Doctor of Philosophy in Physics 

School of Physics Thesis Dissertation Defense

Julia Cohen

Dr. Michael Chapman, School of Physics, Georgia Institute of Technology (Advisor)

Interaction-enabled coherent control of collective spin excitations in a driven spinor BEC

Date: Wednesday, September 9, 2026

Time: 2:00 p.m.

Location: Howey N201/202

Virtual: https://teams.microsoft.com/meet/289136347395392?p=BfoTZ7yZ80Zfq4mxC5

Thesis Committee: 

Dr. Colin Parker, School of Physics, Georgia Institute of Technology

Dr. T. A. Brian Kennedy, School of Physics, Georgia Institute of Technology

Dr. Martin Mourigal, School of Physics, Georgia Institute of Technology

Dr. Thai M. Hoang, NASA Jet Propulsion Laboratory, California Institute of Technology

Abstract:

The ability to control quantum systems is fundamental to the development of quantum technology. Single-particle control techniques are ubiquitous but cannot be used to generate quantum entanglement. Multi-particle interactions are needed to produce entangled states, but controlling interactions is often non-trivial. In this dissertation, I computationally and experimentally explore how collective interactions and weak modulation of an applied magnetic field can be used to induce spin fraction excitations and how doing so can be used for coherent quantum control. As part of my doctoral work, I established a model for the driven system based off its similarities with a well-understood classical system in the mean field limit, and I used numerical simulations to predict the system's response to the magnetic driving. I performed experiments on a spin-1 Bose-Einstein condensate of rubidium-87 atoms, the results of which are described here and compared to those of the simulations. The observations showed the expected behavior in response to external driving, including resonant direct excitation and coherent spin fraction oscillations, all of which are generated via the spin-dependent interactions between the atoms.