School of Physics Thesis Dissertation Defense
Alexandra Crawford
Advisor: Dr. Chandra Raman, School of Physics, Georgia Institute of Technology
Cavity Quantum Electrodynamics (CQED) in your pocket
Date: Friday, September 19, 2025
Time: 9:00 a.m.
Location: Howey W401
Committee Members:
Dr. Ali Adibi - School of Electrical and Computer Engineering, Georgia Institute of Technology
Dr. Colin Parker - School of Physics, Georgia Institute of Technology
Dr. David Citrin - School of Electrical and Computer Engineering, Georgia Institute of Technology
Dr. Brian Sawyer - Georgia Tech Research Institute (GTRI), Georgia Institute of Technology
Abstract:
Quantum systems now achieve unprecedented levels of sensing precision and stability in the laboratory, yet many—such as quantum computers—remain large, benchtop-scale platforms with limited practical deployment. Miniaturization is essential for portable and scalable devices, yet current approaches face major challenges. In cold atom cavity quantum electrodynamics (CQED), a key figure of merit is the cooperativity, which quantifies the strength of atom–cavity interactions. High cooperativity can be achieved in these systems, but doing so requires bulky infrastructure such as ultra-high-vacuum chambers, laser cooling, and complex field control, making chip-scale integration difficult. Vapor-cell devices offer a more scalable path, but in thermal vapors the random trajectories of atoms through the cavity mode restrict usable interactions.
This work explores CQED with collimated atomic beams as a scalable alternative. Collimated beams increase the atomic flux through the cavity mode, improve coherence times by suppressing collisions, and allow controlled delivery of atoms to prevent contamination of optical components. To enable strong coupling with thermal atoms, microfabricated Fabry–Pérot cavities and resonators with small mode volumes are designed and characterized, with cavity mode maxima shifted into free space to maximize atom–light interaction. Both cavity structures and atomic beam sources are engineered for compatibility with MEMS fabrication, ensuring pathways toward wafer-scale manufacturing. These developments demonstrate how CQED can move beyond laboratory-scale experiments toward the long-standing goal of chip-compatible architectures, positioning it as a practical platform for single-photon generation, quantum communication, and next-generation portable quantum technologies. This thesis contributes to that vision by exploring pathways for realizing CQED in scalable, chip-integrated systems.