Archimedean-Spiral-Based Microchip Ring Waveguide for Cold Atoms

We present a scheme for generating a ring magnetic waveguide on a single-layer atom chip. The wire layout consists of two interleaved Archimedean spirals of the same size. The waveguide avoids the trapping perturbation caused by the input and output ports, resulting in an enclosed guiding loop for neutral atoms in weak-field seeking states. Such a configuration can create a tight and deep trap potential with a small current. Taking the \F = 2, m(F) = 2] state of Rb-87 as an example, the trap frequency and depth are estimated to be 18 kHz and 335 mu K, respectively, with a dc current of 2 A.