Periodic array of Bose-Einstein condensates in a magnetic lattice

Abstract

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...

Stability of a trapped-atom clock on a chip

“…Nevertheless, it needs to be investigated, whether better detection and/or imaging at long time-of-flight, may reduce this error. The magnetic field stability may be improved by refined power supplies, the use of multi-wire traps [75], microwave dressing [57] or ultimately the use of atom chips with permanent magnetic material [76][77][78]. If the magnetic field fluctuations can be reduced, the temperature fluctuations may also reduce.…”

Twisted Toroidal Vortex Solitons in Inhomogeneous Media with Repulsive Nonlinearity

“…Using crossed fields induced by barrelshaped solenoids with trapped magnetic flux F , whose radii vary along r (realized here as the coordinate running along the solenoidʹs axis) as 32], one may construct the required approximately isotropic pattern. It can be created in a more accurate form by means of recently developed techniques, viz., magnetic lattices [24][25][26], field concentrators [33], and current circuitry integrated with the trap [34]. An estimate for the 7 Li BEC, where the FR was studied in detail [21], suggests that the present system may be realized with magnetic-field gradients 10 T/m  .…”

“…[17][18][19], where it was shown that repulsive spatially inhomogeneous nonlinearity, with the local strength, ( ) s r , growing as a function of radial variable r faster than 3 r , creates stable fundamental-and vortex-soliton states. In BEC, the required spatial modulation of the nonlinearity strength may be induced by means of suitable Feshbach resonances (FRs) [20][21][22][23] controlled by inhomogeneous magnetic [24][25][26] or laser [27] fields (necessary physical conditions for that are considered below).…”

Exact states in waveguides with periodically modulated nonlinearity

“…The same model, with propagation distance z replaced by time t, represents the scaled Gross-Pitaevskii equation for the mean-field wave function of an atomic BoseEinstein condensate (BEC), for which the periodic nonlinearity modulation can be induced by means of the Feshbach resonance in a spatially non-uniform magnetic or optical field. In particular, the necessary periodic profile of the magnetic field can be accurately implemented by means of the known technique based on the use of appropriately designed magnetic lattices [25]. Furthermore, the spatially periodic distribution of the local nonlinearity coefficient in BEC has been experimentally realized by means of an optical lattice [26].…”