A class of permanent magnetic lattices for ultracold atoms
  We report on a class of configurations of permanent magnets on an atom chip for producing 1D and 2D periodic arrays of magnetic microtraps with non-zero potential minima and variable barrier height for trapping and manipulating ultracold atoms and quantum degenerate gases. We present analytical expressions for the relevant physical quantities and compare them with our numerical results and with some previous numerical calculations. In one of the configurations of permanent magnets, we show how it is possible by changing the angle between the crossed periodic arrays of magnets to go from a 1D array of 2D microtraps to a 2D array of 3D microtraps and thus to continuously vary the barrier heights between the microtraps. This suggests the possibility of performing a type of `mechanical' BEC to Mott insulator quantum phase transition in a magnetic lattice. We also discuss a configuration of magnets which could realize a two-qubit quantum gate in a magnetic lattice. 
Saeed Ghanbari, Tien D Kieu and Peter Hannaford