Directly Trapping Atoms in a U-Shaped Magneto-Optical Trap Using a Mini Atom Chip

We experimentally demonstrate the trapping of ⁸⁵Rb atoms directly on a chip-size U-shaped magneto-optical trap (U-MOT). The trap includes a U-shaped wire on the chip, two bias magnetic field coils and laser beams. The capture volume of the U-MOT is theoretically calculated, and the trap is experimentally realized. With 2A current applied to the U-shaped wire and 2-Gauss horizontal bias field, more than 2×10^⁶ atoms are trapped. In contrast with an ordinary mirror-MOT, this U-MOT captures atoms directly from the background, thus the trap size is greatly reduced. Based on this mini trap scheme, it is possible to realize a chip-size atom trap array for quantum information processing.