in a variety of material systems, including those with cubic (Kerr), quadratic, photorefractive, and liquid-crystal nonlinearities. In all cases the underlying periodicity or discreteness can lead to new families of optical solitons that have no counterpart whatsoever in continuous systems. Interestingly, these results paved the way for observations in other physical systems obeying similar evolution equations like Bose-Einstein condensates. New developments in laser writing ultrashort femtosecond laser pulses, now allow the realization of all-optical switching networks in fully 3D environments using nonlinear discrete optics. Using this approach all-optical routing can be achieved using blocking operations. The spatio-temporal evolution of optical pulses in both normally and anomalously dispersive arrays can lead to novel schemes for mode

  8. Quantum simulation of frustrated classical magnetism in triangular optical lattices.

    PubMed

    Struck, J; Ölschläger, C; Le Targat, R; Soltan-Panahi, P; Eckardt, A; Lewenstein, M; Windpassinger, P; Sengstock, K

    2011-08-19

    Magnetism plays a key role in modern technology and stimulates research in several branches of condensed matter physics. Although the theory of classical magnetism is well developed, the demonstration of a widely tunable experimental system has remained an elusive goal. Here, we present the realization of a large-scale simulator for classical magnetism on a triangular lattice by exploiting the particular properties of a quantum system. We use the motional degrees of freedom of atoms trapped in an optical lattice to simulate a large variety of magnetic phases: ferromagnetic, antiferromagnetic, and even frustrated spin configurations. A rich phase diagram is revealed with different types of phase transitions. Our results provide a route to study highly debated phases like spin-liquids as well as the dynamics of quantum phase transitions.

  9. Criterion for Bosonic Superfluidity in an Optical Lattice

    SciTech Connect

    Diener, Roberto B.; Zhou Qi; Zhai Hui; Ho, T.-L.

    2007-05-04

    We show that the current method of determining superfluidity in optical lattices based on a visibly sharp bosonic momentum distribution n(k) can be misleading, for even a normal Bose gas can have a similarly sharp n(k). We show that superfluidity in a homogeneous system can be detected from the so-called visibility (v) of n(k)--that v must be 1 within O(N{sup -2/3}), where N is the number of bosons. We also show that the T=0 visibility of trapped lattice bosons is far higher than what is obtained in some current experiments, suggesting strong temperature effects and that these states can be normal. These normal states allow one to explore the physics in the quantum critical region.

  10. Synthetic Spin-Orbit Coupling in an Optical Lattice Clock

    NASA Astrophysics Data System (ADS)

    Wall, Michael L.; Koller, Andrew P.; Li, Shuming; Zhang, Xibo; Cooper, Nigel R.; Ye, Jun; Rey, Ana Maria

    2016-01-01

    We propose the use of optical lattice clocks operated with fermionic alkaline-earth atoms to study spin-orbit coupling (SOC) in interacting many-body systems. The SOC emerges naturally during the clock interrogation, when atoms are allowed to tunnel and accumulate a phase set by the ratio of the "magic" lattice wavelength to the clock transition wavelength. We demonstrate how standard protocols such as Rabi and Ramsey spectroscopy that take advantage of the sub-Hertz resolution of state-of-the-art clock lasers can perform momentum-resolved band tomography and determine SOC-induced s -wave collisions in nuclear-spin-polarized fermions. With the use of a second counterpropagating clock beam, we propose a method for engineering controlled atomic transport and study how it is modified by p - and s -wave interactions. The proposed spectroscopic probes provide clean and well-resolved signatures at current clock operating temperatures.

  11. Synthetic Spin-Orbit Coupling in an Optical Lattice Clock.

    PubMed

    Wall, Michael L; Koller, Andrew P; Li, Shuming; Zhang, Xibo; Cooper, Nigel R; Ye, Jun; Rey, Ana Maria

    2016-01-22

    We propose the use of optical lattice clocks operated with fermionic alkaline-earth atoms to study spin-orbit coupling (SOC) in interacting many-body systems. The SOC emerges naturally during the clock interrogation, when atoms are allowed to tunnel and accumulate a phase set by the ratio of the "magic" lattice wavelength to the clock transition wavelength. We demonstrate how standard protocols such as Rabi and Ramsey spectroscopy that take advantage of the sub-Hertz resolution of state-of-the-art clock lasers can perform momentum-resolved band tomography and determine SOC-induced s-wave collisions in nuclear-spin-polarized fermions. With the use of a second counterpropagating clock beam, we propose a method for engineering controlled atomic transport and study how it is modified by p- and s-wave interactions. The proposed spectroscopic probes provide clean and well-resolved signatures at current clock operating temperatures.

  12. Quantum simulations of lattice gauge theories using ultracold atoms in optical lattices.

    PubMed

    Zohar, Erez; Cirac, J Ignacio; Reznik, Benni

    2016-01-01

    Can high-energy physics be simulated by low-energy, non-relativistic, many-body systems such as ultracold atoms? Such ultracold atomic systems lack the type of symmetries and dynamical properties of high energy physics models: in particular, they manifest neither local gauge invariance nor Lorentz invariance, which are crucial properties of the quantum field theories which are the building blocks of the standard model of elementary particles. However, it turns out, surprisingly, that there are ways to configure an atomic system to manifest both local gauge invariance and Lorentz invariance. In particular, local gauge invariance can arise either as an effective low-energy symmetry, or as an exact symmetry, following from the conservation laws in atomic interactions. Hence, one could hope that such quantum simulators may lead to a new type of (table-top) experiments which will be used to study various QCD (quantum chromodynamics) phenomena, such as the confinement of dynamical quarks, phase transitions and other effects, which are inaccessible using the currently known computational methods. In this report, we review the Hamiltonian formulation of lattice gauge theories, and then describe our recent progress in constructing the quantum simulation of Abelian and non-Abelian lattice gauge theories in 1  +  1 and 2  +  1 dimensions using ultracold atoms in optical lattices.

  13. Addressable, large-field second harmonic generation microscopy based on 2D acousto-optical deflector and spatial light modulator.

    PubMed

    Shao, Yonghong; Liu, Honghai; Qin, Wan; Qu, Junle; Peng, Xiang; Niu, Hanben; Gao, Bruce Z

    2012-09-01

    We present an addressable, large-field second harmonic generation microscope by combining a 2D acousto-optical deflector with a spatial light modulator. The SLM shapes an incoming mode-locked, near-infrared Ti:Sapphire laser beam into a multifocus array, which can be rapidly scanned by changing the incident angle of the laser beam using a 2D acousto-optical deflector. Compared to the single-beam-scan technique, the multifocus array scan can increase the scanning rate and the field-of-view size with the multi-region imaging ability.

  14. Addressable, large-field second harmonic generation microscopy based on 2D acousto-optical deflector and spatial light modulator

    PubMed Central

    Shao, Yonghong; Liu, Honghai; Qin, Wan; Qu, Junle; Peng, Xiang; Niu, Hanben

    2013-01-01

    We present an addressable, large-field second harmonic generation microscope by combining a 2D acousto-optical deflector with a spatial light modulator. The SLM shapes an incoming mode-locked, near-infrared Ti:Sapphire laser beam into a multifocus array, which can be rapidly scanned by changing the incident angle of the laser beam using a 2D acousto-optical deflector. Compared to the single-beam-scan technique, the multifocus array scan can increase the scanning rate and the field-of-view size with the multi-region imaging ability. PMID:24307756

  15. A 2D Rods-in-Air Square-Lattice Photonic Crystal Optical Switch

    DTIC Science & Technology

    2009-03-01

    photonic crystal switches, IEEE Photon. Technol. Lett. 18 (2) (2006) 358–360. [8] Y. Kanamori , K. Inoue, K. Horie, K. Hane, Photonic crystal switch by...Waikoloa, Hawaii, USA, pp. 107–108. [9] K. Umemori, Y. Kanamori , K. Hane, A photonic crystal waveguide switch with a movable bridge slab, in: Proceedings of...Umemori, Yoshiaki Kanamori , Kazuhiro Hane, Photonic crystal waveguide switch with a microelectromechanical actuator, Appl. Phys. Lett. 89 (2) (2006

  16. Optical trapping via guided resonance modes in a Slot-Suzuki-phase photonic crystal lattice.

    PubMed

    Ma, Jing; Martínez, Luis Javier; Povinelli, Michelle L

    2012-03-12

    A novel photonic crystal lattice is proposed for trapping a two-dimensional array of particles. The lattice is created by introducing a rectangular slot in each unit cell of the Suzuki-Phase lattice to enhance the light confinement of guided resonance modes. Large quality factors on the order of 10⁵ are predicted in the lattice. A significant decrease of the optical power required for optical trapping can be achieved compared to our previous design.

  17. Optical contrast of 2D InSe on SiO2/Si and transparent substrates using bandpass filters.

    PubMed

    Brotons-Gisbert, M; Andres-Penares, D; Martínez-Pastor, J P; Cros, A; Sánchez-Royo, J F

    2017-03-17

    The particular optical and electronic properties recently reported for 2D InSe depict this 2D material as being very versatile for future electronic and optoelectronic devices with tunable and optimized functionalities. For its fundamental study and the development of practical applications, rapid and accurate identification methods of atomically thin InSe are essential. Here, we demonstrate an enhancement of the optical contrast between InSe nanosheets and the underlying SiO2/Si substrate by illuminating with a 40 nm wide bandpass filter centered at 500 nm. Moreover, we study the optical contrast of 2D InSe on transparent substrates. Our results suggest that a good optical contrast is achieved for transparent substrates with low real refractive indices such as LiF or a viscoelastic polydimethylsiloxane stamp. In this case, an optimum optical contrast would be achieved by using a bandpass filter centered at 450 nm. These results can be very useful for speeding up the continuously growing research on 2D InSe and its applications.

  18. Optical contrast of 2D InSe on SiO2/Si and transparent substrates using bandpass filters

    NASA Astrophysics Data System (ADS)

    Brotons-Gisbert, M.; Andres-Penares, D.; Martínez-Pastor, J. P.; Cros, A.; Sánchez-Royo, J. F.

    2017-03-01

    The particular optical and electronic properties recently reported for 2D InSe depict this 2D material as being very versatile for future electronic and optoelectronic devices with tunable and optimized functionalities. For its fundamental study and the development of practical applications, rapid and accurate identification methods of atomically thin InSe are essential. Here, we demonstrate an enhancement of the optical contrast between InSe nanosheets and the underlying SiO2/Si substrate by illuminating with a 40 nm wide bandpass filter centered at 500 nm. Moreover, we study the optical contrast of 2D InSe on transparent substrates. Our results suggest that a good optical contrast is achieved for transparent substrates with low real refractive indices such as LiF or a viscoelastic polydimethylsiloxane stamp. In this case, an optimum optical contrast would be achieved by using a bandpass filter centered at 450 nm. These results can be very useful for speeding up the continuously growing research on 2D InSe and its applications.

  19. Dynamical phase diagram of Gaussian wave packets in optical lattices

    NASA Astrophysics Data System (ADS)

    Hennig, H.; Neff, T.; Fleischmann, R.

    2016-03-01

    We study the dynamics of self-trapping in Bose-Einstein condensates (BECs) loaded in deep optical lattices with Gaussian initial conditions, when the dynamics is well described by the discrete nonlinear Schrödinger equation (DNLSE). In the literature an approximate dynamical phase diagram based on a variational approach was introduced to distinguish different dynamical regimes: diffusion, self-trapping, and moving breathers. However, we find that the actual DNLSE dynamics shows a completely different diagram than the variational prediction. We calculate numerically a detailed dynamical phase diagram accurately describing the different dynamical regimes. It exhibits a complex structure that can readily be tested in current experiments in BECs in optical lattices and in optical waveguide arrays. Moreover, we derive an explicit theoretical estimate for the transition to self-trapping in excellent agreement with our numerical findings, which may be a valuable guide as well for future studies on a quantum dynamical phase diagram based on the Bose-Hubbard Hamiltonian.

  20. Dynamical phase diagram of Gaussian wave packets in optical lattices.

    PubMed

    Hennig, H; Neff, T; Fleischmann, R

    2016-03-01

    We study the dynamics of self-trapping in Bose-Einstein condensates (BECs) loaded in deep optical lattices with Gaussian initial conditions, when the dynamics is well described by the discrete nonlinear Schrödinger equation (DNLSE). In the literature an approximate dynamical phase diagram based on a variational approach was introduced to distinguish different dynamical regimes: diffusion, self-trapping, and moving breathers. However, we find that the actual DNLSE dynamics shows a completely different diagram than the variational prediction. We calculate numerically a detailed dynamical phase diagram accurately describing the different dynamical regimes. It exhibits a complex structure that can readily be tested in current experiments in BECs in optical lattices and in optical waveguide arrays. Moreover, we derive an explicit theoretical estimate for the transition to self-trapping in excellent agreement with our numerical findings, which may be a valuable guide as well for future studies on a quantum dynamical phase diagram based on the Bose-Hubbard Hamiltonian.

  1. Proposals for quantum simulating simple lattice gauge theory models using optical lattices

    NASA Astrophysics Data System (ADS)

    Zhang, Jin; Unmuth-Yockey, Judah; Bazavov, Alexei; Meurice, Yannick; Tsai, Shan-Wen

    We derive an effective spin Hamiltonian for the (1 +1)-dimensional Abelian Higgs model in the strongly coupled region by integrating out the link variables. With finite spin truncations, the Hamiltonian can be matched with a 1-dimensional two-species Bose Hubbard model in the strong-coupling limit that can be implemented with cold atoms on an optical lattice. We study the phase diagram of the original Abelian Higgs model with Monte Carlo simulation and Tensor Renormalization Group methods. The results show a crossover line which terminates near the Kosterlitz-Thouless transition point. The effective quantum Hamiltonian is also studied with the DMRG method, and we find that they have a similar behavior. We discuss practical experimental implementations for our quantum simulator. Species-dependent optical lattices and ladder systems with double-well potentials are considered. We show how to obtain each of the interaction parameters required in the Bose-Hubbard model that we obtained, and confirm the possibility of tuning these interactions to the region in which our mapping is valid. We emphasize that this proposal for quantum simulating a gauge theory uses a manifestly gauge-invariant formulation and Gauss's Law is therefore automatically satisfied. Supported by DoD ARO under Grant No. W911NF-13-1-0119 and by the NSF under Grants No. DMR-1411345.

  2. Controlled and Uncontrolled Disorder in Optical Lattice Emulators

    DTIC Science & Technology

    2014-12-16

    matter potentially realizable with...Our  work  studies  novel  phases  of   matter  potentially  realizable  with  ultracold  atomic  gases   confined  in... matter  with  optical  lattices.    Our  work  discovered  new  classes  of   many-­‐body  models  that  meet

  3. Ultracold Heteronuclear Molecules in a 3D Optical Lattice

    SciTech Connect

    Ospelkaus, C.; Ospelkaus, S.; Humbert, L.; Ernst, P.; Sengstock, K.; Bongs, K.

    2006-09-22

    We report on the creation of ultracold heteronuclear molecules assembled from fermionic {sup 40}K and bosonic {sup 87}Rb atoms in a 3D optical lattice. Molecules are produced at a heteronuclear Feshbach resonance on both the attractive and the repulsive sides of the resonance. We precisely determine the binding energy of the heteronuclear molecules from rf spectroscopy across the Feshbach resonance. We characterize the lifetime of the molecular sample as a function of magnetic field and measure lifetimes between 20 and 120 ms. The efficiency of molecule creation via rf association is measured and is found to decrease as expected for more deeply bound molecules.

  4. Defect-mediated discrete solitons in optically induced photorefractive lattices

    SciTech Connect

    Li Yongyao; Pang Wei; Chen Yongzhu; Yu Zhiqiang; Zhou Jianying; Zhang Huarong

    2009-10-15

    Theoretical analysis to the defect mediated discrete solitons in one- and two-dimensional periodical waveguide lattices is presented. The waveguide arrays with these functional defects are assumed to respond to the light field as an optically induced photorefraction and they are patterned by a holographic technique. It is found that the spatial energy distributions of the solitary waves can be controlled by the defects in the waveguide arrays, and this gives rise to an additional freedom to externally shaping the light field distribution to a special shape.

  5. Metastable superfluidity of repulsive fermionic atoms in optical lattices.

    PubMed

    Rosch, Achim; Rasch, David; Binz, Benedikt; Vojta, Matthias

    2008-12-31

    In the fermionic Hubbard model, doubly occupied states have an exponentially large lifetime for strong repulsive interactions U. We show that this property can be used to prepare a metastable s-wave superfluid state for fermionic atoms in optical lattices described by a large-U Hubbard model. When an initial band-insulating state is expanded, the doubly occupied sites Bose condense. A mapping to the ferromagnetic Heisenberg model in an external field allows for a reliable solution of the problem. Nearest-neighbor repulsion and pair hopping are important in stabilizing superfluidity.

  6. Self-guiding of matter waves in optical lattices

    SciTech Connect

    Alexander, Tristram J.

    2011-04-15

    It is shown numerically that Bose-Einstein condensates in optical lattices may be localized as self-induced waveguides and that these waveguides may take complex forms, including bends and X junctions. The waveguides are found to support continuous condensate flow, even around multiple right-angle bends. It is demonstrated that pulsed matter-wave transport may also occur along single-site waveguides in the form of solitons and that these solitons may propagate around bends and collide without change of shape or dependence on phase. A scheme based on single-site addressability techniques and the Kibble-Zurek mechanism is proposed for observing these effects.

  7. Fermions in Optical Lattices Swept across Feshbach Resonances

    SciTech Connect

    Diener, Roberto B.; Ho, T.-L.

    2006-01-13

    We point out that the recent experiments at ETH on fermions in optical lattices, where a band insulator evolves continuously into states occupying many bands as the system is swept adiabatically across Feshbach resonance, have implications on a wide range of fundamental issues in condensed matter. We derive the effective Hamiltonian of these systems, obtain expressions for their energies and band populations, and point out the increasing quantum entanglement of the ground state during the adiabatic sweep. Our results also explain why only specific regions in k space can be populated after the sweep as found at ETH.

  8. Wilson fermions and axion electrodynamics in optical lattices.

    PubMed

    Bermudez, A; Mazza, L; Rizzi, M; Goldman, N; Lewenstein, M; Martin-Delgado, M A

    2010-11-05

    We show that ultracold Fermi gases in optical superlattices can be used as quantum simulators of relativistic lattice fermions in 3+1 dimensions. By exploiting laser-assisted tunneling, we find an analogue of the so-called naive Dirac fermions, and thus provide a realization of the fermion doubling problem. Moreover, we show how to implement Wilson fermions, and discuss how their mass can be inverted by tuning the laser intensities. In this regime, our atomic gas corresponds to a phase of matter where Maxwell electrodynamics is replaced by axion electrodynamics: a 3D topological insulator.

  9. Unveiling square and triangular optical lattices: a comparative study.

    PubMed

    Silva, Juarez G; Jesus-Silva, Alcenísio J; Alencar, Márcio A R C; Hickmann, Jandir M; Fonseca, Eduardo J S

    2014-02-15

    We study square and triangular optical lattice formation using a diffraction technique with light-possessing orbital angular momentum (OAM). We demonstrate that it is possible to use Fraunhofer diffraction of light by a square aperture to unveil OAM about two times bigger than would be possible with a triangular aperture. We notice that the pattern remains truncated until a topological charge (TC) equal to 20 with good precision. Even though a square pattern cannot be used to determine the TC sign, it is possible to measure high order of the modulus and sign of the TC up to 20, combining patterns of the triangular and square apertures.

  10. Optical lattice clocks near the QPN limit: a tenfold improvement in optical clock stability

    NASA Astrophysics Data System (ADS)

    Nicholson, Travis

    2013-05-01

    Two classes of optical atomic clocks have surpassed microwave frequency standards: single-ion clocks and optical lattice clocks. Single-ion clocks hold the record for the lowest systematic uncertainty; however, many-atom lattice clocks have the potential to outperform single-ion clocks because the standard quantum limit to atomic clock instability (known as quantum projection noise or QPN) scales as 1 /√{Natoms}. For realistic atom numbers and coherence times, QPN-limited lattice clocks could average down to a given stability hundreds of times faster than the best ion clocks. Up to now lattice clocks with 1000 atoms have not shown improvement over the stability of single-ion clocks. Lattice clock stability has been limited by laser noise (via the optical Dick effect). To address this problem, we constructed a new clock laser with a thermal noise floor of 1 ×10-16 -an order of magnitude improvement over our previous clock laser. With this laser, we compare two lattice clocks, reaching instability of 1 ×10-17 in 2000 s for a single clock. This instability is within a factor of 2 of the theoretical QPN limit for 1000 atoms, representing the lowest reported instability for an independent clock. The high stability of many-particle clocks can come at the price of larger systematic uncertainty due to a frequency shift from atomic interactions. To minimize this shift, we use a cavity-enhanced lattice for our second clock. The high circulating power inside the cavity allows for a large trap volume, yielding a density at 2000 atoms that is 27 times smaller (than in our first clock) and permitting us to trap as many as 5 ×104 atoms. For 2000 atoms in our lattice, we measure a value for this shift (which is linear in density) of - 3 . 11 ×10-17 with an uncertainty of 8 . 2 ×10-19.

  11. Bose-Einstein condensation in a frustrated triangular optical lattice

    NASA Astrophysics Data System (ADS)

    Janzen, Peter; Huang, Wen-Min; Mathey, L.

    2016-12-01

    The recent experimental condensation of ultracold atoms in a triangular optical lattice with a negative effective tunneling parameter paves the way for the study of frustrated systems in a controlled environment. Here, we explore the critical behavior of the chiral phase transition in such a frustrated lattice in three dimensions. We represent the low-energy action of the lattice system as a two-component Bose gas corresponding to the two minima of the dispersion. The contact repulsion between the bosons separates into intra- and intercomponent interactions, referred to as V0 and V12, respectively. We first employ a Huang-Yang-Luttinger approximation of the free energy. For V12/V0=2 , which corresponds to the bare interaction, this approach suggests a first-order phase transition, at which both the U (1 ) symmetry of condensation and the Z2 symmetry of the emergent chiral order are broken simultaneously. Furthermore, we perform a renormalization-group calculation at one-loop order. We demonstrate that the coupling regime 0 1 we show that V0 flows to a negative value, while V12 increases and remains positive. This results in a breakdown of the effective quartic-field theory due to a cubic anisotropy and, again, suggests a discontinuous phase transition.

  12. Sparsity and level set regularization for diffuse optical tomography using a transport model in 2D

    NASA Astrophysics Data System (ADS)

    Prieto, Kernel; Dorn, Oliver

    2017-01-01

    In this paper we address an inverse problem for the time-dependent linear transport equation (or radiative transfer equation) in 2D having in mind applications in diffuse optical tomography (DOT). We propose two new reconstruction algorithms which so far have not been applied to such a situation and compare their performances in certain practically relevant situations. The first of these reconstruction algorithms uses a sparsity promoting regularization scheme, whereas the second one uses a simultaneous level set reconstruction scheme for two parameters of the linear transport equation. We will also compare the results of both schemes with a third scheme which is a more traditional L 2-based Landweber-Kaczmarz scheme. We focus our attention on the DOT application of imaging the human head of a neonate where the simpler diffusion approximation is not well-suited for the inversion due to the presence of a clear layer beneath the skull which is filled with ‘low-scattering’ cerebrospinal fluid. This layer, even if its location and characteristics are known a priori, poses significant difficulties for most reconstruction schemes due to its ‘wave-guiding’ property which reduces sensitivity of the data to the interior regions. A further complication arises due to the necessity to reconstruct simultaneously two different parameters of the linear transport equation, the scattering and the absorption cross-section, from the same data set. A significant ‘cross-talk’ between these two parameters is usually expected. Our numerical experiments indicate that each of the three considered reconstruction schemes do have their merits and perform differently but reasonably well when the clear layer is a priori known. We also demonstrate the behavior of the three algorithms in the particular situation where the clear layer is unknown during the reconstruction.

  13. Quantum state control and characterization in an optical lattice

    NASA Astrophysics Data System (ADS)

    Myrskog, Stefan Henrik

    In this dissertation I present experimental work on the measurement and manipulation of the center-of-mass motion of laser-cooled atoms. The first experiment described demonstrates cooling of an atom cloud by 'delta-kick cooling'. A thermal cloud of atoms in a vacuum expands ballistically, generating correlations between position and momentum. An appropriate momentum kick, proportional to position, results in slowing down all the atoms in the cloud. Through this technique a cloud of atoms can be cooled by greater than a factor of 10, preserving phase-space density, but decreasing the number density of atoms. By using laser-cooled atoms, it is also possible to confine atoms in potentials created by the AC-Stark shift of the atomic energy levels. Using interfering lasers to create the Stark shift, atoms are confined in a sinusoidal potential called an optical lattice. After preparing atoms in the lowest-energy band of the lattice, a spatial displacement can create coherent superpositions of many states of the potential. A combination of time delays and secondary displacements allows the measurement of the Q (Husimi) and W (Wigner) quasi-probability distributions, each of which completely characterizes the motional state of the atoms. Alternatively, a shallow lattice that only support two long-lived states can be used. The two-state system may be characterized with far fewer measurements, and furthermore, can be used as a model system for a qubit, a quantum representation of a single bit of information, useful for quantum computation. We demonstrate reconstruction of the density matrix in the 2-state system. The two-state system has be further used to characterize the physical action of an operation. By preparing a complete set of input density matrices we perform quantum process tomography for the intrinsic decoherence of the lattice, and two operations that correspond to single qubit rotations.

  14. Stability improvements for the NIST Yb optical lattice clock

    NASA Astrophysics Data System (ADS)

    Fasano, R. J.; Schioppo, M.; McGrew, W. F.; Brown, R. C.; Hinkley, N.; Yoon, T. H.; Beloy, K.; Oates, C. W.; Ludlow, A. D.

    2016-05-01

    To reach the fundamental limit given by quantum projection noise, optical lattice clocks require advanced laser stabilization techniques. The NIST ytterbium clock has benefited from several generations of extremely high finesse optical cavities, with cavity linewidths below 1 kHz. Characterization of the cavity drift rate has allowed compensation to the mHz/s level, improving the medium-term stability of the cavity. Based on recent measurements using Ramsey spectroscopy with synchronous interrogation, we report a fractional instability σy(1s) <=10-16 , dominated by atom number fluctuation noise. We also provide updates on our cryogenic sapphire cavity with a reduced thermal noise floor, which will improve our Dick-limited fractional instability at 1 s to below 10-16. Also at University of Colorado.

  15. Subwavelength optical lattices induced by position-dependent dark states

    SciTech Connect

    Sun Qingqing; Evers, Joerg; Kiffner, Martin; Zubairy, M. Suhail

    2011-05-15

    A method for the generation of subwavelength optical lattices based on multilevel dark states is proposed. The dark state is formed by a suitable combination of standing wave light fields, leading to position-dependent populations of the ground states. An additional field coupling dispersively to one of the ground states translates this position dependence into a subwavelength optical potential. We provide two semiclassical approaches to understand the involved physics, and demonstrate that they lead to identical results in a certain meaningful limit. Then we apply a Monte Carlo simulation technique to study the full quantum dynamics of the subwavelength trapping. Finally, we discuss the relevant time scales for the trapping, optimum conditions, and possible implementations.

  16. Accurate Optical Lattice Clock with {sup 87}Sr Atoms

    SciTech Connect

    Le Targat, Rodolphe; Baillard, Xavier; Fouche, Mathilde; Brusch, Anders; Tcherbakoff, Olivier; Rovera, Giovanni D.; Lemonde, Pierre

    2006-09-29

    We report a frequency measurement of the {sup 1}S{sub 0}-{sup 3}P{sub 0} transition of {sup 87}Sr atoms in an optical lattice clock. The frequency is determined to be 429 228 004 229 879(5) Hz with a fractional uncertainty that is comparable to state-of-the-art optical clocks with neutral atoms in free fall. The two previous measurements of this transition were found to disagree by about 2x10{sup -13}, i.e., almost 4 times the combined error bar and 4 to 5 orders of magnitude larger than the claimed ultimate accuracy of this new type of clocks. Our measurement is in agreement with one of these two values and essentially resolves this discrepancy.

  17. Simulation of non-resonant gas-optical lattice interaction

    NASA Astrophysics Data System (ADS)

    Kungurtsev, P. V.; Shevyrin, A. A.; Bondar, Ye. A.; Kashkovsky, A. V.; Gimelshein, S. F.; Shneider, M. N.

    2016-10-01

    Self-consistent interaction of a non-resonant optical lattice with a gas of polarizable particles is considered. We investigate periodic modulations of gas density in the field of high-intensity laser radiation from two opposing sources and potential's evolution due to intense Bragg reflection. The self-consistent model of laser field and gas interaction is developed and implemented into the SMILE++ software system based on the Direct Simulation Monte Carlo method. We observed noticeable variation of the force acting on the particles in the interaction region, especially in its central part. Taking into account the arising spatial inhomogeneity of the optical potential we demonstrated noticeable effects on the evolution of the self-consistent system if the interaction region has a macroscopic size.

  18. Observation of optical solitons in PT-symmetric lattices

    PubMed Central

    Wimmer, Martin; Regensburger, Alois; Miri, Mohammad-Ali; Bersch, Christoph; Christodoulides, Demetrios N.; Peschel, Ulf

    2015-01-01

    Controlling light transport in nonlinear active environments is a topic of considerable interest in the field of optics. In such complex arrangements, of particular importance is to devise strategies to subdue chaotic behaviour even in the presence of gain/loss and nonlinearity, which often assume adversarial roles. Quite recently, notions of parity-time (PT) symmetry have been suggested in photonic settings as a means to enforce stable energy flow in platforms that simultaneously employ both amplification and attenuation. Here we report the experimental observation of optical solitons in PT-symmetric lattices. Unlike other non-conservative nonlinear arrangements where self-trapped states appear as fixed points in the parameter space of the governing equations, discrete PT solitons form a continuous parametric family of solutions. The possibility of synthesizing PT-symmetric saturable absorbers, where a nonlinear wave finds a lossless path through an otherwise absorptive system is also demonstrated. PMID:26215165

  19. Proposal for generating synthetic magnetic fields in hexagonal optical lattices

    NASA Astrophysics Data System (ADS)

    Tian, Binbin; Endres, Manuel; Pekker, David

    2015-05-01

    We propose a new approach to generating synthetic magnetic fields in ultra cold atom systems that does not rely on either Raman transitions nor periodic drive. Instead, we consider a hexagonal optical lattice produced by the intersection of three laser beams at 120 degree angles, where the intensity of one or more of the beams is spatially non-uniform. The resulting optical lattice remains hexagonal, but has spatially varying hopping matrix elements. For atoms near the Dirac points, these spatial variations appear as a gauge field, similar to the fictitious gauge field that is induced for for electrons in strained graphene. We suggest that a robust way to generate a gauge field that corresponds to a uniform flux is to aligning three gaussian beams to intersect in an equilateral triangle. Using realistic experimental parameters, we show how the proposed setup can be used to observe cyclotron motion of an atom cloud - the conventional Hall effect and distinct Landau levels - the integer quantum Hall effect.

  20. Exact matter-wave vortices in a driven optical lattice

    NASA Astrophysics Data System (ADS)

    Deng, Yan; Hai, Wenhua; Zhou, Zheng

    2013-07-01

    We investigate vortex dynamics of a periodically driven Bose-Einstein condensate confined in a spatially two-dimensional optical lattice. An exact Floquet solution of the Gross-Pitaevskii equation is obtained for a certain parameter region which can be divided into the phase-jumping and phase-continuing regions. In the former region, the exact solution can describe spatiotemporal evolution of multiple vortices. For a small ratio of driving strength to optical lattice depth the vortices keep nearly unmoved. With the increase of the ratio, the vortices undergo an effective interaction and periodically evolve along some fixed circular orbits that leads the vortex dipoles and quadrupoles to produce and break alternatively. There is a critical ratio in the phase-jumping region beyond which the vortices generate and melt periodically. In the phase-continuing region, the condensate in the exact Floquet state evolves periodically without zero-density nodes. It is numerically demonstrated that the exact solution is stable under an initial perturbation for both parameter regions, except for a subregion of the phase-jumping region in which stability of the condensate is lost. However, the solution is structurally stable under a small parameter perturbation only for the phase-continuing region, while for the whole phase-jumping region the structural stability is destroyed. The results suggest a scheme for creating and controlling matter-wave vortices.

  1. Probing many-body interactions in an optical lattice clock

    NASA Astrophysics Data System (ADS)

    Rey, A. M.; Gorshkov, A. V.; Kraus, C. V.; Martin, M. J.; Bishof, M.; Swallows, M. D.; Zhang, X.; Benko, C.; Ye, J.; Lemke, N. D.; Ludlow, A. D.

    2014-01-01

    We present a unifying theoretical framework that describes recently observed many-body effects during the interrogation of an optical lattice clock operated with thousands of fermionic alkaline earth atoms. The framework is based on a many-body master equation that accounts for the interplay between elastic and inelastic p-wave and s-wave interactions, finite temperature effects and excitation inhomogeneity during the quantum dynamics of the interrogated atoms. Solutions of the master equation in different parameter regimes are presented and compared. It is shown that a general solution can be obtained by using the so called Truncated Wigner Approximation which is applied in our case in the context of an open quantum system. We use the developed framework to model the density shift and decay of the fringes observed during Ramsey spectroscopy in the JILA 87Sr and NIST 171Yb optical lattice clocks. The developed framework opens a suitable path for dealing with a variety of strongly-correlated and driven open-quantum spin systems.

  2. Topological superfluid state of fermions on a p-band optical square lattice

    NASA Astrophysics Data System (ADS)

    Wu, Ya-Jie; He, Jing; Zang, Chun-Li; Kou, Su-Peng

    2012-08-01

    In this paper we study an interacting mixture of ultracold spinless fermions on the s band and bosons on the p band in a 2D square optical lattice, of which the effective model is reduced to a p-band fermionic system with nearest-neighbor attractive interaction. From this effective p-band model, we find a translation symmetry protected Z2 topological superfluid that is characterized by a special fermion parity pattern at high-symmetry points in momentum space k=(0,0), (0,π), (π,0), (π,π). Such Z2 topological superfluid supports the robust Majorana edge modes and a new type of low-energy excitation—(supersymmetric) Z2 link excitation.

  3. Gravitational wave detection with optical lattice atomic clocks

    NASA Astrophysics Data System (ADS)

    Kolkowitz, S.; Pikovski, I.; Langellier, N.; Lukin, M. D.; Walsworth, R. L.; Ye, J.

    2016-12-01

    We propose a space-based gravitational wave (GW) detector consisting of two spatially separated, drag-free satellites sharing ultrastable optical laser light over a single baseline. Each satellite contains an optical lattice atomic clock, which serves as a sensitive, narrowband detector of the local frequency of the shared laser light. A synchronized two-clock comparison between the satellites will be sensitive to the effective Doppler shifts induced by incident GWs at a level competitive with other proposed space-based GW detectors, while providing complementary features. The detected signal is a differential frequency shift of the shared laser light due to the relative velocity of the satellites, and the detection window can be tuned through the control sequence applied to the atoms' internal states. This scheme enables the detection of GWs from continuous, spectrally narrow sources, such as compact binary inspirals, with frequencies ranging from ˜3 mHz - 10 Hz without loss of sensitivity, thereby bridging the detection gap between space-based and terrestrial optical interferometric GW detectors. Our proposed GW detector employs just two satellites, is compatible with integration with an optical interferometric detector, and requires only realistic improvements to existing ground-based clock and laser technologies.

  4. Beam evolutions of solitons in strongly nonlocal media with fading optical lattices

    NASA Astrophysics Data System (ADS)

    Dai, Zhi-Ping; Lu, Shi-Zhuan; You, Kai-Ming

    2013-01-01

    We address the impact of imprinted fading optical lattices on the beam evolution of solitons in strongly nonlocal nonlinear media. The results show that the width of the soliton experiences a change with the increasing propagation distance, the critical power for the soliton varies with the lattice fading away, and the soliton breathing is affected by the initial lattice depth and the nonlocality degree.

  5. Nearest-neighbor detection of atoms in a 1D optical lattice by fluorescence imaging.

    PubMed

    Karski, M; Förster, L; Choi, J M; Alt, W; Widera, A; Meschede, D

    2009-02-06

    We overcome the diffraction limit in fluorescence imaging of neutral atoms in a sparsely filled one-dimensional optical lattice. At a periodicity of 433 nm, we reliably infer the separation of two atoms down to nearest neighbors. We observe light induced losses of atoms occupying the same lattice site, while for atoms in adjacent lattice sites, no losses due to light induced interactions occur. Our method points towards characterization of correlated quantum states in optical lattice systems with filling factors of up to one atom per lattice site.

  6. Ultraviolet laser spectroscopy of neutral mercury in a one-dimensional optical lattice

    SciTech Connect

    Mejri, S.; McFerran, J. J.; Yi, L.; Le Coq, Y.; Bize, S.

    2011-09-15

    We present details on the ultraviolet lattice spectroscopy of the (6s{sup 2}) {sup 1}S{sub 0}{r_reversible} (6s6p) {sup 3}P{sub 0} transition in neutral mercury, specifically {sup 199}Hg. Mercury atoms are loaded into a one-dimensional vertically aligned optical lattice from a magneto-optical trap with an rms temperature of {approx}60 {mu}K. We describe aspects of the magneto-optical trapping, the lattice cavity design, and the techniques employed to trap and detect mercury in an optical lattice. The clock-line frequency dependence on lattice depth is measured at a range of lattice wavelengths. We confirm the magic wavelength to be 362.51(0.16) nm. Further observations to those reported by Yi et al.[Phys. Rev. Lett. 106, 073005 (2011)] are presented regarding the laser excitation of a Wannier-Stark ladder of states.

  7. State diagrams for harmonically trapped bosons in optical lattices

    SciTech Connect

    Rigol, Marcos; Batrouni, George G.; Rousseau, Valery G.; Scalettar, Richard T.

    2009-05-15

    We use quantum Monte Carlo simulations to obtain zero-temperature state diagrams for strongly correlated lattice bosons in one and two dimensions under the influence of a harmonic confining potential. Since harmonic traps generate a coexistence of superfluid and Mott insulating domains, we use local quantities such as the quantum fluctuations of the density and a local compressibility to identify the phases present in the inhomogeneous density profiles. We emphasize the use of the 'characteristic density' to produce a state diagram that is relevant to experimental optical lattice systems, regardless of the number of bosons or trap curvature and of the validity of the local-density approximation. We show that the critical value of U/t at which Mott insulating domains appear in the trap depends on the filling in the system, and it is in general greater than the value in the homogeneous system. Recent experimental results by Spielman et al. [Phys. Rev. Lett. 100, 120402 (2008)] are analyzed in the context of our two-dimensional state diagram, and shown to exhibit a value for the critical point in good agreement with simulations. We also study the effects of finite, but low (T{<=}t/2), temperatures. We find that in two dimensions they have little influence on our zero-temperature results, while their effect is more pronounced in one dimension.

  8. Measuring Z2 topological invariants in optical lattices using interferometry

    NASA Astrophysics Data System (ADS)

    Grusdt, F.; Abanin, D.; Demler, E.

    2014-04-01

    We propose an interferometric method to measure Z2 topological invariants of time-reversal invariant topological insulators realized with optical lattices in two and three dimensions. We suggest two schemes which both rely on a combination of Bloch oscillations with Ramsey interferometry and can be implemented using standard tools of atomic physics. In contrast to topological Zak phase and Chern number, defined for individual one-dimensional and two-dimensional Bloch bands, the formulation of the Z2 invariant involves at least two Bloch bands related by time-reversal symmetry which one must keep track of in measurements. In one of our schemes this can be achieved by the measurement of Wilson loops, which are non-Abelian generalizations of Zak phases. The winding of their eigenvalues is related to the Z2 invariant. We thereby demonstrate that Wilson loops are not just theoretical concepts but can be measured experimentally. For the second scheme we introduce a generalization of time-reversal polarization which is continuous throughout the Brillouin zone. We show that its winding over half the Brillouin zone yields the Z2 invariant. To measure this winding, our protocol only requires Bloch oscillations within a single band, supplemented by coherent transitions to a second band which can be realized by lattice shaking.

  9. Experimental realization of an optical second with strontium lattice clocks.

    PubMed

    Le Targat, R; Lorini, L; Le Coq, Y; Zawada, M; Guéna, J; Abgrall, M; Gurov, M; Rosenbusch, P; Rovera, D G; Nagórny, B; Gartman, R; Westergaard, P G; Tobar, M E; Lours, M; Santarelli, G; Clairon, A; Bize, S; Laurent, P; Lemonde, P; Lodewyck, J

    2013-01-01

    Progress in realizing the SI second had multiple technological impacts and enabled further constraint of theoretical models in fundamental physics. Caesium microwave fountains, realizing best the second according to its current definition with a relative uncertainty of 2-4 × 10(-16), have already been overtaken by atomic clocks referenced to an optical transition, which are both more stable and more accurate. Here we present an important step in the direction of a possible new definition of the second. Our system of five clocks connects with an unprecedented consistency the optical and the microwave worlds. For the first time, two state-of-the-art strontium optical lattice clocks are proven to agree within their accuracy budget, with a total uncertainty of 1.5 × 10(-16). Their comparison with three independent caesium fountains shows a degree of accuracy now only limited by the best realizations of the microwave-defined second, at the level of 3.1 × 10(-16).

  10. Frequency comparison of optical lattice clocks beyond the Dick limit

    NASA Astrophysics Data System (ADS)

    Takamoto, Masao; Takano, Tetsushi; Katori, Hidetoshi

    2011-05-01

    The supreme accuracy of atomic clocks relies on the universality of atomic transition frequencies. The stability of a clock, meanwhile, measures how quickly the clock's statistical uncertainties are reduced. The ultimate measure of stability is provided by the quantum projection noise, which improves as 1/√N by measuring N uncorrelated atoms. Quantum projection noise limited stabilities have been demonstrated in caesium clocks and in single-ion optical clocks, where the quantum noise overwhelms the Dick effect attributed to local oscillator noise. Here, we demonstrate a synchronous frequency comparison of two optical lattice clocks using 87Sr and 88Sr atoms, respectively, for which the Allan standard deviation reached 1 × 10-17 in an averaging time of 1,600 s by cancelling out the Dick effect to approach the quantum projection noise limit. The scheme demonstrates the advantage of using a large number (N ~ 1,000) of atoms in optical clocks and paves the way to investigating the inherent uncertainties of clocks and relativistic geodesy on a timescale of tens of minutes.

  11. Dynamics of pattern-loaded fermions in bichromatic optical lattices

    NASA Astrophysics Data System (ADS)

    Reichl, Matthew D.; Mueller, Erich J.

    2016-03-01

    Motivated by experiments in Munich [M. Schreiber et al., Science 349, 842 (2015)., 10.1126/science.aaa7432], we study the dynamics of interacting fermions initially prepared in charge density wave states in one-dimensional bichromatic optical lattices. The experiment sees a marked lack of thermalization, which has been taken as evidence for an interacting generalization of Anderson localization, dubbed "many-body localization." We model the experiments using an interacting Aubry-Andre model and develop a computationally efficient low-density cluster expansion to calculate the even-odd density imbalance as a function of interaction strength and potential strength. Our calculations agree with the experimental results and shed light on the phenomena. We also explore a two-dimensional generalization. The cluster expansion method we develop should have broad applicability to similar problems in nonequilibrium quantum physics.

  12. General Hubbard Model for Fermions in an Optical Lattice

    NASA Astrophysics Data System (ADS)

    Kestner, Jason; Duan, Luming

    2009-03-01

    For two-component fermions in an optical lattice, an effective general Hubbard model (GHM) with tunable on-site attraction/repulsion and occupation-dependent hopping rates emerges from very general arguments [1]. This model is quite interesting, containing as special cases both the t-J and the XXZ models. However, the experimental range of applicability and the connection between the model parameters and the actual experimental parameters must be determined explicitly. To this end, we have used a stochastic variational approach with a correlated gaussian wavefunction to numerically find the eigenstates of two atoms interacting in a 3D few-well trap. By matching the few-site spectrum of the GHM to the variational spectrum obtained, the validity of the model and the relationship between experimental and model parameters are determined. [1] L.-M. Duan, Euro. Phys. Lett. 81, 20001 (2008).

  13. Localization of collisionally inhomogeneous condensates in a bichromatic optical lattice

    SciTech Connect

    Cheng Yongshan; Adhikari, S. K.

    2011-02-15

    By direct numerical simulation and variational solution of the Gross-Pitaevskii equation, we studied the stationary and dynamic characteristics of a cigar-shaped, localized, collisionally inhomogeneous Bose-Einstein condensate trapped in a one-dimensional bichromatic quasiperiodic optical-lattice potential, as used in a recent experiment on the localization of a Bose-Einstein condensate [Roati et al., Nature (London) 453, 895 (2008)]. The effective potential characterizing the spatially modulated nonlinearity is obtained. It is found that the collisional inhomogeneity has influence not only on the central region but also on the tail of the Bose-Einstein condensate. The influence depends on the sign and value of the spatially modulated nonlinearity coefficient. We also demonstrate the stability of the stationary localized state by performing a standard linear stability analysis. Where possible, the numerical results are shown to be in good agreement with the variational results.

  14. Simulating the Wess-Zumino Supersymmetry Model in Optical Lattices

    SciTech Connect

    Yu Yue; Yang Kun

    2010-10-08

    We study a cold atom-molecule mixture in two-dimensional optical lattices. We show that, by fine-tuning the atomic and molecular interactions, the Wess-Zumino supersymmetry (SUSY) model in 2+1 dimensions emerges in the low-energy limit and can be simulated in such mixtures. At zero temperature, SUSY is not spontaneously broken, which implies identical relativistic dispersions of the atom and its superpartner, a bosonic diatom molecule. This defining signature of SUSY can be probed by single-particle spectroscopies. Thermal breaking of SUSY at a finite temperature is accompanied by a thermal Goldstone fermion, i.e., phonino excitation. This and other signatures of broken SUSY can also be probed experimentally.

  15. Non-standard Hubbard models in optical lattices: a review.

    PubMed

    Dutta, Omjyoti; Gajda, Mariusz; Hauke, Philipp; Lewenstein, Maciej; Lühmann, Dirk-Sören; Malomed, Boris A; Sowiński, Tomasz; Zakrzewski, Jakub

    2015-06-01

    Originally, the Hubbard model was derived for describing the behavior of strongly correlated electrons in solids. However, for over a decade now, variations of it have also routinely been implemented with ultracold atoms in optical lattices, allowing their study in a clean, essentially defect-free environment. Here, we review some of the vast literature on this subject, with a focus on more recent non-standard forms of the Hubbard model. After giving an introduction to standard (fermionic and bosonic) Hubbard models, we discuss briefly common models for mixtures, as well as the so-called extended Bose-Hubbard models, that include interactions between neighboring sites, next-neighbor sites, and so on. The main part of the review discusses the importance of additional terms appearing when refining the tight-binding approximation for the original physical Hamiltonian. Even when restricting the models to the lowest Bloch band is justified, the standard approach neglects the density-induced tunneling (which has the same origin as the usual on-site interaction). The importance of these contributions is discussed for both contact and dipolar interactions. For sufficiently strong interactions, the effects related to higher Bloch bands also become important even for deep optical lattices. Different approaches that aim at incorporating these effects, mainly via dressing the basis, Wannier functions with interactions, leading to effective, density-dependent Hubbard-type models, are reviewed. We discuss also examples of Hubbard-like models that explicitly involve higher p orbitals, as well as models that dynamically couple spin and orbital degrees of freedom. Finally, we review mean-field nonlinear Schrödinger models of the Salerno type that share with the non-standard Hubbard models nonlinear coupling between the adjacent sites. In that part, discrete solitons are the main subject of consideration. We conclude by listing some open problems, to be addressed in the future.

  16. Orbit, optics and chromaticity correction for PS2 negative momentum compaction lattices

    SciTech Connect

    Papaphilippou,Y.; Barranco, J.; Bartmann, W.; Benedikt, M.; Carli, C.; de Maria, R.; Peggs, S.; Trbojevic, D.

    2009-05-04

    The effect of magnet misalignments in the beam orbit and linear optics functions are reviewed and correction schemes are applied to the negative momentum compaction lattice of PS2. Chromaticity correction schemes are also proposed and tested with respect to off-momentum optics properties. The impact of the correction schemes in the dynamic aperture of the lattice is finally evaluated.

  17. Optical method of measuring angular displacement using a 2-D charge coupled device.

    PubMed

    Sato, K; Yamamoto, S; Ami, M; Fukushima, K

    1990-08-10

    We investigated a quick noncontact method of measuring angular displacement with a simple system comprising a 2-D CCD and a personal computer. According to this method the angular displacement can be measured even when the rotational axis is not known, and even when the system moves parallel to the plane.

  18. Compact optical true time delay beamformer for a 2D phased array antenna using tunable dispersive elements.

    PubMed

    Ye, Xingwei; Zhang, Fangzheng; Pan, Shilong

    2016-09-01

    A hardware-compressive optical true time delay architecture for 2D beam steering in a planar phased array antenna is proposed using fiber-Bragg-grating-based tunable dispersive elements (TDEs). For an M×N array, the proposed system utilizes N TDEs and M wavelength-fixed optical carriers to control the time delays. Both azimuth and elevation beam steering are realized by programming the settings of the TDEs. An experiment is carried out to demonstrate the delay controlling in a 2×2 array, which is fed by a wideband pulsed signal. Radiation patterns calculated from the experimentally measured waveforms at the four antennas match well with the theoretical results.

  19. The strontium optical lattice clock: Optical spectroscopy with sub-hertz accuracy

    NASA Astrophysics Data System (ADS)

    Ludlow, Andrew D.

    One of the most well-developed applications of coherent interaction with atoms is atomic frequency standards and clocks. Atomic clocks find significant roles in a number of scientific and technological settings. State-of-the-art, laser-cooled, Cs-fountain microwave clocks have demonstrated impressive frequency measurement accuracy, with fractional uncertainties below the 10-15 level. On the other hand, frequency standards based on optical transitions have made substantial steps forward over the last decade, benefiting from their high operational frequencies. An interesting approach to such an optical standard uses atomic strontium confined in an optical lattice. The tight atomic confinement allows for nearly complete elimination of Doppler and recoil-related effects which can otherwise trouble the precise atomic interrogation. At the same time, the optical lattice is designed to equally perturb the two electronic clock states so that the confinement introduces a net zero shift of the natural transition frequency. This thesis describes the design and realization of an optical frequency standard using 87Sr confined in a 1-D optical lattice. Techniques for atomic manipulation and control are described, including two-stage laser cooling, proper design of atomic confinement in a lattice potential, and optical pumping techniques. With the development of an ultra-stable coherent laser light source, atomic spectral linewidths of the optical clock transition are observed below 2 Hz. High accuracy spectroscopy of the clock transition is carried out utilizing a femtosecond frequency comb referenced to the NIST-F1 Cs fountain. To explore the performance of an improved, spin-polarized Sr standard, a coherent optical phase transfer link is established between JILA and NIST. This enables remote comparison of the Sr standard against optical standards at NIST, such as the cold Ca standard. The high frequency stability of a Sr-Ca comparison (3 x 10-16 at 200 s) is used to make

  20. Auto- and hetero-associative memory using a 2-D optical logic gate

    NASA Technical Reports Server (NTRS)

    Chao, Tien-Hsin

    1989-01-01

    An optical associative memory system suitable for both auto- and hetero-associative recall is demonstrated. This system utilizes Hamming distance as the similarity measure between a binary input and a memory image with the aid of a two-dimensional optical EXCLUSIVE OR (XOR) gate and a parallel electronics comparator module. Based on the Hamming distance measurement, this optical associative memory performs a nearest neighbor search and the result is displayed in the output plane in real-time. This optical associative memory is fast and noniterative and produces no output spurious states as compared with that of the Hopfield neural network model.

  1. Dynamic photorefractive self-amplified angular-multiplex 2-D optical beam-array generation

    NASA Astrophysics Data System (ADS)

    Zhou, Shaomin; Yeh, Pochi; Liu, Hua-Kuang

    1993-01-01

    A real-time 2-D angular-multiplex beam-array holographic storage and reconstruction technique using electrically-addressed spatial light modulators(E-SLM's) and photorefractive crystals is described. Using a liquid crystal television (LCTV) spatial light modulator (SLM) for beam steering and lithium niobate photorefractive crystal for holographic recording, experimental results of generating large and complicated arrays of laser beams with high diffraction efficiency and good uniformity are presented.

  2. Development of a strontium optical lattice clock for space applications

    NASA Astrophysics Data System (ADS)

    Singh, Yeshpal

    2016-07-01

    With timekeeping being of paramount importance for modern life, much research and major scientific advances have been undertaken in the field of frequency metrology, particularly over the last few years. New Nobel-prize winning technologies have enabled a new era of atomic clocks; namely the optical clock. These have been shown to perform significantly better than the best microwave clocks reaching an inaccuracy of 1.6x10-18 [1]. With such results being found in large lab based apparatus, the focus now has shifted to portability - to enable the accuracy of various ground based clocks to be measured, and compact autonomous performance - to enable such technologies to be tested in space. This could lead to a master clock in space, improving not only the accuracy of technologies on which modern life has come to require such as GPS and communication networks. But also more fundamentally, this could lead to the redefinition of the second and tests of fundamental physics including applications in the fields of ground based and satellite geodesy, metrology, positioning, navigation, transport and logistics etc. Within the European collaboration, Space Optical Clocks (SOC2) [2-3] consisting of various institutes and industry partners across Europe we have tried to tackle this problem of miniaturisation whilst maintaining stability, accuracy (5x10-17) and robustness whilst keeping power consumption to a minimum - necessary for space applications. We will present the most recent results of the Sr optical clock in SOC2 and also the novel compact design features, new methods employed and outlook. References [1] B. J. Bloom, T. L. Nicholson, J. R. Williams, S. L. Campbell, M. Bishof, X. Zhang, W. Zhang, S. L. Bromley, and J. Ye, "An optical lattice clock with accuracy and stability at the 10-18 level," Nature 506, 71-75 (2014). [2] S. Schiller et al. "Towards Neutral-atom Space Optical Clocks (SOC2): Development of high-performance transportable and breadboard optical clocks and

  3. 2-1/2-D electromagnetic modeling of nodular defects in high-power multilayer optical coatings

    SciTech Connect

    Molau, N.E.; Brand, H.R.; Kozlowski, M.R.; Shang, C.C.

    1996-07-01

    Advances in the design and production of high damage threshold optical coatings for use in mirrors and polarizers have been driven by the design requirements of high-power laser systems such as the proposed 1.8-MJ National Ignition Facility (NIF) and the prototype 12- kJ Beamlet laser system. The present design of the NIF will include 192 polarizers and more than 1100 mirrors. Currently, the material system of choice for high-power multilayer optical coatings with high damage threshold applications near 1.06 {mu}m are e-beam deposited HfO{sub 2}/Si0{sub 2} coatings. However, the optical performance and laser damage thresholds of these coatings are limited by micron-scale defects and insufficient control over layer thickness. In this report, we will discuss the results of our 2-1/2-D finite-element time- domain (FDTD) EM modeling effort for rotationally-symmetric nodular defects in multilayer dielectric HR coatings. We have added a new diagnostic to the 2-1/2-D FDTD EM code, AMOS, that enables us to calculate the peak steady-state electric fields throughout a 2-D planar region containing a 2-D r-z cross-section of the axisymmetric nodular defect and surrounding multilayer dielectric stack. We have also generated a series of design curves to identify the range of loss tangents for Si0{sub 2} and HfO{sub 2} consistent with the experimentally determined power loss of the HR coatings. In addition, we have developed several methods to provide coupling between the EM results and the thermal-mechanical simulation effort.

  4. Stationary and traveling solitons via local dissipation in Bose-Einstein condensates in ring optical lattices

    NASA Astrophysics Data System (ADS)

    Campbell, Russell; Oppo, Gian-Luca

    2016-10-01

    A model of a Bose-Einstein condensate in a ring optical lattice with atomic dissipations applied at a stationary or at a moving location on the ring is presented. The localized dissipation is shown to generate and stabilize both stationary and traveling lattice solitons. Among many localized solutions, we have generated spatially stationary quasiperiodic lattice solitons and a family of traveling lattice solitons with two intensity peaks per potential well with no counterpart in the discrete case. Collisions between traveling and stationary lattice solitons as well as between two traveling lattice solitons display a critical dependence from the lattice depth. Stable counterpropagating solitons in ring lattices can find applications in gyroscope interferometers with ultracold gases.

  5. Low noise optical lattices for a Li-6 Fermi gas microscope

    NASA Astrophysics Data System (ADS)

    Mazurenko, Anton; Parsons, Maxwell; Chiu, Christie; Huber, Florian; Blatt, Sebastian; Greiner, Markus

    2015-05-01

    We report on recent progress towards single-site resolved imaging of fermions in an optical lattice. Fermionic 6-Li atoms are trapped in an optical lattice 10 μm below a high-quality reference surface in the image plane of a high resolution (NA 0.85) imaging system. We have created a highly intensity-stable optical lattice whose depth remains adjustable over three orders of magnitude. The high optical resolution enables a band mapping technique that allows detection of less than 1000 atoms in the ground band of the lattice. We use this technique to measure the decay of the radial ground band population and find lifetimes up to 70 seconds, limited by spontaneous scattering of lattice light. ARO DARPA OLE, ARO MURI, NSF, AFOSR MURI, and The Moore Foundation.

  6. Structural, electronic transport and optical properties of functionalized quasi-2D TiC2 from first-principles calculations

    NASA Astrophysics Data System (ADS)

    Berdiyorov, G. R.; Madjet, M. E.

    2016-12-01

    Using the first-principles density functional theory, we study the effect of surface functionalization on the structural and optoelectronic properties of recently proposed quasi-two-dimensional material TiC2 [T. Zhao, S. Zhang, Y. Guo, Q. Wang, Nanoscale 8 (2016) 233]. Hydrogenated, fluorinated, oxidized and hydroxylated surfaces are considered. Significant changes in the lattice parameters and partial charge distributions are found due to the surface termination. Direct contribution of the adatoms to the system density of states near the Fermi level is obtained, which has a major impact on the optoelectronic properties of the material. For example, surface termination results in larger absorption in the visible range of the spectrum. The electronic transport is also affected by the surface functionalization: the current in the system can be reduced by an order of magnitude. These findings indicate the importance of the effects of surface passivation on optoelectronic properties of this quasi-2D material.

  7. Optical properties of GaAs 2D hexagonal and cubic photonic crystal

    SciTech Connect

    Arab, F. Assali, A.; Grain, R.; Kanouni, F.

    2015-03-30

    In this paper we present our theoretical study of 2D hexagonal and cubic rods GaAs in air, with plan wave expansion (PWE) and finite difference time domain (FDTD) by using BandSOLVE and FullWAVE of Rsoft photonic CAD package. In order to investigate the effect of symmetry and radius, we performed calculations of the band structures for both TM and TE polarization, contour and electromagnetic propagation and transmission spectra. Our calculations show that the hexagonal structure gives a largest band gaps compare to cubic one for a same filling factor.

  8. Design and implementation of a 2-D endoscopic optical fiber scanner

    NASA Astrophysics Data System (ADS)

    Liu, Zhihai; Fu, Ling; Gao, Fei; Zhang, Xiongbo

    2008-12-01

    We have designed a small type of endoscopic 2D fiber scanner probe to incorporate OCT with endoscopy imaging. The new probe consists with two piezoelectric ceramics plated with electrode, a conductive thin-film with non-inverse piezoelectric effect and a piece of nude fiber with coating layers removed. To accomplish the scanning, the only thing need to be done is to drive the two piezoelectric ceramic sheets which provides simpler structure and at the same time minimizes the probe effectively. Here we have obtained some preliminary results and verified the feasibility of the program.

  9. Terahertz all-optical NOR and AND logic gates based on 2D photonic crystals

    NASA Astrophysics Data System (ADS)

    Parandin, Fariborz; Karkhanehchi, Mohammad Mehdi

    2017-01-01

    Usually, photonic crystals are used in designing optical logic gates. This study focuses on the design and simulation of an all optical NOR and AND logic gates based on two dimensional photonic crystals. The simplicity of the proposed structure is a characteristic feature of this designation. Finite Difference Time Domain (FDTD) as well as Plane Wave Expansion (PWE) methods have been used for this structural analysis. The simulation results revealed an increase in the interval between "zero" and "one" logic levels. Also, the simple structure and its small size demonstrate the usefulness of this structure in optical integrated circuits. The proposed optical gates can operate with a bit rate of about 1.54 Tbit/s.

  10. 2D optical manipulation and assembly of shape-complementary planar microstructures.

    PubMed

    Rodrigo, Peter John; Kelemen, Lóránd; Alonzo, Carlo Amadeo; Perch-Nielsen, Ivan R; Dam, Jeppe Seidelin; Ormos, Pál; Glückstad, Jesper

    2007-07-09

    Optical trapping and manipulation offer great flexibility as a non-contact microassembly tool. Its application to the assembly of microscale building blocks may open new doors for micromachine technology. In this work, we demonstrate all-optical assembly of microscopic puzzle pieces in a fluidic environment using programmable arrays of trapping beams. Identical shape-complimentary pieces are optically fabricated with submicron resolution using two-photon polymerization (2PP) technique. These are efficiently assembled into space-filling tessellations by a multiple-beam optical micromanipulation system. The flexibility of the system allows us to demonstrate both user-interactive and computer-automated modes of serial and parallel assembly of microscale objects with high spatial and angular positioning precision.

  11. Characterization of the bistable wideband optical filter on the basis of nonlinear 2D photonic crystal

    SciTech Connect

    Guryev, I. V. Sukhoivanov, I. A. Andrade Lucio, J. A. Manzano, O. Ibarra Rodriguez, E. Vargaz Gonzales, D. Claudio Chavez, R. I. Mata Gurieva, N. S.

    2014-05-15

    In our work, we investigated the wideband optical filter on the basis of nonlinear photonic crystal. The all-optical flip-flop using ultra-short pulses with duration lower than 200 fs is obtained in such filters. Here we pay special attention to the stability problem of the nonlinear element. To investigate this problem, the temporal response demonstrating the flip-flop have been computed within the certain range of the wavelengths as well as at different input power.

  12. Optical nanostructures in 2D for wide-diameter and broadband beam collimation.

    PubMed

    Clark, James; Anguita, José V; Chen, Ying; Silva, S Ravi P

    2016-01-06

    Eliminating curved refracting lensing components used in conventional projection, imaging and sensing optical assemblies, is critical to enable compactness and miniaturisation of optical devices. A suitable means is replacing refracting lenses with two-dimensional optical media in flat-slab form, to achieve an equivalent optical result. One approach, which has been the focus of intense research, uses a Veselago lens which features a negative-index metamaterial. However, practical implementations rely on resonance techniques, thus broadband operation at optical frequencies imposes significant technical challenges that have been difficult to overcome. Here, we demonstrate a highly-collimated, broadband, wide-diameter beam from a compact source in flat-slab form, based on light collimation using nanomaterials ordered in patterns and embedded into flexible polymers. These provide a highly anisotropic absorption coefficient due to patterns created by vertical carbon nanotube structures grown on glass, and the anisotropic electrical conductivity of the nanotubes. We show this nanostructure strongly absorbs unwanted off-axis light rays, whilst transmitting the desired on-axis rays, to achieve the required optical effect over broadband, from visible to short-infrared, thus circumventing some technical limitations of negative-index metamaterials. We further show a low substrate-temperature system for nanotube growth, allowing direct implementation into heat-sensitive large-area devices.

  13. Optical nanostructures in 2D for wide-diameter and broadband beam collimation

    NASA Astrophysics Data System (ADS)

    Clark, James; Anguita, José V.; Chen, Ying; Silva, S. Ravi P.

    2016-01-01

    Eliminating curved refracting lensing components used in conventional projection, imaging and sensing optical assemblies, is critical to enable compactness and miniaturisation of optical devices. A suitable means is replacing refracting lenses with two-dimensional optical media in flat-slab form, to achieve an equivalent optical result. One approach, which has been the focus of intense research, uses a Veselago lens which features a negative-index metamaterial. However, practical implementations rely on resonance techniques, thus broadband operation at optical frequencies imposes significant technical challenges that have been difficult to overcome. Here, we demonstrate a highly-collimated, broadband, wide-diameter beam from a compact source in flat-slab form, based on light collimation using nanomaterials ordered in patterns and embedded into flexible polymers. These provide a highly anisotropic absorption coefficient due to patterns created by vertical carbon nanotube structures grown on glass, and the anisotropic electrical conductivity of the nanotubes. We show this nanostructure strongly absorbs unwanted off-axis light rays, whilst transmitting the desired on-axis rays, to achieve the required optical effect over broadband, from visible to short-infrared, thus circumventing some technical limitations of negative-index metamaterials. We further show a low substrate-temperature system for nanotube growth, allowing direct implementation into heat-sensitive large-area devices.

  14. Optical nanostructures in 2D for wide-diameter and broadband beam collimation

    PubMed Central

    Clark, James; Anguita, José V.; Chen, Ying; Silva, S. Ravi P.

    2016-01-01

    Eliminating curved refracting lensing components used in conventional projection, imaging and sensing optical assemblies, is critical to enable compactness and miniaturisation of optical devices. A suitable means is replacing refracting lenses with two-dimensional optical media in flat-slab form, to achieve an equivalent optical result. One approach, which has been the focus of intense research, uses a Veselago lens which features a negative-index metamaterial. However, practical implementations rely on resonance techniques, thus broadband operation at optical frequencies imposes significant technical challenges that have been difficult to overcome. Here, we demonstrate a highly-collimated, broadband, wide-diameter beam from a compact source in flat-slab form, based on light collimation using nanomaterials ordered in patterns and embedded into flexible polymers. These provide a highly anisotropic absorption coefficient due to patterns created by vertical carbon nanotube structures grown on glass, and the anisotropic electrical conductivity of the nanotubes. We show this nanostructure strongly absorbs unwanted off-axis light rays, whilst transmitting the desired on-axis rays, to achieve the required optical effect over broadband, from visible to short-infrared, thus circumventing some technical limitations of negative-index metamaterials. We further show a low substrate-temperature system for nanotube growth, allowing direct implementation into heat-sensitive large-area devices. PMID:26732851

  15. Laser cooling of cesium atoms in far-detuned optical lattices

    NASA Astrophysics Data System (ADS)

    Winoto, Sugiharto Lukman

    1999-11-01

    High-density cold Cesium atoms from a transiently compressed magneto-optical trap (MOT) are loaded into far red-detuned optical lattice traps. A subsequent independent laser cooling of the atoms in the trap is shown to be of the polarization gradient cooling (PGC) type. The PGC produces strong localization of atoms in the periodic anti-nodes of lattice sites corresponding to significant occupation of the lattice vibrational ground states. Adiabatic relaxation of the 3D optical lattice trap results in the highest phase-space density achievable for a large number of atoms through a purely optical method of cooling and trapping. The resulting atom cloud is to be loaded into a conservative optical dipole trap for an experimental search of Cesium Bose- Einstein condensation (BEC) through a method of evaporative cooling in the dipole trap.

  16. Atomic Bloch-Zener oscillations and Stückelberg interferometry in optical lattices.

    PubMed

    Kling, Sebastian; Salger, Tobias; Grossert, Christopher; Weitz, Martin

    2010-11-19

    We report on experiments investigating quantum transport and band interferometry of an atomic Bose-Einstein condensate in an optical lattice with a two-band miniband structure, realized with a Fourier-synthesized optical lattice potential. Bloch-Zener oscillations, the coherent superposition of Bloch oscillations and Landau-Zener tunneling between the two bands, are observed. When the relative phase between paths in different bands is varied, an interference signal is observed, demonstrating the coherence of the dynamics in the miniband system. Measured fringe patterns of this Stückelberg interferometer allow us to interferometrically map out the band structure of the optical lattice over the full Brillouin zone.

  17. Atomic Bloch-Zener Oscillations and Stueckelberg Interferometry in Optical Lattices

    SciTech Connect

    Kling, Sebastian; Salger, Tobias; Grossert, Christopher; Weitz, Martin

    2010-11-19

    We report on experiments investigating quantum transport and band interferometry of an atomic Bose-Einstein condensate in an optical lattice with a two-band miniband structure, realized with a Fourier-synthesized optical lattice potential. Bloch-Zener oscillations, the coherent superposition of Bloch oscillations and Landau-Zener tunneling between the two bands, are observed. When the relative phase between paths in different bands is varied, an interference signal is observed, demonstrating the coherence of the dynamics in the miniband system. Measured fringe patterns of this Stueckelberg interferometer allow us to interferometrically map out the band structure of the optical lattice over the full Brillouin zone.

  18. Lattice-Induced Frequency Shifts in Sr Optical Lattice Clocks at the 10{sup -17} Level

    SciTech Connect

    Westergaard, P. G.; Lodewyck, J.; Lecallier, A.; Millo, J.; Lemonde, P.; Lorini, L.; Burt, E. A.; Zawada, M.

    2011-05-27

    We present a comprehensive study of the frequency shifts associated with the lattice potential in a Sr lattice clock by comparing two such clocks with a frequency stability reaching 5x10{sup -17} after a 1 h integration time. We put the first experimental upper bound on the multipolar M1 and E2 interactions, significantly smaller than the recently predicted theoretical upper limit, and give a 30-fold improved upper limit on the effect of hyperpolarizability. Finally, we report on the first observation of the vector and tensor shifts in a Sr lattice clock. Combining these measurements, we show that all known lattice related perturbations will not affect the clock accuracy down to the 10{sup -17} level, even for lattices as deep as 150 recoil energies.

  19. Adiabatic dynamics with classical noise in optical lattice

    NASA Astrophysics Data System (ADS)

    Xu, Guanglei; Daley, Andrew

    2016-05-01

    The technique of adiabatic state preparation is an interesting potential tool for the realisation of sensitive many-body states with ultra-cold atoms at low temperatures. However, questions remain regarding the influence of classical noise in these adiabatic dynamics. We investigate such dynamics in a situation where a level dressing scheme can make amplitude noise in an optical lattice proportional to the Hamiltonian, leading to a quantum Zeno effect for non-adiabatic transitions. We compute the dynamics using stochastic many-body Schrödinger equation and master equation approaches. Taking the examples of 1D Bose-Hubbard model from Mott insulator phase to superfluid phase and comparing with analytical calculations for a two-level system, we demonstrate that when the total time for the process is limited, properly transformed noise can lead to an increased final fidelity in the state preparation. We consider the dynamics also in the presence of imperfections, studying the resulting heating and dephasing for the many-body states, and identifying optimal regimes for future experiments.

  20. The optical system design and application of micro 2D barcode

    NASA Astrophysics Data System (ADS)

    Zhu, Yi-jia; Li, Liang-liang; Qian, Cheng; Liang, Zhong-cheng

    2010-11-01

    We show an optical system of micro visual tag which is based on the principle of microscope and the property of QR Code. Unlike current optical tag, such as barcodes, must be read within a short rang and occupy valuable physical space on products, the new tags can be shrunk to several millimeters and captured from a distance of over 0.5 meters. We design the transmitter according to the parameters of camera lens. We also take the detection range and apertures into account, meanwhile conduct simulations and experiments. The result shows that: the tag can be captured from a long distance, and the amplified image is able to accurately be decoded.

  1. Optical signatures of a hypercritical 1D potential in a 2D Dirac metal

    NASA Astrophysics Data System (ADS)

    Jiang, Bor-Yuan; Ni, Guangxin; Pan, Cheng; Fei, Zhe; Cheng, Bin; Lau, Chun Ning; Bockrath, Marc; Basov, Dimitri; Fogler, Michael

    Generation of quasi-bound states in graphene near strong charged perturbations is a solid-state analog of atomic collapse of superheavy elements or particle production by hypothetical cosmic strings. We show, for the case of a linelike perturbation, that as the perturbation grows in strength, quasi-bound states are generated sequentially. Each of these critical events is signaled by a sharp change in the local optical conductivity. Tunable linelike perturbations can be realized in experiment using nanowire or nanotube electrostatic gates. We report measurements of local conductivity for such systems obtained through near-field optical microscopy.

  2. Non-abelian gauge fields and topological insulators in shaken optical lattices.

    PubMed

    Hauke, Philipp; Tieleman, Olivier; Celi, Alessio; Olschläger, Christoph; Simonet, Juliette; Struck, Julian; Weinberg, Malte; Windpassinger, Patrick; Sengstock, Klaus; Lewenstein, Maciej; Eckardt, André

    2012-10-05

    Time-periodic driving like lattice shaking offers a low-demanding method to generate artificial gauge fields in optical lattices. We identify the relevant symmetries that have to be broken by the driving function for that purpose and demonstrate the power of this method by making concrete proposals for its application to two-dimensional lattice systems: We show how to tune frustration and how to create and control band touching points like Dirac cones in the shaken kagome lattice. We propose the realization of a topological and a quantum spin Hall insulator in a shaken spin-dependent hexagonal lattice. We describe how strong artificial magnetic fields can be achieved for example in a square lattice by employing superlattice modulation. Finally, exemplified on a shaken spin-dependent square lattice, we develop a method to create strong non-abelian gauge fields.

  3. Optical position feedback of quasi-static 2D MOEMS mirrors

    NASA Astrophysics Data System (ADS)

    Tortschanoff, A.; Baumgart, M.; Holzmann, D.; Lenzhofer, M.; Sandner, T.; Kenda, A.

    2013-05-01

    Recently, we have realized a new position sensing device for MOEMS mirrors applicable to arbitrary trajectories, which is based on the measurement of a reflected light beam with a quadrant diode. In this work we present the characteristics of this device, showing first experimental results obtained with a test set-up, but also theoretical considerations and optical ray-tracing simulations.

  4. Open Quantum System Studies of Optical Lattices and Nonlinear Optical Cavities: A Comprehensive Development of Atomtronics

    NASA Astrophysics Data System (ADS)

    Pepino, Ronald A.

    2011-12-01

    A generalized open quantum theory that models the transport properties of bosonic systems is derived from first principles. This theory is shown to correctly describe the long-time behavior of a specific class of non-Markovian system-reservoir interactions. Starting with strongly-interacting bosons in optical lattices, we use this theory to construct a novel, one-to-one analogy with electronic systems, components, and devices. Beginning with the concept of a wire, we demonstrate theoretically the ultracold boson analog of a semiconductor diode, a field-effect transistor, and a bipolar junction transistor. In a manner directly analogous to electronics, we show that it is possible to construct combinatorial logic structures from the fundamental electronic-emulating devices just described. In this sense, our proposal for atomtronic devices is a useful starting point for arrangements with more complex functionality. In addition we show that the behavior of the proposed diode should also be possible utilizing a weakly-interacting, coherent bosonic drive. After demonstrating the formal equivalence between systems comprised of bosons in optical lattices and photons in nonlinear cavity networks, we use the formalism to extend the ideas and concepts developed earlier in ultracold boson systems to nonlinear optical systems. We adapt the open quantum system theory to this new physical environment, and demonstrate theoretically how a few-photon optical diode can be realized in a coupled nonlinear cavity system. An analysis of different practical cavity quantum electrodynamics systems is presented and experimentally-viable candidates are evaluated.

  5. Comparing a mercury optical lattice clock with microwave and optical frequency standards

    NASA Astrophysics Data System (ADS)

    Tyumenev, R.; Favier, M.; Bilicki, S.; Bookjans, E.; Le Targat, R.; Lodewyck, J.; Nicolodi, D.; Le Coq, Y.; Abgrall, M.; Guéna, J.; De Sarlo, L.; Bize, S.

    2016-11-01

    In this paper we report the evaluation of an optical lattice clock based on neutral mercury with a relative uncertainty of 1.7× {10}-16. Comparing this characterized frequency standard to a 133Cs atomic fountain we determine the absolute frequency of the {}1{{{S}}}0\\to {}3{{{P}}}0 transition of 199Hg as {ν }{Hg}=1128 575 290 808 154.62 {Hz}+/- 0.19 {Hz}({statistical})+/- 0.38 {Hz} (systematic), limited solely by the realization of the SI second. Furthermore, by comparing the mercury optical lattice clock to a 87Rb atomic fountain, we determine for the first time to our knowledge the ratio between the 199Hg clock transition and the 87Rb ground state hyperfine transition. Finally we present a direct optical to optical measurement of the 199Hg/87Sr frequency ratio. The obtained value of {ν }{Hg}/{ν }{Sr} = 2.629 314 209 898 909 15 with a fractional uncertainty of 1.8× {10}-16 is in excellent agreement with a similar measurement obtained by Yamanaka et al (2015 Phys. Rev. Lett. 114 230801). This makes this frequency ratio one of the few physical quantities agreed upon by different laboratories to this level of uncertainty. Frequency ratio measurements of the kind reported in this paper have a strong impact for frequency metrology and fundamental physics as they can be used to monitor putative variations of fundamental constants.

  6. HP-Lattice QSAR for dynein proteins: experimental proteomics (2D-electrophoresis, mass spectrometry) and theoretic study of a Leishmania infantum sequence.

    PubMed

    Dea-Ayuela, María Auxiliadora; Pérez-Castillo, Yunierkis; Meneses-Marcel, Alfredo; Ubeira, Florencio M; Bolas-Fernández, Francisco; Chou, Kuo-Chen; González-Díaz, Humberto

    2008-08-15

    The toxicity and inefficacy of actual organic drugs against Leishmaniosis justify research projects to find new molecular targets in Leishmania species including Leishmania infantum (L. infantum) and Leishmaniamajor (L. major), both important pathogens. In this sense, quantitative structure-activity relationship (QSAR) methods, which are very useful in Bioorganic and Medicinal Chemistry to discover small-sized drugs, may help to identify not only new drugs but also new drug targets, if we apply them to proteins. Dyneins are important proteins of these parasites governing fundamental processes such as cilia and flagella motion, nuclear migration, organization of the mitotic splinde, and chromosome separation during mitosis. However, despite the interest for them as potential drug targets, so far there has been no report whatsoever on dyneins with QSAR techniques. To the best of our knowledge, we report here the first QSAR for dynein proteins. We used as input the Spectral Moments of a Markov matrix associated to the HP-Lattice Network of the protein sequence. The data contain 411 protein sequences of different species selected by ClustalX to develop a QSAR that correctly discriminates on average between 92.75% and 92.51% of dyneins and other proteins in four different train and cross-validation datasets. We also report a combined experimental and theoretic study of a new dynein sequence in order to illustrate the utility of the model to search for potential drug targets with a practical example. First, we carried out a 2D-electrophoresis analysis of L. infantum biological samples. Next, we excised from 2D-E gels one spot of interest belonging to an unknown protein or protein fragment in the region M<20,200 and pI<4. We used MASCOT search engine to find proteins in the L. major data base with the highest similarity score to the MS of the protein isolated from L. infantum. We used the QSAR model to predict the new sequence as dynein with probability of 99.99% without

  7. Exploring the Néel phase using a compensated optical lattice

    NASA Astrophysics Data System (ADS)

    Yang, Tsung-Lin; Coleman, Seth T.; Duarte, Pedro M.; Hart, Russell A.; Hulet, Randall G.

    2015-05-01

    We have realized the Fermi-Hubbard model with fermionic 6Li atoms in a three-dimensional optical lattice. The red-detuned optical lattice is compensated by three additional blue-detuned laser beams which overlap each of the lattice beams, but are not retro-reflected. Using the compensated optical lattice, we have reached temperatures low enough to produce short-range antiferromagnetic (AF) spin correlations, which we detect via Bragg scattering of light. Previously, we reached temperatures down to 1.4 times that of the AFM phase transition, more than a factor of 2 below temperatures obtained previously in 3D optical lattices with fermions. However, the alignment stability of the lattice beams and the lack of tunability of the relative size of the lattice and compensating beam sizes hindered the optimization of the temperature. We have implemented an improved experimental setup which allows us to adjust the lattice beam waist ratios with better long-term stability. We will report on the status of these efforts and our progress on cooling deep into the Néel phase. Work supported by ARO, ONR, NSF and the Welch Foundation.

  8. Auto and hetero-associative memory using a 2-D optical logic gate

    NASA Technical Reports Server (NTRS)

    Chao, Tien-Hsin (Inventor)

    1992-01-01

    An optical system for auto-associative and hetero-associative recall utilizing Hamming distance as the similarity measure between a binary input image vector V(sup k) and a binary image vector V(sup m) in a first memory array using an optical Exclusive-OR gate for multiplication of each of a plurality of different binary image vectors in memory by the input image vector. After integrating the light of each product V(sup k) x V(sup m), a shortest Hamming distance detection electronics module determines which product has the lowest light intensity and emits a signal that activates a light emitting diode to illuminate a corresponding image vector in a second memory array for display. That corresponding image vector is identical to the memory image vector V(sup m) in the first memory array for auto-associative recall or related to it, such as by name, for hetero-associative recall.

  9. Leveraging Nanocavity Harmonics for Control of Optical Processes in 2D Semiconductors.

    PubMed

    Akselrod, Gleb M; Ming, Tian; Argyropoulos, Christos; Hoang, Thang B; Lin, Yuxuan; Ling, Xi; Smith, David R; Kong, Jing; Mikkelsen, Maiken H

    2015-05-13

    Optical cavities with multiple tunable resonances have the potential to provide unique electromagnetic environments at two or more distinct wavelengths--critical for control of optical processes such as nonlinear generation, entangled photon generation, or photoluminescence (PL) enhancement. Here, we show a plasmonic nanocavity based on a nanopatch antenna design that has two tunable resonant modes in the visible spectrum separated by 350 nm and with line widths of ∼60 nm. The importance of utilizing two resonances simultaneously is demonstrated by integrating monolayer MoS2, a two-dimensional semiconductor, into the colloidally synthesized nanocavities. We observe a 2000-fold enhancement in the PL intensity of MoS2--which has intrinsically low absorption and small quantum yield--at room temperature, enabled by the combination of tailored absorption enhancement at the first harmonic and PL quantum-yield enhancement at the fundamental resonance.

  10. A LATTICE THEORY OF THE ELECTRO-OPTIC EFFECTS IN SEMICONDUCTORS.

    DTIC Science & Technology

    A unified lattice theory of the electro - optic effect in semiconductor crystals, which encompasses the piezo-electric and elasto-optic effects, is...presented. Expressions are derived for the constant stress and constant strain electro - optic coefficients and the results are specialized to crystals of the zincblende structure. (Author)

  11. Optical properties of two-dimensional (2D) CdSe nanostructures

    NASA Astrophysics Data System (ADS)

    Cherevkov, S. A.; Baranov, A. V.; Fedorov, A. V.; Litvin, A. P.; Artemyev, M. V.; Prudnikau, A. V.

    2013-09-01

    The resonant and off-resonant Raman spectra of optical phonons in two-dimensional CdSe nanocrystals of 5, 6, and 7 monolayers are analysed. The spectra are dominated by SO and LO phonon bands of CdSe, whose frequencies are thickness-independent in the off-resonant Raman scattering but demonstrate an evident thickness dependence in the case of the resonant Raman scattering.

  12. Integrated packaging of 2D MOEMS mirrors with optical position feedback

    NASA Astrophysics Data System (ADS)

    Baumgart, M.; Lenzhofer, M.; Kremer, M. P.; Tortschanoff, A.

    2015-02-01

    Many applications of MOEMS microscanners rely on accurate position feedback. For MOEMS devices which do not have intrinsic on-chip feedback, position information can be provided with optical methods, most simply by using a reflection from the backside of a MOEMS scanner. By measuring the intensity distribution of the reflected beam across a quadrant diode, one can precisely detect the mirror's deflection angles. Previously, we have presented a position sensing device, applicable to arbitrary trajectories, which is based on the measurement of the position of the reflected laser beam with a quadrant diode. In this work, we present a novel setup, which comprises the optical position feedback functionality integrated into the device package itself. The new device's System-in-Package (SiP) design is based on a flip-folded 2.5D PCB layout and fully assembled as small as 9.2×7×4 mm³ in total. The device consists of four layers, which supply the MOEMS mirror, a spacer to provide the required optical path length, the quadrant photo-diode and a laser diode to serve as the light source. In addition to describing the mechanical setup of the novel device, we will present first experimental results and optical simulation studies. Accurate position feedback is the basis for closed-loop control of the MOEMS devices, which is crucial for some applications as image projection for example. Position feedback and the possibility of closed-loop control will significantly improve the performance of these devices.

  13. Optical Observation of Plasmonic Nonlocal Effects in a 2D Superlattice of Ultrasmall Gold Nanoparticles.

    PubMed

    Shen, Hao; Chen, Li; Ferrari, Lorenzo; Lin, Meng-Hsien; Mortensen, N Asger; Gwo, Shangjr; Liu, Zhaowei

    2017-04-12

    The advances in recent nanofabrication techniques have facilitated explorations of metal structures into nanometer scales, where the traditional local-response Drude model with hard-wall boundary conditions fails to accurately describe their optical responses. The emerging nonlocal effects in single ultrasmall silver nanoparticles have been experimentally observed in single-particle spectroscopy enabled by the unprecedented high spatial resolution of electron energy loss spectroscopy (EELS). However, the unambiguous optical observation of such new effects in gold nanoparticles has yet not been reported, due to the extremely weak scattering and the obscuring fingerprint of strong interband transitions. Here we present a nanosystem, a superlattice monolayer formed by sub-10 nm gold nanoparticles. Plasmon resonances are spectrally well-separated from interband transitions, while exhibiting clearly distinguishable blueshifts compared to predictions by the classical local-response model. Our far-field spectroscopy was performed by a standard optical transmission and reflection setup, and the results agreed excellently with the hydrodynamic nonlocal model, opening a simple and widely accessible way for addressing quantum effects in nanoplasmonic systems.

  14. Enhanced Doppler reflectometry power response: physical optics and 2D full wave modelling

    NASA Astrophysics Data System (ADS)

    Pinzón, J. R.; Happel, T.; Blanco, E.; Conway, G. D.; Estrada, T.; Stroth, U.

    2017-03-01

    The power response of a Doppler reflectometer is investigated by means of the physical optics model; a simple model which considers basic scattering processes at the reflection layer. Apart from linear and saturated scattering regimes, non-linear regimes with an enhanced backscattered power are found. The different regimes are characterized and understood based on analytical calculations. The power response is also studied with two-dimensional full wave simulations, where the enhanced backscattered power regimes are also found in qualitative agreement with the physical optics results. The ordinary and extraordinary modes are compared for the same angle of incidence, with the conclusion that the ordinary mode is better suited for Doppler reflectometry turbulence level measurements due to the linearity of its response. The scattering efficiency is studied and a first approximation to describe it is proposed. At the end, the application of the physical optics results to experimental data analysis is discussed. In particular, a formula to assess the linearity of Doppler reflectometry measurements is provided.

  15. Algorithm of Shaping Multiple-beam Braggs Acousto-optic Diffraction Laser Field Into 1D and 2D Patterns

    NASA Astrophysics Data System (ADS)

    Zakharchenko, S.; Baturin, A.

    2015-09-01

    Algorithm of solving a direct problem of acousto-optic interaction between laser emission and acoustic signal consisting of a set of equidistant frequency components is proposed. An infinite system of coupled wave differential equations is reduced to eigenvalue problem. The contribution of the higher rediffraction orders is analyzed separately. Inverse problem of finding an optimal set of equidistant frequency components of a driving acoustic signal to form the objective diffraction pattern is also considered and a few optimization approaches are analyzed. A naïve heuristic method of splitting 2D pattern into subframes, each suitable for simultaneous projection by two acousto-optical deflectors driven by multifrequency composite signal, is developed.

  16. Observation of Landau-Zener tunneling through atomic current in the optical lattices

    SciTech Connect

    Yan Jieyun; Duan Suqing; Zhang Wei; Zhao Xiangeng

    2009-05-15

    The atomic current in the Fourier-synthesized optical lattices under a constant external force is investigated theoretically. Based on a two-band model, the atomic current is derived by solving the Boltzmann equations. We find that the stationary atomic current changes with the probability of Landau-Zener tunneling, depending on the adjustable energy structure of the optical lattices. In contrast to the classical results of an electron in superlattices given by the Esaki-Tsu equations, the relation between the stationary atomic current and the strength of the external force in optical lattices is modified significantly. Both these characteristics can be taken as an effective way to observe the Landau-Zener tunneling in the optical lattices.

  17. Ultra-low power threshold for laser induced changes in optical properties of 2D molybdenum dichalcogenides

    NASA Astrophysics Data System (ADS)

    Cadiz, Fabian; Robert, Cedric; Wang, Gang; Kong, Wilson; Fan, Xi; Blei, Mark; Lagarde, Delphine; Gay, Maxime; Manca, Marco; Taniguchi, Takashi; Watanabe, Kenji; Amand, Thierry; Marie, Xavier; Renucci, Pierre; Tongay, Sefaattin; Urbaszek, Bernhard

    2016-12-01

    The optical response of traditional semiconductors depends on the laser excitation power used in experiments. For two-dimensional (2D) semiconductors, laser excitation effects are anticipated to be vastly different due to complexity added by their ultimate thinness, high surface to volume ratio, and laser-membrane interaction effects. We show in this article that under laser excitation the optical properties of 2D materials undergo irreversible changes in vacuum. Most surprisingly these effects take place even at low steady state excitation, which is commonly thought to be non-intrusive. In low temperature photoluminescence (PL) we show for monolayer (ML) MoSe2 samples grown by different techniques that laser treatment increases significantly the trion (i.e. charged exciton) contribution to the emission compared to the neutral exciton emission. Comparison between samples exfoliated onto different substrates shows that laser induced doping is more efficient for ML MoSe2 on SiO2/Si compared to h-BN and gold. For ML MoS2 we show that exposure to laser radiation with an average power in the μW μm- 2 range does not just increase the trion-to-exciton PL emission ratio, but may result in the irreversible disappearance of the neutral exciton PL emission and a shift of the main PL peak to lower energy.

  18. Suppression of photothermal convection of microparticles in two dimensional nanoplasmonic optical lattice

    NASA Astrophysics Data System (ADS)

    Chen, Yi-Chung; Yossifon, Gilad; Yang, Ya-Tang

    2016-11-01

    Photothermal convection has been a major obstacle for stable particle trapping in plasmonic optical tweezer at high optical power. Here, we demonstrate a strategy to suppress the plasmonic photothermal convection by using vanishingly small thermal expansion coefficient of water at low temperature. A simple square nanoplasmonic array is illuminated with a loosely Gaussian beam to produce a two dimensional optical lattice for trapping of micro particles. We observe stable particle trapping due to near-field optical gradient forces at elevated optical power at low temperature. In contrast, for the same optical power at room temperature, the particles are convected away from the center of the optical lattice without their accumulation. This technique will greatly increase usable optical power and enhance the trapping capability of plasmonic optical tweezer.

  19. Detecting quantum coherence of Bose gases in optical lattices by scattering light intensity in cavity.

    PubMed

    Zhou, Xiaoji; Xu, Xu; Yin, Lan; Liu, W M; Chen, Xuzong

    2010-07-19

    We propose a new method of detecting quantum coherence of a Bose gas trapped in a one-dimensional optical lattice by measuring the light intensity from Raman scattering in cavity. After pump and displacement process, the intensity or amplitude of scattering light is different for different quantum states of a Bose gas, such as superfluid and Mott-Insulator states. This method can also be useful to detect quantum states of atoms with two components in an optical lattice.

  20. Crosstalk comparison of lattice-form optical interleaver with different coupler structures

    NASA Astrophysics Data System (ADS)

    Wan, Zhujun; Luo, Fengguang; Luo, Zhixiang

    2009-05-01

    Lattice circuit made from a cascade of couplers and delay-lines is a popular approach for optical interleaver based on planar lightwave circuit (PLC) technology. Different coupler structures can be employed in the lattice circuit, including 1-stage directional couplers (DCs), 4-stage DCs, and 2-stage multimode interference (MMI) couplers. We fabricated optical interleavers with above three coupler structures, respectively. The experimental results prove that the latter two coupler structures can help to reduce crosstalk, which meets the simulation results well.

  1. Variable FOV optical illumination system with constant aspect ratio for 2-D array lasers diodes

    NASA Astrophysics Data System (ADS)

    Arasa, J.; de la Fuente, M. C.; Ibañez, C.

    2008-09-01

    In this contribution we present a compact system to create an illumination distribution with a constant aspect ratio 3:4 and FOV from 0.4 to 1 degree. Besides, the system must delivery 40 W from 170 individual laser diodes placed in a regular 2-D array distribution of 10 x 20 mm. The main problem that must be solved is the high asymmetry of the individual sources; emission divergence's ratio 3:73 (0.3 vs. 7.4 degree) combined with the flux holes due to the laser's heat drain. In one axis (divergence of 0.3º) the best design strategy approach is a Galileo telescope but in the other axis a collimator configuration is the best solution. To manage both solutions at the same time is the aim of this contribution. Unfortunately for the Galileo strategy, source dimensions are too large so aspheric surfaces are needed, and the collimator configuration requires an EFL that must change from 573 to 1432 mm. The presented solution uses a set of three fixed anamorphic lenses, two of them pure cylinders, combined with a wheel of anamorphic lenses that have the function to change the FOV of the system. The most important contribution of the design is to obtain a constant final ratio 3:4 from an initial ratio of 3:73 with no losses of energy. The proposed solution produces an illumination pattern with peaks and valleys lower than 40%. This pattern distribution might be unacceptable for a standard illumination solution. However, the actual FOV is used to illuminate far away targets thus air turbulence is enough to homogenize the distribution on the target.

  2. Localization and delocalization of ultracold bosonic atoms in finite optical lattices

    SciTech Connect

    Luehmann, Dirk-Soeren; Pfannkuche, Daniela; Bongs, Kai; Sengstock, Klaus

    2008-02-15

    We study bosonic atoms in small optical lattices by exact diagonalization and observe a striking similarity to the superfluid to Mott insulator transition in macroscopic systems. The momentum distribution, the formation of an energy gap, and the pair correlation function show only a weak size dependence. For noncommensurate filling we reveal in deep lattices a mixture of localized and delocalized particles, which is sensitive to lattice imperfections. Breaking the lattice symmetry causes a Bose-glass-like behavior. We discuss the nature of excited states and orbital effects by using an exact diagonalization technique that includes higher bands.

  3. Three-dimensional magnetic trap lattice on an atom chip with an optically induced fictitious magnetic field

    SciTech Connect

    Yan Hui

    2010-05-15

    A robust type of three-dimensional magnetic trap lattice on an atom chip combining optically induced fictitious magnetic field with microcurrent-carrying wires is proposed. Compared to the regular optical lattice, the individual trap in this three-dimensional magnetic trap lattice can be easily addressed and manipulated.

  4. Three-dimensional magnetic trap lattice on an atom chip with an optically induced fictitious magnetic field

    NASA Astrophysics Data System (ADS)

    Yan, Hui

    2010-05-01

    A robust type of three-dimensional magnetic trap lattice on an atom chip combining optically induced fictitious magnetic field with microcurrent-carrying wires is proposed. Compared to the regular optical lattice, the individual trap in this three-dimensional magnetic trap lattice can be easily addressed and manipulated.

  5. Intensifying the response of distributed optical fibre sensors using 2D and 3D image restoration

    PubMed Central

    Soto, Marcelo A.; Ramírez, Jaime A.; Thévenaz, Luc

    2016-01-01

    Distributed optical fibre sensors possess the unique capability of measuring the spatial and temporal map of environmental quantities that can be of great interest for several field applications. Although existing methods for performance enhancement have enabled important progresses in the field, they do not take full advantage of all information present in the measured data, still giving room for substantial improvement over the state-of-the-art. Here we propose and experimentally demonstrate an approach for performance enhancement that exploits the high level of similitude and redundancy contained on the multidimensional information measured by distributed fibre sensors. Exploiting conventional image and video processing, an unprecedented boost in signal-to-noise ratio and measurement contrast is experimentally demonstrated. The method can be applied to any white-noise-limited distributed fibre sensor and can remarkably provide a 100-fold improvement in the sensor performance with no hardware modification. PMID:26927698

  6. 2D metal profile detector using a polymeric fiber optic sensor

    NASA Astrophysics Data System (ADS)

    Hua, Wei-Shu; Hooks, Joshua R.; Erwin, Nicholas A.; Wu, Wen-Jong; Wang, Wei-Chih

    2012-04-01

    As sensors become integrated in more applications, interest in magnetostrictive sensor technology has blossomed. Magnetostrictive materials have many advantages and useful applications in daily life, such as high efficient coupling between elastic and polymer material, large displacement, magnetic field sensors, micro actuator and motion motor, etc. The purpose of this paper is to develop a metal sensor which is capable of detecting different geometries and shapes of metal objects. The main configuration is using a Mach-Zehnder fiber-optic interferometer coated with magnetostrictive material. The metal detector system is a novel design of metal detector, easy to fabricate and capable of high sensitivity. In our design, metal detection is made possible by disrupting the magnetic flux density that encompasses the magnetostriction sensor. In this paper, experimental setups are described and metal sensing results are presented. The results of detecting complex metal's geometry and metal's mapping results are discussed.

  7. Phase-Stable Free-Space Optical Lattices for Trapped Ions.

    PubMed

    Schmiegelow, C T; Kaufmann, H; Ruster, T; Schulz, J; Kaushal, V; Hettrich, M; Schmidt-Kaler, F; Poschinger, U G

    2016-01-22

    We demonstrate control of the absolute phase of an optical lattice with respect to a single trapped ion. The lattice is generated by off-resonant free-space laser beams, and we actively stabilize its phase by measuring its ac-Stark shift on a trapped ion. The ion is localized within the standing wave to better than 2% of its period. The locked lattice allows us to apply displacement operations via resonant optical forces with a controlled direction in phase space. Moreover, we observe the lattice-induced phase evolution of spin superposition states in order to analyze the relevant decoherence mechanisms. Finally, we employ lattice-induced phase shifts for inferring the variation of the ion position over the 157  μm range along the trap axis at accuracies of better than 6 nm.

  8. Phase-Stable Free-Space Optical Lattices for Trapped Ions

    NASA Astrophysics Data System (ADS)

    Schmiegelow, C. T.; Kaufmann, H.; Ruster, T.; Schulz, J.; Kaushal, V.; Hettrich, M.; Schmidt-Kaler, F.; Poschinger, U. G.

    2016-01-01

    We demonstrate control of the absolute phase of an optical lattice with respect to a single trapped ion. The lattice is generated by off-resonant free-space laser beams, and we actively stabilize its phase by measuring its ac-Stark shift on a trapped ion. The ion is localized within the standing wave to better than 2% of its period. The locked lattice allows us to apply displacement operations via resonant optical forces with a controlled direction in phase space. Moreover, we observe the lattice-induced phase evolution of spin superposition states in order to analyze the relevant decoherence mechanisms. Finally, we employ lattice-induced phase shifts for inferring the variation of the ion position over the 157 μ m range along the trap axis at accuracies of better than 6 nm.

  9. Dynamics of two coupled Bose-Einstein Condensate solitons in an optical lattice.

    PubMed

    Cheng, Yongshan; Gong, Rongzhou; Li, Hong

    2006-04-17

    The characteristics of two coupled Bose-Einstein Condensate (BEC) bright solitons trapped in an optical lattice are investigated with the variational approach and direct numerical simulations of the Gross-Pitaevskii equation. It is found that the optical lattice can be controllably used to capture and drag the coupled BEC solitons. Its effect depends on the initial location of the BEC solitons, the lattice amplitude and wave-number, and the amplitude of the coupled BEC solitons. The effective interaction between the two coupled solitons is the attractive effect.

  10. Construction of 'resonant' magneto-optical lattices with controlled momentum compaction factor

    SciTech Connect

    Senichev, Yu. V. Chechenin, A. N.

    2007-12-15

    On the basis of the theory of 'resonant' magneto-optical lattices for synchrotrons with complex transition energy developed in [1], methods for construction of such lattices with application to various accelerators are proposed. Apart from allowing elimination of transition energy crossing by accelerated particles, these lattices should meet a number of important requirements. In particular, they must have dispersion-free straight sections intended for accommodation of RF cavities, Siberian snakes and detectors, and a large enough dynamic aperture for minimizing the effect of magnetic optics nonlinearity on the beam parameters after chromaticity correction by sextupoles.

  11. 2D quasiperiodic plasmonic crystals

    PubMed Central

    Bauer, Christina; Kobiela, Georg; Giessen, Harald

    2012-01-01

    Nanophotonic structures with irregular symmetry, such as quasiperiodic plasmonic crystals, have gained an increasing amount of attention, in particular as potential candidates to enhance the absorption of solar cells in an angular insensitive fashion. To examine the photonic bandstructure of such systems that determines their optical properties, it is necessary to measure and model normal and oblique light interaction with plasmonic crystals. We determine the different propagation vectors and consider the interaction of all possible waveguide modes and particle plasmons in a 2D metallic photonic quasicrystal, in conjunction with the dispersion relations of a slab waveguide. Using a Fano model, we calculate the optical properties for normal and inclined light incidence. Comparing measurements of a quasiperiodic lattice to the modelled spectra for angle of incidence variation in both azimuthal and polar direction of the sample gives excellent agreement and confirms the predictive power of our model. PMID:23209871

  12. Fabrication and demonstration of square lattice two-dimensional rod-type photonic bandgap crystal optical intersections

    NASA Astrophysics Data System (ADS)

    Teo, Selin H. G.; Liu, A. Q.; Yu, M. B.; Singh, J.

    2006-05-01

    This paper reports fabrication and demonstration of optical intersections in two-dimensional (2D) rod-type photonic crystal (PhC) structures. High resolution and aspect ratio 2D square lattice PhC waveguide intersections were designed and fabricated for application at the optical communication wavelengths centered at 1550 nm. In the silicon processing front, challenges resolved to overcome issues of drastically reduced process windows caused by the dense PhC rods arrays with critical dimensions (CDs) reduced to only a few hundred nanometers were addressed not only in terms of critical process flow design but also in the development of each processing module. In the lithographic process of deep ultraviolet laser system working at 248 nm, PhC rods of sub-lithographic wavelength CDs (115 nm in radii) were realized in high resolution, even near periphery regions where proximity errors were prone. In the deep etching module, stringent requirements on etch angle control and low sidewall scallops (undulations arising from time multiplexed etch and passivation actions) were satisfied, to prevent catastrophic etch failures, and enable optical quality facets. The successfully fabricated PhCs were also monolithically integrated with large scale optical testing fiber grooves that enabled macro optical fiber assisted coupling to the micro scale PhC devices. In the optical experiments, the transmission and crosstalk properties for the PhC intersection devices with different rod radii at the center of the PhC optical waveguides crossings were measured with repeatability. The properties of the PhC intersections were therefore optimized and verified to correspond well with first principle finite difference time domain simulations.

  13. 2D Optical Streaking for Ultra-Short Electron Beam Diagnostics

    SciTech Connect

    Ding, Y.T.; Huang, Z.; Wang, L.; /SLAC

    2011-12-14

    field ionization, which occurs in plasma case, gases species with high field ionization threshold should be considered. For a linear polarized laser, the kick to the ionized electrons depends on the phase of the laser when the electrons are born and the unknown timing jitter between the electron beam and laser beam makes the data analysis very difficult. Here we propose to use a circular polarized laser to do a 2-dimensional (2D) streaking (both x and y) and measure the bunch length from the angular distribution on the screen, where the phase jitter causes only a rotation of the image on the screen without changing of the relative angular distribution. Also we only need to know the laser wavelength for calibration. A similar circular RF deflecting mode was used to measure long bunches. We developed a numerical particle-in-Cell (PIC) code to study the dynamics of ionization electrons with the high energy beam and the laser beam.

  14. Bloch Oscillations in Optical and Zeeman Lattices in the Presence of Spin-Orbit Coupling

    NASA Astrophysics Data System (ADS)

    Kartashov, Yaroslav V.; Konotop, Vladimir V.; Zezyulin, Dmitry A.; Torner, Lluis

    2016-11-01

    We address Bloch oscillations of a spin-orbit coupled atom in periodic potentials of two types: optical and Zeeman lattices. We show that in optical lattices the spin-orbit coupling allows controlling the direction of atomic motion and may lead to complete suppression of the oscillations at specific values of the coupling strength. In Zeeman lattices the energy bands are found to cross each other at the boundaries of the Brillouin zone, resulting in period doubling of the oscillations. In all cases, the oscillations are accompanied by rotation of the pseudospin, with a dynamics that is determined by the strength of the spin-orbit coupling. The predicted effects are discussed also in terms of a Wannier-Stark ladder, which in optical lattices consist of two mutually shifted equidistant subladders.

  15. Lattice design of the integrable optics test accelerator and optical stochastic cooling experiment at Fermilab

    SciTech Connect

    Kafka, Gene

    2015-05-01

    The Integrable Optics Test Accelerator (IOTA) storage ring at Fermilab will serve as the backbone for a broad spectrum of Advanced Accelerator R&D (AARD) experiments, and as such, must be designed with signi cant exibility in mind, but without compromising cost e ciency. The nonlinear experiments at IOTA will include: achievement of a large nonlinear tune shift/spread without degradation of dynamic aperture; suppression of strong lattice resonances; study of stability of nonlinear systems to perturbations; and studies of di erent variants of nonlinear magnet design. The ring optics control has challenging requirements that reach or exceed the present state of the art. The development of a complete self-consistent design of the IOTA ring optics, meeting the demands of all planned AARD experiments, is presented. Of particular interest are the precise control for nonlinear integrable optics experiments and the transverse-to-longitudinal coupling and phase stability for the Optical Stochastic Cooling Experiment (OSC). Since the beam time-of- ight must be tightly controlled in the OSC section, studies of second order corrections in this section are presented.

  16. Titanium trisulfide (TiS3): a 2D semiconductor with quasi-1D optical and electronic properties

    NASA Astrophysics Data System (ADS)

    Island, Joshua O.; Biele, Robert; Barawi, Mariam; Clamagirand, José M.; Ares, José R.; Sánchez, Carlos; van der Zant, Herre S. J.; Ferrer, Isabel J.; D’Agosta, Roberto; Castellanos-Gomez, Andres

    2016-03-01

    We present characterizations of few-layer titanium trisulfide (TiS3) flakes which, due to their reduced in-plane structural symmetry, display strong anisotropy in their electrical and optical properties. Exfoliated few-layer flakes show marked anisotropy of their in-plane mobilities reaching ratios as high as 7.6 at low temperatures. Based on the preferential growth axis of TiS3 nanoribbons, we develop a simple method to identify the in-plane crystalline axes of exfoliated few-layer flakes through angle resolved polarization Raman spectroscopy. Optical transmission measurements show that TiS3 flakes display strong linear dichroism with a magnitude (transmission ratios up to 30) much greater than that observed for other anisotropic two-dimensional (2D) materials. Finally, we calculate the absorption and transmittance spectra of TiS3 in the random-phase-approximation (RPA) and find that the calculations are in qualitative agreement with the observed experimental optical transmittance.

  17. Grade-2 Teflon (AF1601) PCF for optical communication using 2D FDTD technique: a simplest design

    NASA Astrophysics Data System (ADS)

    Muduli, N.; Achary, J. S. N.; Padhy, Hemanta ku.

    2016-04-01

    A nonlinear ytterbium-doped rectangular proposed PCF structure of inner and outer cladding is used to analyze effective mode field area (Aeff), nonlinear coefficient (γ), dispersion (D), and confinement loss (CL) in a wide range of wavelength. The fabrication of PCF structure is due to different size doped air hole, pitch, and air hole diameter in a regular periodic geometrical array fashion. The various property of PCF structure such as mode field area, nonlinear coefficient, dispersion, and confinement loss are analyzed by implementing 2D FDTD technique. The above PCF property investigated using suitable parameters like Λ1, ?, ?, and ? in three different situations is discussed in simulation. The high nonlinear coefficient and dispersion property of PCF structure are tailored by setting the cladding parameter. However, highly nonlinear fibers with nonzero dispersion at the wavelength of 1.55 μm are very attractive for a range of optical communication application such as laser amplifier, pulse compression, wavelength conversion, all optical switching, and supercontinuum generation. So our newly proposed ytterbium-doped PCF seems to be most suitable exclusively for supercontinuum generation and nonlinear fiber optics. Finally, it is observed that ytterbium-doped Teflon (AF1601) PCF has more nonlinear coefficient (γ(λ) = 65.27 W-1 km-1) as compared to pure silica PCF (γ(λ) = 52 W-1 km-1) design to have same mode field area (Aeff) 1.7 μm2 at an operating wavelength of 1.55 μm.

  18. Application of Fresnel diffraction from a 2D array of reflective disks in optical profilometry of a flat surface

    NASA Astrophysics Data System (ADS)

    Darudi, Ahmad; Asgari, Pegah; Pourvais, Yousef

    2015-05-01

    Optical methods of three-dimensional profilometry have been of growing interest in both industrial and scientific applications. These techniques provide absolutely non-destructive measurement due to their non-contact nature and maintain their high precision in a large field of view. Most of these techniques however, are based on interferometry which happens to be considerably sensitive to environmental noises such as turbulence and vibration. We have used the phenomena of Fresnel diffraction from phase-steps instead of interferometry to maintain a higher precision and reduce sensitivity to environmental noises. This phenomena has been recently introduced as a method for precise measurement of wavelength, thickness and refractive index. A 2D array of reflective disks are placed above the test surface to provide the required phase-steps. In this paper, theoretical principles of Fresnel diffraction from phase-steps are discussed and the experimental results of testing an optical flat surface are presented. A flat mirror surface has been tested as an optical test surface and is been profiled. The results show that the method is precise and is not sensitive to environmental noises such as vibration and turbulence. Furthermore, the method seems to be a powerful means for testing of curved surfaces, too.

  19. Titanium trisulfide (TiS3): a 2D semiconductor with quasi-1D optical and electronic properties

    PubMed Central

    Island, Joshua O.; Biele, Robert; Barawi, Mariam; Clamagirand, José M.; Ares, José R.; Sánchez, Carlos; van der Zant, Herre S. J.; Ferrer, Isabel J.; D’Agosta, Roberto; Castellanos-Gomez, Andres

    2016-01-01

    We present characterizations of few-layer titanium trisulfide (TiS3) flakes which, due to their reduced in-plane structural symmetry, display strong anisotropy in their electrical and optical properties. Exfoliated few-layer flakes show marked anisotropy of their in-plane mobilities reaching ratios as high as 7.6 at low temperatures. Based on the preferential growth axis of TiS3 nanoribbons, we develop a simple method to identify the in-plane crystalline axes of exfoliated few-layer flakes through angle resolved polarization Raman spectroscopy. Optical transmission measurements show that TiS3 flakes display strong linear dichroism with a magnitude (transmission ratios up to 30) much greater than that observed for other anisotropic two-dimensional (2D) materials. Finally, we calculate the absorption and transmittance spectra of TiS3 in the random-phase-approximation (RPA) and find that the calculations are in qualitative agreement with the observed experimental optical transmittance. PMID:26931161

  20. An algorithm for circular test and improved optical configuration by two-dimensional (2D) laser heterodyne interferometer.

    PubMed

    Tang, Shanzhi; Yu, Shengrui; Han, Qingfu; Li, Ming; Wang, Zhao

    2016-09-01

    Circular test is an important tactic to assess motion accuracy in many fields especially machine tool and coordinate measuring machine. There are setup errors due to using directly centring of the measuring instrument for both of contact double ball bar and existed non-contact methods. To solve this problem, an algorithm for circular test using function construction based on matrix operation is proposed, which is not only used for the solution of radial deviation (F) but also should be applied to obtain two other evaluation parameters especially circular hysteresis (H). Furthermore, an improved optical configuration with a single laser is presented based on a 2D laser heterodyne interferometer. Compared with the existed non-contact method, it has a more pure homogeneity of the laser sources of 2D displacement sensing for advanced metrology. The algorithm and modeling are both illustrated. And error budget is also achieved. At last, to validate them, test experiments for motion paths are implemented based on a gantry machining center. Contrast test results support the proposal.

  1. An algorithm for circular test and improved optical configuration by two-dimensional (2D) laser heterodyne interferometer

    NASA Astrophysics Data System (ADS)

    Tang, Shanzhi; Yu, Shengrui; Han, Qingfu; Li, Ming; Wang, Zhao

    2016-09-01

    Circular test is an important tactic to assess motion accuracy in many fields especially machine tool and coordinate measuring machine. There are setup errors due to using directly centring of the measuring instrument for both of contact double ball bar and existed non-contact methods. To solve this problem, an algorithm for circular test using function construction based on matrix operation is proposed, which is not only used for the solution of radial deviation (F) but also should be applied to obtain two other evaluation parameters especially circular hysteresis (H). Furthermore, an improved optical configuration with a single laser is presented based on a 2D laser heterodyne interferometer. Compared with the existed non-contact method, it has a more pure homogeneity of the laser sources of 2D displacement sensing for advanced metrology. The algorithm and modeling are both illustrated. And error budget is also achieved. At last, to validate them, test experiments for motion paths are implemented based on a gantry machining center. Contrast test results support the proposal.

  2. Condensate fraction in a 2D Bose gas measured across the Mott-insulator transition.

    PubMed

    Spielman, I B; Phillips, W D; Porto, J V

    2008-03-28

    We realize a single-band 2D Bose-Hubbard system with Rb atoms in an optical lattice and measure the condensate fraction as a function of lattice depth, crossing from the superfluid to the Mott-insulating phase. We quantitatively identify the location of the superfluid to normal transition by observing when the condensed fraction vanishes. Our measurement agrees with recent quantum Monte Carlo calculations for a finite-sized 2D system to within experimental uncertainty.

  3. A compact acousto-optic lens for 2D and 3D femtosecond based 2-photon microscopy

    PubMed Central

    Kirkby, Paul A.; Naga Srinivas, N.K.M.; Silver, R. Angus

    2010-01-01

    We describe a high speed 3D Acousto-Optic Lens Microscope (AOLM) for femtosecond 2-photon imaging. By optimizing the design of the 4 AO Deflectors (AODs) and by deriving new control algorithms, we have developed a compact spherical AOL with a low temporal dispersion that enables 2-photon imaging at 10-fold lower power than previously reported. We show that the AOLM can perform high speed 2D raster-scan imaging (>150 Hz) without scan rate dependent astigmatism. It can deflect and focus a laser beam in a 3D random access sequence at 30 kHz and has an extended focusing range (>137 μm; 40X 0.8NA objective). These features are likely to make the AOLM a useful tool for studying fast physiological processes distributed in 3D space PMID:20588506

  4. Deriving eigenmode excitation spectrum of synthetic photonic lattices by means of optical heterodyning

    NASA Astrophysics Data System (ADS)

    Tikan, A. M.; Vatnik, I. D.; Churkin, D. V.; Sukhorukov, A. A.

    2017-02-01

    A method based on optical heterodyning is proposed for measuring relative optical phases of pulses circulating in synthetic photonic lattices (SPL). The knowledge of the phases can be further used for qualitative reconstruction of an eigenmode excitation spectrum in the SPL.

  5. Trapping of neutral mercury atoms and prospects for optical lattice clocks.

    PubMed

    Hachisu, H; Miyagishi, K; Porsev, S G; Derevianko, A; Ovsiannikov, V D; Pal'chikov, V G; Takamoto, M; Katori, H

    2008-02-08

    We report vapor-cell magneto-optical trapping of Hg isotopes on the (1)S(0)-(3)P(1) intercombination transition. Six abundant isotopes, including four bosons and two fermions, were trapped. Hg is the heaviest nonradioactive atom trapped so far, which enables sensitive atomic searches for "new physics" beyond the standard model. We propose an accurate optical lattice clock based on Hg and evaluate its systematic accuracy to be better than 10;{-18}. Highly accurate and stable Hg-based clocks will provide a new avenue for the research of optical lattice clocks and the time variation of the fine-structure constant.

  6. Trapping of Neutral Mercury Atoms and Prospects for Optical Lattice Clocks

    SciTech Connect

    Hachisu, H.; Takamoto, M.; Katori, H.; Miyagishi, K.; Porsev, S. G.; Derevianko, A.; Ovsiannikov, V. D.; Pal'chikov, V. G.

    2008-02-08

    We report vapor-cell magneto-optical trapping of Hg isotopes on the {sup 1}S{sub 0}-{sup 3}P{sub 1} intercombination transition. Six abundant isotopes, including four bosons and two fermions, were trapped. Hg is the heaviest nonradioactive atom trapped so far, which enables sensitive atomic searches for ''new physics'' beyond the standard model. We propose an accurate optical lattice clock based on Hg and evaluate its systematic accuracy to be better than 10{sup -18}. Highly accurate and stable Hg-based clocks will provide a new avenue for the research of optical lattice clocks and the time variation of the fine-structure constant.

  7. FD-TD modeling of 2-D dielectric waveguides for propagation and scattering of femtosecond optical solitons

    NASA Technical Reports Server (NTRS)

    Joseph, Rose; Goorjian, Peter; Taflove, Allen

    1993-01-01

    Experimentalists have produced all-optical switches capable of 100-fs responses. To adequately model such switches, nonlinear effects in optical materials (both instantaneous and dispersive) must be included. In principle, the behavior of electromagnetic fields in nonlinear dielectrics can be determined by solving Maxwell's equations subject to the assumption that the electric polarization has a nonlinear relation to the electric field. However, until our previous work, the resulting nonlinear Maxwell's equations have not been solved directly. Rather, approximations have been made that result in a class of generalized nonlinear Schrodinger equations (GNLSE) that solve only for the envelope of the optical pulses. In this paper, we present first-time calculations from the vector nonlinear Maxwell's equations of femtosecond soliton propagation and scattering, including carrier waves, in two-dimensional systems of dielectric waveguides exhibiting the Kerr and Raman quantum effects. We use the finite-difference time-domain (FD-TD) method in an extension of our 1-D work. There, in a fundamental innovation, we treated the linear and nonlinear convolutions for the electric polarization as new dependent variables. By differentiating these convolutions in the time domain, we derived an equivalent system of coupled, nonlinear second-order ODE's. These equations together with Maxwell's equations form the system that is solved to determine the electromagnetic fields in inhomogeneous nonlinear dispersive media. Backstorage in time is limited to only that needed by the time-integration algorithm for the ODE's, rather than that needed to store the time-history of the kernel functions of the convolutions (1000-10,000 time steps). Thus, a 2-D nonlinear optics model from Maxwell's equations is now feasible.

  8. Matter-wave two-dimensional solitons in crossed linear and nonlinear optical lattices

    SciTech Connect

    Luz, H. L. F. da; Gammal, A.; Abdullaev, F. Kh.; Salerno, M.; Tomio, Lauro

    2010-10-15

    The existence of multidimensional matter-wave solitons in a crossed optical lattice (OL) with a linear optical lattice (LOL) in the x direction and a nonlinear optical lattice (NOL) in the y direction, where the NOL can be generated by a periodic spatial modulation of the scattering length using an optically induced Feshbach resonance is demonstrated. In particular, we show that such crossed LOLs and NOLs allow for stabilizing two-dimensional solitons against decay or collapse for both attractive and repulsive interactions. The solutions for the soliton stability are investigated analytically, by using a multi-Gaussian variational approach, with the Vakhitov-Kolokolov necessary criterion for stability; and numerically, by using the relaxation method and direct numerical time integrations of the Gross-Pitaevskii equation. Very good agreement of the results corresponding to both treatments is observed.

  9. Normal Mode Splitting and Mechanical Effects of an Optical Lattice in a Ring Cavity

    NASA Astrophysics Data System (ADS)

    Klinner, Julian; Lindholdt, Malik; Nagorny, Boris; Hemmerich, Andreas

    2006-01-01

    A novel regime of atom-cavity physics is explored, arising when large atom samples dispersively interact with high-finesse optical cavities. A stable far-detuned optical lattice of several million rubidium atoms is formed inside an optical ring resonator by coupling equal amounts of laser light to each propagation direction of a longitudinal cavity mode. An adjacent longitudinal mode, detuned by about 3 GHz, is used to perform probe transmission spectroscopy of the system. The atom-cavity coupling for the lattice beams and the probe is dispersive and dissipation results only from the finite photon-storage time. The observation of two well-resolved normal modes demonstrates the regime of strong cooperative coupling. The details of the normal mode spectrum reveal mechanical effects associated with the retroaction of the probe upon the optical lattice.

  10. Normal mode splitting and mechanical effects of an optical lattice in a ring cavity.

    PubMed

    Klinner, Julian; Lindholdt, Malik; Nagorny, Boris; Hemmerich, Andreas

    2006-01-20

    A novel regime of atom-cavity physics is explored, arising when large atom samples dispersively interact with high-finesse optical cavities. A stable far-detuned optical lattice of several million rubidium atoms is formed inside an optical ring resonator by coupling equal amounts of laser light to each propagation direction of a longitudinal cavity mode. An adjacent longitudinal mode, detuned by about 3 GHz, is used to perform probe transmission spectroscopy of the system. The atom-cavity coupling for the lattice beams and the probe is dispersive and dissipation results only from the finite photon-storage time. The observation of two well-resolved normal modes demonstrates the regime of strong cooperative coupling. The details of the normal mode spectrum reveal mechanical effects associated with the retroaction of the probe upon the optical lattice.

  11. Normal Mode Splitting and Mechanical Effects of an Optical Lattice in a Ring Cavity

    SciTech Connect

    Klinner, Julian; Lindholdt, Malik; Nagorny, Boris; Hemmerich, Andreas

    2006-01-20

    A novel regime of atom-cavity physics is explored, arising when large atom samples dispersively interact with high-finesse optical cavities. A stable far-detuned optical lattice of several million rubidium atoms is formed inside an optical ring resonator by coupling equal amounts of laser light to each propagation direction of a longitudinal cavity mode. An adjacent longitudinal mode, detuned by about 3 GHz, is used to perform probe transmission spectroscopy of the system. The atom-cavity coupling for the lattice beams and the probe is dispersive and dissipation results only from the finite photon-storage time. The observation of two well-resolved normal modes demonstrates the regime of strong cooperative coupling. The details of the normal mode spectrum reveal mechanical effects associated with the retroaction of the probe upon the optical lattice.

  12. Matter-wave two-dimensional solitons in crossed linear and nonlinear optical lattices

    NASA Astrophysics Data System (ADS)

    da Luz, H. L. F.; Abdullaev, F. Kh.; Gammal, A.; Salerno, M.; Tomio, Lauro

    2010-10-01

    The existence of multidimensional matter-wave solitons in a crossed optical lattice (OL) with a linear optical lattice (LOL) in the x direction and a nonlinear optical lattice (NOL) in the y direction, where the NOL can be generated by a periodic spatial modulation of the scattering length using an optically induced Feshbach resonance is demonstrated. In particular, we show that such crossed LOLs and NOLs allow for stabilizing two-dimensional solitons against decay or collapse for both attractive and repulsive interactions. The solutions for the soliton stability are investigated analytically, by using a multi-Gaussian variational approach, with the Vakhitov-Kolokolov necessary criterion for stability; and numerically, by using the relaxation method and direct numerical time integrations of the Gross-Pitaevskii equation. Very good agreement of the results corresponding to both treatments is observed.

  13. p-Wave Cold Collisions in an Optical Lattice Clock

    SciTech Connect

    Lemke, N. D.; Sherman, J. A.; Oates, C. W.; Ludlow, A. D.; Stecher, J. von; Rey, A. M.

    2011-09-02

    We study ultracold collisions in fermionic ytterbium by precisely measuring the energy shifts they impart on the atoms' internal clock states. Exploiting Fermi statistics, we uncover p-wave collisions, in both weakly and strongly interacting regimes. With the higher density afforded by two-dimensional lattice confinement, we demonstrate that strong interactions can lead to a novel suppression of this collision shift. In addition to reducing the systematic errors of lattice clocks, this work has application to quantum information and quantum simulation with alkaline-earth atoms.

  14. Spontaneous soliton symmetry breaking in two-dimensional coupled Bose-Einstein condensates supported by optical lattices

    SciTech Connect

    Gubeskys, Arthur; Malomed, Boris A.

    2007-10-15

    Models of two-dimensional (2D) traps, with double-well structure in the third direction, for Bose-Einstein condensates are introduced with attractive or repulsive interactions between atoms. The models are based on systems of linearly coupled 2D Gross-Pitaevskii equations, where the coupling accounts for tunneling between the wells. Each well carries an optical lattice (OL) (stable 2D solitons cannot exist without OLs). The linear coupling splits each finite band gap in the spectrum of the single-component model into two subgaps. The main subject of the work is spontaneous symmetry breaking (SSB) in two-component 2D solitons and localized vortices (SSB was not considered before in 2D settings). Using variational approximation (VA) and numerical methods, we demonstrate that, in a system with attraction or repulsion, SSB occurs in families of symmetric or antisymmetric solitons (or vortices), respectively. The corresponding bifurcation destabilizes the original solution branch and gives rise to a stable branch of asymmetric solitons or vortices. The VA provides for an accurate description of the emerging branch of asymmetric solitons. In the model with attraction, all stable branches eventually terminate due to the onset of collapse. Stable asymmetric solitons in higher finite band gaps and vortices with a multiple topological charge are found too. The models also give rise to first examples of embedded solitons and embedded vortices (the states located inside Bloch bands) in two dimensions. In the linearly coupled system with opposite signs of the nonlinearity in the two cores, two distinct types of stable solitons and vortices are found, dominated by either the self-attractive component or the self-repulsive one. In the system with a mismatch between the two OLs, a pseudobifurcation is found: when the mismatch attains its largest value ({pi}), the bifurcation does not happen, as branches of different solutions asymptotically approach each other, but fail to merge.

  15. Interaction-induced excited-band condensate in a double-well optical lattice

    SciTech Connect

    Zhou Qi; Das Sarma, S.; Porto, J. V.

    2011-09-15

    We show theoretically that interaction effects in a double-well optical lattice can induce condensates in an excited band. For a symmetric double-well lattice, bosons condense into the bottom of the excited band at the edge of the Brillouin zone if the chemical potential is above a critical value. For an asymmetric lattice, a condensate with zero momentum is automatically induced in the excited band by the condensate in the lowest band. This is due to a combined effect of interaction and lattice potential, which reduces the band gap and breaks the inversion symmetry. Our work can be generalized to a superlattice composed of multiple-well potentials at each lattice site, where condensates can be induced in even higher bands.

  16. Ultracold nonreactive molecules in an optical lattice: connecting chemistry to many-body physics

    NASA Astrophysics Data System (ADS)

    Mukherjee, Rick; Ewart, Kevin; Alam, Shah; Wall, Michael; Doçaj, Andris; Hazzard, Kaden

    2016-05-01

    We derive effective lattice models for ultracold bosonic or fermionic nonreactive molecules (NRMs) in an optical lattice. In stark contrast to the standard Hubbard model, which is commonly assumed to accurately describe NRMs, we find that the single on-site interaction parameter U is replaced by a multi-channel interaction. The complex, multi-channel collisional physics is unrelated to dipolar interactions, and so occurs even in the absence of an electric field or for homonuclear molecules. We find a crossover between coherent few-channel models and fully incoherent single-channel models as the lattice depth is increased. We devise ways to control the effective model parameters using external fields and lattice anisotropy. We show that these parameters can be determined in lattice modulation experiments, which measure molecular collision dynamics with a vastly sharper energy resolution than experiments in an ultracold gas. We will report our progress calculating this novel model's ground state phase diagram.

  17. 1 kHz 2D Visual Motion Sensor Using 20 × 20 Silicon Retina Optical Sensor and DSP Microcontroller.

    PubMed

    Liu, Shih-Chii; Yang, MinHao; Steiner, Andreas; Moeckel, Rico; Delbruck, Tobi

    2015-04-01

    Optical flow sensors have been a long running theme in neuromorphic vision sensors which include circuits that implement the local background intensity adaptation mechanism seen in biological retinas. This paper reports a bio-inspired optical motion sensor aimed towards miniature robotic and aerial platforms. It combines a 20 × 20 continuous-time CMOS silicon retina vision sensor with a DSP microcontroller. The retina sensor has pixels that have local gain control and adapt to background lighting. The system allows the user to validate various motion algorithms without building dedicated custom solutions. Measurements are presented to show that the system can compute global 2D translational motion from complex natural scenes using one particular algorithm: the image interpolation algorithm (I2A). With this algorithm, the system can compute global translational motion vectors at a sample rate of 1 kHz, for speeds up to ±1000 pixels/s, using less than 5 k instruction cycles (12 instructions per pixel) per frame. At 1 kHz sample rate the DSP is 12% occupied with motion computation. The sensor is implemented as a 6 g PCB consuming 170 mW of power.

  18. Floquet Realization and Signatures of One-Dimensional Anyons in an Optical Lattice

    NASA Astrophysics Data System (ADS)

    Sträter, Christoph; Srivastava, Shashi C. L.; Eckardt, André

    2016-11-01

    We propose a simple scheme for mimicking the physics of one-dimensional anyons in an optical-lattice experiment. It relies on a bosonic representation of the anyonic Hubbard model to be realized via lattice-shaking-induced resonant tunneling against potential offsets, which are created by a combination of a lattice tilt and strong on-site interactions. No lasers additional to those used for the creation of the optical lattice are required. We also discuss experimental signatures of the continuous interpolation between bosons and fermions when the statistical angle θ is varied from 0 to π . Whereas the real-space density of the bosonic atoms corresponds directly to that of the simulated anyonic model, this is not the case for the momentum distribution. Therefore, we propose to use Friedel oscillations in the density as a probe for continuous fermionization of the bosonic atoms.

  19. Simulating Dirac fermions with Abelian and non-Abelian gauge fields in optical lattices

    SciTech Connect

    Alba, E.; Fernandez-Gonzalvo, X.; Mur-Petit, J.; Garcia-Ripoll, J.J.; Pachos, J.K.

    2013-01-15

    In this work we present an optical lattice setup to realize a full Dirac Hamiltonian in 2+1 dimensions. We show how all possible external potentials coupled to the Dirac field can arise from perturbations of the existing couplings of the honeycomb lattice pattern. This greatly simplifies the proposed implementations, requiring only spatial modulations of the intensity of the laser beams to induce complex non-Abelian potentials. We finally suggest several experiments to observe the properties of the quantum field theory in the setup. - Highlights: Black-Right-Pointing-Pointer This work provides a very flexible setup for simulating Dirac fermions. Black-Right-Pointing-Pointer The manuscript contains a detailed study of optical lattice deformations. Black-Right-Pointing-Pointer The link between lattice deformations and effective gauge Hamiltonians is studied.

  20. Weyl points in three-dimensional optical lattices: synthetic magnetic monopoles in momentum space

    NASA Astrophysics Data System (ADS)

    Buljan, Hrvoje; Dubcek, Tena; Kennedy, Colin; Lu, Ling; Ketterle, Wolfgang; Soljacic, Marin

    2015-05-01

    We show that Hamiltonians with Weyl points can be realized for ultracold atoms using laser-assisted tunneling in three-dimensional (3D) optical lattices. Weyl points are synthetic magnetic monopoles that exhibit a robust, 3D linear dispersion (e.g., see). They are associated with many interesting topological states of matter, such as Weyl semimetals and chiral Weyl fermions. However, Weyl points have yet to be experimentally observed in any system. We show that this elusive goal is well-within experimental reach with an extension of the techniques recently used to obtain the Harper Hamiltonian. We propose using laser assisted tunneling to create a 3D optical lattice, with specifically designed hopping between lattice sites that breaks inversion symmetry. The design leads to creation of four Weyl points in the Brillouin zone of the lattice, which are verified to be monopoles of the synthetic magnetic field. Supported by the Unity through Knowledge Fund (Grant 5/13).

  1. Resolved Sideband Spectroscopy and Cooling of Strontium in a 532-nm Optical Lattice

    NASA Astrophysics Data System (ADS)

    Aman, James; Hill, Joshua; Killian, T. C.

    2016-05-01

    Resolved sideband cooling is a powerful and well established technique for driving ultracold atoms in optical lattices to the motional ground state of individual lattice sites. Here we present spectroscopy of the narrow 5s21S0 --> 5 s 5 p3P1 transition for neutral strontium-84 in a 532nm optical lattice. Resolved red- and blue-detuned sidebands are observed corresponding to changes in the motional state in the lattice sites. Driving the red sideband, we demonstrate cooling into the ground state, which increases the initial phase-space density before forced evaporative cooling. This is a promising technique for improving the production of strontium quantum degenerate gases. Research supported by the Robert A, Welch Foundation under Grant No. C-1844.

  2. Quantum phases of the extended Bose-Hubbard hamiltonian: possibility of a supersolid state of cold atoms in optical lattices.

    PubMed

    Scarola, V W; Das Sarma, S

    2005-07-15

    Cold atom optical lattices typically simulate zero-range Hubbard models. We discuss the theoretical possibility of using excited states of optical lattices to generate extended range Hubbard models. We find that bosons confined to higher bands of optical lattices allow for a rich phase diagram, including the supersolid phase. Using Gutzwiller, mean-field theory we establish the parameter regime necessary to maintain metastable states generated by an extended Bose-Hubbard model.

  3. 1-D, 2-D and 3-D Negative-Refraction Metamaterials at Optical Frequencies: Optical Nano-Transmission-Line and Circuit Theory

    NASA Astrophysics Data System (ADS)

    Engheta, Nader; Alu, Andrea

    2006-03-01

    In recent years metamaterials have offered new possibilities for overcoming some of the intrinsic limitations in wave propagation. Their realization at microwave frequencies has followed two different paths; one consisting of embedding resonant inclusions in a host dielectric, and the other following a transmission-line approach, i.e., building 1-D, 2-D, or 3-D cascades of circuit elements, respectively, as linear, planar or bulk right- or left-handed metamaterials. The latter is known to provide larger bandwidth and better robustness to ohmic losses. Extending these concepts to optical frequencies is a challenging task, due to changes in material response to electromagnetic waves at these frequencies. However, recently we have studied theoretically how it may be possible to have circuit nano-elements at these frequencies by properly exploiting plasmonic resonances. Here we present our theoretical work on translating the circuit concepts of right- and left-handed metamaterials into optical frequencies by applying the analogy between nanoparticles and nanocircuit elements in transmission lines. We discuss how it is possible to synthesize optical negative-refraction metamaterials by properly cascading plasmonic and non-plasmonic elements in 1-D, 2-D and 3-D geometries.

  4. Driving Defect Modes of Bose-Einstein Condensates in Optical Lattices

    SciTech Connect

    Brazhnyi, Valeriy A.; Konotop, Vladimir V.; Perez-Garcia, Victor M.

    2006-02-17

    We present an approximate analytical theory and direct numerical computation of defect modes of a Bose-Einstein condensate loaded in an optical lattice and subject to an additional localized (defect) potential. Some of the modes are found to be remarkably stable and can be driven along the lattice by means of a defect moving following a steplike function defined by the period of Josephson oscillations and the macroscopic stability of the atoms.

  5. Spin-Orbit-Coupled Bose-Einstein Condensates in a One-Dimensional Optical Lattice

    NASA Astrophysics Data System (ADS)

    Hamner, C.; Zhang, Yongping; Khamehchi, M. A.; Davis, Matthew J.; Engels, P.

    2015-02-01

    We investigate a spin-orbit-coupled Bose-Einstein condensate loaded into a translating optical lattice. We experimentally demonstrate the lack of Galilean invariance in the spin-orbit-coupled system, which leads to anisotropic behavior of the condensate depending on the direction of translation of the lattice. The anisotropy is theoretically understood by an effective dispersion relation. We experimentally confirm this theoretical picture by probing the dynamical instability of the system.

  6. Roton-maxon excitation spectrum of Bose condensates in a shaken optical lattice.

    PubMed

    Ha, Li-Chung; Clark, Logan W; Parker, Colin V; Anderson, Brandon M; Chin, Cheng

    2015-02-06

    We present experimental evidence showing that an interacting Bose condensate in a shaken optical lattice develops a roton-maxon excitation spectrum, a feature normally associated with superfluid helium. The roton-maxon feature originates from the double-well dispersion in the shaken lattice, and can be controlled by both the atomic interaction and the lattice modulation amplitude. We determine the excitation spectrum using Bragg spectroscopy and measure the critical velocity by dragging a weak speckle potential through the condensate-both techniques are based on a digital micromirror device. Our dispersion measurements are in good agreement with a modified Bogoliubov model.

  7. Dynamics of a Bose-Einstein condensate in a horizontally vibrating shallow optical lattice

    SciTech Connect

    Valizadeh, A.; Jahanbani, Kh.; Kolahchi, M. R.

    2010-02-15

    We consider a solitonic solution of the self-attractive Bose-Einstein condensate in a one-dimensional external potential of a shallow optical lattice with large periodicity when the lattice is horizontally shaken. We investigate the dynamics of the bright soliton through the properties of the fixed points. The special type of bifurcation results in a simple criterion for the stability of the fixed points depending only on the amplitude of the shaking lattice. Because of the similarity of the equations with those of an ac-driven Josephson junction, some results may find applications in other branches of physics.

  8. Vortex Formation of Rotating Bose-Einstein Condensates in Synthetic Magnetic Field with Optical Lattice

    NASA Astrophysics Data System (ADS)

    Zhao, Qiang

    2016-02-01

    Motivated by recent experiments carried out by Spielman's group at NIST, we study the vortex formation in a rotating Bose-Einstein condensate in synthetic magnetic field confined in a harmonic potential combined with an optical lattice. We obtain numerical solutions of the two-dimensional Gross-Pitaevskii equation and compare the vortex formation by synthetic magnetic field method with those by rotating frame method. We conclude that a large angular momentum indeed can be created in the presence of the optical lattice. However, it is still more difficult to rotate the condensate by the synthetic magnetic field than by the rotating frame even if the optical lattice is added, and the chemical potential and energy remain almost unchanged by increasing rotational frequency.

  9. Modeling the Stability of Topological Matter in Optical Lattices

    DTIC Science & Technology

    2013-05-18

    We find that competing types of spiral order depend strongly on the spin- orbit coupling strength and effective Zeeman field. Fig. 5 shows examples of...show an emergent dispersion due to quantum effects . • Figure 5: Spin structure factors for different quantum phases. The upper panels show the results...apply to other systems: quantum wire arrays containing topological superconductors, quantum Hall effects , fractional Chern insulator lattice models

  10. Low-Entropy States of Neutral Atoms in Polarization-Synthesized Optical Lattices.

    PubMed

    Robens, Carsten; Zopes, Jonathan; Alt, Wolfgang; Brakhane, Stefan; Meschede, Dieter; Alberti, Andrea

    2017-02-10

    We create low-entropy states of neutral atoms by utilizing a conceptually new optical-lattice technique that relies on a high-precision, high-bandwidth synthesis of light polarization. Polarization-synthesized optical lattices provide two fully controllable optical lattice potentials, each of them confining only atoms in either one of the two long-lived hyperfine states. By employing one lattice as the storage register and the other one as the shift register, we provide a proof of concept using four atoms that selected regions of the periodic potential can be filled with one particle per site. We expect that our results can be scaled up to thousands of atoms by employing an atom-sorting algorithm with logarithmic complexity, which is enabled by polarization-synthesized optical lattices. Vibrational entropy is subsequently removed by sideband cooling methods. Our results pave the way for a bottom-up approach to creating ultralow-entropy states of a many-body system.

  11. A quantum gas of polar KRb molecules in an optical lattice

    NASA Astrophysics Data System (ADS)

    Covey, Jacob; Miecnikowski, Matthew; Moses, Steven; Fu, Zhengkun; Jin, Deborah; Ye, Jun

    2016-05-01

    Ultracold polar molecules provide new opportunities for investigation of strongly correlated many-body spin systems such as many-body localization and quantum magnetism. In an effort to access such phenomena, we load polar KRb molecules into a three-dimensional optical lattice. In this system, we observed many-body spin dynamics between molecules pinned in a deep lattice, even though the filling fraction of the molecules was only 5%. We have recently performed a thorough investigation of the molecule creation process in an optical lattice, and consequently improved our filling fraction to 30% by preparing and overlapping Mott and band insulators of the initial atomic gases. More recently, we switched to a second generation KRb apparatus that will allow application of large, stable electric fields as well as high-resolution addressing and detection of polar molecules in optical lattices. We plan to use these capabilities to study non-equilibrium spin dynamics in an optical lattice with nearly single site resolution. I will present the status and direction of the second generation apparatus.

  12. Low-Entropy States of Neutral Atoms in Polarization-Synthesized Optical Lattices

    NASA Astrophysics Data System (ADS)

    Robens, Carsten; Zopes, Jonathan; Alt, Wolfgang; Brakhane, Stefan; Meschede, Dieter; Alberti, Andrea

    2017-02-01

    We create low-entropy states of neutral atoms by utilizing a conceptually new optical-lattice technique that relies on a high-precision, high-bandwidth synthesis of light polarization. Polarization-synthesized optical lattices provide two fully controllable optical lattice potentials, each of them confining only atoms in either one of the two long-lived hyperfine states. By employing one lattice as the storage register and the other one as the shift register, we provide a proof of concept using four atoms that selected regions of the periodic potential can be filled with one particle per site. We expect that our results can be scaled up to thousands of atoms by employing an atom-sorting algorithm with logarithmic complexity, which is enabled by polarization-synthesized optical lattices. Vibrational entropy is subsequently removed by sideband cooling methods. Our results pave the way for a bottom-up approach to creating ultralow-entropy states of a many-body system.

  13. Detection of antiferromagnetic order by cooling atoms in an optical lattice

    NASA Astrophysics Data System (ADS)

    Yang, Tsung-Lin; Teles, Rafael; Hazzard, Kaden; Hulet, Randall; Rice University Collaboration

    2016-05-01

    We have realized the Fermi-Hubbard model with fermionic 6 Li atoms in a three-dimensional compensated optical lattice. The compensated optical lattice has provided low enough temperatures to produce short-range antiferromagnetic (AF) spin correlations, which we detect via Bragg scattering of light. Previously, we reached temperatures down to 1.4 times that of the AFM phase transition, more than a factor of 2 below temperatures obtained previously in 3D optical lattices with fermions. In order to further reduce the entropy in the compensated lattice, we implement an entropy conduit - which is a single blue detuned laser beam with a waist size smaller than the overall atomic sample size. This repulsive narrow potential provides a conductive metallic path between the low entropy core and the edges of the atomic sample where atoms may be evaporated. In addition, the entropy conduit may store entropy, thus further lowering the entropy in the core. We will report on the status of these efforts to further cool atoms in the optical lattice. Work supported by ARO MURI Grant, NSF and The Welch Foundation.

  14. Facile synthesis of 2-D Cu doped WO3 nanoplates with structural, optical and differential anti cancer characteristics

    NASA Astrophysics Data System (ADS)

    Mehmood, Faisal; Iqbal, Javed; Gul, Asma; Ahmed, Waqqar; Ismail, M.

    2017-04-01

    Simple chemical co-precipitation method has been employed to synthesize two dimensional copper (Cu) doped tungsten oxide (WO3) nanoplates. A numbers of characterization techniques have been used to investigate their structural, optical and biocompatible anti cancer properties. The XRD results have confirmed the monoclinic crystal structure of WO3 nanoplates, and also successful doping of Cu ions into the WO3 crystal lattice. The presence of functional groups and chemical bonding have been verified through FTIR and Raman spectroscopy. The SEM images demonstrate that both undoped and Cu doped WO3 samples have squares plate like morphology. The EDX spectra confirm the presence of Cu, W and O ions. Diffuse reflectance spectroscopy (DRS) analysis has revealed a substantial red-shift in the absorption edge and a decrease in the band gap energy of nanoplates with Cu doping. Photoluminescence spectroscopy has been used to study the presence of defects like oxygen vacancies. Furthermore, the differential cytotoxic properties of Cu doped WO3 samples have been evaluated against human breast (MCF-7) and liver (Hep-2) cancer cells with ectocervical epithelial (HECE) healthy cells. The present findings confirm that the Cu doped WO3 nanoplates can be used as an efficient biocompatible anti cancer agent.

  15. Flat bands, Dirac cones, and atom dynamics in an optical lattice

    SciTech Connect

    Apaja, V.; Hyrkaes, M.; Manninen, M.

    2010-10-15

    We study atoms trapped with a harmonic confinement in an optical lattice characterized by a flat band and Dirac cones. We show that such an optical lattice can be constructed which can be accurately described with the tight-binding or Hubbard models. In the case of fermions the release of the harmonic confinement removes fast atoms occupying the Dirac cones while those occupying the flat band remain immobile. Using exact diagonalization and dynamics we demonstrate that a similar strong occupation of the flat band does not happen in the bosonic case and furthermore that the mean-field model is not capable of describing the dynamics of the boson cloud.

  16. Design and Analysis of a Bypass Lattice for Optical Stochastic Cooling

    NASA Astrophysics Data System (ADS)

    Zholents, A.; Zolotorev, M.; Wan, W.

    1997-05-01

    An example of the beam line to bypass an optical amplifier in the method of Optical Stochastic Cooling is presented. Specific requirements to the lattice associated with cooling technique are considered. Tolerances to the alignment errors, tilt errors, magnetic field non linearities, power supply ripple are determined. A simple technique for initial tuning of the lattice to circumvent calibration errors of magnets and power supplies is proposed. Tolerances to the beam transverse oscillations and energy oscillations are defined. An experiment to test a bypass with the electron beam extracted from the Booster Synchrotron of the Advance Light Source of Lawrence Berkeley National Laboratory at the energy of 250 MeV is discussed.

  17. A spectral collocation method for a rotating Bose-Einstein condensation in optical lattices

    NASA Astrophysics Data System (ADS)

    Li, Z.-C.; Chen, S.-Y.; Chien, C.-S.; Chen, H.-S.

    2011-06-01

    We extend the study of spectral collocation methods (SCM) in Li et al. (2009) [1] for semilinear elliptic eigenvalue problems to that for a rotating Bose-Einstein condensation (BEC) and a rotating BEC in optical lattices. We apply the Lagrange interpolants using the Legendre-Gauss-Lobatto points to derive error bounds for the SCM. The optimal error bounds are derived for both H-norm and L-norm. Extensive numerical experiments on a rotating Bose-Einstein condensation and a rotating BEC in optical lattices are reported. Our numerical results show that the convergence rate of the SCM is exponential, and is independent of the collocation points we choose.

  18. Competing bosonic condensates in optical lattice with a mixture of single and pair hoppings

    NASA Astrophysics Data System (ADS)

    Travin, V. M.; Kopeć, T. K.

    2017-01-01

    A system of ultra-cold atoms with single boson and pair tunneling of bosonic atoms is considered in an optical lattice at arbitrary temperature. A mean-field theory was applied to the extended Bose-Hubbard Hamiltonian describing the system in order to investigate the competition between superfluid and pair superfluid as a function of the chemical potential and the temperature. To this end we have applied a method based on the Laplace transform method for the efficient calculation of the statistical sum for the quantum Hamiltonian. These results may be of interest for experiments on cold atom systems in optical lattices.

  19. Linear optics design of negative momentum compaction lattices for PS2

    SciTech Connect

    Papaphilippou,Y.; de Maria,R.; Barranco, J.; Bartmann, W.; Benedikt, M.; Carli, C.; Goddard, B.; Peggs, S.; Trbojevic, D.

    2009-05-04

    In view of the CERN Proton Synchrotron proposed replacement with a new ring (PS2), a detailed optics design has been undertaken following the evaluation of several lattice options. The basic arc module consists of cells providing negative momentum compaction. The straight section is formed with a combination of FODO and quadrupole triplet cells, to accommodate the injection and extraction systems, in particular the H{sup -} injection elements. The arc is matched to the straight section with a dispersion suppressor and matching module. Different lattices are compared with respect to their linear optics functions, tuning flexibility and geometrical acceptance properties.

  20. Stability of binary condensates with spatial modulations of quintic nonlinearities in optical lattices

    NASA Astrophysics Data System (ADS)

    Mboumba, M. D.; Moubissi, A. B.; Ekogo, T. B.; Belobo Belobo, D.; Ben-Bolie, G. H.; Kofane, T. C.

    2015-10-01

    The stability and collective excitations of binary Bose-Einstein condensates with cubic and quintic nonlinearities in variable anharmonic optical lattices are investigated. By using the variational approach, the influences of the quintic nonlinearities and the shape of the external potential on the stability are discussed in details. It is found that the quintic intraspecies and interspecies interatomic interactions profoundly affect the stability criterion and collective excitations of the system. The shape dependent potential form that characterizes the optical lattice deeply alters the stability regions. Direct numerical simulations of the mean-field coupled Gross-Pitaevskii equation describing the system agree well with the analytical predictions.

  1. Hidden-symmetry-protected quantum pseudo-spin Hall effect in optical lattices

    NASA Astrophysics Data System (ADS)

    Hou, Jing-Min; Chen, Wei

    2016-06-01

    We propose a scheme to realize a Z2 topological insulator in a square optical lattice. Different from the conventional topological insulator protected by the time-reversal symmetry, here the optical lattice possesses a hidden symmetry, which is responsible for the present Z2 topological order. With a properly defined pseudospin, such a topological insulator is characterized by the helical edge states that exhibits pseudo-spin-momentum locking, so it can be considered as a quantum pseudo-spin Hall insulator. The Z2 topological invariant is derived and its experimental detection is discussed as well.

  2. Self-consistent Hartree-Fock approach for interacting bosons in optical lattices

    NASA Astrophysics Data System (ADS)

    Lü, Qin-Qin; Patton, Kelly R.; Sheehy, Daniel E.

    2014-12-01

    A theoretical study of interacting bosons in a periodic optical lattice is presented. Instead of the commonly used tight-binding approach (applicable near the Mott-insulating regime of the phase diagram), the present work starts from the exact single-particle states of bosons in a cubic optical lattice, satisfying the Mathieu equation, an approach that can be particularly useful at large boson fillings. The effects of short-range interactions are incorporated using a self-consistent Hartree-Fock approximation, and predictions for experimental observables such as the superfluid transition temperature, condensate fraction, and boson momentum distribution are presented.

  3. A hybrid-trap BEC for radiofrequency-dressed optical lattice experiments

    NASA Astrophysics Data System (ADS)

    Lundblad, Nathan; Moody, Joanna

    2013-05-01

    Recent work in lattice-based ultracold atomic physics has focused on the development of increasingly precise and complex apparatus to push the boundaries of what can be measured with such systems. Historically such experiments have generally been confined to simple-cubic lattices with recent forays into systems both more fertile and more challenging, such as the honeycomb lattice or even the kagome net. We report progress towards nonstandard-geometry optical-lattice experiments using a recently-constructed BEC apparatus at Bates College. We summarize laser system construction, document the design and construction of a spin-flip Zeeman slower, present characterization of the laser cooling process, and present the results of magnetic trapping and evaporative cooling, including recent results showing transfer to a 1064 nm fiber-laser dipole trap and the resulting path to BEC. We also report on progress toward observation of adiabatic eigenstates in radiofrequency-dressed spin-dependent lattices loaded from said BEC, and present plans for observations of toroidal Wannier-function lattices. We also present a discussion of other possible nonstandard-geometry lattices that will be explored with this new apparatus. We acknowledge support from AFOSR and NSF.

  4. The Sr optical lattice clock at JILA: A new record in atomic clock performance

    NASA Astrophysics Data System (ADS)

    Nicholson, Travis; Bloom, Benjamin; Williams, Jason; Campbell, Sara; Bishof, Michael; Zhang, Xibo; Zhang, Wei; Bromley, Sarah; Hutson, Ross; McNally, Rees; Ye, Jun

    2014-05-01

    The exquisite control exhibited over quantum states of individual particles has revolutionized the field of precision measurement, as exemplified by highly accurate atomic clocks. Optical clocks have been the most accurate frequency standards for the better part of a decade, surpassing even the cesium microwave fountains upon which the SI second is based. Two classes of optical clocks have outperformed cesium: single-ion clocks and optical lattice clocks. Historically ion clocks have always been more accurate, and the precision of ion clocks and lattice clocks has been comparable. For years it has been unclear if lattice clocks can overcome key systematics and become more accurate than ion clocks. In this presentation I report the first lattice clock that has surpassed ion clocks in both precision and accuracy. These measurements represent a tenfold improvement in precision and a factor of 20 improvement in accuracy over the previous best lattice clock results. This work paves the way for a better realization of SI units, the development of more sophisticated quantum sensors, and precision tests of the fundamental laws of nature.

  5. Dicke superradiance as nondestructive probe for the state of atoms in optical lattices

    NASA Astrophysics Data System (ADS)

    Brinke, Nicolai ten; Schützhold, Ralf

    2016-05-01

    We present a proposal for a probing scheme utilizing Dicke superradiance to obtain information about ultracold atoms in optical lattices. A probe photon is absorbed collectively by an ensemble of lattice atoms generating a Dicke state. The lattice dynamics (e.g., tunneling) affects the coherence properties of that Dicke state and thus alters the superradiant emission characteristics - which in turn provides insight into the lattice (dynamics). Comparing the Bose-Hubbard and the Fermi-Hubbard model, we find similar superradiance in the strongly interacting Mott insulator regime, but crucial differences in the weakly interacting (superfluid or metallic) phase. Furthermore, we study the possibility to detect whether a quantum phase transition between the two regimes can be considered adiabatic or a quantum quench.

  6. Zitterbewegung with spin-orbit coupled ultracold atoms in a fluctuating optical lattice

    NASA Astrophysics Data System (ADS)

    Argonov, V. Yu; Makarov, D. V.

    2016-09-01

    The dynamics of non-interacting ultracold atoms with artificial spin-orbit coupling is considered. Spin-orbit coupling is created using two moving optical lattices with orthogonal polarizations. Our main goal is to study influence of lattice noise on Rabi oscillations. Special attention is paid to the phenomenon of the Zitterbewegung being trembling motion caused by Rabi transitions between states with different velocities. Phase and amplitude fluctuations of lattices are modelled by means of the two-dimensional stochastic Ornstein-Uhlenbeck process, also known as harmonic noise. In the the noiseless case the problem is solved analytically in terms of the momentum representation. It is shown that lattice noise significantly extends duration of the Zitterbewegung as compared to the noiseless case. This effect originates from noise-induced decoherence of Rabi oscillations.

  7. Geometric stability spectra of dipolar Bose gases in tunable optical lattices

    NASA Astrophysics Data System (ADS)

    Corson, John P.; Wilson, Ryan M.; Bohn, John L.

    2013-07-01

    We examine the stability of quasi-two-dimensional dipolar Bose-Einstein condensates in the presence of weak optical lattices of various geometries. We find that when the condensate possesses a roton-maxon quasiparticle dispersion, the conditions for stability exhibit a strong dependence both on the lattice geometry and the polarization tilt. This results in rich structures in the system's stability diagram akin to spectroscopic signatures. We show how these structures originate from the mode matching of rotons to the perturbing lattice. In the case of a one-dimensional lattice, some of the features emerge only when the polarization axis is tilted into the plane of the condensate. Our results suggest that the stability diagram may be used as a novel means to spectroscopically measure rotons in dipolar condensates.

  8. Toolbox for linear optics in a one-dimensional lattice via minimal control

    NASA Astrophysics Data System (ADS)

    Compagno, Enrico; Banchi, Leonardo; Bose, Sougato

    2015-08-01

    Tight-binding lattices offer a unique platform in which particles may be either static or mobile depending on the potential barrier between the sites. How to harness this mobility in a many-site lattice for useful operations is still an open question. We show how effective linear opticslike operations between arbitrary lattice sites can be implemented by a minimal local control which introduces a local impurity in the middle of the lattice. In particular we show how striking is the difference of the two possible correlations with and without the impurity. Our scheme enables the observation of the Hong-Ou-Mandel effect between distant wells without moving them next to each other with, e.g., tweezers. Moreover, we show that a tunable Mach-Zehnder interferometer is implemented adding a steplike potential, and we prove the robustness of our linear optics scheme to interparticle interactions.

  9. Characterization of Al2O3 optically stimulated luminescence films for 2D dosimetry using a 6 MV photon beam

    NASA Astrophysics Data System (ADS)

    Ahmed, M. F.; Shrestha, N.; Schnell, E.; Ahmad, S.; Akselrod, M. S.; Yukihara, E. G.

    2016-11-01

    This work evaluates the dosimetric properties of newly developed optically stimulated luminescence (OSL) films, fabricated with either Al2O3:C or Al2O3:C,Mg, using a prototype laser scanning reader, a developed image reconstruction algorithm, and a 6 MV therapeutic photon beam. Packages containing OSL films (Al2O3:C and Al2O3:C,Mg) and a radiochromic film (Gafchromic EBT3) were irradiated using a 6 MV photon beam using different doses, field sizes, with and without wedge filter. Dependence on film orientation of the OSL system was also tested. Diode-array (MapCHECK) and ionization chamber measurements were performed for comparison. The OSLD film doses agreed with the MapCHECK and ionization chamber data within the experimental uncertainties (<2% at 1.5 Gy). The system background and minimum detectable dose (MDD) were  <0.5 mGy, and the dose response was approximately linear from the MDD up to a few grays (the linearity correction was  <10% up to ~2-4 Gy), with no saturation up to 30 Gy. The dose profiles agreed with those obtained using EBT3 films (analyzed using the triple channel method) in the high dose regions of the images. In the low dose regions, the dose profiles from the OSLD films were more reproducible than those from the EBT3 films. We also demonstrated that the OSL film data are independent on scan orientation and field size over the investigated range. The results demonstrate the potential of OSLD films for 2D dosimetry, particularly for the characterization of small fields, due to their wide dynamic range, linear response, resolution and dosimetric properties. The negligible background and potential simple calibration make these OSLD films suitable for remote audits. The characterization presented here may motivate further commercial development of a 2D dosimetry system based on the OSL from Al2O3:C or Al2O3:C,Mg.

  10. Progress towards a permanent electron electric dipole moment search using cold atoms in an optical lattice

    NASA Astrophysics Data System (ADS)

    Solmeyer, Neal E.; Zhu, Kunyan; Weiss, David S.

    2011-05-01

    Observation of a permanent electric dipole moment of the electron would imply CP violating effects not contained in the Standard Model. We present our progress towards measuring the electron EDM using laser-cooled cesium and rubidium atoms trapped in a one dimensional optical lattice. We have collected Cs atoms in a MOT and have launched them 90 cm vertically using two cavity-enhanced optical lattice guides. In that region, which is suitable for measurement, we re-cooled and re-trapped the atoms with an overall transfer efficiency from the MOT of 50%. The two 1D lattice traps thread through three specially-coated glass electric field plates. Very low frequency Ramsey-like spectroscopy will be sensitive to an EDM with an ultimate precision of 3 ×10-30 e-cm.

  11. Bending light via adiabatic optical transition in longitudinally modulated photonic lattices.

    PubMed

    Han, Bin; Xu, Lei; Dou, Yiling; Xu, Jingjun; Zhang, Guoquan

    2015-10-29

    Bending light in a controllable way is desired in various applications such as beam steering, navigating and cloaking. Different from the conventional way to bend light by refractive index gradient, transformation optics or special beams through wavefront design such as Airy beams and surface plasmons, we proposed a mechanism to bend light via resonant adiabatic optical transition between Floquet-Bloch (FB) modes from different FB bands in longitudinally modulated photonic lattices. The band structure of longitudinally modulated photonic lattices was calculated by employing the concept of quasi-energy based on the Floquet-Bloch theory, showing the existence of band discontinuities at specific resonant points which cannot be revealed by the coupled-mode theory. Interestingly, different FB bands can be seamlessly connected at these resonant points in longitudinally modulated photonic lattices driven by adiabatically varying the longitudinal modulation period along the propagation direction, which stimulates the adiabatic FB mode transition between different FB bands.

  12. Heterodimer of two distinguishable atoms in a one-dimensional optical lattice

    SciTech Connect

    Odong, Otim; Sanders, Jerome C.; Javanainen, Juha

    2011-09-15

    Within the Bose-Hubbard model, we theoretically determine the stationary states of two distinguishable atoms in a one-dimensional optical lattice and compare with the case of two identical bosons. A heterodimer has odd-parity dissociated states that do not depend on the interactions between the atoms, and the lattice momenta of the two atomic species may have different averages even for a bound state of the dimer. We discuss methods to detect the dimer. The different distributions of the quasimomenta of the two species may be observed in suitable time-of-flight experiments. Also, an asymmetry in the lineshape as a function of the modulation frequency may reveal the presence of the odd-parity dissociated states when a heterodimer is dissociated by modulating the depth of the optical lattice.

  13. Bose-Einstein quantum phase transition in an optical lattice model

    SciTech Connect

    Aizenman, Michael; Lieb, Elliott H.; Seiringer, Robert; Solovej, Jan Philip; Yngvason, Jakob

    2004-08-01

    Bose-Einstein condensation (BEC) in cold gases can be turned on and off by an external potential, such as that presented by an optical lattice. We present a model of this phenomenon which we are able to analyze rigorously. The system is a hard core lattice gas at half of the maximum density and the optical lattice is modeled by a periodic potential of strength {lambda}. For small {lambda} and temperature, BEC is proved to occur, while at large {lambda} or temperature there is no BEC. At large {lambda} the low-temperature states are in a Mott insulator phase with a characteristic gap that is absent in the BEC phase. The interparticle interaction is essential for this transition, which occurs even in the ground state. Surprisingly, the condensation is always into the p=0 mode in this model, although the density itself has the periodicity of the imposed potential.

  14. Bending light via adiabatic optical transition in longitudinally modulated photonic lattices

    PubMed Central

    Han, Bin; Xu, Lei; Dou, Yiling; Xu, Jingjun; Zhang, Guoquan

    2015-01-01

    Bending light in a controllable way is desired in various applications such as beam steering, navigating and cloaking. Different from the conventional way to bend light by refractive index gradient, transformation optics or special beams through wavefront design such as Airy beams and surface plasmons, we proposed a mechanism to bend light via resonant adiabatic optical transition between Floquet-Bloch (FB) modes from different FB bands in longitudinally modulated photonic lattices. The band structure of longitudinally modulated photonic lattices was calculated by employing the concept of quasi-energy based on the Floquet-Bloch theory, showing the existence of band discontinuities at specific resonant points which cannot be revealed by the coupled-mode theory. Interestingly, different FB bands can be seamlessly connected at these resonant points in longitudinally modulated photonic lattices driven by adiabatically varying the longitudinal modulation period along the propagation direction, which stimulates the adiabatic FB mode transition between different FB bands. PMID:26511890

  15. Engineering Stark Potentials for Precision Measurements: Optical Lattice Clock and Electrodynamic Surface Trap

    SciTech Connect

    Katori, Hidetoshi; Takamoto, Masao; Hachisu, Hidekazu; Fujiki, Jun; Higashi, Ryoichi; Yasuda, Masami; Kishimoto, Tetsuo

    2005-05-05

    Employing the engineered electric fields, we demonstrate novel platforms for precision measurements with neutral atoms. (1) Applying the light shift cancellation technique, atoms trapped in an optical lattice reveal 50-Hz-narrow optical spectrum, yielding nearly an order of magnitude improvement over existing neutral-atom-based clocks. (2) Surface Stark trap has been developed to manipulate scalar atoms that are intrinsically robust to decoherence.

  16. Matter-wave exact periodic solutions in optical lattices with periodic potential

    NASA Astrophysics Data System (ADS)

    Liu, Changfu; Zhu, Aijun

    2013-10-01

    Some special matter-wave periodic solutions for the Gross-Pitaevskii equation with periodic potential in the multidimensional optical lattices, are obtained through restricting parameters and some balance conditions between the optical potentials and interaction energies. The results show that the same type of periodic solutions in the same dimension possesses the same norm but different phases and they are all bounded. Especially, the numerics shows that two class (2+1)-dimensional periodic solutions are stable.

  17. Amplified short-wavelength light scattered by relativistic electrons in the laser-induced optical lattice

    NASA Astrophysics Data System (ADS)

    Andriyash, I. A.; Tikhonchuk, V. T.; Malka, V.; D'Humières, E.; Balcou, Ph.

    2015-05-01

    The scheme of the x-ray free electron laser based on the optical undulator created by two overlapped transverse laser beams is analyzed. A kinetic theoretical description and an ad hoc numerical model are developed to account for the finite energy spread, angular divergence, and the spectral properties of the electron beam in the optical lattice. The theoretical findings are compared to the results of the one- and three-dimensional numerical modeling with the spectral free electron laser code plares.

  18. Multiparticle Entanglement and Spatial Addressability of Ultracold Atoms in Optical Lattices

    DTIC Science & Technology

    2009-02-01

    Immanuel F. Bloch Stefan Kuhr Johannes Gutenberg-University Mainz Institute Fuer Physik/Quantum Mainz, Germany 55099 EOARD GRANT 07-3090...PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) Johannes Gutenberg University Mainz Institute Fuer Physik/Quantum Mainz, Germany 55099 8...Entanglement and Spatial Addressability of Ultracold Atoms in Optical Lattices Prof. Dr. Immanuel Bloch Dr. Stefan Kuhr Johannes

  19. Low-acceleration instability of a Bose-Einstein condensate in an optical lattice.

    PubMed

    Zheng, Yi; Kostrun, Marijan; Javanainen, Juha

    2004-12-03

    We study a Bose-Einstein condensate in a one-dimensional accelerated optical lattice using the mean-field version of the Bose-Hubbard model. Reminiscent of recent experiments [M. Cristiani et al., Opt. Express 12, 4 (2004)], we find a new type of an instability in this system that occurs in the limit when the acceleration is small.

  20. Effective-mass analysis of Bose-Einstein condensates in optical lattices: Stabilization and levitation

    SciTech Connect

    Pu, H.; Zhang, W.; Meystre, P.; Baksmaty, L.O.; Bigelow, N.P.

    2003-04-01

    We investigate the time evolution of a Bose-Einstein condensate in a periodic optical potential. Using an effective mass formalism, we study the equation of motion for the envelope function modulating the Bloch states of the lattice potential. In particular, we show how the negative effective-mass affects the dynamics of the condensate.

  1. Landau-Zener tunneling of Bose-Einstein condensates in an optical lattice

    SciTech Connect

    Konotop, V.V.; Kevrekidis, P.G.; Salerno, M.

    2005-08-15

    A theory of the nonsymmetric Landau-Zener tunneling of Bose-Einstein condensates in deep optical lattices is presented. It is shown that periodic exchange of matter between the bands is described by a set of linearly coupled nonlinear Schroedinger equations. The key role of the modulational instability in rendering the interband transitions irreversible is highlighted.

  2. Control of diffusion of nanoparticles in an optical vortex lattice

    NASA Astrophysics Data System (ADS)

    Zapata, Ivar; Delgado-Buscalioni, Rafael; Sáenz, Juan José

    2016-06-01

    A two-dimensional periodic optical force field, which combines conservative dipolar forces with vortices from radiation pressure, is proposed in order to influence the diffusion properties of optically susceptible nanoparticles. The different deterministic flow patterns are identified. In the low-noise limit, the diffusion coefficient is computed from a mean first passage time and the most probable escape paths are identified for those flow patterns which possess a stable stationary point. Numerical simulations of the associated Langevin equations show remarkable agreement with the analytically deduced expressions. Modifications of the force field are proposed so that a wider range of phenomena could be tested.

  3. Optically induced zener tunneling in one-dimensional lattices.

    PubMed

    Fratalocchi, Andrea; Assanto, Gaetano; Brzdakiewicz, Kasia A; Karpierz, Mirek A

    2006-03-15

    We investigate Landau-Zener tunneling in one-dimensional liquid crystalline waveguide arrays by all-optical impression of acceleration with an additional beam. We derive the Zener model from the governing equations and demonstrate a novel approach to Floquet-Bloch band tunneling.

  4. Imaging and addressing of individual fermionic atoms in an optical lattice

    NASA Astrophysics Data System (ADS)

    Trotzky, Stefan; Edge, Graham; Anderson, Rhys; Xu, Peihang; Venu, Vijin; Jervis, Dylan; McKay, Dave; Day, Ryan; Thywissen, Joseph

    2016-05-01

    The implementation of site-resolved imaging of atoms in short-period optical lattices constitutes a milestone achievement in the study of strongly correlated matter with these systems. Its realization with bosons six years ago has boosted progress in the field. In the last year, site-resolved imaging was demonstrated for fermions in five independent experiments. We present our newest results on site-resolved microscopy of ultracold 40 K in a 527nm-period optical lattice. Atoms remain pinned during imaging due to EIT cooling on the 770nm D1 transition. We observe pinning fidelities of up to 96% for an illumination time of 2.6s during which the atoms scatter > 2000 photons. A 0.8NA objective collects the fluorescence light to be imaged onto a EMCCD camera, giving a 600nm -wide PSF. In conjunction with the known lattice geometry, this allows us to reconstruct the lattice-site occupations from the images. The imaging technique is implemented in an apparatus capable of simulating the Fermi-Hubbard model. The use of tomographic tools enables us to select single lattice planes for background free imaging. We also address in-plane patterns with straight and circular boundaries in order to eliminate inhomogeneity effects on the imaging fidelity, or for controlled entropy removal.

  5. Magnetic field-induced spectroscopy of forbidden optical transitions with application to lattice-based optical atomic clocks.

    PubMed

    Taichenachev, A V; Yudin, V I; Oates, C W; Hoyt, C W; Barber, Z W; Hollberg, L

    2006-03-03

    We develop a method of spectroscopy that uses a weak static magnetic field to enable direct optical excitation of forbidden electric-dipole transitions that are otherwise prohibitively weak. The power of this scheme is demonstrated using the important application of optical atomic clocks based on neutral atoms confined to an optical lattice. The simple experimental implementation of this method--a single clock laser combined with a dc magnetic field--relaxes stringent requirements in current lattice-based clocks (e.g., magnetic field shielding and light polarization), and could therefore expedite the realization of the extraordinary performance level predicted for these clocks. We estimate that a clock using alkaline-earth-like atoms such as Yb could achieve a fractional frequency uncertainty of well below 10(-17) for the metrologically preferred even isotopes.

  6. Three-level Haldane-like model on a dice optical lattice

    NASA Astrophysics Data System (ADS)

    Andrijauskas, T.; Anisimovas, E.; RačiÅ«nas, M.; Mekys, A.; Kudriašov, V.; Spielman, I. B.; JuzeliÅ«nas, G.

    2015-09-01

    We consider ultracold atoms in a two-dimensional optical lattice of the dice geometry in a tight-binding regime. The atoms experience a laser-assisted tunneling between the nearest neighbor sites of the dice lattice accompanied by the momentum recoil. This allows one to engineer staggered synthetic magnetic fluxes over plaquettes, and thus pave a way towards the realization of topologically nontrivial band structures. In such a lattice the real-valued next-nearest neighbor transitions are not needed to reach a topological regime. Yet, such transitions can increase a variety of the obtained topological phases. The dice lattice represents a triangular Bravais lattice with a three-site basis consisting of a hub site connected to two rim sites. As a consequence, the dice lattice supports three energy bands. From this point of view, our model can be interpreted as a generalization of the paradigmatic Haldane model which is reproduced if one of the two rim sublattices is eliminated. We demonstrate that the proposed upgrade of the Haldane model creates a significant added value, including an easy access to topological semimetal phases relying only on the nearest neighbor coupling, as well as enhanced topological band structures featuring Chern numbers higher than one leading to physics beyond the usual quantum Hall effect. The numerical investigation is supported and complemented by an analytical scheme based on the study of singularities in the Berry connection.

  7. Characterizing the antiferromagnetic ordering of fermions in a compensated optical lattice

    NASA Astrophysics Data System (ADS)

    Duarte, P. M.; Hart, R. A.; Yang, T. L.; Liu, X.; Hulet, R. G.; Paiva, T. C. L.; Huse, D.; Scalettar, R.; Trivedi, N.

    2014-05-01

    We realize the Fermi-Hubbard model with fermionic 6Li atoms in a three-dimensional, red-detuned optical lattice. The lattice is compensated by the addition of three blue-detuned gaussian beams which overlap each of the lattice laser beams, but are not retro-reflected. Using the compensated lattice potential, we have reached temperatures low enough to produce antiferromagnetic (AF) spin correlations, which we detect via Bragg scattering of light. The variation of the measured AF correlations as a function of the Hubbard interaction strength, U / t , provides a way to determine the temperature of the atoms in the lattice by comparison with quantum Monte Carlo calculations. This method suggests our temperature is in the range of 2-3 times the Néel ordering temperature. In this poster we present our Bragg scattering results along with our studies of the effect of the compensating potential in helping us cool the atoms in the lattice and also enlarge the size of the AF phase. Work supported by DARPA, ONR, NSF and The Welch Foundation.

  8. Extended Bose Hubbard model of interacting bosonic atoms in optical lattices: From superfluidity to density waves

    SciTech Connect

    Mazzarella, G.; Giampaolo, S. M.; Illuminati, F.

    2006-01-15

    For systems of interacting, ultracold spin-zero neutral bosonic atoms, harmonically trapped and subject to an optical lattice potential, we derive an Extended Bose Hubbard (EBH) model by developing a systematic expansion for the Hamiltonian of the system in powers of the lattice parameters and of a scale parameter, the lattice attenuation factor. We identify the dominant terms that need to be retained in realistic experimental conditions, up to nearest-neighbor interactions and nearest-neighbor hoppings conditioned by the on-site occupation numbers. In the mean field approximation, we determine the free energy of the system and study the phase diagram both at zero and at finite temperature. At variance with the standard on site Bose Hubbard model, the zero-temperature phase diagram of the EBH model possesses a dual structure in the Mott insulating regime. Namely, for specific ranges of the lattice parameters, a density wave phase characterizes the system at integer fillings, with domains of alternating mean occupation numbers that are the atomic counterparts of the domains of staggered magnetizations in an antiferromagnetic phase. We show as well that in the EBH model, a zero-temperature quantum phase transition to pair superfluidity is, in principle, possible, but completely suppressed at the lowest order in the lattice attenuation factor. Finally, we determine the possible occurrence of the different phases as a function of the experimentally controllable lattice parameters.

  9. Long distance transport of ultracold atoms using a 1D optical lattice

    NASA Astrophysics Data System (ADS)

    Schmid, Stefan; Thalhammer, Gregor; Winkler, Klaus; Lang, Florian; Hecker Denschlag, Johannes

    2006-08-01

    We study the horizontal transport of ultracold atoms over macroscopic distances of up to 20 cm with a moving 1D optical lattice. By using an optical Bessel beam to form the optical lattice, we can achieve nearly homogeneous trapping conditions over the full transport length, which is crucial in order to hold the atoms against gravity for such a wide range. Fast transport velocities of up to 6 m s-1 (corresponding to about 1100 photon recoils) and accelerations of up to 2600 m s-2 are reached. Even at high velocities the momentum of the atoms is precisely defined with an uncertainty of less than one photon recoil. This allows for construction of an atom catapult with high kinetic energy resolution, which might have applications in novel collision experiments.

  10. Possibility of triple magic trapping of clock and Rydberg states of divalent atoms in optical lattices

    NASA Astrophysics Data System (ADS)

    Topcu, T.; Derevianko, A.

    2016-07-01

    We predict the possibility of ‘triply magic’ optical lattice trapping of neutral divalent atoms. In such a lattice, the {}1{{{S}}}0 and {}3{{{P}}}0 clock states and an additional Rydberg state experience identical optical potentials, fully mitigating detrimental effects of the motional decoherence. In particular, we show that this triply magic trapping condition can be satisfied for Yb atom at optical wavelengths and for various other divalent systems (Ca, Mg, Hg and Sr) in the UV region. We assess the quality of triple magic trapping conditions by estimating the probability of excitation out of the motional ground state as a result of the excitations between the clock and the Rydberg states. We also calculate trapping laser-induced photoionization rates of divalent Rydberg atoms at magic frequencies. We find that such rates are below the radiative spontaneous-emission rates, due to the presence of Cooper minima in photoionization cross-sections.

  11. Optical lattice-like cladding waveguides by direct laser writing: fabrication, luminescence, and lasing.

    PubMed

    Nie, Weijie; He, Ruiyun; Cheng, Chen; Rocha, Uéslen; Rodríguez Vázquez de Aldana, Javier; Jaque, Daniel; Chen, Feng

    2016-05-15

    We report on the fabrication of optical lattice-like waveguide structures in an Nd:YAP laser crystal by using direct femtosecond laser writing. With periodically arrayed laser-induced tracks, the waveguiding cores can be located in either the regions between the neighbored tracks or the central zone surrounded by a number of tracks as outer cladding. The polarization of the femtosecond laser pulses for the inscription has been found to play a critical role in the anisotropic guiding behaviors of the structures. The confocal photoluminescence investigations reveal different stress-induced modifications of the structures inscribed by different polarization of the femtosecond laser beam, which are considered to be responsible for the refractive index changes of the structures. Under optical pump at 808 nm, efficient waveguide lasing at ∼1  μm wavelength has been realized from the optical lattice-like structure, which exhibits potential applications as novel miniature light sources.

  12. Optical resonance problem in metamaterial arrays: a lattice dynamics approach

    NASA Astrophysics Data System (ADS)

    Liu, Wanguo

    2016-11-01

    A systematic dynamic theory is established to deal with the optical collective resonance in metamaterial arrays. As a reference model, we consider an infinite split ring resonator (SRR) array illuminated by a linearly polarized wave and introduce an N-degree-of-freedom forced oscillator equation to simplify the coupled-mode vibration problem. We derive a strict formula of resonance frequency (RF) and its adjustable range from the steady-state response. Unlike a single SRR possesses invariant RF, it successfully explains the mechanism of RF shift effect in the SRR array when the incident angle changes. Instead of full wave analysis, only one or two adjacent resonance modes can give an accurate response line shape. Our approach is applicable for metallic arrays with any N-particle cell at all incident angles and well matched with numerical results. It provides a versatile way to study the vibration dynamics in optical periodic many-body systems.

  13. Optical techniques for Rydberg physics in lattice geometries. A technical guide

    NASA Astrophysics Data System (ADS)

    Naber, Julian B.; Vos, Jannie; Rengelink, Robert J.; Nusselder, Rosanne J.; Davtyan, David

    2016-12-01

    We address the technical challenges when performing quantum information experiments with ultracold Rydberg atoms in lattice geometries. We discuss the following key aspects: (i) the coherent manipulation of atomic ground states, (ii) the coherent excitation of Rydberg states, and (iii) spatial addressing of individual lattice sites. We briefly review methods and solutions which have been successfully implemented, and give examples based on our experimental apparatus. This includes an optical phase-locked loop, an intensity and frequency stabilization setup for lasers, and a nematic liquid-crystal spatial light modulator.

  14. Magic wavelength to make optical lattice clocks insensitive to atomic motion.

    PubMed

    Katori, Hidetoshi; Hashiguchi, Koji; Il'inova, E Yu; Ovsiannikov, V D

    2009-10-09

    In a standing wave of light, a difference in spatial distributions of multipolar atom-field interactions may introduce atomic-motion dependent clock uncertainties in optical lattice clocks. We show that the magic wavelength can be defined so as to eliminate the spatial mismatch in electric dipole, magnetic dipole, and electric quadrupole interactions for specific combinations of standing waves by allowing a spatially constant light shift arising from the latter two interactions. Experimental prospects of such lattices used with a blue magic wavelength are discussed.

  15. Observation and cancellation of a perturbing dc stark shift in strontium optical lattice clocks.

    PubMed

    Lodewyck, Jérôme; Zawada, Michal; Lorini, Luca; Gurov, Mikhail; Lemonde, Pierre

    2012-03-01

    We report on the observation of a dc Stark frequency shift at the 10-(13) level by comparing two strontium optical lattice clocks. This frequency shift arises from the presence of electric charges trapped on dielectric surfaces placed under vacuum close to the atomic sample. We show that these charges can be eliminated by shining UV light on the dielectric surfaces, and characterize the residual dc Stark frequency shift on the clock transition at the 10-(18) level by applying an external electric field. This study shows that the dc Stark shift can play an important role in the accuracy budget of lattice clocks, and should be duly taken into account.

  16. Collisional Losses, Decoherence, and Frequency Shifts in Optical Lattice Clocks with Bosons

    SciTech Connect

    Lisdat, Ch.; Winfred, J. S. R. Vellore; Middelmann, T.; Riehle, F.; Sterr, U.

    2009-08-28

    We have quantified collisional losses, decoherence and the collision shift in a one-dimensional optical lattice clock on the highly forbidden transition {sup 1}S{sub 0}-{sup 3}P{sub 0} at 698 nm with bosonic {sup 88}Sr. We were able to distinguish two loss channels: inelastic collisions between atoms in the upper and lower clock state and atoms in the upper clock state only. Based on the measured coefficients, we determine the operation parameters at which a 1D-lattice clock with {sup 88}Sr shows no degradation due to collisions on the fractional uncertainty level of 10{sup -16}.

  17. Quantum Two-breathers Formed by Ultracold Bosonic Atoms in Optical Lattices

    NASA Astrophysics Data System (ADS)

    Tang, Bing

    2016-06-01

    Two-discrete breathers are the bound states of two localized modes that can appear in classical nonlinear lattices. I investigate the quantum signature of two-discrete breathers in the system of ultracold bosonic atoms in optical lattices, which is modeled as Bose-Hubbard model containing n bosons. When the number of bosons is small, I find numerically quantum two-breathers by making use of numerical diagonalization and perturbation theory. For the cases of a large number of bosons, I can successfully construct quantum two-breather states in the Hartree approximation.

  18. Micromagic Clock: Microwave Clock Based on Atoms in an Engineered Optical Lattice

    SciTech Connect

    Beloy, K.; Derevianko, A.; Dzuba, V. A.; Flambaum, V. V.

    2009-03-27

    We propose a new class of atomic microwave clocks based on the hyperfine transitions in the ground state of aluminum or gallium atoms trapped in optical lattices. For such elements magic wavelengths exist at which both levels of the hyperfine doublet are shifted at the same rate by the lattice laser field, canceling its effect on the clock transition. A similar mechanism for the magic wavelengths may work in microwave hyperfine transitions in other atoms which have the fine-structure multiplets in the ground state.

  19. Magic Wavelength to Make Optical Lattice Clocks Insensitive to Atomic Motion

    SciTech Connect

    Katori, Hidetoshi; Hashiguchi, Koji; Il'inova, E. Yu.; Ovsiannikov, V. D.

    2009-10-09

    In a standing wave of light, a difference in spatial distributions of multipolar atom-field interactions may introduce atomic-motion dependent clock uncertainties in optical lattice clocks. We show that the magic wavelength can be defined so as to eliminate the spatial mismatch in electric dipole, magnetic dipole, and electric quadrupole interactions for specific combinations of standing waves by allowing a spatially constant light shift arising from the latter two interactions. Experimental prospects of such lattices used with a blue magic wavelength are discussed.

  20. Defect modes of a Bose-Einstein condensate in an optical lattice with a localized impurity

    SciTech Connect

    Brazhnyi, Valeriy A.; Konotop, Vladimir V.; Perez-Garcia, Victor M.

    2006-08-15

    We study defect modes of a Bose-Einstein condensate in an optical lattice with a localized defect within the framework of the one-dimensional Gross-Pitaevskii equation. It is shown that for a significant range of parameters the defect modes can be accurately described by an expansion over Wannier functions, whose envelope is governed by the coupled nonlinear Schroedinger equations with a {delta} impurity. The stability of the defect modes is verified by direct numerical simulations of the underlying Gross-Pitaevskii equation with a periodic and defect potentials. We also discuss possibilities of driving defect modes through the lattice and suggest ideas for their experimental generation.

  1. Bragg resonances and Zener tunneling in quasiperiodic two-dimensional optical lattices and photonic crystals

    SciTech Connect

    Shchesnovich, Valery S.

    2007-09-15

    Nonresonant Zener tunneling in decagonal quasiperiodic structures in two spatial dimensions is defined by its relation to Bragg resonance and is studied by direct numerical simulations and an analytical approach. It is shown that, in the shallow lattice limit, the tunneling dynamics about the Bragg resonances is described by the multilevel Landau-Zener-Majorana models, which capture the essential peaks of the complicated Fourier spectrum. The results have applications to dynamics of cold atoms and Bose-Einstein condensates in quasiperiodic optical lattices, light propagation in quasiperiodic photonic crystals, and ultrasonic experiments with quasiperiodic structures.

  2. Atomic Landau-Zener tunneling in Fourier-synthesized optical lattices.

    PubMed

    Salger, Tobias; Geckeler, Carsten; Kling, Sebastian; Weitz, Martin

    2007-11-09

    We report on an experimental study of quantum transport of atoms in variable periodic optical potentials. The band structure of both ratchet-type asymmetric and symmetric lattice potentials is explored. The variable atom potential is realized by superimposing a conventional standing wave potential of lambda/2 spatial periodicity with a fourth-order multiphoton potential of lambda/4 periodicity. We find that the Landau-Zener tunneling rate between the first and the second excited Bloch band depends critically on the relative phase between the two spatial lattice harmonics.

  3. Atomic Landau-Zener Tunneling in Fourier-Synthesized Optical Lattices

    SciTech Connect

    Salger, Tobias; Geckeler, Carsten; Kling, Sebastian; Weitz, Martin

    2007-11-09

    We report on an experimental study of quantum transport of atoms in variable periodic optical potentials. The band structure of both ratchet-type asymmetric and symmetric lattice potentials is explored. The variable atom potential is realized by superimposing a conventional standing wave potential of {lambda}/2 spatial periodicity with a fourth-order multiphoton potential of {lambda}/4 periodicity. We find that the Landau-Zener tunneling rate between the first and the second excited Bloch band depends critically on the relative phase between the two spatial lattice harmonics.

  4. The CU 2-D-MAX-DOAS instrument - Part 2: Raman scattering probability measurements and retrieval of aerosol optical properties

    NASA Astrophysics Data System (ADS)

    Ortega, Ivan; Coburn, Sean; Berg, Larry K.; Lantz, Kathy; Michalsky, Joseph; Ferrare, Richard A.; Hair, Johnathan W.; Hostetler, Chris A.; Volkamer, Rainer

    2016-08-01

    The multiannual global mean of aerosol optical depth at 550 nm (AOD550) over land is ˜ 0.19, and that over oceans is ˜ 0.13. About 45 % of the Earth surface shows AOD550 smaller than 0.1. There is a need for measurement techniques that are optimized to measure aerosol optical properties under low AOD conditions. We present an inherently calibrated retrieval (i.e., no need for radiance calibration) to simultaneously measure AOD and the aerosol phase function parameter, g, based on measurements of azimuth distributions of the Raman scattering probability (RSP), the near-absolute rotational Raman scattering (RRS) intensity. We employ radiative transfer model simulations to show that for solar azimuth RSP measurements at solar elevation and solar zenith angle (SZA) smaller than 80°, RSP is insensitive to the vertical distribution of aerosols and maximally sensitive to changes in AOD and g under near-molecular scattering conditions. The University of Colorado two-dimensional Multi-AXis Differential Optical Absorption Spectroscopy (CU 2-D-MAX-DOAS) instrument was deployed as part of the Two Column Aerosol Project (TCAP) at Cape Cod, MA, during the summer of 2012 to measure direct sun spectra and RSP from scattered light spectra at solar relative azimuth angles (SRAAs) between 5 and 170°. During two case study days with (1) high aerosol load (17 July, 0.3 < AOD430 < 0.6) and (2) near-molecular scattering conditions (22 July, AOD430 < 0.13) we compare RSP-based retrievals of AOD430 and g with data from a co-located CIMEL sun photometer, Multi-Filter Rotating Shadowband Radiometer (MFRSR), and an airborne High Spectral Resolution Lidar (HSRL-2). The average difference (relative to DOAS) for AOD430 is +0.012 ± 0.023 (CIMEL), -0.012 ± 0.024 (MFRSR), -0.011 ± 0.014 (HSRL-2), and +0.023 ± 0.013 (CIMELAOD - MFRSRAOD) and yields the following expressions for correlations between different instruments

  5. Optical lattices of excitons in InGaN/GaN quantum well systems

    SciTech Connect

    Chaldyshev, V. V. Bolshakov, A. S. Zavarin, E. E.; Sakharov, A. V.; Lundin, V. V.; Tsatsulnikov, A. F.; Yagovkina, M. A.

    2015-01-15

    Optical lattices of excitons in periodic systems of InGaN quantum wells with GaN barriers are designed, implemented, and investigated. Due to the collective interaction of quasi-two-dimensional excitons with light and a fairly high binding energy of excitons in GaN, optical Bragg reflection at room temperature is significantly enhanced. To increase the resonance optical response of the system, new structures with two quantum wells in a periodic supercell are designed and implemented. Resonance reflection of 40% at room temperatures for structures with 60 periods is demonstrated.

  6. High-Accuracy Measure of Atomic Polarizability in an Optical Lattice Clock

    DTIC Science & Technology

    2011-12-11

    AND SUBTITLE Sa. CONTRACT NUMBER High-Accuracy Measurement of Atomic Polarizability in an VV911~-11 - 1 -0202 Optical Lattice Clock Sb. GRANT NUMBER...modem optical atomic clock through blackbody radiation. By employing an ultracold, trapped atomic ensemble and high stability optical clock, we...1,U~ (1,’T, TI~ \\ 1\\ ( ,., ) Tl-.~ ~1 ~~1,1~ +.-~~+: ~~~ 1 ··~~~··+~:~+. • ...1 • • ~ +~ ··~~-~ 1S. SUBJECT TERMS atomic frequency standards

  7. Frequency ratios of optical lattice clocks at the 17th decimal place

    NASA Astrophysics Data System (ADS)

    Katori, Hidetoshi

    2016-05-01

    Optical lattice clocks benefit from a low quantum-projection noise by simultaneously interrogating a large number of atoms, which are trapped in an optical lattice tuned to the ``magic wavelength'' to largely cancel out light shift perturbation in the clock transition. About a thousand atoms enable the clocks to achieve 10-18 instability in a few hours of operation, allowing intensive investigation and control of systematic uncertainties. As optical lattice clocks have reached inaccuracies approaching 10-18, it is now the uncertainty of the SI second (~ 10-16) itself that restricts the measurement of the absolute frequencies of such optical clocks. Direct comparisons of optical clocks are, therefore, the only way to investigate and utilize their superb performance beyond the SI second. In this presentation, we report on frequency comparisons of optical lattice clocks with neutral strontium (87 Sr), ytterbium (171 Yb) and mercury (199 Hg) atoms. By referencing cryogenic Sr clocks, we determine frequency ratios, νYb/νSr and νHg/νSr, of a cryogenic Yb clock and a Hg clock with uncertainty at the mid 10-17 level. Such ratios provide an access to search for temporal variation of the fundamental constants. We also present remote comparisons between cryogenic Sr clocks located at RIKEN and the University of Tokyo over a 30-km-long phase-stabilized fiber link. The gravitational red shift Δν /ν0 ~ 1.1× 10-18 Δh cm-1 reads out the height difference of Δh ~ 15 m between the two clocks with uncertainty of 5 cm, which demonstrates a step towards relativistic geodesy. ERATO, JST.

  8. Three-dimensional optical lattice clock with bosonic {sup 88}Sr atoms

    SciTech Connect

    Akatsuka, Tomoya; Takamoto, Masao; Katori, Hidetoshi

    2010-02-15

    We present detailed analyses of our recent experiment on the three-dimensional (3D) optical lattice clock with bosonic {sup 88}Sr atoms in which the collisional frequency shift was suppressed by applying a single-occupancy lattice. Frequency shifts in magnetically induced spectroscopy on the {sup 1}S{sub 0}-{sup 3}P{sub 0} clock transition ({lambda}=698 nm) of {sup 88}Sr were experimentally investigated by referencing a one-dimensional (1D) lattice clock based on spin-polarized {sup 87}Sr atoms. We discuss that the clock stability is limited by the current laser stability as well as the experimental sequence of the clock operation, which may be improved to {sigma}{sub y}({tau})=2x10{sup -16}/{radical}({tau}) by optimizing the cycle time of the clock operation.

  9. Coexistence of Mott and superfluid domains of bosons confined in optical lattice

    NASA Astrophysics Data System (ADS)

    Khanore, Mukesh; Dey, Bishwajyoti

    2015-06-01

    We investigate ground state properties of the attractive Bose-gas confined on square optical lattice and superimposed wine-bottle-bottom or Mexican hat trap potential. The system is modeled by two-dimensional Bose-Hubbard model with attractive interactions and inhomogeneous lattice potential. We calculate the energy spectrum, the on-site number fluctuation, local density and local compressibility using numerical exact diagonalization method for incommensurate lattice filling. The trap potential has several degenerate minimum sites distributed along a ring at the wine-bottle-bottom. It is shown that beyond a certain value of the attractive interaction strength there is phase coherent condensate on these degenerate sites with finite value of the on-site number fluctuation and local compressibility giving rise to localized superfluidity or superfluidity on a ring. For the same value of the interaction strength the non-degenerate sites produces Mott region.

  10. Cold atom dynamics in a quantum optical lattice potential.

    PubMed

    Maschler, Christoph; Ritsch, Helmut

    2005-12-31

    We study a generalized cold atom Bose-Hubbard model, where the periodic optical potential is formed by a cavity field with quantum properties. On the one hand, the common coupling of all atoms to the same mode introduces cavity-mediated long-range atom-atom interactions, and, on the other hand, atomic backaction on the field introduces atom-field entanglement. This modifies the properties of the associated quantum phase transitions and allows for new correlated atom-field states, including superposition of different atomic quantum phases. After deriving an approximative Hamiltonian including the new long-range interaction terms, we exhibit central physical phenomena at generic configurations of few atoms in few wells. We find strong modifications of population fluctuations and next-nearest-neighbor correlations near the phase transition point.

  11. Controlling chaos of a Bose-Einstein condensate loaded into a moving optical Fourier-synthesized lattice.

    PubMed

    Chacón, R; Bote, D; Carretero-González, R

    2008-09-01

    We study the chaotic properties of steady-state traveling-wave solutions of the particle number density of a Bose-Einstein condensate with an attractive interatomic interaction loaded into a traveling optical lattice of variable shape. We demonstrate theoretically and numerically that chaotic traveling steady states can be reliably suppressed by small changes of the traveling optical lattice shape while keeping the remaining parameters constant. We find that the regularization route as the optical lattice shape is continuously varied is fairly rich, including crisis phenomena and period-doubling bifurcations. The conditions for a possible experimental realization of the control method are discussed.

  12. Realization of the Harper Hamiltonian with Artificial Gauge Fields in Optical Lattices

    NASA Astrophysics Data System (ADS)

    Miyake, Hirokazu; Siviloglou, Georgios; Kennedy, Colin; Burton, William Cody; Ketterle, Wolfgang

    2014-03-01

    Systems of charged particles in magnetic fields have led to many discoveries in science-such as the integer and fractional quantum Hall effects-and have become important paradigms of quantum many-body physics. We have proposed and implemented a scheme which realizes the Harper Hamiltonian, a lattice model for charged particles in magnetic fields, whose energy spectrum is the fractal Hofstadter butterfly. We experimentally realize this Hamiltonian for ultracold, charge neutral bosonic particles of 87Rb in a two-dimensional optical lattice by creating an artificial gauge field using laser-assisted tunneling and a potential energy gradient provided by gravity. Laser-assisted tunneling processes are characterized by studying the expansion of the atoms in the lattice. Furthermore, this scheme can be extended to realize spin-orbit coupling and the spin Hall effect for neutral atoms in optical lattices by modifying the motion of atoms in a spin-dependent way by laser recoil and Zeeman shifts created with a magnetic field gradient. Major advantages of our scheme are that it does not rely on near-resonant laser light to couple different spin states and should work even for fermionic particles. Our work is a step towards studying novel topological phenomena with ultracold atoms. Currently at the RAND Corporation.

  13. Chaos and band structure in a three-dimensional optical lattice.

    PubMed

    Boretz, Yingyue; Reichl, L E

    2015-04-01

    Classical chaos is known to affect wave propagation because it signifies the presence of broken symmetries. The effect of chaos has been observed experimentally for matter waves, electromagnetic waves, and acoustic waves. When these three types of waves propagate through a spatially periodic medium, the allowed propagation energies form bands. For energies in the band gaps, no wave propagation is possible. We show that optical lattices provide a well-defined system that allows a study of the effect of chaos on band structure. We have determined the band structure of a body-centered-cubic optical lattice for all theoretically possible couplings, and we find that the band structure for those lattices realizable in the laboratory differs significantly from that expected for the bands in an "empty" body-centered-cubic crystal. However, as coupling is increased, the lattice becomes increasingly chaotic and it becomes possible to produce band structure that has behavior qualitatively similar to the "empty" body-centered-cubic band structure, although with fewer degeneracies.

  14. Energy band gap and optical transition of metal ion modified double crossover DNA lattices.

    PubMed

    Dugasani, Sreekantha Reddy; Ha, Taewoo; Gnapareddy, Bramaramba; Choi, Kyujin; Lee, Junwye; Kim, Byeonghoon; Kim, Jae Hoon; Park, Sung Ha

    2014-10-22

    We report on the energy band gap and optical transition of a series of divalent metal ion (Cu(2+), Ni(2+), Zn(2+), and Co(2+)) modified DNA (M-DNA) double crossover (DX) lattices fabricated on fused silica by the substrate-assisted growth (SAG) method. We demonstrate how the degree of coverage of the DX lattices is influenced by the DX monomer concentration and also analyze the band gaps of the M-DNA lattices. The energy band gap of the M-DNA, between the lowest unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital (HOMO), ranges from 4.67 to 4.98 eV as judged by optical transitions. Relative to the band gap of a pristine DNA molecule (4.69 eV), the band gap of the M-DNA lattices increases with metal ion doping up to a critical concentration and then decreases with further doping. Interestingly, except for the case of Ni(2+), the onset of the second absorption band shifts to a lower energy until a critical concentration and then shifts to a higher energy with further increasing the metal ion concentration, which is consistent with the evolution of electrical transport characteristics. Our results show that controllable metal ion doping is an effective method to tune the band gap energy of DNA-based nanostructures.

  15. Geopotential measurements with synchronously linked optical lattice clocks

    NASA Astrophysics Data System (ADS)

    Takano, Tetsushi; Takamoto, Masao; Ushijima, Ichiro; Ohmae, Noriaki; Akatsuka, Tomoya; Yamaguchi, Atsushi; Kuroishi, Yuki; Munekane, Hiroshi; Miyahara, Basara; Katori, Hidetoshi

    2016-10-01

    According to Einstein's theory of relativity, the passage of time changes in a gravitational field. On Earth, raising a clock by 1 cm increases its apparent tick rate by 1.1 parts in 1018, allowing chronometric levelling through comparison of optical clocks. Here, we demonstrate such geopotential measurements by determining the height difference of master and slave clocks separated by 15 km with an uncertainty of 5 cm. A subharmonic of the master clock laser is delivered through a telecom fibre to synchronously operate the distant clocks. Clocks operated under such phase coherence reject clock laser noise and facilitate proposals for linking clocks and interferometers. Taken over half a year, 11 measurements determine the fractional frequency difference between the two clocks to be 1,652.9(5.9) × 10-18, consistent with an independent measurement by levelling and gravimetry. Our system demonstrates a building block for an internet of clocks, which may constitute ‘quantum benchmarks’, serving as height references with dynamic responses.

  16. Systematic studies on the effect of linear lattice optics for space-charge limited beams

    NASA Astrophysics Data System (ADS)

    Fitterer, M.; Carli, C.; Molodozhentsev, A.; Müller, A.-S.

    2015-12-01

    The HL-LHC (High Luminosity LHC) project aims to an increase of the luminosity of the LHC by a factor of 10. In order to realize this ambitious goal, the LHC itself has to undergo a major upgrade accompanied by an extensive upgrade of the complete injector complex referred to as LHC injector upgrade (LIU). In the framework of the LIU project, a new rapid cycling synchrotron (RCS) as an alternative to the energy upgrade of the existing PS Booster has been proposed. Motivated by the optics studies conducted for this RCS, the more general question of the influence of the linear optics on the machine performance has been raised. In this paper, we want to investigate this question by comparing different lattices with the final aim of identifying lattice characteristics advantageous under strong space-charge effects.

  17. Selective distillation phenomenon in two-species Bose-Einstein condensates in open boundary optical lattices

    NASA Astrophysics Data System (ADS)

    Bai, Xiao-Dong; Zhang, Mei; Xiong, Jun; Yang, Guo-Jian; Deng, Fu-Guo

    2015-11-01

    We investigate the formation of discrete breathers (DBs) and the dynamics of the mixture of two-species Bose-Einstein condensates (BECs) in open boundary optical lattices using the discrete nonlinear Schrödinger equations. The results show that the coupling of intra- and interspecies interaction can lead to the existence of pure single-species DBs and symbiotic DBs (i.e., two-species DBs). Furthermore, we find that there is a selective distillation phenomenon in the dynamics of the mixture of two-species BECs. One can selectively distil one species from the mixture of two-species BECs and can even control dominant species fraction by adjusting the intra- and interspecies interaction in optical lattices. Our selective distillation mechanism may find potential application in quantum information storage and quantum information processing based on multi-species atoms.

  18. Fractional quantum Hall states of dipolar fermions in a strained optical lattice

    NASA Astrophysics Data System (ADS)

    Fujita, Hiroyuki; Nakagawa, Yuya O.; Ashida, Yuto; Furukawa, Shunsuke

    2016-10-01

    We study strongly correlated ground states of dipolar fermions in a honeycomb optical lattice with spatial variations in hopping amplitudes. Similar to strained graphene, such nonuniform hopping amplitudes produce valley-dependent pseudomagnetic fields for fermions near the two Dirac points, resulting in the formation of Landau levels. The dipole moments aligned perpendicular to the honeycomb plane yield a long-range repulsive interaction. By exact diagonalization in the zeroth-Landau-level basis, we show that this repulsive interaction stabilizes a variety of valley-polarized fractional quantum Hall states such as Laughlin and composite-fermion states. The present system thus offers an intriguing platform for emulating fractional quantum Hall physics in a static optical lattice. We calculate the energy gaps above these incompressible states and discuss the temperature scales required for their experimental realization.

  19. Disorder-induced heating of ultracold neutral plasmas created from atoms in partially filled optical lattices

    NASA Astrophysics Data System (ADS)

    Murphy, D.; Sparkes, B. M.

    2016-08-01

    We quantify the disorder-induced heating (DIH) of ultracold neutral plasmas (UCNPs) created from cold atoms in optical lattices with partial filling fractions, using a conservation of energy model involving the spatial correlations of the initial state and the equation of state in thermal equilibrium for a one-component plasma. We show, for experimentally achievable filling fractions, that the ionic Coulomb coupling parameter could be increased to a degree comparable to other proposed DIH-mitigation schemes. Molecular dynamics simulations were performed with compensation for finite-size and periodic boundary effects, which agree with calculations using the model. Reduction of DIH using optical lattices will allow for the study of strongly coupled plasma physics using low-density, low-temperature, laboratory-based plasmas, and lead to improved brightness in UCNP-based cold electron and ion beams, where DIH is otherwise a fundamental limitation to beam focal sizes and diffraction imaging capability.

  20. Dzyaloshinskii-Moriya Interaction and Spiral Order in Spin-orbit Coupled Optical Lattices

    PubMed Central

    Gong, Ming; Qian, Yinyin; Yan, Mi; Scarola, V. W.; Zhang, Chuanwei

    2015-01-01

    We show that the recent experimental realization of spin-orbit coupling in ultracold atomic gases can be used to study different types of spin spiral order and resulting multiferroic effects. Spin-orbit coupling in optical lattices can give rise to the Dzyaloshinskii-Moriya (DM) spin interaction which is essential for spin spiral order. By taking into account spin-orbit coupling and an external Zeeman field, we derive an effective spin model in the Mott insulator regime at half filling and demonstrate that the DM interaction in optical lattices can be made extremely strong with realistic experimental parameters. The rich finite temperature phase diagrams of the effective spin models for fermions and bosons are obtained via classical Monte Carlo simulations. PMID:26014458

  1. Selective distillation phenomenon in two-species Bose-Einstein condensates in open boundary optical lattices

    PubMed Central

    Bai, Xiao-Dong; Zhang, Mei; Xiong, Jun; Yang, Guo-Jian; Deng, Fu-Guo

    2015-01-01

    We investigate the formation of discrete breathers (DBs) and the dynamics of the mixture of two-species Bose-Einstein condensates (BECs) in open boundary optical lattices using the discrete nonlinear Schrödinger equations. The results show that the coupling of intra- and interspecies interaction can lead to the existence of pure single-species DBs and symbiotic DBs (i.e., two-species DBs). Furthermore, we find that there is a selective distillation phenomenon in the dynamics of the mixture of two-species BECs. One can selectively distil one species from the mixture of two-species BECs and can even control dominant species fraction by adjusting the intra- and interspecies interaction in optical lattices. Our selective distillation mechanism may find potential application in quantum information storage and quantum information processing based on multi-species atoms. PMID:26597592

  2. Controlling and detecting spin correlations of ultracold atoms in optical lattices.

    PubMed

    Trotzky, Stefan; Chen, Yu-Ao; Schnorrberger, Ute; Cheinet, Patrick; Bloch, Immanuel

    2010-12-31

    We report on the controlled creation of a valence bond state of delocalized effective-spin singlet and triplet dimers by means of a bichromatic optical superlattice. We demonstrate a coherent coupling between the singlet and triplet states and show how the superlattice can be employed to measure the singlet-fraction employing a spin-blockade effect. Our method provides a reliable way to detect and control nearest-neighbor spin correlations in many-body systems of ultracold atoms. Being able to measure these correlations is an important ingredient in studying quantum magnetism in optical lattices. We furthermore employ a SWAP operation between atoms which are part of different triplets, thus effectively increasing their bond-length. Such a SWAP operation provides an important step towards the massively parallel creation of a multiparticle entangled state in the lattice.

  3. Topological states in a ladder-like optical lattice containing ultracold atoms in higher orbital bands

    NASA Astrophysics Data System (ADS)

    Li, Xiaopeng; Zhao, Erhai; Vincent Liu, W.

    2013-02-01

    Topological insulators are classified according to their symmetries. Discovery of them in electronic solids is thus restricted by orbital and crystalline symmetries available in nature. Synthetic quantum matter, such as the recent double-well optical lattices loaded with s and p orbital ultracold atoms, can exploit symmetries and interaction beyond natural conditions. Here we unveil a topological phase of interacting fermionic atoms on a two-leg ladder derived from the above experimental optical lattice by dimension reduction. The topological band structure originates from the staggered phases of sp orbital tunnelling, requiring neither spin-orbit coupling nor other known mechanisms like p-wave pairing, artificial gauge field or rotation. Upon crossing over to two-dimensional coupled ladders, the edge modes from individual ladder form a parity-protected flat band at zero energy. Experimental signatures are found in density correlations and phase transitions to trivial band and Mott insulators.

  4. Artificial topological models based on a one-dimensional spin-dependent optical lattice

    NASA Astrophysics Data System (ADS)

    Zheng, Zhen; Pu, Han; Zou, Xubo; Guo, Guangcan

    2017-01-01

    Topological matter is a popular topic in both condensed matter and cold-atom research. In the past decades, a variety of models have been identified with fascinating topological features. Some, but not all, of the models can be found in materials. As a fully controllable system, cold atoms trapped in optical lattices provide an ideal platform to simulate and realize these topological models. Here we present a proposal for synthesizing topological models in cold atoms based on a one-dimensional spin-dependent optical lattice potential. In our system, features such as staggered tunneling, staggered Zeeman field, nearest-neighbor interaction, beyond-near-neighbor tunneling, etc. can be readily realized. They underlie the emergence of various topological phases. Our proposal can be realized with current technology and hence has potential applications in quantum simulation of topological matter.

  5. Surface-modified Wannier-Stark states in a one-dimensional optical lattice

    NASA Astrophysics Data System (ADS)

    Maury, A.; Donaire, M.; Gorza, M.-P.; Lambrecht, A.; Guérout, R.

    2016-11-01

    We study the energy spectrum of atoms trapped in a vertical one-dimensional optical lattice in close proximity to a reflective surface. We propose an effective model to describe the interaction between the atoms and the surface at any distance. Our model includes the long-range Casimir-Polder potential together with a short-range Lennard-Jones potential, which are considered nonperturbatively with respect to the optical lattice potential. We find an intricate energy spectrum which contains a pair of loosely bound states localized close to the surface in addition to a surface-modified Wannier-Stark ladder at long distances. Atomic interferometry involving those loosely bound atom-surface states is proposed to probe the adsorption dynamics of atoms on mirrors.

  6. Wannier-Stark electro-optical effect, quasi-guided and photonic modes in 2D macroporous silicon structures with SiO2 coatings

    NASA Astrophysics Data System (ADS)

    Karachevtseva, L.; Goltviansky, Yu.; Sapelnikova, O.; Lytvynenko, O.; Stronska, O.; Bo, Wang; Kartel, M.

    2016-12-01

    Opportunities to enhance the properties of structured surfaces were demonstrated on 2D macroporous silicon structures with SiO2 coatings. We investigated the IR light absorption oscillations in macroporous silicon structures with SiO2 coatings 0-800 nm thick. The Wannier-Stark electro-optical effect due to strong electric field on Si-SiO2boundary and an additional electric field of quasi-guided optical modes were taken into account. The photonic modes and band gaps were also considered as peculiarities in absorbance spectra of macroporous silicon structures with a thick SiO2 coating. The photonic modes do not coincide with the quasi-guided modes in the silicon matrix and do not appear in absorption spectra of 2D macroporous silicon structures with surface nanocrystals.

  7. Nonlinear Sensing With Collective States of Ultracold Atoms in Optical Lattices

    DTIC Science & Technology

    2015-04-02

    decimation algorithm , a method that takes into account quantum correlations. B.1. In collaboration with D. Blume and X.Y. Yin at Washington State...Office P.O. Box 12211 Research Triangle Park, NC 27709-2211 Nonlinear quantum sensing, quantum metrology, ultracold atoms, optical lattices REPORT...with applications to interaction-based quantum metrology, Physical Review A, (10 2014): 0. doi: 10.1103/PhysRevA.90.041602 Khan W Mahmud, Lei Jiang

  8. Fiber-optic signal processor with applications to matrix-vector multiplication and lattice filtering.

    PubMed

    Tur, M; Goodman, J W; Moslehi, B; Bowers, J E; Shaw, H J

    1982-09-01

    A new fiber-optic signal processor is proposed to implement systolic matrix-vector multipliers and lattice filters. 10(9) multiplications/sec can be achieved with currently available components for matrix-vector multiplications that involve Toeplitz matrices. A 2 x 2 (Toeplitz) matrix-vector multiplier has been experimentally demonstrated using single-mode fibers and directional couplers. The filtering characteristics of the device are also discussed.

  9. Investigation of Density Perturbations in Molecular Nitrogen Formed by Pulsed Optical Lattices

    DTIC Science & Technology

    2011-06-01

    configuration with the appropriate gas properties. During the last 0.02% of the simulation, cells were sampled to give flow field values. With...from the lattice induced gas gratings was measured as a function of ambient pressure and pump energy. The results obtained from the numerical...an Optical Cavity,” Proceedings of the 26th International Symposium on Rarefied Gas Dynamics, ed. T. Abe, (AIP, New York, 2009), pp. 533-538 8

  10. The Bose-Hubbard model: from Josephson junction arrays to optical lattices

    NASA Astrophysics Data System (ADS)

    Bruder, C.; Fazio, R.; Schön, G.

    2005-09-01

    [Dedicated to Bernhard Mühlschlegel on the occasion ofhis 80th birthday]The Bose-Hubbard model is a paradigm for the study of strongly correlated bosonic systems. We review some of its properties with emphasis on the implications on quantum phase transitions of Josephson junction arrays and quantum dynamics of topological excitations as well as the properties of ultra-cold atoms in optical lattices.

  11. Optical gain in Si/SiO2 lattice: Experimental evidence with nanosecond pulses

    NASA Astrophysics Data System (ADS)

    Khriachtchev, Leonid; Räsänen, Markku; Novikov, Sergei; Sinkkonen, Juha

    2001-08-01

    Experimental evidence of population inversion and amplified spontaneous emission was found for Si nanocrystallites embedded in SiO2 surrounding under pumping with 5 ns light pulses at 380, 400, and 500 nm. As an important property, our experiments show a short lifetime of the population inversion allowing a generation of short (a few nanosecond) amplified light pulses in the Si/SiO2 lattice. The estimate for optical gain in the present samples is 6 cm-1 at 720 nm.

  12. Quantum Computation with Neutral Atoms at Addressable Optical Lattice Sites and Atoms in Confined Geometries

    DTIC Science & Technology

    2014-10-13

    SECURITY CLASSIFICATION OF: We have performed a set of experiments using arrays of 1D Bose gases in various configurations. Uncoupled 1D gases have been...used to study the limits of statistical mechanics near integrable points. We have shown that nearly integrable gases thermalize at an even slower...NAME(S) AND ADDRESS (ES) U.S. Army Research Office P.O. Box 12211 Research Triangle Park, NC 27709-2211 ultracold atoms, optical lattices, 1D gases

  13. Nonlinear patterns in Bose-Einstein condensates in dissipative optical lattices

    SciTech Connect

    Bludov, Yu. V.; Konotop, V. V.

    2010-01-15

    It is shown that the one-dimensional nonlinear Schroedinger equation with a dissipative periodic potential, nonlinear losses, and a linear pump allow for the existence of stable nonlinear Bloch states which are attractors. The model describes a Bose-Einstein condensate with inelastic two- and three-body interactions loaded in an optical lattice with losses due to inelastic interactions of the atoms with photons.

  14. Higher-order effects on uncertainties of clocks of Mg atoms in an optical lattice

    NASA Astrophysics Data System (ADS)

    Ovsiannikov, V. D.; Marmo, S. I.; Mokhnenko, S. N.; Palchikov, V. G.

    2017-01-01

    Multipole, nonlinear and anharmonic effects on the optical-lattice-based clocks of Mg atoms are evaluated theoretically. Dipole polarizabilities, hyperpolarizabilities and multipolar polarizabilities for Mg atoms are calculated in the single-electron approximation with the use of analytical presentations for the wave and Green’s functions in the modified model-potential approach. For comparison, the data are also given for atoms of the group IIb elements (Zn, Cd, Hg).

  15. Visibility of cold atomic gases in optical lattices for finite temperatures

    SciTech Connect

    Hoffmann, Alexander; Pelster, Axel

    2009-05-15

    In nearly all experiments with ultracold atoms time-of-flight pictures are the only data available. In this paper we present an analytical strong-coupling calculation for those time-of-flight pictures of bosons in a three-dimensional optical lattice in the Mott phase. This allows us to determine the visibility, which quantifies the contrast of peaks in the time-of-flight pictures, and we suggest how to use it as a thermometer.

  16. Delocalizing transition in one-dimensional condensates in optical lattices due to inhomogeneous interactions

    SciTech Connect

    Bludov, Yu. V.; Brazhnyi, V. A.; Konotop, V. V.

    2007-08-15

    It is shown that inhomogeneous nonlinear interactions in a Bose-Einstein condensate loaded in an optical lattice can result in a delocalizing transition in one dimension, which sharply contrasts to the known behavior of discrete and periodic systems with homogeneous nonlinearity. The transition can be originated either by decreasing the amplitude of the linear periodic potential or by the change of the mean value of the periodic nonlinearity. The dynamics of the delocalizing transition is studied.

  17. Smart time-pulse coding photoconverters as basic components 2D-array logic devices for advanced neural networks and optical computers

    NASA Astrophysics Data System (ADS)

    Krasilenko, Vladimir G.; Nikolsky, Alexander I.; Lazarev, Alexander A.; Michalnichenko, Nikolay N.

    2004-04-01

    The article deals with a conception of building arithmetic-logic devices (ALD) with a 2D-structure and optical 2D-array inputs-outputs as advanced high-productivity parallel basic operational training modules for realization of basic operation of continuous, neuro-fuzzy, multilevel, threshold and others logics and vector-matrix, vector-tensor procedures in neural networks, that consists in use of time-pulse coding (TPC) architecture and 2D-array smart optoelectronic pulse-width (or pulse-phase) modulators (PWM or PPM) for transformation of input pictures. The input grayscale image is transformed into a group of corresponding short optical pulses or time positions of optical two-level signal swing. We consider optoelectronic implementations of universal (quasi-universal) picture element of two-valued ALD, multi-valued ALD, analog-to-digital converters, multilevel threshold discriminators and we show that 2D-array time-pulse photoconverters are the base elements for these devices. We show simulation results of the time-pulse photoconverters as base components. Considered devices have technical parameters: input optical signals power is 200nW_200μW (if photodiode responsivity is 0.5A/W), conversion time is from tens of microseconds to a millisecond, supply voltage is 1.5_15V, consumption power is from tens of microwatts to a milliwatt, conversion nonlinearity is less than 1%. One cell consists of 2-3 photodiodes and about ten CMOS transistors. This simplicity of the cells allows to carry out their integration in arrays of 32x32, 64x64 elements and more.

  18. Analysis of the blackbody-radiation shift in an ytterbium optical lattice clock

    NASA Astrophysics Data System (ADS)

    Xu, Yi-Lin; Xu, Xin-Ye

    2016-10-01

    We accurately evaluate the blackbody-radiation shift in a 171Yb optical lattice clock by utilizing temperature measurement and numerical simulation. In this work. three main radiation sources are considered for the blackbody-radiation shift, including the heated atomic oven, the warm vacuum chamber, and the room-temperature vacuum windows. The temperatures on the outer surface of the vacuum chamber are measured during the clock operation period by utilizing seven calibrated temperature sensors. Then we infer the temperature distribution inside the vacuum chamber by numerical simulation according to the measured temperatures. Furthermore, we simulate the temperature variation around the cold atoms while the environmental temperature is fluctuating. Finally, we obtain that the total blackbody-radiation shift is -1.289(7) Hz with an uncertainty of 1.25 × 10-17 for our 171Yb optical lattice clock. The presented method is quite suitable for accurately evaluating the blackbody-radiation shift of the optical lattice clock in the case of lacking the sensors inside the vacuum chamber. Project supported by the National Key Basic Research and Development Program of China (Grant No. 2012CB821302), the National Natural Science Foundation of China (Grant No. 11134003), the National High Technology Research and Development Program of China (Grant No. 2014AA123401), and the Shanghai Excellent Academic Leaders Program of China (Grant No. 12XD1402400).

  19. Exploring spin-orbit coupling in a non-degenerate optical lattice clock

    NASA Astrophysics Data System (ADS)

    Wall, Michael L.; Koller, Andrew P.; Li, Shuming; Rey, Ana Maria

    2015-05-01

    Optical lattice clocks have progressed in recent years to become not only precise timekeepers, but also sensitive probes of many-body physics. We consider a 1D optical lattice clock in which the wavelength of the laser that interrogates the clock transition is comparable to the optical lattice spacing. This light-matter coupling imprints a spatially dependent phase on the atomic internal state superposition, and this phase can be interpreted as a spin-orbit coupling. We show that this spin-orbit coupling manifests itself in Ramsey spectroscopy as an s-wave density shift in otherwise identically prepared fermions, even at temperatures significantly larger than the tunneling. Further, we show that Rabi spectroscopy can be mapped to a Hofstadter model on a two-leg ladder with chiral eigenstates. Using a modified Rabi procedure, we show how to extract momentum-resolved signatures of chirality solely by spectroscopic means. The effects of finite temperature, gaussian transverse confinement, and non-separability between transverse and axial degrees of freedom are discussed. This work has been financially supported by JILA-NSF-PFC-1125844, NSF-PIF-1211914, ARO, AFOSR, AFOSR-MURI, NDSEG, and NRC.

  20. Quantum phases from competing short- and long-range interactions in an optical lattice.

    PubMed

    Landig, Renate; Hruby, Lorenz; Dogra, Nishant; Landini, Manuele; Mottl, Rafael; Donner, Tobias; Esslinger, Tilman

    2016-04-28

    Insights into complex phenomena in quantum matter can be gained from simulation experiments with ultracold atoms, especially in cases where theoretical characterization is challenging. However, these experiments are mostly limited to short-range collisional interactions; recently observed perturbative effects of long-range interactions were too weak to reach new quantum phases. Here we experimentally realize a bosonic lattice model with competing short- and long-range interactions, and observe the appearance of four distinct quantum phases--a superfluid, a supersolid, a Mott insulator and a charge density wave. Our system is based on an atomic quantum gas trapped in an optical lattice inside a high-finesse optical cavity. The strength of the short-range on-site interactions is controlled by means of the optical lattice depth. The long (infinite)-range interaction potential is mediated by a vacuum mode of the cavity and is independently controlled by tuning the cavity resonance. When probing the phase transition between the Mott insulator and the charge density wave in real time, we observed a behaviour characteristic of a first-order phase transition. Our measurements have accessed a regime for quantum simulation of many-body systems where the physics is determined by the intricate competition between two different types of interactions and the zero point motion of the particles.

  1. Antiresonant reflection and inhibited coupling in hollow-core square lattice optical fibres.

    PubMed

    Argyros, Alexander; Leon-Saval, Sergio G; Pla, Jarryd; Docherty, Andrew

    2008-04-14

    We propose a guidance mechanism in hollow-core optical fibres dominated by antiresonant reflection from struts of solid material in the cladding. Resonances with these struts determine the high loss bands of the fibres, and vector effects become important in determining the width of these bands through the non-degeneracy of the TE and TM polarised strut modes near cut-off. Away from resonances the light is confined through the inhibited coupling mechanism. This is demonstrated in a square lattice hollow-core microstructured polymer optical fibre.

  2. Bloch oscillations of cold atoms in two-dimensional optical lattices

    SciTech Connect

    Kolovsky, A. R.; Korsch, H. J.

    2003-06-01

    Bloch oscillations of cold atoms in two-dimensional optical lattices are studied. The cases of separable and nonseparable potentials are compared by simulating the wave-packet dynamics. For these two classes of optical potential, the Bloch oscillations were found to be qualitatively the same in the case of a weak static field but fundamentally different in the case of a strong field. In addition, the dynamics of the atoms in a double-period potential (which can easily be realized in two dimensions) is studied for the regime of a weak static field.

  3. Inner-shell magnetic dipole transition in Tm atoms: A candidate for optical lattice clocks

    NASA Astrophysics Data System (ADS)

    Sukachev, D.; Fedorov, S.; Tolstikhina, I.; Tregubov, D.; Kalganova, E.; Vishnyakova, G.; Golovizin, A.; Kolachevsky, N.; Khabarova, K.; Sorokin, V.

    2016-08-01

    We consider a narrow magneto-dipole transition in the 169Tm atom at the wavelength of 1.14 μ m as a candidate for a two-dimensional-optical lattice clock. Calculating dynamic polarizabilities of the two clock levels [Xe] 4 f136 s2(J =7 /2 ) and [Xe] 4 f136 s2(J =5 /2 ) in the spectral range from 250 to 1200 nm, we find a "magic" wavelength for the optical lattice at 807 nm. Frequency shifts due to black-body radiation (BBR), the van der Waals interaction, the magnetic dipole-dipole interaction, and other effects which can perturb the transition frequency are calculated. The transition at 1.14 μ m demonstrates low sensitivity to the BBR shift corresponding to 8 ×10-17 in fractional units at room temperature which makes it an interesting candidate for high-performance optical clocks. The total estimated frequency uncertainty is less than 5 ×10-18 in fractional units. By direct excitation of the 1.14 μ m transition in Tm atoms loaded into an optical dipole trap, we set the lower limit for the lifetime of the upper clock level [Xe] 4 f136 s2(J =5 /2 ) of 112 ms which corresponds to a natural spectral linewidth narrower than 1.4 Hz. The polarizability of the Tm ground state was measured by the excitation of parametric resonances in the optical dipole trap at 532 nm.

  4. Label-free optical detection of C-reactive protein by nanoimprint lithography-based 2D-photonic crystal film.

    PubMed

    Endo, Tatsuro; Kajita, Hiroshi; Kawaguchi, Yukio; Kosaka, Terumasa; Himi, Toshiyuki

    2016-06-01

    The development of high-sensitive, and cost-effective novel biosensors have been strongly desired for future medical diagnostics. To develop novel biosensor, the authors focused on the specific optical characteristics of photonic crystal. In this study, a label-free optical biosensor, polymer-based two-dimensional photonic crystal (2D-PhC) film fabricated using nanoimprint lithography (NIL), was developed for detection of C-reactive protein (CRP) in human serum. The nano-hole array constructed NIL-based 2D-PhC (hole diameter: 230 nm, distance: 230, depth: 200 nm) was fabricated on a cyclo-olefin polymer (COP) film (100 µm) using thermal NIL and required surface modifications to reduce nonspecific adsorption of target proteins. Antigen-antibody reactions on the NIL-based 2D-PhC caused changes to the surrounding refractive index, which was monitored as reflection spectrum changes in the visible region. By using surface modified 2D-PhC, the calculated detection limit for CRP was 12.24 pg/mL at an extremely short reaction time (5 min) without the need for additional labeling procedures and secondary antibody. Furthermore, using the dual-functional random copolymer, CRP could be detected in a pooled blood serum diluted 100× with dramatic reduction of nonspecific adsorption. From these results, the NIL-based 2D-PhC film has great potential for development of an on-site, high-sensitivity, cost-effective, label-free biosensor for medical diagnostics applications.

  5. 2D and 3D optical diagnostic techniques applied to Madonna dei Fusi by Leonardo da Vinci

    NASA Astrophysics Data System (ADS)

    Fontana, R.; Gambino, M. C.; Greco, M.; Marras, L.; Materazzi, M.; Pampaloni, E.; Pelagotti, A.; Pezzati, L.; Poggi, P.; Sanapo, C.

    2005-06-01

    3D measurement and modelling have been traditionally applied to statues, buildings, archeological sites or similar large structures, but rarely to paintings. Recently, however, 3D measurements have been performed successfully also on easel paintings, allowing to detect and document the painting's surface. We used 3D models to integrate the results of various 2D imaging techniques on a common reference frame. These applications show how the 3D shape information, complemented with 2D colour maps as well as with other types of sensory data, provide the most interesting information. The 3D data acquisition was carried out by means of two devices: a high-resolution laser micro-profilometer, composed of a commercial distance meter mounted on a scanning device, and a laser-line scanner. The 2D data acquisitions were carried out using a scanning device for simultaneous RGB colour imaging and IR reflectography, and a UV fluorescence multispectral image acquisition system. We present here the results of the techniques described, applied to the analysis of an important painting of the Italian Reinassance: `Madonna dei Fusi', attributed to Leonardo da Vinci.

  6. Creating topological interfaces and detecting chiral edge modes in a two-dimensional optical lattice

    NASA Astrophysics Data System (ADS)

    Goldman, N.; Jotzu, G.; Messer, M.; Görg, F.; Desbuquois, R.; Esslinger, T.

    2016-10-01

    We propose a general scheme to create chiral topological edge modes within the bulk of two-dimensional engineered quantum systems. Our method is based on the implementation of topological interfaces, designed within the bulk of the system, where topologically protected edge modes localize and freely propagate in a unidirectional manner. This scheme is illustrated through an optical-lattice realization of the Haldane model for cold atoms [G. Jotzu et al., Nature (London) 515, 237 (2014), 10.1038/nature13915], where an additional spatially varying lattice potential induces distinct topological phases in separated regions of space. We present two realistic experimental configurations, which lead to linear and radial-symmetric topological interfaces, which both allow one to significantly reduce the effects of external confinement on topological edge properties. Furthermore, the versatility of our method opens the possibility of tuning the position, the localization length, and the chirality of the edge modes, through simple adjustments of the lattice potentials. In order to demonstrate the unique detectability offered by engineered interfaces, we numerically investigate the time evolution of wave packets, indicating how topological transport unambiguously manifests itself within the lattice. Finally, we analyze the effects of disorder on the dynamics of chiral and nonchiral states present in the system. Interestingly, engineered disorder is shown to provide a powerful tool for the detection of topological edge modes in cold-atom setups.

  7. Optical induction of Bessel-like lattices in methyl-red doped liquid crystal cells

    NASA Astrophysics Data System (ADS)

    Mantashyan, Paytsar; Drampyan, Rafael; Beeckman, Jeroen; Willekens, Oliver; Neyts, Kristiaan

    2015-03-01

    The optical induction of annular photonic lattices by a traveling Bessel beam has been investigated in Methyl-red (MR) doped nematic liquid crystal (LC). Non-diffracting Bessel beams were formed by an axicon. The induced Bessel-like lattice had a ~15 μm period in the radial direction. The lattice was tested by measuring the forward diffracted power of the recording Bessel beam. The dependency on the angle between the polarization of the laser beam and the director of the LC and on the axial position of the LC cell had been investigated. A diffraction efficiency of 14% had been obtained. Investigations have been performed for different MR dye doping concentrations. An erasure time of the lattice of 60 s has been determined by a 532 nm probe Gaussian beam of 2 mW in a LC cell with MR dye concentration of 1.15 wt%. The induced periodically varying refractive index in the LC medium is analogous to microstructured fibers and allows the study of light localization and soliton behavior in highly nonlinear waveguide arrays.

  8. Theoretical description of two ultracold atoms in finite three-dimensional optical lattices using realistic interatomic interaction potentials

    SciTech Connect

    Grishkevich, Sergey; Sala, Simon; Saenz, Alejandro

    2011-12-15

    A theoretical approach is described for an exact numerical treatment of a pair of ultracold atoms interacting via a central potential and that are trapped in a finite three-dimensional optical lattice. The coupling of center-of-mass and relative-motion coordinates is treated using an exact diagonalization (configuration-interaction) approach. The orthorhombic symmetry of an optical lattice with three different but orthogonal lattice vectors is explicitly considered as is the fermionic or bosonic symmetry in the case of indistinguishable particles.

  9. Thermally-induced single-crystal-to-single-crystal transformations from a 2D two-fold interpenetrating square lattice layer to a 3D four-fold interpenetrating diamond framework and its application in dye-sensitized solar cells.

    PubMed

    Gao, Song; Fan, Rui Qing; Wang, Xin Ming; Wei, Li Guo; Song, Yang; Du, Xi; Xing, Kai; Wang, Ping; Yang, Yu Lin

    2016-07-28

    In this work, a rare 2D → 3D single-crystal-to-single-crystal transformation (SCSC) is observed in metal-organic coordination complexes, which is triggered by thermal treatment. The 2D two-fold interpenetrating square lattice layer [Cd(IBA)2]n (1) is irreversibly converted into a 3D four-fold interpenetrating diamond framework {[Cd(IBA)2(H2O)]·2.5H2O}n (2) (HIBA = 4-(1H-imidazol-1-yl)benzoic acid). Consideration is given to these two complexes with different interpenetrating structures and dimensionality, and their influence on photovoltaic properties are studied. Encouraged by the UV-visible absorption and HOMO-LUMO energy states matched for sensitizing TiO2, the two complexes are employed in combination with N719 in dye-sensitized solar cells (DSSCs) to compensate absorption in the ultraviolet and blue-violet region, offset competitive visible light absorption of I3(-) and reducing charge the recombination of injected electrons. After co-sensitization with 1 and 2, the device co-sensitized by 1/N719 and 2/N719 to yield overall efficiencies of 7.82% and 8.39%, which are 19.94% and 28.68% higher than that of the device sensitized only by N719 (6.52%). Consequently, high dimensional interpenetrating complexes could serve as excellent co-sensitizers and have application in DSSCs.

  10. Coherent driving and freezing of bosonic matter wave in an optical Lieb lattice

    PubMed Central

    Taie, Shintaro; Ozawa, Hideki; Ichinose, Tomohiro; Nishio, Takuei; Nakajima, Shuta; Takahashi, Yoshiro

    2015-01-01

    Although kinetic energy of a massive particle generally has quadratic dependence on its momentum, a flat, dispersionless energy band is realized in crystals with specific lattice structures. Such macroscopic degeneracy causes the emergence of localized eigenstates and has been a key concept in the context of itinerant ferromagnetism. We report the realization of a “Lieb lattice” configuration with an optical lattice, which has a flat energy band as the first excited state. Our optical lattice potential has various degrees of freedom in its manipulation, which enables coherent transfer of a Bose-Einstein condensate into the flat band. In addition to measuring lifetime of the flat band population for different tight-binding parameters, we investigate the inter-sublattice dynamics of the system by projecting the sublattice population onto the band population. This measurement clearly shows the formation of the localized state with the specific sublattice decoupled in the flat band, and even detects the presence of flat-band breaking perturbations, resulting in the delocalization. Our results will open up the possibilities of exploring the physics of flat bands with a highly controllable quantum system. PMID:26665167

  11. A technique for individual atom delivery into a crossed vortex bottle beam trap using a dynamic 1D optical lattice

    NASA Astrophysics Data System (ADS)

    Dinardo, Brad A.; Anderson, Dana Z.

    2016-12-01

    We describe a system for loading a single atom from a reservoir into a blue-detuned crossed vortex bottle beam trap using a dynamic 1D optical lattice. The lattice beams are frequency chirped using acousto-optic modulators, which causes the lattice to move along its axial direction and behave like an optical conveyor belt. A stationary lattice is initially loaded with approximately 6000 atoms from a reservoir, and the conveyor belt transports them 1.1 mm from the reservoir to a bottle beam trap, where a single atom is loaded via light-assisted collisions. Photon counting data confirm that an atom can be delivered and loaded into the bottle beam trap 13.1% of the time.

  12. Roton-maxon excitation spectrum of Bose condensates in a shaken optical lattice

    NASA Astrophysics Data System (ADS)

    Ha, Li-Chung; Clark, Logan W.; Parker, Colin V.; Xu, Chen-Yu; Chin, Cheng

    2015-05-01

    We present a resonant lattice shaking technique for engineering the dispersion of a cesium Bose condensate. Through phase modulating an optical lattice at a frequency near the band splitting, the dispersion of the condensate can evolve from quadratic to quartic and finally into a double-well structure. We observe effective ferromagnetism in the double-well regime, and atoms form domains within one well in momentum space. We study the elementary excitations of this system by implementing projection-based Bragg spectroscopy and find a roton-maxon feature in the excitation spectrum in agreement with a Bogoliubov calculation. Consistent with Landau's prediction, we observe a suppressed superfluid critical velocity due to the existence of the roton. We will introduce more precise characterizations of the dispersion in an effort to pinpoint the critical point at which the dispersion is purely quartic, and study the dynamics of particles in that case. This work is supported by NSF, ARO and Chicago MRSEC.

  13. Entanglement and the ground state of fermions trapped in optical lattices

    NASA Astrophysics Data System (ADS)

    Silva-Valencia, J.; Franco, R.; Figueira, M. S.

    2009-10-01

    Using White's density matrix renormalization group technique we calculate entanglement of fermions confined in a one-dimensional trap with an underlying lattice. The system is modeled using a repulsive Hubbard model plus a quadratic potential. Due to the confining potential, metallic and Mott-insulating domains coexist in the system. The entanglement is measured by the on-site entropy and the block entropy, and these quantities are calculated as a function of the local repulsion and the curvature of the trap. We found that local entropy decreases with the curvature for a fixed on-site repulsion. As a function of the on-site repulsion the local entropy first increases and then diminishes. Our most important goal is to show that local and block entropy are useful tools for characterization of the ground states of fermions trapped in optical lattices.

  14. Frequency Ratio of (199)Hg and (87)Sr Optical Lattice Clocks beyond the SI Limit.

    PubMed

    Yamanaka, Kazuhiro; Ohmae, Noriaki; Ushijima, Ichiro; Takamoto, Masao; Katori, Hidetoshi

    2015-06-12

    We report on a frequency ratio measurement of a (199)Hg-based optical lattice clock referencing a (87)Sr-based clock. Evaluations of lattice light shift, including atomic-motion-dependent shift, enable us to achieve a total systematic uncertainty of 7.2×10(-17) for the Hg clock. The frequency ratio is measured to be νHg/νSr=2.629 314 209 898 909 60(22) with a fractional uncertainty of 8.4×10(-17), which is smaller than the uncertainty of the realization of the International System of Units (SI) second, i.e., the SI limit.

  15. Shaken not stirred: creating exotic angular momentum states by shaking an optical lattice

    NASA Astrophysics Data System (ADS)

    Kiely, Anthony; Benseny, Albert; Busch, Thomas; Ruschhaupt, Andreas

    2016-11-01

    We propose a method to create higher orbital states of ultracold atoms in the Mott regime of an optical lattice. This is done by periodically modulating the position of the trap minima (known as shaking) and controlling the interference term of the lasers creating the lattice. These methods are combined with techniques of shortcuts to adiabaticity. As an example of this, we show specifically how to create an anti-ferromagnetic type ordering of angular momentum states of atoms. The specific pulse sequences are designed using Lewis-Riesenfeld invariants and a four-level model for each well. The results are compared with numerical simulations of the full Schrödinger equation.

  16. Observation of Nonlinear Looped Band Structure of Bose-Einstein condensates in an optical lattice

    NASA Astrophysics Data System (ADS)

    Goldschmidt, Elizabeth; Koller, Silvio; Brown, Roger; Wyllie, Robert; Wilson, Ryan; Porto, Trey

    2016-05-01

    We study experimentally the stability of excited, interacting states of bosons in a double-well optical lattice in regimes where the nonlinear interactions are expected to induce ``swallow-tail'' looped band structure. By carefully preparing different initial coherent states and observing their subsequent decay, we observe distinct decay rates, which provide direct evidence for multi-valued band structure. The double well lattice both stabilizes the looped band structure and allows for dynamic preparation of different initial states, including states within the loop structure. We confirm our state preparation procedure with dynamic Gross-Pitaevskii calculations. The excited loop states are found to be more stable than dynamically unstable ground states, but decay faster than expected based on a mean-field stability calculation, indicating the importance of correlations beyond a mean-field description. Now at Georgia Tech Research Institute.

  17. Topological Properties of Ultracold Bosons in One-Dimensional Quasiperiodic Optical Lattice

    NASA Astrophysics Data System (ADS)

    Matsuda, Fuyuki; Tezuka, Masaki; Kawakami, Norio

    2014-08-01

    We analyze the topological properties of the one-dimensional Bose-Hubbard model with a quasiperiodic superlattice potential. This system can be realized in interacting ultracold bosons in an optical lattice in the presence of an incommensurate superlattice potential. We first analyze the quasiperiodic superlattice formed by the cosine function, which we call the Harper-like Bose-Hubbard model. We compute the Chern number and observe gap-closing behavior as the interaction strength U is changed. Also, we discuss the bulk-edge correspondence in our system. Furthermore, we explore the phase diagram as a function of U and a continuous deformation parameter β between the Harper-like model and another important quasiperiodic lattice, the Fibonacci model. We numerically confirm that the incommensurate charge density wave (ICDW) phase is topologically nontrivial and that it is topologically equivalent in the whole ICDW region.

  18. Gap solitons in the nonlinear fractional Schrödinger equation with an optical lattice.

    PubMed

    Huang, Changming; Dong, Liangwei

    2016-12-15

    We predict the existence of gap solitons in the nonlinear fractional Schrödinger equation (NLFSE) with an imprinted optically harmonic lattice. Symmetric/antisymmetric nonlinear localized modes bifurcate from the lower/upper edge of the first/second band in defocusing/focusing Kerr media. A unique feature we revealed is that, in focusing Kerr media, stable solitons appear in the finite bandgaps with the decrease of the Lévy index, which is in sharp contrast to the standard NLSE with a focusing nonlinearity. Nonlinear bound states composed by in-phase and out-of-phase soliton units supported by the NLFSE are also uncovered. Our work may pave the way for the study of spatial lattice solitons in fractional dimensions.

  19. Beam dynamics in disordered P T -symmetric optical lattices based on eigenstate analyses

    NASA Astrophysics Data System (ADS)

    Yao, Xiankun; Liu, Xueming

    2017-03-01

    Wave functions will experience a localization process when evolving in disordered lattices. Here, we have demonstrated the effects of disordered P T -symmetric potentials on wave-function characteristics in optics based on eigenstate analyses. In weak-disorder cases, by using the tight-binding approximation method, a conclusion is obtained that the increasing of the imaginary part of potential can enhance the diffraction, while the increasing disorder will block the diffraction and lead to localization. In the general case, band theory is used for band-structure analysis of three bands. We find that the disorder has a smaller effect on the higher-order band, which is proved by the beam evolutions. Our work may be instructive for realizing beam path control by manipulating the strengths of disorder and gain and/or loss of lattice.

  20. Experimental Realization of Strong Effective Magnetic Fields in an Optical Lattice

    SciTech Connect

    Aidelsburger, M.; Atala, M.; Trotzky, S.; Chen, Y.-A.; Bloch, I.; Nascimbene, S.

    2011-12-16

    We use Raman-assisted tunneling in an optical superlattice to generate large tunable effective magnetic fields for ultracold atoms. When hopping in the lattice, the accumulated phase shift by an atom is equivalent to the Aharonov-Bohm phase of a charged particle exposed to a staggered magnetic field of large magnitude, on the order of 1 flux quantum per plaquette. We study the ground state of this system and observe that the frustration induced by the magnetic field can lead to a degenerate ground state for noninteracting particles. We provide a measurement of the local phase acquired from Raman-induced tunneling, demonstrating time-reversal symmetry breaking of the underlying Hamiltonian. Furthermore, the quantum cyclotron orbit of single atoms in the lattice exposed to the magnetic field is directly revealed.

  1. Proposed formation and dynamical signature of a chiral Bose liquid in an optical lattice.

    PubMed

    Li, Xiaopeng; Paramekanti, Arun; Hemmerich, Andreas; Liu, W Vincent

    2014-01-01

    Recent experiments on p-orbital atomic bosons have suggested the emergence of a spectacular ultracold superfluid with staggered orbital currents in optical lattices. This raises fundamental questions concerning the effects of thermal fluctuations as well as possible ways of directly observing such chiral order. Here we show via Monte Carlo simulations that thermal fluctuations destroy this superfluid in an unexpected two-step process, unveiling an intermediate normal phase with spontaneously broken time-reversal symmetry, dubbed a 'chiral Bose liquid'. For integer fillings (n≥2) in the chiral Mott regime, thermal fluctuations are captured by an effective orbital Ising model, and Onsager's powerful exact solution is adopted to determine the transition from this intermediate liquid to the para-orbital normal phase at high temperature. A lattice quench is designed to convert the staggered angular momentum, previously thought by experts difficult to directly probe, into coherent orbital oscillations, providing a time-resolved dynamical signature of chiral order.

  2. Flow-induced charge modulation in superfluid atomic fermions loaded into an optical kagome lattice.

    PubMed

    Yamamoto, Daisuke; Sato, Chika; Nikuni, Tetsuro; Tsuchiya, Shunji

    2013-04-05

    We study the superfluid state of atomic fermions in a tunable optical kagome lattice motivated by recent experiments. We show that the imposed superflow induces spatial modulations in the density and order parameter of the pair condensate and leads to a charge modulated superfluid state analogous to a supersolid state. The spatial modulations in the superfluid emerge due to the geometric effect of the kagome lattice that introduces anisotropy in hopping amplitudes of fermion pairs in the presence of superflow. We also study superflow instabilities and find that the critical current limited by the dynamical instability is quite enhanced due to the large density of states associated with the flatband. The charge modulated superfluid state can sustain high temperatures close to the transition temperature that is also enhanced due to the flatband and is therefore realizable in experiments.

  3. Exploring the promising properties of 2D exfoliated black phosphorus for optoelectronic applications under 1.55 μm optical excitation

    NASA Astrophysics Data System (ADS)

    Penillard, A.; Tripon-Canseliet, C.; Maksimovic, I.; Rosticher, M.; Servet, B.; Liu, Z.; Géron, E.

    2016-04-01

    A great interest has been lately initiated in the optoelectronics field for 2D materials with a tunable bandgap. Being able to choose the bandgap of a material is a huge progress in optoelectronics, since it would permit to overcome the limitation imposed by the graphene lack of energy bandgap, but also the restriction imposed by already used semiconductor whose bandgap are fixed and cannot apply for IR-NIR applications. From DFT simulations predictions, Black Phosphorus (bP) becomes a bidimensional semiconducting material with a direct tunable energy bandgap from 0.3 eV to 2 eV by controlling number of layers. This material also has a picosecond carrier response and exceptional mobilities under external excitation. Hence black phosphorus is a promising 2D material candidate for photoconductive switching under a NIR optical excitation as in telecommunication wavelength range of 1.55 μm. In this paper, material electromagnetic properties analysis is described in a large frequency band from optical to microwave measurements executed on different samples allowing energy bandgap and work function dependency to fabrication techniques, anisotropy and multiscale optoelectronic device realization by switch contact engineering and material passivation or encapsulation. Material implementation in microwave devices opens the route to new broadband electronic functionalities triggered by optics, thanks to light/matter extreme confinement degree. In this paper we present fabrication method of bP based microwave photoconductive switch, with a focus on black phosphorus Raman characterization, and obtained performances.

  4. LBNE lattice & optics for proton extraction at MI-10 and transport to a target above grade

    SciTech Connect

    Johnstone, John A.; /Fermilab

    2011-09-01

    For the Long Baseline Neutrino Experiment (LBNE) at Fermilab 120 GeV/c protons will be transported from the Main Injector (MI) to an on-site production target. The lattice design and optics discussed here has the beam extracted vertically upwards from MI-10 and the keeps the majority of the line at an elevation above the glacial till/rock interface and terminates on a target at 10 ft above grade. The LBNE beamline discussed here is a modular optics design comprised of 3 distinct lattice configurations, including the specialized MI {yields} LBNE matching section and Final Focus. The remainder of the line is defined by six FODO cells, in which the length and phase advance are chosen specifically such that beam size does not exceed that of the MI while also making the most efficient use of space for achromatic insertions. Dispersion generated by variations in the beam trajectory are corrected locally and can not bleed out to corrupt the optics elsewhere in the line. Aperture studies indicate that the line should be able to transport the worst quality beam that the Main Injector might provide. New IDS dipole correctors located at every focusing center provide high-quality orbit control and further ensure that LBNE meets the stringent requirements for environmental protection.

  5. Demonstration of a fast-reconfigurable silicon CMOS optical lattice filter.

    PubMed

    Ibrahim, Salah; Fontaine, Nicolas K; Djordjevic, Stevan S; Guan, Binbin; Su, Tiehui; Cheung, Stanley; Scott, Ryan P; Pomerene, Andrew T; Seaford, Liberty L; Hill, Craig M; Danziger, Steve; Ding, Zhi; Okamoto, K; Yoo, S J B

    2011-07-04

    We demonstrate a fully-reconfigurable fourth-order optical lattice filter built by cascading identical unit cells consisting of a Mach-Zehnder interferometer (MZI) and a ring resonator. The filter is fabricated using a commercial silicon complementary metal oxide semiconductor (CMOS) process and reconfigured by current injection into p-i-n diodes with a reconfiguration time of less than 10 ns. The experimental results show full control over the single unit cell pole and zero, switching the unit cell transfer function between a notch filter and a bandpass filter, narrowing the notch width down to 400 MHz, and tuning the center wavelength over the full free spectral range (FSR) of 10 GHz. Theoretical and experimental results show tuning dynamics and associated optical losses in the reconfigurable filters. The full-control of each of the four cascaded single unit cells resulted in demonstrations of a number of fourth-order transfer functions. The multimedia experimental data show live tuning and reconfiguration of optical lattice filters.

  6. Transportable Optical Lattice Clock with 7 ×10-17 Uncertainty

    NASA Astrophysics Data System (ADS)

    Koller, S. B.; Grotti, J.; Vogt, St.; Al-Masoudi, A.; Dörscher, S.; Häfner, S.; Sterr, U.; Lisdat, Ch.

    2017-02-01

    We present a transportable optical clock (TOC) with Sr 87 . Its complete characterization against a stationary lattice clock resulted in a systematic uncertainty of 7.4 ×10-17, which is currently limited by the statistics of the determination of the residual lattice light shift, and an instability of 1.3 ×10-15/√{τ } with an averaging time τ in seconds. Measurements confirm that the systematic uncertainty can be reduced to below the design goal of 1 ×10-17. To our knowledge, these are the best uncertainties and instabilities reported for any transportable clock to date. For autonomous operation, the TOC has been installed in an air-conditioned car trailer. It is suitable for chronometric leveling with submeter resolution as well as for intercontinental cross-linking of optical clocks, which is essential for a redefinition of the International System of Units (SI) second. In addition, the TOC will be used for high precision experiments for fundamental science that are commonly tied to precise frequency measurements and its development is an important step to space-borne optical clocks.

  7. Chiral phase from three-spin interactions in an optical lattice

    SciTech Connect

    D'Cruz, Christian; Pachos, Jiannis K.

    2005-10-15

    A spin-1/2 chain model that includes three-spin interactions can effectively describe the dynamics of two species of bosons trapped in an optical lattice with a triangular-ladder configuration. A perturbative theoretical approach and numerical study of its ground state is performed that reveals a rich variety of phases and criticalities. We identify phases with periodicity one, two, or three, as well as critical points that belong in the same universality class as the Ising or the three-state Potts model. We establish a range of parameters, corresponding to a large degeneracy present between phases with period 2 and 3, that nests a gapless incommensurate chiral phase.

  8. Trapped Fermi Gases in Rotating Optical Lattices: Realization and Detection of the Topological Hofstadter Insulator

    SciTech Connect

    Umucalilar, R. O.; Oktel, M. Oe.; Zhai Hui

    2008-02-22

    We consider a gas of noninteracting spinless fermions in a rotating optical lattice and calculate the density profile of the gas in an external confinement potential. The density profile exhibits distinct plateaus, which correspond to gaps in the single particle spectrum known as the Hofstadter butterfly. The plateaus result from insulating behavior whenever the Fermi energy lies within a gap. We discuss the necessary conditions to realize the Hofstadter insulator in a cold atom setup and show how the quantized Hall conductance can be measured from density profiles using the Streda formula.

  9. Phase boundary of the boson Mott insulator in a rotating optical lattice

    SciTech Connect

    Umucalilar, R. O.; Oktel, M. Oe.

    2007-11-15

    We consider the Bose-Hubbard model in a two-dimensional rotating optical lattice and investigate the consequences of the effective magnetic field created by rotation. Using a Gutzwiller-type variational wave function, we find an analytical expression for the Mott insulator (MI)-superfluid (SF) transition boundary in terms of the maximum eigenvalue of the Hofstadter butterfly. The dependence of phase boundary on the effective magnetic field is complex, reflecting the self-similar properties of the single particle energy spectrum. Finally, we argue that fractional quantum Hall phases exist close to the MI-SF transition boundaries, including MI states with particle densities greater than one.

  10. Coherent Addressing of Individual Neutral Atoms in a 3D Optical Lattice.

    PubMed

    Wang, Yang; Zhang, Xianli; Corcovilos, Theodore A; Kumar, Aishwarya; Weiss, David S

    2015-07-24

    We demonstrate arbitrary coherent addressing of individual neutral atoms in a 5×5×5 array formed by an optical lattice. Addressing is accomplished using rapidly reconfigurable crossed laser beams to selectively ac Stark shift target atoms, so that only target atoms are resonant with state-changing microwaves. The effect of these targeted single qubit gates on the quantum information stored in nontargeted atoms is smaller than 3×10^{-3} in state fidelity. This is an important step along the path of converting the scalability promise of neutral atoms into reality.

  11. Generating topological optical flux lattices for ultracold atoms by modulated Raman and radio-frequency couplings

    NASA Astrophysics Data System (ADS)

    Yu, Jinlong; Xu, Zhi-Fang; You, Li

    2017-01-01

    We propose a scheme to dynamically generate optical flux lattices with nontrivial band topology using amplitude-modulated Raman lasers and radio-frequency (rf) magnetic fields. By tuning the strength of Raman and rf fields, three distinct phases are realized at unit filling for a unit cell. Respectively, these three phases correspond to normal insulator, topological Chern insulator, and semimetal. Nearly nondispersive bands are found to appear in the topological phase, which promises opportunities for investigating strongly correlated quantum states within a simple cold-atom setup. The validity of our proposal is confirmed by comparing the Floquet quasienergies from the evolution operator with the spectrum of the effective Hamiltonian.

  12. Rydberg Spectroscopy in an Optical Lattice: Blackbody Thermometry for Atomic Clocks

    SciTech Connect

    Ovsiannikov, Vitali D.; Derevianko, Andrei; Gibble, Kurt

    2011-08-26

    We show that optical spectroscopy of Rydberg states can provide accurate in situ thermometry at room temperature. Transitions from a metastable state to Rydberg states with principal quantum numbers of 25-30 have 200 times larger fractional frequency sensitivities to blackbody radiation than the strontium clock transition. We demonstrate that magic-wavelength lattices exist for both strontium and ytterbium transitions between the metastable and Rydberg states. Frequency measurements of Rydberg transitions with 10{sup -16} accuracy provide 10 mK resolution and yield a blackbody uncertainty for the clock transition of 10{sup -18}.

  13. Rydberg spectroscopy in an optical lattice: blackbody thermometry for atomic clocks.

    PubMed

    Ovsiannikov, Vitali D; Derevianko, Andrei; Gibble, Kurt

    2011-08-26

    We show that optical spectroscopy of Rydberg states can provide accurate in situ thermometry at room temperature. Transitions from a metastable state to Rydberg states with principal quantum numbers of 25-30 have 200 times larger fractional frequency sensitivities to blackbody radiation than the strontium clock transition. We demonstrate that magic-wavelength lattices exist for both strontium and ytterbium transitions between the metastable and Rydberg states. Frequency measurements of Rydberg transitions with 10(-16) accuracy provide 10 mK resolution and yield a blackbody uncertainty for the clock transition of 10(-18).

  14. Chaos control of a Bose-Einstein condensate in a moving optical lattice

    NASA Astrophysics Data System (ADS)

    Zhang, Zhiying; Feng, Xiuqin; Yao, Zhihai

    2016-07-01

    Chaos control of a Bose-Einstein condensate (BEC) loaded into a moving optical lattice with attractive interaction is investigated on the basis of Lyapunov stability theory. Three methods are designed to control chaos in BEC. As a controller, a bias constant, periodic force, or wavelet function feedback is added to the BEC system. Numerical simulations reveal that chaotic behavior can be well controlled to achieve periodicity by regulating control parameters. Different periodic orbits are available for different control parameters only if the maximal Lyapunov exponent of the system is negative. The abundant effect of chaotic control is also demonstrated numerically. Chaos control can be realized effectively by using our proposed control strategies.

  15. Interaction effects on Wannier functions for bosons in an optical lattice

    NASA Astrophysics Data System (ADS)

    Zhu, Shaoqi; Wu, Biao

    2015-12-01

    We have numerically calculated the single-band Wannier functions for interacting Bose gases in optical lattices with a self-consistent approach. We find that the Wannier functions are broadened by repulsive interaction. The tunneling parameter J and the on-site interaction U computed with the broadened Wannier functions are found to change significantly with the number of atoms per site. Our theory can explain the nonuniform atomic clock shift observed in Campbell et al., Science 313, 649 (2006), 10.1126/science.1130365.

  16. Weyl Points in Three-Dimensional Optical Lattices: Synthetic Magnetic Monopoles in Momentum Space.

    PubMed

    Dubček, Tena; Kennedy, Colin J; Lu, Ling; Ketterle, Wolfgang; Soljačić, Marin; Buljan, Hrvoje

    2015-06-05

    We show that a Hamiltonian with Weyl points can be realized for ultracold atoms using laser-assisted tunneling in three-dimensional optical lattices. Weyl points are synthetic magnetic monopoles that exhibit a robust, three-dimensional linear dispersion, identical to the energy-momentum relation for relativistic Weyl fermions, which are not yet discovered in particle physics. Weyl semimetals are a promising new avenue in condensed matter physics due to their unusual properties such as the topologically protected "Fermi arc" surface states. However, experiments on Weyl points are highly elusive. We show that this elusive goal is well within experimental reach with an extension of techniques recently used in ultracold gases.

  17. Generation of uniform synthetic magnetic fields by split driving of an optical lattice

    NASA Astrophysics Data System (ADS)

    Creffield, C. E.; Sols, F.

    2014-08-01

    We describe a method to generate a synthetic gauge potential for ultracold atoms held in an optical lattice. Our approach uses a time-periodic driving potential based on quickly alternating two Hamiltonians to engineer the appropriate Aharonov-Bohm phases, and permits the simulation of a uniform tunable magnetic field. We explicitly demonstrate that our split-driving scheme reproduces the behavior of a charged quantum particle in a magnetic field over the complete range of field strengths, and obtain the Hofstadter butterfly band structure for the Floquet quasienergies.

  18. Dynamics and stability of Bose-Einstein solitons in tilted optical lattices

    SciTech Connect

    Diaz, E.; Dominguez-Adame, F.; Gaul, C.; Lima, R. P. A.; Mueller, C. A.

    2010-05-15

    Bloch oscillations of Bose-Einstein condensates realize sensitive matter-wave interferometers. We investigate the dynamics and stability of bright-soliton wave packets in one-dimensional tilted optical lattices with a modulated mean-field interaction g(t). By means of a time-reversal argument, we prove the stability of Bloch oscillations of breathing solitons that would be quasistatically unstable. Floquet theory shows that these breathing solitons can be more stable against certain experimental perturbations than rigid solitons or even noninteracting wave packets.

  19. Quantum Correlations of Two SPIN-1 Particles in the Optical Lattice

    NASA Astrophysics Data System (ADS)

    Shi, Jia-Dong; Wu, Tao; Song, Xue-Ke; Ye, Liu

    2014-01-01

    In this paper, we investigate the dynamical behaviors of quantum correlations witnessed by geometric discord and negativity when two three-level spin-1 atoms exist in the optical lattice. The results show that the GD can detect the critical point K = J at finite temperature associated with the quantum phase transition which separates the superfluid phase from the Mott insulator phase, while the negativity cannot. In addition, the system undergoes an entanglement sudden death (ESD), but the GD always exists, meanwhile, the GD is more robust than negativity against temperature T.

  20. Quantum dynamics of hard-core bosons in tilted bichromatic optical lattices

    SciTech Connect

    Cai Xiaoming; Chen Shu; Wang Yupeng

    2011-09-15

    We study the dynamics of strongly repulsive Bose gas in tilted or driven bichromatic optical lattices. Using the Bose-Fermi mapping and exact numerical method, we calculate the reduced single-particle density matrices, and study the dynamics of the density profile, the momentum distribution, and the condensate fraction. We show the oscillating and breathing mode of the dynamics, and the depletion of condensate for short-time dynamics. For long-time dynamics, we clearly show the reconstruction of system at integer multiples of Bloch-Zener time. We also show how to achieve clear Bloch oscillation and Landau-Zener tunneling for many-particle systems.

  1. Discerning Incompressible and Compressible Phases of Cold Atoms in Optical Lattices

    NASA Astrophysics Data System (ADS)

    Scarola, V. W.; Pollet, L.; Oitmaa, J.; Troyer, M.

    2009-04-01

    Experiments with cold atoms trapped in optical lattices offer the potential to realize a variety of novel phases but suffer from severe spatial inhomogeneity that can obscure signatures of new phases of matter and phase boundaries. We use a high temperature series expansion to show that compressibility in the core of a trapped Fermi-Hubbard system is related to measurements of changes in double occupancy. This core compressibility filters out edge effects, offering a direct probe of compressibility independent of inhomogeneity. A comparison with experiments is made.

  2. Influence of trapping potentials on the phase diagram of bosonic atoms in optical lattices

    SciTech Connect

    Giampaolo, S.M.; Illuminati, F.; Mazzarella, G.; De Siena, S.

    2004-12-01

    We study the effect of external trapping potentials on the phase diagram of bosonic atoms in optical lattices. We introduce a generalized Bose-Hubbard Hamiltonian that includes the structure of the energy levels of the trapping potential, and show that these levels are in general populated both at finite and zero temperature. We characterize the properties of the superfluid transition for this situation and compare them with those of the standard Bose-Hubbard description. We briefly discuss similar behaviors for fermionic systems.

  3. Formation of metallic magnetic clusters in a Kondo-lattice metal: evidence from an optical study.

    PubMed

    Kovaleva, N N; Kugel, K I; Bazhenov, A V; Fursova, T N; Löser, W; Xu, Y; Behr, G; Kusmartsev, F V

    2012-01-01

    Magnetic materials are usually divided into two classes: those with localised magnetic moments, and those with itinerant charge carriers. We present a comprehensive experimental (spectroscopic ellipsomerty) and theoretical study to demonstrate that these two types of magnetism do not only coexist but complement each other in the Kondo-lattice metal, Tb(2)PdSi(3). In this material the itinerant charge carriers interact with large localised magnetic moments of Tb(4f) states, forming complex magnetic lattices at low temperatures, which we associate with self-organisation of magnetic clusters. The formation of magnetic clusters results in low-energy optical spectral weight shifts, which correspond to opening of the pseudogap in the conduction band of the itinerant charge carriers and development of the low- and high-spin intersite electronic transitions. This phenomenon, driven by self-trapping of electrons by magnetic fluctuations, could be common in correlated metals, including besides Kondo-lattice metals, Fe-based and cuprate superconductors.

  4. Formation of metallic magnetic clusters in a Kondo-lattice metal: Evidence from an optical study

    NASA Astrophysics Data System (ADS)

    Kovaleva, N. N.; Kugel, K. I.; Bazhenov, A. V.; Fursova, T. N.; Löser, W.; Xu, Y.; Behr, G.; Kusmartsev, F. V.

    2012-11-01

    Magnetic materials are usually divided into two classes: those with localised magnetic moments, and those with itinerant charge carriers. We present a comprehensive experimental (spectroscopic ellipsomerty) and theoretical study to demonstrate that these two types of magnetism do not only coexist but complement each other in the Kondo-lattice metal, Tb2PdSi3. In this material the itinerant charge carriers interact with large localised magnetic moments of Tb(4f) states, forming complex magnetic lattices at low temperatures, which we associate with self-organisation of magnetic clusters. The formation of magnetic clusters results in low-energy optical spectral weight shifts, which correspond to opening of the pseudogap in the conduction band of the itinerant charge carriers and development of the low- and high-spin intersite electronic transitions. This phenomenon, driven by self-trapping of electrons by magnetic fluctuations, could be common in correlated metals, including besides Kondo-lattice metals, Fe-based and cuprate superconductors.

  5. Formation of metallic magnetic clusters in a Kondo-lattice metal: Evidence from an optical study

    PubMed Central

    Kovaleva, N. N.; Kugel, K. I.; Bazhenov, A. V.; Fursova, T. N.; Löser, W.; Xu, Y.; Behr, G.; Kusmartsev, F. V.

    2012-01-01

    Magnetic materials are usually divided into two classes: those with localised magnetic moments, and those with itinerant charge carriers. We present a comprehensive experimental (spectroscopic ellipsomerty) and theoretical study to demonstrate that these two types of magnetism do not only coexist but complement each other in the Kondo-lattice metal, Tb2PdSi3. In this material the itinerant charge carriers interact with large localised magnetic moments of Tb(4f) states, forming complex magnetic lattices at low temperatures, which we associate with self-organisation of magnetic clusters. The formation of magnetic clusters results in low-energy optical spectral weight shifts, which correspond to opening of the pseudogap in the conduction band of the itinerant charge carriers and development of the low- and high-spin intersite electronic transitions. This phenomenon, driven by self-trapping of electrons by magnetic fluctuations, could be common in correlated metals, including besides Kondo-lattice metals, Fe-based and cuprate superconductors. PMID:23189239

  6. Nonlinear localized modes in dipolar Bose-Einstein condensates in optical lattices

    SciTech Connect

    Rojas-Rojas, S.; Vicencio, R. A.; Molina, M. I.; Abdullaev, F. Kh.

    2011-09-15

    Modulational instability and discrete matter wave solitons in dipolar BECs, loaded into a deep optical lattice, are investigated analytically and numerically. The process of modulational instability of nonlinear plane matter waves in a dipolar nonlinear lattice is studied and the regions of instability are established. The existence and stability of bulk discrete solitons are analyzed analytically and confirmed by numerical simulations. In marked contrast with the usual discrete nonlinear Schroedinger behavior (no dipolar interactions), we found a region where the two fundamental modes are simultaneously unstable, allowing enhanced mobility across the lattice for large norm values. To study the existence and properties of surface discrete solitons, an analysis of the dimer configuration is performed. The properties of symmetric and antisymmetric modes including stability diagrams and bifurcations are investigated in closed form. For the case of a bulk medium, properties of fundamental on-site and intersite localized modes are analyzed. On-site and intersite surface localized modes are studied, and we find that they do not exist when nonlocal interactions predominate with respect to local ones.

  7. Gap solitons in rocking optical lattices and waveguides with undulating gratings

    SciTech Connect

    Mayteevarunyoo, Thawatchai; Malomed, Boris A.

    2009-07-15

    We report results of a systematic analysis of the stability of one-dimensional solitons in a model including the self-repulsive or attractive cubic nonlinearity and a linear potential represented by a periodically shaking lattice, which was recently implemented in experiments with Bose-Einstein condensates. In optics, the same model applies to undulated waveguiding arrays, which are also available to the experiment. In the case of the repulsive nonlinearity, stability regions are presented, in relevant parameter planes, for fundamental gap solitons and their two-peak and three-peak bound complexes, in the first and second finite band gaps. In the model with the attractive nonlinearity, stability regions are produced for fundamental solitons and their bound states populating the semi-infinite gap. In the first finite and semi-infinite gaps, unstable solitons gradually decay into radiation, while, in the second finite band gap, they are transformed into more complex states, which may represent new species of solitons. For a large amplitude of the rocking-lattice drive, the model is tantamount to that with a 'flashing' lattice potential, which is controlled by periodic sequences of instantaneous kicks. Using this correspondence, we explain generic features of the stability diagrams for the solitons. We also derive a limit case of the latter system, in the form of coupled-mode equations with a 'flashing' linear coupling.

  8. Boresight calibration of construction misalignments for 3D scanners built with a 2D laser range finder rotating on its optical center.

    PubMed

    Morales, Jesús; Martínez, Jorge L; Mandow, Anthony; Reina, Antonio J; Pequeño-Boter, Alejandro; García-Cerezo, Alfonso

    2014-10-24

    Many applications, like mobile robotics, can profit from acquiring dense, wide-ranging and accurate 3D laser data. Off-the-shelf 2D scanners are commonly customized with an extra rotation as a low-cost, lightweight and low-power-demanding solution. Moreover, aligning the extra rotation axis with the optical center allows the 3D device to maintain the same minimum range as the 2D scanner and avoids offsets in computing Cartesian coordinates. The paper proposes a practical procedure to estimate construction misalignments based on a single scan taken from an arbitrary position in an unprepared environment that contains planar surfaces of unknown dimensions. Inherited measurement limitations from low-cost 2D devices prevent the estimation of very small translation misalignments, so the calibration problem reduces to obtaining boresight parameters. The distinctive approach with respect to previous plane-based intrinsic calibration techniques is the iterative maximization of both the flatness and the area of visible planes. Calibration results are presented for a case study. The method is currently being applied as the final stage in the production of a commercial 3D rangefinder.

  9. Boresight Calibration of Construction Misalignments for 3D Scanners Built with a 2D Laser Rangefinder Rotating on Its Optical Center

    PubMed Central

    Morales, Jesús; Martínez, Jorge L.; Mandow, Anthony; Reina, Antonio J.; Pequeño-Boter, Alejandro; García-Cerezo, Alfonso

    2014-01-01

    Many applications, like mobile robotics, can profit from acquiring dense, wide-ranging and accurate 3D laser data. Off-the-shelf 2D scanners are commonly customized with an extra rotation as a low-cost, lightweight and low-power-demanding solution. Moreover, aligning the extra rotation axis with the optical center allows the 3D device to maintain the same minimum range as the 2D scanner and avoids offsets in computing Cartesian coordinates. The paper proposes a practical procedure to estimate construction misalignments based on a single scan taken from an arbitrary position in an unprepared environment that contains planar surfaces of unknown dimensions. Inherited measurement limitations from low-cost 2D devices prevent the estimation of very small translation misalignments, so the calibration problem reduces to obtaining boresight parameters. The distinctive approach with respect to previous plane-based intrinsic calibration techniques is the iterative maximization of both the flatness and the area of visible planes. Calibration results are presented for a case study. The method is currently being applied as the final stage in the production of a commercial 3D rangefinder. PMID:25347585

  10. Optical generation of a spatially variant two-dimensional lattice structure by using a phase only spatial light modulator

    SciTech Connect

    Kumar, Manish Joseph, Joby

    2014-08-04

    We propose a simple and straightforward method to generate spatially variant lattice structures by optical interference lithography method. Using this method, it is possible to independently vary the orientation and period of the two-dimensional lattice. The method consists of two steps which are: numerical synthesis of corresponding phase mask by employing a two-dimensional integrated gradient calculations and experimental implementation of synthesized phase mask by making use of a phase only spatial light modulator in an optical 4f Fourier filtering setup. As a working example, we provide the experimental fabrication of a spatially variant square lattice structure which has the possibility to guide a Gaussian beam through a 90° bend by photonic crystal self-collimation phenomena. The method is digitally reconfigurable, is completely scalable, and could be extended to other kind of lattices as well.

  11. Electron and lattice dynamics of transition metal thin films observed by ultrafast electron diffraction and transient optical measurements

    PubMed Central

    Nakamura, A.; Shimojima, T.; Nakano, M.; Iwasa, Y.; Ishizaka, K.

    2016-01-01

    We report the ultrafast dynamics of electrons and lattice in transition metal thin films (Au, Cu, and Mo) investigated by a combination of ultrafast electron diffraction (UED) and pump-probe optical methods. For a single-crystalline Au thin film, we observe the suppression of the diffraction intensity occuring in 10 ps, which direcly reflects the lattice thermalization via the electron-phonon interaction. By using the two-temperature model, the electron-phonon coupling constant (g) and the electron and lattice temperatures (Te, Tl) are evaluated from UED, with which we simulate the transient optical transmittance. The simulation well agrees with the experimentally obtained transmittance data, except for the slight deviations at the initial photoexcitation and the relaxed quasi-equilibrium state. We also present the results similarly obtained for polycrystalline Au, Cu, and Mo thin films and demonstrate the electron and lattice dynamics occurring in metals with different electron-phonon coupling strengths. PMID:28004010

  12. Loading of a Bose-Einstein condensate into an optical lattice: The excitation of collective modes

    NASA Astrophysics Data System (ADS)

    Plata, J.

    2004-03-01

    The dynamics of a Bose-Einstein condensate in a harmonic trap with a nonadiabatically loaded optical lattice is studied analytically. As the global effect of the optical potential can be described in terms of a renormalized interaction coupling constant and of an effective mass in the laser direction, a fast loading can be understood as a sudden change of those characteristic parameters. In this approach, a standard scaling transformation is applied to study the resulting dynamics, in particular, the generation of collective modes. The relevance of the excited modes to the interference patterns obtained after free expansion is analyzed. The applicability of trap-frequency adjustments as a strategy for suppressing the loading induced excitations is discussed.

  13. Cold-collision-shift cancellation and inelastic scattering in a Yb optical lattice clock

    SciTech Connect

    Ludlow, A. D.; Lemke, N. D.; Sherman, J. A.; Oates, C. W.; Quemener, G.; Stecher, J. von; Rey, A. M.

    2011-11-15

    Recently, p-wave cold collisions were shown to dominate the density-dependent shift of the clock transition frequency in a {sup 171}Yb optical lattice clock. Here we demonstrate that by operating such a system at the proper excitation fraction, the cold-collision shift is canceled below the 5x10{sup -18} fractional frequency level. We report inelastic two-body loss rates for {sup 3} P{sub 0} -{sup 3} P{sub 0} and {sup 1} S{sub 0} -{sup 3} P{sub 0} scattering. We also measure interaction shifts in an unpolarized atomic sample. Collision measurements for this spin-1/2 {sup 171}Yb system are relevant for high-performance optical clocks as well as strongly interacting systems for quantum information and quantum simulation applications.

  14. Three-dimensional Dirac-like fermions in an optical lattice

    SciTech Connect

    Yang Mou; Zhu Shiliang

    2010-12-15

    We present a scheme to realize three-dimensional Dirac-like fermions with an edge-centered cubic optical lattice. We propose a method to construct the optical edge-centered cubic crystals and then determine the parameters required for the description of the systems with a tight-binding model. Interestingly, we show that the low-energy quasiparticles are three-dimensional massive or massless Dirac-like fermions determined by the parameters of the system. In addition, two three-dimensional degenerate flat bands lie between the upper and the lower branches of the Dirac dispersion. Furthermore, we demonstrate that the Dirac dispersion relation and the flat bands can be verified by the density profile measurement.

  15. Stability of emergent kinetics in optical lattices with artificial spin-orbit coupling

    NASA Astrophysics Data System (ADS)

    Chen, Mengsu; Scarola, V. W.

    2016-10-01

    Artificial spin-orbit coupling in optical lattices can be engineered to tune band structure into extreme regimes where the single-particle band flattens leaving only interparticle interactions to define many-body states of matter. Lin et al. [F. Lin, C. Zhang, and V. W. Scarola, Phys. Rev. Lett. 112, 110404 (2014), 10.1103/PhysRevLett.112.110404] showed that under such conditions interactions lead to a Wigner crystal of fermionic atoms under approximate conditions: no bandwidth or band mixing. The excitations were shown to possess emergent kinetics with fractionalized charge derived entirely from interactions. In this work we use numerical exact diagonalization to study a more realistic model with nonzero bandwidth and band mixing. We map out the stability phase diagram of the Wigner crystal. We find that emergent properties of the Wigner crystal excitations remain stable for realistic experimental parameters. Our results validate the approximations made by Lin et al. and define parameter regimes where strong interaction effects generate emergent kinetics in optical lattices.

  16. Resonantly enhanced tunneling and transport of ultracold atoms on tilted optical lattices

    SciTech Connect

    Rubbo, Chester P.; Manmana, Salvatore R.; Peden, Brandon M.; Holland, Murray J.; Rey, Ana Maria

    2011-09-15

    We investigate the resonantly enhanced tunneling dynamics of ultracold bosons loaded on a tilted one-dimensional optical lattice, which can be used to simulate a chain of Ising spins and associated quantum phase transitions. The center-of-mass motion after a sudden tilt both at commensurate and incommensurate fillings is obtained via analytic, time-dependent exact diagonalization and density-matrix renormalization-group methods. We identify a maximum in the amplitude of the center-of-mass oscillations at the quantum critical point of the effective spin system. For the dynamics of incommensurate systems, which cannot be mapped to a spin model, we develop an analytical approach in which the time evolution is obtained by projecting onto resonant families of small clusters. We compare the results of this approach at low fillings to the exact time evolution and find good agreement even at filling factors as large as 2/3. Using this projection onto small clusters, we propose a controllable transport scheme applicable in the context of Atomtronic devices on optical lattices (''slinky scheme'').

  17. Observation of Spin Polarized Clock Transition in 87Sr Optical Lattice Clock

    NASA Astrophysics Data System (ADS)

    Wang, Qiang; Lin, Yi-Ge; Li, Ye; Lin, Bai-Ke; Meng, Fei; Zang, Er-Jun; Li, Tian-Chu; Fang, Zhan-Jun

    2014-12-01

    We report our observation of the spin polarized 1S0 → 3P0 clock transition spectrum in an optical lattice clock based on fermionic 87Sr. The atoms are trapped and pre-cooled to about 2 μK with two stages of laser cooling at 461 nm and 689 nm, respectively. Then the atoms are loaded into an optical lattice formed by the interference of counter-propagating laser beams at 813 nm. An external cavity diode laser at 698 nm, which is stabilized to a high finesse cavity with a linewidth of about 5 Hz and a drift rate of less than 0.2 Hz/s, is used to excite the atoms to the 3P0 state. The π-polarized clock transition spectrum of resolvable mF states is obtained by applying a small bias magnetic field along the polarization axis of the probe beam. A spin polarized clock transition spectrum as narrow as 10 Hz with an 80 ms probe pulse is obtained.

  18. Phase diagram of 1D spin-orbit coupled Fermi gases in optical lattices

    NASA Astrophysics Data System (ADS)

    Qu, Chunlei; Gong, Ming; Zhang, Chuanwei

    2013-03-01

    We consider a one dimensional spin-orbit coupled Fermi gas in optical lattices with open boundary condition. This system belongs to the BDI symmetry class because the Hamiltonian can be made real when the Zeeman field is assumed to be along the z direction, thus the topological superfluid is characterized by Z, instead of Z2 class. In the optical lattice system, each site admits at most two fermions. The system can host plenty of phases depending on the filling factor and the Zeeman field. At finite Zeeman field we observe a strong competition between the topological superfluid phase and the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase. The latter phase is more likely to be observed near the half filling. The spin-orbit coupling plays the role of enhancing the topological superfluid phase and suppressing the FFLO phase, which the Hartree shift plays an utterly opposite role. The possible observation of topological phase is also discussed in the presence of a harmonic trap. This work is supported by ARO, AFOSR, and NSF

  19. Quantum and classical dynamics of a Bose-Einstein condensate in a large-period optical lattice

    SciTech Connect

    Huckans, J. H.; Spielman, I. B.; Phillips, W. D.; Porto, J. V.; Tolra, B. Laburthe

    2009-10-15

    We experimentally investigate diffraction of a {sup 87}Rb Bose-Einstein condensate from a one-dimensional optical lattice. We use a range of lattice periods and timescales, including those beyond the Raman-Nath limit. We compare the results to numerical solutions of the Gross-Pitaevskii equation and classical calculations, with quantitative and qualitative agreement, respectively. The classical calculations predict that the envelope of the time-evolving diffraction pattern is shaped by caustics: singularities in the phase-space density of classical trajectories. This behavior becomes increasingly clear as the lattice period grows.

  20. Semi-automated 2D Bruch's membrane shape analysis in papilledema using spectral-domain optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Wang, Jui-Kai; Sibony, Patrick A.; Kardon, Randy H.; Kupersmith, Mark J.; Garvin, Mona K.

    2015-03-01

    Recent studies have shown that the Bruch's membrane (BM) and retinal pigment epithelium (RPE), visualized on spectral-domain optical coherence tomography (SD-OCT), is deformed anteriorly towards the vitreous in patients with intracranial hypertension and papilledema. The BM/RPE shape has been quantified using a statistical-shape-model approach; however, to date, the approach has involved the tedious and time-consuming manual placement of landmarks and correspondingly, only the shape (and shape changes) of a limited number of patients has been studied. In this work, we first present a semi-automated approach for the extraction of 20 landmarks along the BM from an optic-nerve-head (ONH) centered OCT slice from each patient. In the approach, after the manual placement of the two Bruch's membrane opening (BMO) points, the remaining 18 landmarks are automatically determined using a graph-based segmentation approach. We apply the approach to the OCT scans of 116 patients (at baseline) enrolled in the Idiopathic Intracranial Hypertension Treatment Trial and generate a statistical shape model using principal components analysis. Using the resulting shape model, the coefficient (shape measure) corresponding to the second principal component (eigenvector) for each set of landmarks indicates the degree of the BM/RPE is oriented away from the vitreous. Using a subset of 20 patients, we compare the shape measure computed using this semi-automated approach with the resulting shape measure when (1) all landmarks are specified manually (Experiment I); and (2) a different expert specifies the two BMO points (Experiment II). In each case, a correlation coefficient >= 0.99 is obtained.

  1. Frequency ratio measurement of 171Yb and 87Sr optical lattice clocks.

    PubMed

    Akamatsu, Daisuke; Yasuda, Masami; Inaba, Hajime; Hosaka, Kazumoto; Tanabe, Takehiko; Onae, Atsushi; Hong, Feng-Lei

    2014-04-07

    The frequency ratio of the (1)S(0)(F = 1/2)-(3)P(0)(F = 1/2) clock transition in (171)Yb and the (1)S(0)(F = 9/2)-(3)P(0)(F = 9/2) clock transition in (87)Sr is measured by an optical-optical direct frequency link between two optical lattice clocks. We determined the ratio (ν(Yb)/ν(Sr)) to be 1.207 507 039 343 341 2(17) fractional standard uncertainty of 1.4 × 10(-15) [corrected]. The measurement uncertainty of the frequency ratio is smaller than that obtained from absolute frequency measurements using the International Atomic Time (TAI) link. The measured ratio agrees well with that derived from the absolute frequency measurement results obtained at NIST and JILA, Boulder, CO using their Cs-fountain clock. Our measurement enables the first international comparison of the frequency ratios of optical clocks. The measured frequency ratio will be reported to the International Committee for Weights and Measures for a discussion related to the redefinition of the second.

  2. An optical lattice clock with accuracy and stability at the 10(-18) level.

    PubMed

    Bloom, B J; Nicholson, T L; Williams, J R; Campbell, S L; Bishof, M; Zhang, X; Zhang, W; Bromley, S L; Ye, J

    2014-02-06

    Progress in atomic, optical and quantum science has led to rapid improvements in atomic clocks. At the same time, atomic clock research has helped to advance the frontiers of science, affecting both fundamental and applied research. The ability to control quantum states of individual atoms and photons is central to quantum information science and precision measurement, and optical clocks based on single ions have achieved the lowest systematic uncertainty of any frequency standard. Although many-atom lattice clocks have shown advantages in measurement precision over trapped-ion clocks, their accuracy has remained 16 times worse. Here we demonstrate a many-atom system that achieves an accuracy of 6.4 × 10(-18), which is not only better than a single-ion-based clock, but also reduces the required measurement time by two orders of magnitude. By systematically evaluating all known sources of uncertainty, including in situ monitoring of the blackbody radiation environment, we improve the accuracy of optical lattice clocks by a factor of 22. This single clock has simultaneously achieved the best known performance in the key characteristics necessary for consideration as a primary standard-stability and accuracy. More stable and accurate atomic clocks will benefit a wide range of fields, such as the realization and distribution of SI units, the search for time variation of fundamental constants, clock-based geodesy and other precision tests of the fundamental laws of nature. This work also connects to the development of quantum sensors and many-body quantum state engineering (such as spin squeezing) to advance measurement precision beyond the standard quantum limit.

  3. An optical lattice clock with accuracy and stability at the 10-18 level

    NASA Astrophysics Data System (ADS)

    Bloom, B. J.; Nicholson, T. L.; Williams, J. R.; Campbell, S. L.; Bishof, M.; Zhang, X.; Zhang, W.; Bromley, S. L.; Ye, J.

    2014-02-01

    Progress in atomic, optical and quantum science has led to rapid improvements in atomic clocks. At the same time, atomic clock research has helped to advance the frontiers of science, affecting both fundamental and applied research. The ability to control quantum states of individual atoms and photons is central to quantum information science and precision measurement, and optical clocks based on single ions have achieved the lowest systematic uncertainty of any frequency standard. Although many-atom lattice clocks have shown advantages in measurement precision over trapped-ion clocks, their accuracy has remained 16 times worse. Here we demonstrate a many-atom system that achieves an accuracy of 6.4×10-18, which is not only better than a single-ion-based clock, but also reduces the required measurement time by two orders of magnitude. By systematically evaluating all known sources of uncertainty, including in situ monitoring of the blackbody radiation environment, we improve the accuracy of optical lattice clocks by a factor of 22. This single clock has simultaneously achieved the best known performance in the key characteristics necessary for consideration as a primary standard--stability and accuracy. More stable and accurate atomic clocks will benefit a wide range of fields, such as the realization and distribution of SI units, the search for time variation of fundamental constants, clock-based geodesy and other precision tests of the fundamental laws of nature. This work also connects to the development of quantum sensors and many-body quantum state engineering (such as spin squeezing) to advance measurement precision beyond the standard quantum limit.

  4. Optically transparent thin-film transistors based on 2D multilayer MoS2 and indium zinc oxide electrodes

    NASA Astrophysics Data System (ADS)

    Kwon, Junyeon; Hong, Young Ki; Kwon, Hyuk-Jun; Park, Yu Jin; Yoo, Byungwook; Kim, Jiwan; Grigoropoulos, Costas P.; Oh, Min Suk; Kim, Sunkook

    2015-01-01

    We report on optically transparent thin film transistors (TFTs) fabricated using multilayered molybdenum disulfide (MoS2) as the active channel, indium tin oxide (ITO) for the back-gated electrode and indium zinc oxide (IZO) for the source/drain electrodes, respectively, which showed more than 81% transmittance in the visible wavelength. In spite of a relatively large Schottky barrier between MoS2 and IZO, the n-type behavior with a field-effect mobility (μeff) of 1.4 cm2 V-1 s-1 was observed in as-fabricated transparent MoS2 TFT. In order to enhance the performances of transparent MoS2 TFTs, a picosecond pulsed laser was selectively irradiated onto the contact region of the IZO electrodes. Following laser annealing, μeff increased to 4.5 cm2 V-1 s-1, and the on-off current ratio (Ion/Ioff) increased to 104, which were attributed to the reduction of the contact resistance between MoS2 and IZO.

  5. Optical remote sensing of the SO2 plume from Popocatepetl volcano (Mexico): 2D visualization and flux estimations

    NASA Astrophysics Data System (ADS)

    Basaldud, R.; Grutter, M.; Baumgardner, D.; Harig, R.; Junkerman, W.; Rivera-Cardenas, C.; Delgado, H.; Woehrnschimmel, H.

    2007-05-01

    Popocatepetl volcano (19.023N, 98.622W, 5452 masl) is a passively degassing eruptive volcano with a current average emission of 5 kt/d of sulfur dioxide, which is located in the central front of the Mexican Transvolcanic Belt . It is approx. 60 km SE of Mexico City and 45 km NW from Puebla City. SO2 emissions from the volcano are known to interact with urban pollution playing a role in the atmospheric chemistry and the formation of particles. Optical remote sensing techniques were deployed during March 2006 to study the dispersion of the volcanic plume and to quantify the SO2 fluxes. A Scanning Infrared Gas Imaging System (SIGIS) was used to acquire passive IR spectra at 4 cm-1 resolution in a two-dimensional array, from which a false-color image was produced representing the degree of correlation of a specific gaseous pollutant. A real-life animation of the SO2- distribution from the volcanic plume allows understanding dispersion phenomena in various atmospheric conditions. Passive DOAS instruments installed both on ground and from an ultra-light aircraft, allowed for discrete SO2 column measurements below the plume. Flux estimations were done using wind profiles from balloons launched periodically

  6. Preliminary clinical results: an analyzing tool for 2D optical imaging in detection of active inflammation in rheumatoid arthritis

    NASA Astrophysics Data System (ADS)

    Adi Aizudin Bin Radin Nasirudin, Radin; Meier, Reinhard; Ahari, Carmen; Sievert, Matti; Fiebich, Martin; Rummeny, Ernst J.; No"l, Peter B.

    2011-03-01

    Optical imaging (OI) is a relatively new method in detecting active inflammation of hand joints of patients suffering from rheumatoid arthritis (RA). With the high number of people affected by this disease especially in western countries, the availability of OI as an early diagnostic imaging method is clinically highly relevant. In this paper, we present a newly in-house developed OI analyzing tool and a clinical evaluation study. Our analyzing tool extends the capability of existing OI tools. We include many features in the tool, such as region-based image analysis, hyper perfusion curve analysis, and multi-modality image fusion to aid clinicians in localizing and determining the intensity of inflammation in joints. Additionally, image data management options, such as the full integration of PACS/RIS, are included. In our clinical study we demonstrate how OI facilitates the detection of active inflammation in rheumatoid arthritis. The preliminary clinical results indicate a sensitivity of 43.5%, a specificity of 80.3%, an accuracy of 65.7%, a positive predictive value of 76.6%, and a negative predictive value of 64.9% in relation to clinical results from MRI. The accuracy of inflammation detection serves as evidence to the potential of OI as a useful imaging modality for early detection of active inflammation in patients with rheumatoid arthritis. With our in-house developed tool we extend the usefulness of OI imaging in the clinical arena. Overall, we show that OI is a fast, inexpensive, non-invasive and nonionizing yet highly sensitive and accurate imaging modality.-

  7. From optical lattice clocks to the measurement of forces in the Casimir regime

    SciTech Connect

    Wolf, Peter; Lemonde, Pierre; Bize, Sebastien; Landragin, Arnaud; Clairon, Andre; Lambrecht, Astrid

    2007-06-15

    We describe an experiment based on atoms trapped close to a macroscopic surface, to study the interactions between the atoms and the surface at very small separations (0.6-10 {mu}m). In this range the dominant potential is the QED interaction (Casimir-Polder and van der Waals) between the surface and the atom. Additionally, several theoretical models suggest the possibility of Yukawa-type potentials with sub-millimeter range, arising from new physics related to gravity. The proposed setup is very similar to neutral atom optical lattice clocks, but with the atoms trapped in lattice sites close to the reflecting mirror. A sequence of pulses of the probe laser at different frequencies is then used to create an interferometer with a coherent superposition between atomic states at different distances from the mirror (in different lattice sites). Assuming atom interferometry state-of-the-art measurement of the phase difference and a duration of the superposition of about 0.1 s, we expect to be able to measure the potential difference between separated states with an uncertainty of {approx_equal}10{sup -4} Hz. An analysis of systematic effects for different atoms and surfaces indicates no fundamentally limiting effect at the same level of uncertainty, but does influence the choice of atom and surface material. Based on those estimates, we expect that such an experiment would improve the best existing measurements of the atom-wall QED interaction by {>=} 2 orders of magnitude, while gaining up to four orders of magnitude on the best present limits on new interactions in the range between 100 nm and 100 {mu}m.

  8. Nearly-one-dimensional self-attractive Bose-Einstein condensates in optical lattices

    SciTech Connect

    Salasnich, L.; Toigo, F.; Cetoli, A.; Malomed, B. A.

    2007-03-15

    Within the framework of a mean-field description, we investigate atomic Bose-Einstein condensates, with attraction between atoms, under the action of a strong transverse confinement and periodic [optical-lattice (OL)] axial potential. Using a combination of the variational approximation, one-dimensional (1D) nonpolynomial Schroedinger equation, and direct numerical solutions of the underlying 3D Gross-Pitaevskii equation, we show that the ground state of the condensate is a soliton belonging to the semi-infinite band gap of the periodic potential. The soliton may be confined to a single cell of the lattice or extended to several cells, depending on the effective self-attraction strength g (which is proportional to the number of atoms bound in the soliton) and depth of the potential, V{sub 0}, the increase of V{sub 0} leading to strong compression of the soliton. We demonstrate that the OL is an effective tool to control the soliton's shape. It is found that, due to the 3D character of the underlying setting, the ground-state soliton collapses at a critical value of the strength, g=g{sub c}, which gradually decreases with the increase of V{sub 0}; under typical experimental conditions, the corresponding maximum number of {sup 7}Li atoms in the soliton, N{sub max}, ranges between 8000 and 4000. Examples of stable multipeaked solitons are also found in the first finite band gap of the lattice spectrum. The respective critical value g{sub c} again slowly decreases with the increase of V{sub 0}, corresponding to N{sub max}{approx_equal}5000.

  9. Tunneling dynamics of superfluid Fermi gases in an accelerating optical lattice

    SciTech Connect

    Tie Lu; Xue Jukui

    2010-11-15

    The nonlinear Landau-Zener tunneling and the nonlinear Rabi oscillations of superfluid Fermi gases between Bloch bands in an accelerating optical lattice are discussed. Within the hydrodynamic theory and a two-level model, the tunneling probability of superfluid Fermi gases between Bloch bands is obtained. We find that, as the system crosses from the Bose-Einstein condensation (BEC) side to the BCS side, the tunneling rate is closely related to the particle density: when the density is smaller (larger) than a critical value, the tunneling rate at unitarity is larger (smaller) than that in the BEC limit. This is well explained in terms of an effective interaction and an effective potential. Furthermore, the nonlinear Rabi oscillations of superfluid Fermi gases between the bands are discussed by imposing a periodic modulation on the level bias and the strength of the lattice. Analytical expressions of the critical density for suppressing or enhancing the Rabi oscillations are obtained. It is shown that, as the system crosses from the BEC side to the BCS side, the critical density strongly depends on the modulation parameters (i.e., the modulation amplitude and the modulation frequency). For a fixed density, a high-frequency or low-frequency modulation can suppress or enhance the Rabi oscillations both at unitarity and in the BEC limit. For an intermediate modulation frequency, the Rabi oscillations are chaotic along the entire BEC-BCS crossover, especially, on the BCS side. Interestingly, we find that the modulation of the lattice strength only with an intermediate modulation frequency has significant effect on the Rabi oscillations both in the BEC limit and at unitarity; that is, an intermediate-frequency modulation can enhance the Rabi oscillations, especially on the BCS side.

  10. Finite-momentum Bose-Einstein condensates in shaken two-dimensional square optical lattices

    SciTech Connect

    Di Liberto, M.; Tieleman, O.; Smith, C. Morais; Branchina, V.

    2011-07-15

    We consider ultracold bosons in a two-dimensional square optical lattice described by the Bose-Hubbard model. In addition, an external time-dependent sinusoidal force is applied to the system, which shakes the lattice along one of the diagonals. The effect of the shaking is to renormalize the nearest-neighbor-hopping coefficients, which can be arbitrarily reduced, can vanish, or can even change sign, depending on the shaking parameter. Therefore, it is necessary to account for higher-order-hopping terms, which are renormalized differently by the shaking, and to introduce anisotropy into the problem. We show that the competition between these different hopping terms leads to finite-momentum condensates with a momentum that may be tuned via the strength of the shaking. We calculate the boundaries between the Mott insulator and the different superfluid phases and present the time-of-flight images expected to be observed experimentally. Our results open up possibilities for the realization of bosonic analogs of the Fulde, Ferrel, Larkin, and Ovchinnikov phase describing inhomogeneous superconductivity.

  11. Quantum Engineering of a Low-Entropy Gas of Heteronuclear Bosonic Molecules in an Optical Lattice

    NASA Astrophysics Data System (ADS)

    Reichsöllner, Lukas; Schindewolf, Andreas; Takekoshi, Tetsu; Grimm, Rudolf; Nägerl, Hanns-Christoph

    2017-02-01

    We demonstrate a generally applicable technique for mixing two-species quantum degenerate bosonic samples in the presence of an optical lattice, and we employ it to produce low-entropy samples of ultracold Rb 87 Cs 133 Feshbach molecules with a lattice filling fraction exceeding 30%. Starting from two spatially separated Bose-Einstein condensates of Rb and Cs atoms, Rb-Cs atom pairs are efficiently produced by using the superfluid-to-Mott insulator quantum phase transition twice, first for the Cs sample, then for the Rb sample, after nulling the Rb-Cs interaction at a Feshbach resonance's zero crossing. We form molecules out of atom pairs and characterize the mixing process in terms of sample overlap and mixing speed. The dense and ultracold sample of more than 5000 RbCs molecules is an ideal starting point for experiments in the context of quantum many-body physics with long-range dipolar interactions.

  12. Inhomogeneous BCS-BEC crossover for trapped cold atoms in optical lattices

    NASA Astrophysics Data System (ADS)

    Amaricci, A.; Privitera, A.; Capone, M.

    2014-05-01

    The BCS-BEC (Bose-Einstein condensation) crossover in a lattice is a powerful paradigm that describes how a superconductor deviates from the Bardeen-Cooper-Schrieffer physics as the attractive interaction increases. Optical lattices loaded with binary mixtures of cold atoms allow one to access this phenomenon experimentally in a clean and controlled way. We show that, however, the possibility to study this phenomenon in actual cold-atoms experiments is limited by the effect of the trapping potential. Real-space dynamical mean-field theory calculations show indeed that interactions and the confining potential conspire to pack the fermions in the center of the trap, which approaches a band insulator when the attraction becomes sizeable. Interestingly, the energy gap is spatially more homogeneous than the superfluid condensate order parameter. We show how this physics reflects in several observables, and we propose an alternative strategy to disentangle the effect of the harmonic potential and measure the intrinsic properties resulting from the interaction strength.

  13. Topological semimetal: a probable new state of quantum optical lattice gases protected by D4 symmetry

    NASA Astrophysics Data System (ADS)

    Sun, Kai; Liu, W. Vincent; Das Sarma, S.

    2011-03-01

    We demonstrate that a novel topological semimetal emerges as a parity-protected critical theory for fermionic atoms loaded in the p and d orbital bands of a two-dimensional optical lattice. The new quantum state is characterized by a parabolic band-degeneracy point with Berry flux 2 π , in sharp contrast to the π flux of Dirac points as in graphene. We prove that this topological liquid is a universal property for all lattices of D4 point group symmetry and the band degeneracy is protected by odd parity. Turning on interparticle repulsive interaction, the system undergoes a phase transition to a topological insulator, whose experimental signature includes chiral gapless domain-wall modes, reminiscent of quantum Hall edge states. KS and SDS acknowledge the support of JQI-NSF-PFC, AFOSR-MURI, ARO-DARPA-OLE and ARO-MURI. W.V.L. is supported by ARO and ARO-DARPA-OLE. We thank the KITP at UCSB for its hospitality where this research is supported in part by NSF Grant No. PHY05-51164.

  14. Gauge-invariant implementation of the Abelian-Higgs model on optical lattices

    NASA Astrophysics Data System (ADS)

    Bazavov, A.; Meurice, Y.; Tsai, S.-W.; Unmuth-Yockey, J.; Zhang, Jin

    2015-10-01

    We present a gauge-invariant effective action for the Abelian-Higgs model (scalar electrodynamics) with a chemical potential μ on a (1 +1 )-dimensional lattice. This formulation provides an expansion in the hopping parameter κ which we test with Monte Carlo simulations for a broad range of the inverse gauge coupling βp l=1 /g2 and small values of the scalar self-coupling λ . In the opposite limit of infinitely large λ , the partition function can be written as a traced product of local tensors which allows us to write exact blocking formulas. Gauss's law is automatically satisfied and the introduction of μ has consequences only if we have an external electric field, g2=0 or an explicit gauge symmetry breaking. The time-continuum limit of the blocked transfer matrix can be obtained numerically and, for g2=0 and a spin-1 truncation, the small volume energy spectrum is identical to the low energy spectrum of a two-species Bose-Hubbard model in the limit of large on-site repulsion. We extend this procedure for finite βp l and derive a spin-1 approximation of the Hamiltonian. It involves new terms corresponding to transitions among the two species in the Bose-Hubbard model. We propose an optical lattice implementation involving a ladder structure.

  15. First-principles study of the electronic, optical properties and lattice dynamics of tantalum oxynitride.

    PubMed

    Li, Pan; Fan, Weiliu; Li, Yanlu; Sun, Honggang; Cheng, Xiufeng; Zhao, Xian; Jiang, Minhua

    2010-08-02

    First-principles calculations of the electronic, optical properties and lattice dynamics of tantalum oxynitride are performed with the density functional theory plane-wave pseudopotential method. The analysis of the electronic structure shows a covalent nature in Ta-N bonds and Ta-O bonds. The hybridization of anion 2p and Ta 5d states results in enhanced dispersion of the valence band, raising the top of the valence band and leading to the visible-light response in TaON. It has a high dielectric constant, and the anisotropy is displayed obviously in the lower energy region. Our calculation indicated that TaON has excellent dielectric properties along [010] direction. Various optical properties, including the reflectivity, absorption coefficient, refractive index, and the energy-loss spectrum are derived from the complex dielectric function. We also present phonon dispersion relation, zone-center optical mode frequency, density of phonon states, and some thermodynamic properties. The experimental IR modes (B(u) at 808 cm(-1) and A(u) at 863 cm(-1)) are reproduced well and assigned to a combination of stretching and bending vibrations for the Ta-N bond and Ta-O bond. The thermodynamic properties of TaON, such as heat capacity and Debye temperature, which were important parameters for the measurement of crystal physical properties, were first given for reference. Our investigations provide useful information for the potential application of this material.

  16. Energy Deposition into a Collisional Gas from Optical Lattices Formed in an Optical Cavity (PREPRINT)

    DTIC Science & Technology

    2008-07-02

    pp. 1344-1347 2 Kuga et al., “Novel Optical Trap of Atoms with a Doughnut Beam,” Physical Review Letters 78, (1997), pp. 4713-4716 3 Dotsenko et...other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a ...Technical Paper 3. DATES COVERED (From - To) 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER Energy Deposition into a Collisional Gas from

  17. Optical-lattice-influenced geometry of quasi-two-dimensional binary condensates and quasiparticle spectra

    NASA Astrophysics Data System (ADS)

    Suthar, K.; Angom, D.

    2016-06-01

    We explore the collective excitation of two-species Bose-Einstein condensates (TBECs) confined in quasi-two-dimensional optical lattices. For this we use a set of coupled discrete nonlinear Schrödinger equations to describe the system and we employ Hartree-Fock-Bogoliubov theory with the Popov approximation to analyze the quasiparticle spectra at zero temperature. The ground-state geometry, evolution of quasiparticle energies, structure of quasiparticle amplitudes, and dispersion relations are examined in detail. We observe that the TBEC acquires a side-by-side density profile when it is tuned from the miscible to the immiscible phase. In addition, the quasiparticle energies are softened as the system is tuned towards phase separation, but harden after phase separation and mode degeneracies are lifted. In terms of structure, in the miscible phase the quasiparticles have well-defined azimuthal quantum numbers, but that is not the case for the immiscible phase.

  18. Itinerant-localized dual character of a strongly correlated superfluid Bose gas in an optical lattice

    SciTech Connect

    Ohashi, Y.; Kitaura, M.; Matsumoto, H.

    2006-03-15

    We investigate a strongly correlated Bose gas in an optical lattice. Extending the standard-basis operator method developed by Haley and Erdoes to a boson Hubbard model, we calculate excitation spectra in the superfluid phase, as well as in the Mott insulating phase, at T=0. In the Mott phase, the excitation spectrum has a finite energy gap, reflecting the localized character of atoms. In the superfluid phase, the excitation spectrum is shown to have an itinerant-localized dual structure, where the gapless Bogoliubov mode (which describes the itinerant character of superfluid atoms) and a band with a finite energy gap coexist. We also show that the rf-tunneling current measurement would give useful information about the duality of a strongly correlated superfluid Bose gas near the superfluid-insulator transition.

  19. Topological insulator and particle pumping in a one-dimensional shaken optical lattice

    NASA Astrophysics Data System (ADS)

    Mei, Feng; You, Jia-Bin; Zhang, Dan-Wei; Yang, X. C.; Fazio, R.; Zhu, Shi-Liang; Kwek, L. C.

    2014-12-01

    We propose a simple method to simulate and detect topological insulators with cold atoms trapped in a one-dimensional bichromatic optical lattice subjected to a time-periodic modulation. The tight-binding form of this shaken system is equivalent to the periodically driven Aubry-Andre model. We demonstrate that this model can be mapped into a two-dimensional Chern insulator model, whose energy spectrum hosts a topological phase within an experimentally accessible parameter regime. By tuning the laser phase adiabatically, such one-dimensional system constitutes a natural platform to realize topological particle pumping. We show that the Chern number characterizing the topological features of this system can be measured by detecting the density shift after one cycle of pumping.

  20. Localization of a spin-orbit-coupled Bose-Einstein condensate in a bichromatic optical lattice

    NASA Astrophysics Data System (ADS)

    Cheng, Yongshan; Tang, Gaohui; Adhikari, S. K.

    2014-06-01

    We study the localization of a noninteracting and weakly interacting Bose-Einstein condensate (BEC) with spin-orbit coupling loaded in a quasiperiodic bichromatic optical lattice potential using the numerical solution and variational approximation of a binary mean-field Gross-Pitaevskii equation with two pseudospin components. We confirm the existence of the stationary localized states in the presence of the spin-orbit and Rabi couplings for an equal distribution of atoms in the two components. We find that the interaction between the spin-orbit and Rabi couplings favors the localization or delocalization of the BEC depending on the phase difference between the components. We also studied the oscillation dynamics of the localized states for an initial population imbalance between the two components.

  1. Strong interaction effects and criticality of bosons in shaken optical lattices.

    PubMed

    Zheng, Wei; Liu, Boyang; Miao, Jiao; Chin, Cheng; Zhai, Hui

    2014-10-10

    We study the quantum phase transitions and identify a tricritical point between a normal Bose superfluid, a superfluid that breaks additional Z(2) Ising symmetry, and a Mott insulator in a recent shaken optical lattice experiment. We show that near the transition between normal and Z(2) symmetry breaking superfluids, bosons can condense into a momentum state with high or even locally maximum kinetic energies due to the interaction effect. We present a general low-energy effective field theory that treats both the superfluid transition and the Ising transition in a uniform framework. Using the perturbative renormalization group method, we find that the critical behavior of the quantum phase transition belongs to a universality class different from that of a dilute Bose gas.

  2. Pair formation in Fermi systems with population imbalance in one- and two-dimensional optical lattices

    NASA Astrophysics Data System (ADS)

    Batrouni, George

    2011-03-01

    I will discuss pairing in fermionic systems in one- and two-dimensional optical lattices with population imbalance. This will be done in the context of the attractive fermionic Hubbard model using the Stochastic Green Function algorithm in d=1 while for d=2 we use Determinant Quantum Monte Carlo. This is the first exact QMC study examining the effects of finite temperature which is very important in experiments on ultra-cold atoms. Our results show that, in the ground state, the dominant pairing mechanism is at nonzero center of mass momentum, i.e. FFLO. I will then discuss the effect of finite temperature in the uniform and confined systems and present finite temperature phase diagrams. The numerical results will be compared with experiments. With M. J. Wolak (CQT, National University of Singapore) and V. G. Rousseau (Department of Physics and Astronomy, Louisiana State University).

  3. Phase separation of trapped spin-imbalanced Fermi gases in one-dimensional optical lattices

    SciTech Connect

    Heidrich-Meisner, F.; Orso, G.; Feiguin, A. E.

    2010-05-15

    We calculate the density profiles of a trapped spin-imbalanced Fermi gas with attractive interactions in a one-dimensional optical lattice, using both the local-density approximation (LDA) and density-matrix renormalization-group (DMRG) simulations. Based on the exact equation of state obtained by Bethe ansatz, the LDA predicts that the gas phase separates into shells with a partially polarized core and fully paired wings, the latter occurring below a critical spin polarization. This behavior is also seen in numerically exact DMRG calculations at sufficiently large particle numbers. We show that, unlike in the continuum case, the critical polarization is a nonmonotonic function of the interaction strength and vanishes in the limit of large interactions.

  4. Quench-induced resonant tunneling mechanisms of bosons in an optical lattice with harmonic confinement

    NASA Astrophysics Data System (ADS)

    Koutentakis, G. M.; Mistakidis, S. I.; Schmelcher, P.

    2017-01-01

    The nonequilibrium dynamics of small boson ensembles in a one-dimensional optical lattice is explored upon a sudden quench of an additional harmonic trap from strong to weak confinement. We find that the competition between the initial localization and the repulsive interaction leads to a resonant response of the system for intermediate quench amplitudes, corresponding to avoided crossings in the many-body eigenspectrum with varying final trap frequency. In particular, we show that these avoided crossings can be utilized to prepare the system in a desired state. The dynamical response is shown to depend on both the interaction strength as well as the number of atoms manifesting the many-body nature of the tunneling dynamics.

  5. Self-localization of Bose–Einstein condensates in optical lattices

    NASA Astrophysics Data System (ADS)

    Kruse, Johannes; Fleischmann, Ragnar

    2017-03-01

    Mean field and beyond mean field model calculations of Bose–Einstein condensates trapped in optical lattices have shown that initially homogeneous condensates can evolve into self-trapped, strongly localized states in the presence of weak boundary dissipation, a phenomenon called self-localization. A dynamical phase transition from extended to localized states can be observed when the effective nonlinearity exceeds a critical threshold {{{Λ }}}{eff}{{c}}. We investigate this phase transition to self-localization in the mean field approximation of the discrete nonlinear Schrödinger equation. We quantitatively characterize the properties of the discrete breathers, i.e. the nonlinear localized solutions, at the phase transition. This leads us to propose and numerically verify an analytical lower bound {{{Λ }}}{eff}{{L}} for the critical nonlinearity based on the idea of self-induced Anderson localization.

  6. Inelastic collisions and density-dependent excitation suppression in a {sup 87}Sr optical lattice clock

    SciTech Connect

    Bishof, M.; Martin, M. J.; Swallows, M. D.; Benko, C.; Lin, Y.; Quemener, G.; Rey, A. M.; Ye, J.

    2011-11-15

    We observe two-body loss of {sup 3} P{sub 0} {sup 87}Sr atoms trapped in a one-dimensional optical lattice. We measure loss rate coefficients for atomic samples between 1 and 6 {mu}K that are prepared either in a single nuclear-spin sublevel or with equal populations in two sublevels. The measured temperature and nuclear-spin preparation dependence of rate coefficients agree well with calculations and reveal that rate coefficients for distinguishable atoms are only slightly enhanced over those of indistinguishable atoms. We further observe a suppression of excitation and losses during interrogation of the {sup 1} S{sub 0}-{sup 3} P{sub 0} transition as density increases and Rabi frequency decreases, which suggests the presence of strong interactions in our dynamically driven many-body system.

  7. Localization of a Bose-Fermi mixture in a bichromatic optical lattice

    SciTech Connect

    Cheng Yongshan; Adhikari, S. K.

    2011-08-15

    We study the localization of a cigar-shaped superfluid Bose-Fermi mixture in a quasiperiodic bichromatic optical lattice (OL) for interspecies attraction and intraspecies repulsion. The mixture is described by the Gross-Pitaevskii equation for the bosons, coupled to a hydrodynamic mean-field equation for fermions at unitarity. We confirm the existence of the symbiotic localized states in the Bose-Fermi mixture and Anderson localization of the Bose component in the interacting Bose-Fermi mixture on a bichromatic OL. The phase diagram in boson and fermion numbers showing the regions of the symbiotic and Anderson localization of the Bose component is presented. Finally, the stability of symbiotic and Anderson localized states is established under small perturbations.

  8. Multi-peak solitons in PT-symmetric Bessel optical lattices with defects

    NASA Astrophysics Data System (ADS)

    Wang, Hongcheng

    2016-10-01

    This paper presents a theoretical analysis of the existence and stability of multi-peak solitons in parity-time-symmetric Bessel optical lattices with defects in nonlinear media. The results demonstrate that there always exists a critical propagation constant μ c for the existence of multi-peak solitons regardless of whether the nonlinearity is self-focusing or self-defocusing. In self-focusing media, multi-peak solitons exist when the propagation constant μ > μ c . In the self-defocusing case, solitons exist only when μ < μ c . Only low-power solitons can propagate stably when random noise perturbations are present. Positive defects help stabilize the propagation of multi-peak solitons when the nonlinearity is self-focusing. When the nonlinearity is self-defocusing, however, multi-peak solitons in negative defects have wider stable regions than those in positive defects.

  9. The Sagnac effect in optical lattices with laser-assisted tunneling

    NASA Astrophysics Data System (ADS)

    Jiang, Bo-Nan; Wei, Xiao-Gang; Zhang, Guo-Wan; Li, Jia-Hua; Cheng, Yong-Jie; Xu, Cheng

    2016-05-01

    We propose a scheme to realize rotation sensing through the use of optical lattices with laser-assisted tunneling. We theoretically demonstrate that competition between the rotation and the spin-orbit coupling governs the spin-dependent response of the cyclotron dynamics of the spin-orbit coupled bosons. The Sagnac-type cumulative phase can be read out from the envelope of a beat-frequency time evolution of the population imbalance in the spin-balanced system and enhanced by cyclotron motion. We also theoretically show that the sensitivity limit of the spin-orbit-coupled system to rotational motion can reach 4×10-7 \\text{rads}-1\\text{Hz}-1/2 .

  10. Many-Body Dynamics of Dipolar Molecules in an Optical Lattice

    NASA Astrophysics Data System (ADS)

    Hazzard, Kaden R. A.; Gadway, Bryce; Foss-Feig, Michael; Yan, Bo; Moses, Steven A.; Covey, Jacob P.; Yao, Norman Y.; Lukin, Mikhail D.; Ye, Jun; Jin, Deborah S.; Rey, Ana Maria

    2014-11-01

    We use Ramsey spectroscopy to experimentally probe the quantum dynamics of disordered dipolar-interacting ultracold molecules in a partially filled optical lattice, and we compare the results to theory. We report the capability to control the dipolar interaction strength. We find excellent agreement between our measurements of the spin dynamics and theoretical calculations with no fitting parameters, including the dynamics' dependence on molecule number and on the dipolar interaction strength. This agreement verifies the microscopic model expected to govern the dynamics of dipolar molecules, even in this strongly correlated beyond-mean-field regime, and represents the first step towards using this system to explore many-body dynamics in regimes that are inaccessible to current theoretical techniques.

  11. Many-body dynamics of dipolar molecules in an optical lattice.

    PubMed

    Hazzard, Kaden R A; Gadway, Bryce; Foss-Feig, Michael; Yan, Bo; Moses, Steven A; Covey, Jacob P; Yao, Norman Y; Lukin, Mikhail D; Ye, Jun; Jin, Deborah S; Rey, Ana Maria

    2014-11-07

    We use Ramsey spectroscopy to experimentally probe the quantum dynamics of disordered dipolar-interacting ultracold molecules in a partially filled optical lattice, and we compare the results to theory. We report the capability to control the dipolar interaction strength. We find excellent agreement between our measurements of the spin dynamics and theoretical calculations with no fitting parameters, including the dynamics' dependence on molecule number and on the dipolar interaction strength. This agreement verifies the microscopic model expected to govern the dynamics of dipolar molecules, even in this strongly correlated beyond-mean-field regime, and represents the first step towards using this system to explore many-body dynamics in regimes that are inaccessible to current theoretical techniques.

  12. Dynamics of localization phenomena for hard-core bosons in optical lattices

    SciTech Connect

    Horstmann, Birger; Cirac, J. Ignacio; Roscilde, Tommaso

    2007-10-15

    We investigate the behavior of ultracold bosons in optical lattices with a disorder potential generated via a secondary species frozen in random configurations. The statistics of disorder is associated with the physical state in which the secondary species is prepared. The resulting random potential, albeit displaying algebraic correlations, is found to lead to localization of all single-particle states. We then investigate the real-time dynamics of localization for a hardcore gas of mobile bosons which are brought into sudden interaction with the random potential. Regardless of their initial state and for any disorder strength, the mobile particles are found to reach a steady state characterized by exponentially decaying off-diagonal correlations and by the absence of quasicondensation; when the mobile particles are initially confined in a tight trap and then released in the disorder potential, their expansion is stopped and the steady state is exponentially localized in real space, clearly revealing Anderson localization.

  13. LIGHT SOURCE: Optics for the lattice of the compact storage ring for a Compton X-ray source

    NASA Astrophysics Data System (ADS)

    Yu, Pei-Cheng; Wang, Yu; Shen, Xiao-Zhe; Huang, Wen-Hui; Yan, Li-Xin; Du, Ying-Chao; Li, Ren-Kai; Tang, Chuan-Xiang

    2009-06-01

    We present two types of optics for the lattice of a compact storage ring for a Compton X-ray source. The optics design for different operation modes of the storage ring are discussed in detail. For the pulse mode optics, an IBS-suppression scheme is applied to optimize the optics for lower IBS emittance growth rate; as for the steady mode, the method to control momentum compact factor is adopted [Gladkikh P, Phys. Rev. ST Accel. Beams 8, 050702] to obtain stability of the electron beam.

  14. Dynamic localization in optical and Zeeman lattices in the presence of spin-orbit coupling

    NASA Astrophysics Data System (ADS)

    Kartashov, Yaroslav V.; Konotop, Vladimir V.; Zezyulin, Dmitry A.; Torner, Lluis

    2016-12-01

    The dynamic localization of a two-level atom in a periodic potential under the action of spin-orbit coupling and a weak harmonically varying linear force is studied. We consider optical and Zeeman potentials that are either in phase or out of phase in two spinor components, respectively. The expectation value for the position of the atom after one oscillation period of the linear force is recovered in authentic resonances or in pseudoresonances. The frequencies of the linear force corresponding to authentic resonances are determined by the band structure of the periodic potential and are affected by the spin-orbit coupling. The width or dispersion of the wave packet in authentic resonances is usually minimal. The frequencies corresponding to pseudoresonances do not depend on the type of potential and on the strength of the spin-orbit coupling, while the evolution of excitations at the corresponding frequencies is usually accompanied by significant dispersion. Pseudoresonances are determined by the initial phase of the linear force and by the quasimomentum of the wave packet. Due to the spinor nature of the system, the motion of the atom is accompanied by periodic, but not harmonic, spin oscillations. Under the action of spin-orbit coupling the oscillations of the wave packet can be nearly completely suppressed in optical lattices. Dynamic localization in Zeeman lattices is characterized by doubling of the resonant oscillation periods due to band crossing at the boundary of the Brillouin zone. We also show that higher harmonics in the Fourier expansion of the energy band lead to effective dispersion, which can be strong enough to prevent dynamic localization of the Bloch wave packet.

  15. A method of 2D/3D registration of a statistical mouse atlas with a planar X-ray projection and an optical photo

    PubMed Central

    Wang, Hongkai; Stout, David B; Chatziioannou, Arion F

    2013-01-01

    The development of sophisticated and high throughput whole body small animal imaging technologies has created a need for improved image analysis and increased automation. The registration of a digital mouse atlas to individual images is a prerequisite for automated organ segmentation and uptake quantification. This paper presents a fully-automatic method for registering a statistical mouse atlas with individual subjects based on an anterior-posterior X-ray projection and a lateral optical photo of the mouse silhouette. The mouse atlas was trained as a statistical shape model based on 83 organ-segmented micro-CT images. For registration, a hierarchical approach is applied which first registers high contrast organs, and then estimates low contrast organs based on the registered high contrast organs. To register the high contrast organs, a 2D-registration-back-projection strategy is used that deforms the 3D atlas based on the 2D registrations of the atlas projections. For validation, this method was evaluated using 55 subjects of preclinical mouse studies. The results showed that this method can compensate for moderate variations of animal postures and organ anatomy. Two different metrics, the Dice coefficient and the average surface distance, were used to assess the registration accuracy of major organs. The Dice coefficients vary from 0.31±0.16 for the spleen to 0.88±0.03 for the whole body, and the average surface distance varies from 0.54±0.06 mm for the lungs to 0.85±0.10 mm for the skin. The method was compared with a direct 3D deformation optimization (without 2D-registration-back-projection) and a single-subject atlas registration (instead of using the statistical atlas). The comparison revealed that the 2D-registration-back-projection strategy significantly improved the registration accuracy, and the use of the statistical mouse atlas led to more plausible organ shapes than the single-subject atlas. This method was also tested with shoulder xenograft

  16. Suppression of Faraday waves in a Bose-Einstein condensate in the presence of an optical lattice

    SciTech Connect

    Capuzzi, Pablo; Gattobigio, Mario; Vignolo, Patrizia

    2011-01-15

    We study the formation of Faraday waves in an elongated Bose-Einstein condensate in the presence of a one-dimensional optical lattice. The waves are parametrically excited by modulating the radial confinement of the condensate close to a transverse breathing mode of the system. For very shallow optical lattices, phonons with a well-defined wave vector propagate along the condensate, as in the absence of the lattice, and we observe the formation of a Faraday pattern. We find that by increasing the potential depth the local sound velocity decreases, and when it equals the condensate local phase velocity, the condensate develops an incoherent superposition of several modes and the parametric excitation of Faraday waves is suppressed.

  17. Mott-insulator state of cold atoms in tilted optical lattices: Doublon dynamics and multilevel Landau-Zener tunneling

    NASA Astrophysics Data System (ADS)

    Kolovsky, Andrey R.; Maksimov, Dmitrii N.

    2016-10-01

    We discuss the dynamical response of strongly interacting Bose atoms in an adiabatically tilted optical lattice. The analysis is performed in terms of the multilevel Landau-Zener tunneling. Different regimes of tunneling are identified and analytical expressions for the doublon number, which is the quantity measured in laboratory experiments, are derived.

  18. Optoelectronics with 2D semiconductors

    NASA Astrophysics Data System (ADS)

    Mueller, Thomas

    2015-03-01

    Two-dimensional (2D) atomic crystals, such as graphene and layered transition-metal dichalcogenides, are currently receiving a lot of attention for applications in electronics and optoelectronics. In this talk, I will review our research activities on electrically driven light emission, photovoltaic energy conversion and photodetection in 2D semiconductors. In particular, WSe2 monolayer p-n junctions formed by electrostatic doping using a pair of split gate electrodes, type-II heterojunctions based on MoS2/WSe2 and MoS2/phosphorene van der Waals stacks, 2D multi-junction solar cells, and 3D/2D semiconductor interfaces will be presented. Upon optical illumination, conversion of light into electrical energy occurs in these devices. If an electrical current is driven, efficient electroluminescence is obtained. I will present measurements of the electrical characteristics, the optical properties, and the gate voltage dependence of the device response. In the second part of my talk, I will discuss photoconductivity studies of MoS2 field-effect transistors. We identify photovoltaic and photoconductive effects, which both show strong photoconductive gain. A model will be presented that reproduces our experimental findings, such as the dependence on optical power and gate voltage. We envision that the efficient photon conversion and light emission, combined with the advantages of 2D semiconductors, such as flexibility, high mechanical stability and low costs of production, could lead to new optoelectronic technologies.

  19. Direct measurement of lattice dynamics and optical phonon excitation in semiconductor nanocrystals using femtosecond stimulated Raman spectroscopy.

    PubMed

    Hannah, Daniel C; Brown, Kristen E; Young, Ryan M; Wasielewski, Michael R; Schatz, George C; Co, Dick T; Schaller, Richard D

    2013-09-06

    We report femtosecond stimulated Raman spectroscopy measurements of lattice dynamics in semiconductor nanocrystals and characterize longitudinal optical (LO) phonon production during confinement-enhanced, ultrafast intraband relaxation. Stimulated Raman signals from unexcited CdSe nanocrystals produce a spectral shape similar to spontaneous Raman signals. Upon photoexcitation, stimulated Raman amplitude decreases owing to experimentally resolved ultrafast phonon generation rates within the lattice. We find a ∼600  fs, particle-size-independent depletion time attributed to hole cooling, evidence of LO-to-acoustic down-conversion, and LO phonon mode softening.

  20. Chaotic quantum ratchets and filters with cold atoms in optical lattices: Properties of Floquet states

    NASA Astrophysics Data System (ADS)

    Hur, Gwang-Ok

    The -kicked rotor is a paradigm of quantum chaos. Its realisation with clouds of cold atoms in pulsed optical lattices demonstrated the well-known quantum chaos phenomenon of 'dynamical localisation'. In those experi ments by several groups world-wide, the £-kicks were applied at equal time intervals. However, recent theoretical and experimental work by the cold atom group at UCL Monteiro et al 2002, Jonckheere et al 2003, Jones et al 2004 showed that novel quantum and classical dynamics arises if the atomic cloud is pulsed with repeating sequences of unequally spaced kicks. In Mon teiro et al 2002 it was found that the energy absorption rates depend on the momentum of the atoms relative to the optical lattice hence a type of chaotic ratchet was proposed. In Jonckheere et al and Jones et al, a possible mechanism for selecting atoms according to their momenta (velocity filter) was investigated. The aim of this thesis was to study the properties of the underlying eigen values and eigenstates. Despite the unequally-spaced kicks, these systems are still time-periodic, so we in fact investigated the Floquet states, which are eigenstates of U(T), the one-period time evolution operator. The Floquet states and corresponding eigenvalues were obtained by diagonalising a ma trix representation of the operator U(T). It was found that the form of the eigenstates enables us to analyse qual itatively the atomic momentum probability distributions, N(p) measured experimentally. In particular, the momentum width of the individual eigen states varies strongly with < p > as expected from the theoretical and ex- perimental results obtained previously. In addition, at specific < p > close to values which in the experiment yield directed motion (ratchet transport), the probability distribution of the individual Floquet states is asymmetric, mirroring the asymmetric N(p) measured in clouds of cesium atoms. In the penultimate chapter, the spectral fluctuations (eigenvalue statis tics) are