JILA Thesis Defense

Since their invention centuries ago, we have used microscopes to understand ourselves and the world around us. Some of today’s most advanced microscopes use coherent diffractive imaging (CDI) with soft X-rays. Soft X-rays provide excellent resolution and natural contrast with microorganisms in their native state, while CDI is quantitative, minimizes radiation dose, and optimizes resolution. Soft X-ray CDI requires a coherent light source and is currently confined to accelerator facilities with limited access.

Optically pumped magnetometers based on spin-polarized alkali atoms are powerful tools for ultra-sensitive magnetic field measurements, achieving sub-fT precision, but accurate vector measurements remain challenging. In this work, I present a vector magnetometry technique based on RF-driven Rabi oscillations between adjacent Zeeman sublevels in the ground state manifolds of 87Rb. A Floquet-based modeling and calibration framework is developed to account for key systematic effects and accurately map measured Rabi frequencies to magnetic field direction.

Two-dimensional crystals of trapped ions in a Penning trap have enabled advances in quantum simulation and precision measurement. Because the crystal rotates at ~180 kHz, previous experiments were limited to global interactions, and poor cooling of in-plane motion reduced experimental fidelity. In this defense, I describe using a deformable mirror (DM) to apply patterned spin rotations in the rotating frame of the crystal.

Abstract: Understanding the fundamental interactions that influence molecular recognition is essential for advancing applications in drug design, sensing, and materials chemistry. This dissertation uses cryogenic ion vibrational spectroscopy (CIVS) to investigate noncovalent interactions in anion-receptor complexes by studying mass-selected gas-phase ions at cryogenic temperatures, eliminating complexities due to solvation effects.

Due to their strong, long-range, and tunable dipolar interactions, ultracold polar molecules can realize spin-motion models with rich many-body physics. Using a spin encoded in rotational states of fermionic KRb molecules, we demonstrate tuning of Heisenberg XXZ models with electric fields and Floquet engineering of XYZ models with microwave pulse sequences. By controlling motion with optical lattices, we explore highly tunable generalized t-J models. Observing new dynamics and phases predicted for these models also requires low-entropy initial states.

Abstract: Breathomics aims to address the current unmet clinical needs by utilizing exhaled breath contents for non-invasive and real-time medical diagnostics. We demonstrate a frequency comb breathalyzer powered by machine learning for detecting COVID-19, finding 85 % accuracy among a 170-subject cohort. To enhance diagnostic power, we introduce Modulated Ringdown Comb Interferometry, a new technique enabling the quantification of “odor” of arbitrarily complex and unknown contents at new record sensing performance and requiring only simple instruments.

Neutral-atom arrays with single-particle detection and control are a powerful tool for quantum science. In this defense, I present results from two projects, both performed with the same tweezer-programmable neutral-strontium-array apparatus. First, we engineer Rydberg interactions to create entangled spin-squeezed states, whose measurement noise can outperform classical limits. In a synchronous optical-frequency comparison between two spin-squeezed ensembles of atoms, we realize a measurement with a stability better than the standard quantum limit.

Nonequilibrium quantum systems exhibit phenomena not seen in equilibrium but are also less well understood. To study these systems, quantum simulators hold much promise due to their broad tunability and access to measurement observables. In this defense, I present experiments engineering nonequilibrium quantum phases of matter using many strontium atoms in a high-finesse optical cavity. Observations include a first experimental realization of three dynamical phases in quenched BCS superconductors and insights into many-body gap protection in fermionic superfluids.

Abstract