AC & DC Zeeman Interferometric Sensing With Ultracold Trapped Atoms On A Chip

This thesis presents progress in developing a trapped atom interferometer on a chip, based on AC Zeeman potentials. An atom interferometer is a high-precision measuring tool that can detect various types of forces and potentials. The trapped atom interferometer introduced in this thesis targets the shortcomings of traditional ballistic atom interferometers, which are typically meter-scale in height. Notably, a trapped atom interferometer has a localized atomic sample, a potentially longer interferometric phase accumulation time, and the prospect of being the basis for a more compact instrument. This thesis presents multiple projects in the development of a trapped atom interferometer based on the AC Zeeman potentials and traps: 1) production of ultracold potassium on a chip, 2) the theory of potential roughness in chip traps, 3) microwave chip trap design, and 4) a trapped atom interferometer with rubidium atoms, based on a laser dipole trap and an AC Zeeman force. (1) Potassium is a good candidate for the atom interferometer due to its bosonic and fermionic isotopes, multiple magic magnetic fields, and the convenience of RF and microwave trapping. The laser cooling and trapping system were upgraded to improve the temperature and population of potassium atoms in the chip trap. On-chip cooling resulted in a significant inelastic loss, which prevented the production of a potassium Bose-Einstein condensate. (2) Numerical simulations of chip wire defects predict that the AC Zeeman trapping potential should be substantially smoother than its DC Zeeman counterpart: the suppression of the roughness is due to magnetic polarization selection rules and the AC skin effect. (3) Furthermore, the thesis presents a number of studies on the straight and curved microstrip transmission lines that form the building blocks of the microwave atom chip for the AC Zeeman trap. (4) Finally, we constructed a rubidium-based Ramsey interferometer that can be converted to an atom interferometer by applying a spin-dependent AC Zeeman force: the interferometer was used to measure DC and AC Zeeman energy shifts and fringes were observed with an AC Zeeman force