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...

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.

We report site-resolved radio-frequency spectroscopy measurements of Bose-Einstein condensates of 87 Rb atoms in about 100 sites of a one-dimensional (ID) 10-/rm-period magnetic lattice produced by a grooved magnetic film plus bias fields. Site-to-site variations of the trap bottom, atom temperature, condensate fraction, and chemical potential indicate that the magnetic lattice is remarkably uniform, with variations in the trap bottoms of only ± 0.4 mG. At the lowest trap frequencies (radial and axial frequencies of 1.5 kHz and 260 Hz, respectively), temperatures down to 0.16 /iK are achieved in the magnetic lattice, and at the smallest trap depths (50 kHz) condensate fractions up to 80% are observed. With increasing radial trap frequency (up to 20 kHz, or aspect ratio up to ~80) large condensate fractions persist, and the highly elongated clouds approach the quasi-1D Bose gas regime. The temperature estimated from analysis of the spectra is found to increase by a factor of about 5, which may be due to suppression of rethermalizing collisions in the quasi-1D Bose gas. Measurements for different holding times in the lattice indicate a decay of the atom number with a half-life of about 0.9 s due to three-body losses and the appearance of a high-temperature (~1.5 pK ) component which is attributed to atoms that have acquired energy through collisions with energetic three-body decay products.