Bose-Einstein condensation in an atom chip

In the experimental setup the atom chip is combined with a more sturdy copper structure behind the chip for the initial loading. Its H-shape allows U-currents and Z-currents, whose magnetic fields create quadrupole and Ioffe-Pritchard traps, when a homogeneous bias field is added. A vertical double-MOT setup is used with a continuous push beam from a vapour cell MOT, below, to load a mirror-MOT in the ultra-high vacuum chamber on top. The quadrupole field for the MOT is created by separate coils and the chip acts as the mirror. All subsequent trapping fields are generated by combining currents in the copper H-structure or in the chip with bias fields. The 1×1 mm² central wire of the H-structure stands the trapping currents of up to 50 A for over a minute without heating, thus preserving the ultra-high vacuum. Using just the copper H-structure, a Bose-Einstein condensate of 3 × 10^{5 87}Rb atoms in the |F = 2, m_F = 2> state is reached which is then transferred to the chip in typically 100 ms. Thus the setup completely decouples the condensation process from the trap layout of the atom chip, providing a very flexible system.