Atom Chip AC Zeeman Potentials: Trapping and Interferometry

We present a largely underused tool in atom chip technology, the AC Zeeman force, which can push, pull, or trap neutral atoms of any spin state using microwave magnetic fields near atomic hyperfine resonances. We evaluate multiple microstrip chip designs for use in atom trapping and interferometry, and evaluate the effects of detuning, state mixing, and the AC Stark effect on the viability of trapping and interferometric schemes. All trapping schemes involve sending multiple microwave currents with tunable power, frequency detuning, and relative phase through atom chip traces, creating a local microwave magnetic near-field minimum which can target individual spin states, allowing for state-specific trapping and transport. Interferometers based on AC Zeeman traps allow for atom localization, long integration times using trapped atoms, and allow for multi-mode interferometry of thermal atom clouds. A simpler interferometer scheme involves regions with a linear near-field gradient in combination with a laser dipole trap. Current work uses ultracold rubidium-87 at 6.8 GHz, we also anticipate using potassium isotopes with hyperfine splittings in the .25-1.3 GHZ range.