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Single atoms are promising candidates for physically implementing quantum bits, the fundamental unit of quantum information. We have built an apparatus for cooling, trapping and imaging single rubidium atoms in microscopic optical tweezers. The traps are formed from a tightly focused off-resonant laser beam, which traps atoms using the optical dipole force. The traps have a diameter of ~1 μm and a depth of ~1 mK. The novelty of our approach is the use a digital mirror device (DMD) to generate multiple independently movable tweezers from a single laser beam. The DMD consists of an array of micro-mirrors that can be switched on and off, thus acting as a binary amplitude modulator. We use the DMD to imprint a computer-generated hologram on the laser beam, which is converted in to the desired arrangement of traps in the focal plane of a lens. We have developed fast algorithms for calculating binary holograms suitable for the DMD. In addition, we use this method to measure and correct for errors in the phase of the wavefront caused by optical aberrations, which is necessary for producing diffraction-limited focal spots. Using this apparatus, we have trapped arrays of up to 20 atoms with arbitrary geometrical arrangements. We exploit light-assisted collisions between atoms to ensure there is at most one atom per trapping site. We measure the temperature of the atoms in the traps to be 12 μK, and their lifetime to be 1.4 s. Finally, we demonstrate the ability to select individual atoms from an array and transport them over a distance of 14μm with laser cooling, and 5 μm without.

In this work we present the first implementation of the incremental scheme for coupled cluster linear-response frequency-dependent dipole polarizabilities. The implementation is fully automated and makes use of the domain-specific basis set approach. The accuracy of the approach is determined on the basis of a test suite of 47 molecules and small clusters. The local approximation in the coupled cluster singles and doubles polarizability exhibits a mean error of 0.02% and a standard deviation of 0.32% when using a third-order incremental expansion. With the proposed approach, it is possible to compute polarizabilities with larger basis sets compared to the canonical implementation and thus it is possible to obtain higher total accuracy. The incremental scheme yields the smallest errors for weakly-bound and quasi-linear systems, while two- and three-dimensional (cage-like) structures exhibit somewhat larger errors as compared to the full test set. / Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

Two compact planar crossed-dipole antennas loaded with near-field resonant parasitic (NFRP) elements are reported. The NFRP and crossed-dipole elements are designed for the desired circularly polarized (CP) radiation. By placing the NFRP element over the driven element at angles of 0 degrees and 45 degrees, respectively, dual-band and broadband CP antennas are realized. All radiating elements of antennas are 35 mm x 35 mm x 0.508 mm (0.187 lambda(0) x 0.187 lambda(0) x 0.0027 lambda(0) at 1.6 GHz) in size. The dual-band CP antenna has a measured vertical bar S-11 vertical bar < -10-dB bandwidth of 226 MHz (1.473-1.699 GHz) and measured 3-dB axial ratio (AR) bandwidths of 12 MHz (1.530-1.542 GHz) and 35 MHz (1.580-1.615 GHz) with minimum AR CP frequencies of 1.535 GHz (AR = 0.26 dB) and 1.595 GHz (AR = 2.08 dB), respectively. The broadband CP antenna has a measured vertical bar S-11 vertical bar< -10-dB bandwidth of 218 MHz (1.491-1.709 GHz) and a 3-dB AR bandwidth of 145 MHz (1.490-1.635 GHz). These compact antennas yield bidirectional electromagnetic fields with high radiation efficiency across their operational bandwidths.

>Magister Scientiae - MSc / In the standard (‘concordance’) model of Cosmology, there is a fundamental assumption that the Universe is statistically isotropic and homogeneous on large scales, known as the Cosmological Principle. The Cosmological Principle requires that the dipole anisotropy apparent in the CMB should also be observed in galaxy number counts if this signal occurs due to the aberration and Doppler effects from our peculiar motion. This thesis will investigate the accuracy with which the cosmic kinematic dipole can be determined by comparing real data from NRAO VLA Sky Survey (NVSS) catalog with the simulated sky maps following its specifications. The mock maps are generated using FLASK code which assumes a lognormal distribution for the radio count density field from z=0 to z =4 and taking as an entry an angular power spectrum from CAMB which assumed a flat ΛCDM cosmology and a redshift distribution. After analising the kinematic dipole, we turn to the analysis of statistical isotropy in the catalog. We used ANalysis Of Variance (ANOVA) test on patches in the sky of different radii as one of the statistical tools for the analysis. We found that as we go to a higher radius for the patches, we have a better agreement between the theory and the observation as expected. We also saw that the more we are rigorous on the rejection criteria, the smaller is the discrepancy between the observed and simulated number count distribution in the sky. We found an optimum choice of 25◦ as patch size, and if the accepted patches have a maximum of 30% of their pixels masked. Therefore, we find that the NVSS data agrees with the fundamental assumption of statistical isotropy at angular scales > 20◦.

Este trabalho descreve os métodos usados para obtenção de uma amostra ultra-fria de átomos de estrôncio. Os métodos usados para preparar a amostra são: um desacelerador Zeeman e duas armadilhas magneto-ópticas (MOT). O primeiro MOT operando na transição 1S0&minus;1 P1 (azul) e o segundo na transição 1S0&minus;3P1 (vermelha). Com relação ao primeiro estágio, se faz necessário o uso de um laser de comprimento de onda de 497nm, que através da transição 3P2&minus;3D2 recuperam os átomos que sofrem transição para os chamados estados escuros. O último estágio é uma armadilha de dipolo para átomos de estrôncio usando apenas um feixe laser com comprimento de onda de 1064nm. O carregamento dessa armadilha é feito transferindo uma amostra atômica já pré-resfriadas. Explicamos de que maneira é feita a análise e aquisição dos resultados apresentados. Ressaltamos ainda a importância dos resultados obtidos para o projeto atual e para projetos futuros. / The present work describes the methods used to obtain a sample of ultra cold atoms of strontium. The methods necessary for obtaining the sample are: a Zeeman decelerator and a two step magneto-optical trap (MOTs). The first MOT works on the blue transition 1S0&minus;1P1 while the second is operating on the red transition 1S0&minus;3P1 transition. In the first stage a laser operating at 497nm is used to drive the 3P2&minus;3D2 transition in order to prevent atoms accumulating in the 3P1 dark state. The last stage, after cooling, consists in a dipole trap for strontium atoms using only one laser beam with 1064nm wavelength. This trap is loaded by the transfer of a pre cooled atomic sample. We explain how the analysis and acquisition of the presented data are made. We also emphasize the importance of the obtained results for the current project as well as for future ones.

Usando-se a técnica de dicroísmo ótico induzido sobre a banda de absorção ótica em 272m devido o íon Pb++ em NaCl estabelecemos a simetria desse defeito. O momento dipolar com a vacância na posição 110 foi de 3.65 e &#197. Usando-se a mesma técnica além de I.T.C. conseguimos a reorientação dipolar do dipolo I.V. na temperatura de 77&#176K. Essa relaxação é atribuída ao fato do íon Pb++ estar em estado eletrônico excitado. / Using the electric induced dichroism effect on the optical absorption band at 272m due to the Pb++ ion in NaCl, the symmetry of I.V. dipole was discussed. The electric dipole moment for the vacancy in the (110) position was measured and found to be 3.65 &#197. Using the same technique and I.T.C. measurements we found reorientation in temperatures as low as 77&#176K. This relaxation is attributed to be I.V. dipole with the Pb++ ion in an electronic excited state.

Neste trabalho estudamos o processo de ressonância colisional o que nos permitiu aumentar a taxa de formação molecular em até seis vezes. Isto foi feito variando-se a temperatura atômica de uma amostra inicialmente aprisionada em uma armadilha magneto óptica (MOT) através de um passo de resfriamento do tipo melaço óptico (molasses). Uma explicação qualitativa foi apresentada para o efeito observando as soluções das funções de ondas parciais para átomos interagentes no estado fundamental. Carregamos uma armadilha óptica de dipolo formada por um laser de Ti:Safira. Por fim, ressaltamos a importância de tais resultados para o nosso grupo de pesquisas e a sua utilização em futuros experimentos. / In this work, we study a partial wave resonance process which allows us to increase the molecule formation rate up to six times. This was done by an atomic temperature variation which was first trapped in a magneto optical trap (MOT) by applying a molasses stage. A qualitative explanation was presented for the observed effect through the partial waves solutions for ground states interacting atoms. We loaded an optical dipole trap formed by a Ti:Sapphire laser. Finally, we discuss the importance of such results for our research and their use in future experiments.

Filmes amorfos que não apresentam piezoeletricidade intrínseca, podem ser induzidos a mostrar um efeito piezoelétrico linear quando um fluxo de íons é estabelecido através dele. O efeito está relacionado ao efeito piezoelétrico induzido pela corrente elétrica, exceto que ele está presente ainda que o fluxo de íons positivo a negativo sejam iguais (corrente zero). Um filme circular de celofane é colocada entre duas células de vidro, tal que ela separa água pura de uma solução de cloreto de sódio (NaCl). A diferença de nível dos líquidos fornece uma pressão estática que mantém uma curvatura na membrana, ou no sentido da água ou no sentido da solução. Um transdutor eletromagnético acoplado a água e dirigido senoidalmente por um oscilado, deforma o filme ciclicamente, e eletrodos de platinam um de cada lado do filme, levam os sinais elétricos a um detector síncromo com a deformação aplicada. Enquanto o sinal elétrico observado poderia ser devido a efeitos espúrios dos eletrodos, a inversão observada na fase deste sinal com a mudança da curvatura indica que ele é dependente da deformação de um filme separando dois eletrólitos é devido `a modulação da mobilidade iônica pela deformação aplicada / Amorphous films which can have intrinsic piezoelectricity, can be induced to show a linear piezoelectric effect when a flux of ions is established across them. The effect is related to the electric current induced piezoelectric effect, except that is present even though positive and negative ion fluxes are equal (zero-current). A circular cellophane film is put between two glass cell, so that it separates pure water from a NaCl solution. A level difference of liquids provides a static pressure supports a membrane curvature, either towards or away from the water. An electromagnetic transducer, coupled to the water and driven sinusoidally by a oscillator deforms the film cyclically and platinum electrodes on either side of the film lead the electric signals to a detector synchronized with the applied deformation. While the electric signal observed might be due spurious effects from the electrodes, the observed might be due to spurious effects from the electrodes, the observed reversal in phase of the signal with the change of curvature of the film signifies that it is deformation-dependent. The deformation-dependent electricity in a film separating two electrolytes is owing to the modulation of the mobility of the ions by the applied deformation