Time-orbiting-potential chip trap for cold atoms

We present a design for an atom chip trap that uses the time-orbiting potential technique. The design offers several advantages compared to other chip-trap methods. It uses a simple crossed-wire pattern on the chip, along with a rotating bias field. The trap is naturally close to spherically symmetric, and it can be modified to be exactly symmetric in quadratic order of the coordinates. Loading from a magneto-optical trap is facilitated because the trap can be positioned an arbitrary distance from the chip. The fields can be modified to provide a gradient for support against gravity, and the three-dimensional trap can be adiabatically transformed into a two-dimensional guide.