Atomic Sensors for Plasma Field Diagnostics and for Inertial Measurement

Abstract

Quantum sensing exploits the sensitivity of quantum systems to their environment, translating external fields and forces into measurable shifts in quantum-mechanical observables. Neutral atoms constitute a highly effective and scalable sensing platform owing to their identical nature and extended coherence times. This dissertation investigates two implementations of atom-based quantum sensing: electric field diagnostics in low-pressure plasma discharges using Rydberg electromagnetically induced transparency (EIT), and inertial sensing via tractor atom interferometry (TAI). Non-invasive electric field measurement is crucial for understanding plasma dynamics without disturbing the local environment, for which high-resolution, coherent spectroscopy of Rydberg states via EIT is a promising candidate. Deploying EIT in plasma environments requires a systematic characterization of collisional effects. To this end, Rydberg-EIT is analyzed in rubidium vapor interacting with plasma precursor gases such as argon, neon, and nitrogen at pressures up to 5 Torr. The observed frequency shifts and collisional broadening are consistent with semiclassical predictions from the Fermi pseudopotential model. Crucially, collisional broadening remains narrower than typical EIT linewidths below 100 mTorr, identifying this pressure range as an operational window for EIT-based plasma field diagnostics. Rydberg-EIT is subsequently applied to a low-pressure, inductively coupled plasma (ICP). In a custom ultra-high-vacuum plasma chamber, Rydberg Stark shifts of rubidium tracers seeded into a continuous argon discharge are mapped via EIT. Prior to plasma ignition, Rydberg spectra exhibit modulation sidebands driven by both electric and magnetic near-fields of the ICP coil. Upon ignition, the bulk plasma screens the rf drive field, suppressing the sidebands. The resulting in-plasma lineshapes are instead governed by V/cm-scale plasma microfields and collisional broadening. Modeling the microfield with a Holtsmark distribution enables the extraction of plasma electron densities as a function of pressure and rf power. By resolving a Rydberg resonance whose lineshape is governed by the plasma environment rather than by spectroscopic limits, these measurements establish a framework for sensitive and non-invasive plasma field diagnostics. The second part of the dissertation investigates inertial sensing via a tractor atom interferometer (TAI). Unlike free-space propagation, TAI utilizes continuous three-dimensional confinement and coherent atomic transport. This mitigates wave packet dispersion, guarantees path closure, permits variable holding times, and enables complex spatial trajectories. The proposed experimental framework employs a Laguerre-Gaussian ``pinwheel" optical lattice to drive multi-loop interferometric sequences. Numerical simulations confirm that TAI implementations may achieve rotation sensitivities comparable to those of established free-space interferometers. In the fast-transport regime required for large enclosed areas, where nonadiabatic excitations would otherwise degrade contrast, quantum optimal control is used to design acceleration sequences that remain fast while preserving coherence. These results illustrate the versatility of neutral atoms as a sensing platform, probing electromagnetic fields through their internal structure and inertial forces through their center-of-mass motion.