Systems and Protocols for Quantum Sensing of the Magnetic Field Using Atom Arrays

Abstract

Quantum information science has enabled new approaches to simulation, computation, metrology, and sensing. As quantum devices scale to larger numbers of qubits and longer operating times, spatial inhomogeneities and temporal fluctuations and drifts become important limitations to coherent control, characterization, and device performance. Typical characterization techniques often rely on collective observables or require sequential measurements, making them difficult to capture the complete field distribution.

This thesis demonstrates that atom-resolved neutral-atom arrays with periodic geometries enable a new class of quantum sensing protocols that exploit spatial information contained in site-resolved quantum measurements for simultaneous multiparameter estimation of global and spatially varying linear gradient magnetic fields. By combining coherent control, atom-resolved detection, and spatially resolved signal processing, the developed protocols transform a neutral-atom array from a collection of individual sensors into a spatially resolved quantum sensor array capable of in-situ characterization of the fields it interacts with.

To realize this capability, this thesis first develops an experimental platform for preparation and observation of individual atoms trapped in two-dimensional arrays of over one thousand traps. The platform provides coherent quantum control, state preparation, and atom-resolved quantum state readout, establishing the essential capabilities required for spatially resolved quantum sensing. Building upon this system, we introduce and experimentally demonstrate phase-shear correlation spectroscopy, a protocol that exploits spatial correlations across the array to simultaneously estimate uniform magnetic fields and linear magnetic-field gradients from single experimental realizations. The protocol is further applied to perform single-shot multiparameter estimation, precision sensing of magnetic fields, active stabilization of magnetic fields through atomic feedback, and gradient estimation over interrogation times exceeding typical timescales limited by shot-to-shot fluctuations of magnetic field.

The results establish neutral-atom arrays as spatially resolved quantum sensing platforms capable of characterizing and performing precision measurements of spatially and temporally varying fields, as well as actively stabilizing the global magnetic field in large quantum systems. The methods developed in this thesis are broadly applicable to other quantum systems, including quantum processors, quantum simulators, and other quantum sensing platforms. This thesis demonstrates that site-resolved neutral-atom arrays enable a new class of quantum sensing protocols in which the spatial structure of the quantum system is treated not as a source of inhomogeneity to be eliminated, but as a resource from which additional information can be extracted.