We investigate frequency up-conversion of low power cw resonant radiation in Rb vapour as a function of various experimental parameters. We present evidence that the process of four wave mixing is responsible for unidirectional blue light generation and that the phase matching conditions along a light-induced waveguide determine the direction and divergence of the blue light. Velocity-selective excitation to the 5D level via step-wise and two-photon processes results in a Doppler-free dependence on the frequency detuning of the applied laser fields from the respective dipole-allowed transitions. Possible schemes for ultraviolet generation are discussed.

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We report on the loading and trapping of ultracold atoms in a one dimensional permanent magnetic lattice of period 10 µm produced on an atom chip. The grooved structure which generates the magnetic lattice potential is fabricated on a silicon substrate and coated with a perpendicularly magnetized multilayered TbGdFeCo/Cr film of effective thickness 960 nm. Ultracold atoms are evaporatively cooled in a Z-wire magnetic trap and then adiabatically transferred to the magnetic lattice potential by applying an appropriate bias field. Under our experimental conditions trap frequencies of up to 90 kHz in the magnetic lattice are measured and the atoms are trapped at a distance of less than 5 µm from the surface with a measured lifetime of about 450 ms. These results are important in the context of studies of quantum coherence of neutral atoms in periodic magnetic potentials on an atom chip.

Atomic media have played a major role in studies of fast light. One of their attractive features is the ability to manipulate experimental parameters to control the dispersive properties that determine the group velocity of a propagating light pulse. We give an overview of the experimental methods, based on both linear and nonlinear atom–light interaction, that have produced superluminal propagation in atomic media, and discuss some of the significant theoretical contributions to the issues of pulse preservation and reconciling faster-than-light propagation and the principle of causality. The comparison of storage of light, enhanced Kerr nonlinearity and efficient wave mixing processes in slow and fast light atomic media illustrates their common and distinct features.

We report the realization of a periodic array of Bose-Einstein condensates of 87 Rb F =1 atoms trapped in a one-dimensional magnetic lattice close to the surface of an atom chip. A clear signature for the onset of BEC in the magnetic lattice is provided by in-situ site-resolved radiofrequency spectra, which exhibit a pronounced bimodal distribution consisting of a narrow component characteristic of a BEC together with a broad thermal cloud component. Similar bimodal distributions are found for various sites across the magnetic lattice. The realization of a periodic array of BECs in a magnetic lattice represents a major step towards the implementation of magnetic lattices for quantum simulation of many-body condensed matter phenomena in lattices of complex geometry and arbitrary period.PACS numbers: 37.10. Gh, 37.10.Jk, 67.10.Ba, 67.85.Hj Optical lattices based on arrays of optical dipole traps are used extensively to trap periodic arrays of ultracold atoms and quantum degenerate gases in a broad range of applications. These range from simulations of condensed matter phenomena [1] to studies of lowdimensional quantum gases [2], high precision atomic clocks [3] and registers for quantum information processing [4,5]. A potentially powerful alternative approach involves magnetic lattices based on periodic arrays of magnetic microtraps created by permanent magnetic microstructures [6][7][8][9][10][11][12][13][14][15][16], current-carrying wires [17][18][19] or vortex arrays in superconducting films [20]. Magnetic lattices based on patterned magnetic films may, in principle, be tailored to produce 2D (or 1D) arrays of atomic ensembles in arbitrary configurations [12]. Periodicities may range from tens of micrometers, i.e., the interesting range for Rydberg-interacting quantum systems, such as Rydberg-dressed BECs [21] and Rydbergmediated quantum gates [15,22], down to below the optical wavelength where tunneling coupling strengths may exceed those possible with conventional optical lattices. Currently, there is also much interest in creating 2D periodic lattices of complex geometry, such as triangular, honeycomb, Kagome and super-lattices, in order to simulate condensed matter phenomena [23], including exotic quantum phases, such as graphene-like states [24][25][26], which are predicted to occur in lattices with non-cubic symmetry.Despite these prospects for magnetic lattices, little has been achieved to date, compared to optical lattices, in part due to the difficulty in controlling the resulting potentials, including magnetic homogeneity and efficient loading of the microtraps. Another serious challenge is to overcome the inelastic collision losses which can occur at high atom densities and which are accentuated when miniaturizing the traps. For example, previous experiments involving 2D arrays of magnetic microtraps with a period of about 25 µm [11] were limited by rapid three-body loss (decay rates >20 s −1 ) which precluded the formation of Bose-Einstein condensates with observable condensate fractions.In this...

Directional infrared emission at 1.37 and 5.23 μm is generated in Rb vapors that are stepwise excited by low-power cw resonant light. The radiation at 5.23 μm originating from amplified spontaneous emission on the 5D(5/2)→6P(3/2) transition and wave mixing consists of forward- and backward-directed components with distinctive spectral and spatial properties. Diffraction-limited light at 1.37 μm generated in the copropagating direction only is a product of parametric wave mixing around the 5P(3/2)→5D(5/2)→6P(3/2)→6S(1/2)→5P(3/2) transition loop. This highly nondegenerate mixing process involves one externally applied and two internally generated optical fields. Similarities between wave mixing generated blue and 1.37 μm light are demonstrated.

We report on the design, fabrication and characterization of magnetic nanostructures to create a lattice of magnetic traps with sub-micron period for trapping ultracold atoms. These magnetic nanostructures were fabricated by patterning a Co/Pd multilayered magnetic film grown on a silicon substrate using high precision e-beam lithography and reactive ion etching. The Co/Pd film was chosen for its small grain size and high remanent magnetization and coercivity. The fabricated structures are designed to magnetically trap 87 Rb atoms above the surface of the magnetic film with 1D and 2D (triangular and square) lattice geometries and sub-micron period. Such magnetic lattices can be used for quantum tunneling and quantum simulation experiments, including using geometries and periods that may be inaccessible with optical lattices.

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