Physics Commons^™

Quantum Control Of Qubits And Qudits In Neutral Atom Systems, Sri Datta Vikas Buchemmavari

Physics & Astronomy ETDs

This dissertation explores control of neutral atom quantum systems across multiple levels of abstraction, from atomic physics to system-level fault tolerance, using optimal control to improve performance. First, we propose a Rydberg entangling gate based on dressing with only the qubit control field; an interaction energy near the Rabi frequency benefits both gate speed and Rydberg decay. Second, with Sandia National Laboratories, we show that leakage errors in neutral atom systems can be converted to atom loss errors and detected using two entangling gates with an auxiliary atom, where a SWAP-based leakage detection unit outperforms the standard design. Next, we …

Strategies For Large Dynamic Range, Entanglement-Enhanced Quantum Metrology With Experimentally Demonstrated Resources, Tyler G. Thurtell

Physics & Astronomy ETDs

Quantum metrology studies the use of quantum mechanical systems as measurement devices or sensors. Surprisingly, preparing a sensor in an entangled state can enhance measurement precision. The simplest protocols for entanglement enhancement sense only small changes in a quantity. The range of values over which a measurement protocol works is called its dynamic range. For many types of sensors we require end-to-end protocols that describe how to use entanglement to achieve enhanced precision over a large dynamic range. In this dissertation, we describe two approaches to achieving entanglement-enhanced sensing over a large dynamic range. The first approach uses entangling resources …

Extending The Discovery Space Of Tess: Probing Underexplored Exoplanet Populations, Mallory L. Harris

Physics & Astronomy ETDs

This dissertation investigates how cold exoplanets can be identified despite the strong observational bias of exoplanet surveys toward short-period systems. Planets at wider orbital separations remain comparatively poorly constrained, limiting tests of planetary-system formation and the prevalence of outer architectures beyond compact systems. To address this gap, I use two complementary approaches. First, I develop a transit-search pipeline for TESS Full-Frame Images that identifies both isolated and repeated transit-like signals around nearby M dwarfs and characterizes the dominant false-positive classes that limit sensitivity in this regime. I then present TOI-904 c, the coldest planet discovered by TESS around an M …

An Investigation Of Tess M&Ms And The Occurrence Rate Of Transiting Circumbinary Planets, Dominic Oddo

Physics & Astronomy ETDs

Circumbinary planets (CBPs) are worlds which orbit two stars simultaneously. CBPs are excellent tests of the tenacity of planet formation, but are difficult to detect. The space-based NASA Transiting Exoplanet Survey Satellite (TESS) mission is a nearly all-sky survey designed to detect exoplanets transiting nearby stars. In this dissertation, I analyze the performance of TESS by comparing to the photometric precision of the ESA CHEOPS mission. Then, I define a catalog of low-mass eclipsing binaries (M&Ms), which are the best sources to search for CBPs. I describe my custom transit search methodology and apply it to the M&M catalog. I …

Simulating Quantum Field Theories On Fault-Tolerant Quantum Computers, Mason L. Rhodes

Physics & Astronomy ETDs

Quantum field theories are an essential framework in modeling fundamental interactions in nature, yet reliable simulations consume large portions of the world's most powerful supercomputers. In this Dissertation, we explore an alternative simulation paradigm on fault-tolerant quantum hardware, discussing both algorithmic and model advancements. In the former, we construct state-of-the-art algorithmic subroutines that take advantage of useful properties of the Hamiltonian describing the theory to achieve an exponential improvement in resources over prior quantum algorithms. In the latter, we simplify the structure of the Hamiltonian, making it more amenable to quantum simulation. First, we present an improved regularization of the …

Measurements And Studies For Rare Event Searches Using Directional Detectors, Elizabeth Tilly

Physics & Astronomy ETDs

Measuring topology and initial direction of low-energy (keV-MeV) particle tracks is interesting to rare-event searches. While directional dark matter searches have been one of the largest drivers for R&D for low-energy directional detectors, this work is interested in its application to Migdal searches. The Migdal effect—a nuclear recoil and an electron recoil sharing a vertex—has been used as a detection channel for low-mass dark matter but has only recently been measured. Low-energy directional detectors are ideal to measure the canonic Migdal topology. This dissertation discusses 3D reconstruction algorithms developed for the Migdal In Galactic Dark mAtter expLoration (MIGDAL) experiment and …

Exploring The Role Of A Mushy, Crustal Compliant Region In Volcano Deformation, Grant A. Block

Physics & Astronomy ETDs

Volcanoes are both creative and destructive forces that have shaped and continue to shape our world from early geologic time to the present day. Continued study of volcanic processes not only better prepares us for monitoring volcanic hazards but also allows us to better understand processes fundamental to Earth as we know it, such as the generation of the atmosphere and accretion of the continents. This dissertation focuses on an integral part of volcanic processes: the trans-crustal magmatic transport system. Specifically, we investigate regions of these transport systems where magma pools in melt-rich lenses within broader regions of low melt-fraction, …

New Distance Distributions Of Asymptotic Giant Branch Stars And Their Role In Tracing Galactic Structure, Rajorshi Bhattacharya

Physics & Astronomy ETDs

Asymptotic giant branch (AGB) stars are among the final evolutionary stages of low- and intermediate-mass stars and among the most luminous cool stellar populations in the Milky Way (MW). Their strong infrared emission allows them to be observed through regions of high interstellar extinction, making them useful tracers of the inner MW. However, their use is limited by unreliable distances because many are dust-obscured and variable, while geometric parallaxes are often unavailable or uncertain. This thesis develops statistical distance-estimation methods for large samples of oxygen-rich AGB stars. The resulting distances broadly agree with literature estimates, supporting their statistical reliability for …

A Quantum Phase Space Description Of Local Noise In Atomic Ensembles, Andrew Kolmer Forbes

Physics & Astronomy ETDs

Nonclassicality in quantum sensors can improve sensitivity, but often increases susceptibility to noise. Thus, modeling physically relevant noise sources and analyzing their effect on quantum metrology are both of importance to the field of quantum sensing. In this dissertation, I demonstrate that local noise sources, which are present in almost all many-spin systems, can be tractably modeled when assuming permutation symmetry of the noise, and we show that many common local noise sources can be mapped to a Fokker-Planck equation on quantum phase space. We apply this description of noise to study quantum sensing using noisy probe states and establish …

Optical Nuclear Spin Detection In Diamond And Varifocal Metasurface Optics, Maxwell D. Aiello

Physics & Astronomy ETDs

This dissertation presents two experimental investigations at the intersection of quantum sensing and precision optical instrumentation. The primary project demonstrates optically detected nuclear magnetic resonance (NMR) of ¹³C nuclear spins in diamond, using state-selective Landau-Zener transitions under microwave frequency sweeping to bidirectionally transfer spin polarization between nitrogen-vacancy (NV) electron spins and remote ¹³C nuclear spins. This enables optical polarization and readout of large ensembles of polarized nuclear spins at low magnetic fields and room temperature, with spin dephasing times limited by longitudinal relaxation of nearby NV electron spins. The secondary project reports the design, fabrication, and characterization of …

Realizing The Long Wavelength Array Swarm, Craig Anthony Taylor

Physics & Astronomy ETDs

Sensitive modern radio interferometers are costly to build and operate at the university level. The `swarm telescope' concept addresses this challenge by enabling the collaborative use of individual telescope systems, overseen by separate institutions, that come together to form a more powerful and manageable facility. This dissertation focuses on demonstrating this concept using the Long Wavelength Array (LWA) by commissioning an aperture synthesis telescope consisting of interconnected LWA stations, called the LWA Swarm. The presented work details building a cost-efficient prototype LWA platform -- the LWA--North Arm station -- to enable synthesis imaging using the 3-element interferometer comprised of LWA1, …

A Multi-Frequency Investigation Of Compact Symmetric Objects, Evan E. Sheldahl

Physics & Astronomy ETDs

Some of the brightest objects in the radio sky are jetted active galactic nuclei (AGN), supermassive black holes in the centers of galaxies that accelerate relativistic electrons into twin radio jets. One of the biggest questions surrounding AGN is how they produce radio jets in the first place. We search for an answer to this question by exploring a class of AGN that have uniquely well-constrained physical properties and are thought to be in an early stage of AGN development: compact symmetric objects (CSOs). Throughout our journey with these remarkable sources, we quantify their efficacy as calibrator sources for radio …

Full-Stack Quantum Computing, Benjamin C A Morrison

Physics & Astronomy ETDs

Quantum computing is a promising tool for solving computational problems in several areas, including the simulation of physical and chemical systems. The design of practical quantum computing systems for these applications is a daunting task, requiring collaborative work by interdisciplinary teams considering different abstractions of the same systems. This dissertation presents work on the development of those abstractions, and on components that bridge multiple layers of abstraction. I first provide an introduction to quantum circuit model computation, error correction with stabilizer codes, and physics simulation algorithms. In joint work with the QSCOUT software team, I then describe the development of …

A Systematic Approach To The Characterization Of Liquid-Vapor Coexistence In Platinum, Meghan K. Lentz

Physics & Astronomy ETDs

Platinum is a material standard used in high pressure and shock compression experiments at Sandia National Laboratories. During experiments, materials are subjected to a very large range of thermodynamic conditions, during which materials regularly enter the liquid-vapor coexistence region. Despite its status as a standard, the region around the liquid-vapor critical point is poorly understood for platinum, with reported critical temperatures spanning approximately 7000 K. In this dissertation we conduct density functional theory based molecular dynamics (DFTMD) simulations for platinum for a range of temperatures and densities near liquid-vapor coexistence. The phase diagram for platinum is refined near the critical …

Investigating Long-Lasting Meteor Train Phenomena In Optical And Radio Regimes, Logan E. Cordonnier

Physics & Astronomy ETDs

Throughout history, meteors have been regarded as fascinating and portentous events, with bygone astronomers diligently recording their occurrence. The research presented herein continues in this tradition, using modern instruments, software, and data reduction techniques to study long-lasting meteor trail phenomena, specifically in the optical (persistent trains; PTs) and radio (meteor radio afterglows; MRAs) regimes. The overarching goal was to investigate the similarities between these phenomena, which began with the creation of a PT catalog. Many of the prior assumptions about the nature of PTs were found to be unsubstantiated, and several new behaviors were uncovered. This includes the discovery of …

Exploring The Very Early Cosmological History With Dark Matter And Primordial Black Holes, Phuc Duc Loc Ngo

Physics & Astronomy ETDs

We explore the possibilities of nonstandard early cosmological histories and their potential roles to explain DM. We study how particle DM is produced with scenarios of early matter domination (EMD), how primordial black holes (PBHs), which could also be a DM candidate in certain mass ranges, are formed with enhanced curvature perturbation or FOPT and the corresponding gravitational wave (GW) signals, how PBHs could increase their mass by accretion during EMD and the corresponding GW signals.

Challenging $\Lambda$Cdm: Unraveling Cosmic Distances, Dark Sector Phenomenology, And Alternative Primordial B-Mode Sources, Kylar L. Greene

Physics & Astronomy ETDs

The dominant Lambda Cold Dark Matter (LCDM) cosmological model, while remarkably successful, increasingly shows signs that it may not fully describe our Universe, as persistent tensions in expansion rates and structure formation remain unresolved. In this thesis, I challenge the LCDM paradigm using novel theoretical frameworks combined with rigorous numerical analyses. I demonstrate that the expansion-rate tension fundamentally reflects underlying distance disagreements, and that the Thomson scattering rate strongly restricts higher pre-recombination expansion rates without additional physics. Further, I present a novel cosmological model using a mirror dark sector and varying fundamental constants, revealing an observational degeneracy allowing significantly higher …

Scalable Methods For Performant Control Of Hyperfine Qubits In Atoms And Ions, Matthew N. H. Chow

Physics & Astronomy ETDs

Qubits encoded within internal energy levels of atoms and ions have been used to demonstrate high-performance primitives of quantum computing for small numbers of qubits. Yet, the path to achieving sufficient size and fidelity for useful fault-tolerant quantum computation remains daunting. In this dissertation, I present several techniques I developed as steps along this path. These results include high-fidelity, low-loss detection for alkali atoms in optical tweezers, crosstalk-mitigated parallel one-qubit gates, robust entangling gates on trapped ions, and leakage-to-erasure conversion for non-destructive detection of atom loss errors. Through this collection of techniques, I have sought to make full use of …

Entanglement With Neutral Atoms In The Simulation Of Nonequilibrium Dynamics Of One-Dimensional Spin Models, Anupam Mitra

Physics & Astronomy ETDs

Quantum entanglement is a key ingredient for quantum information processing with capabilities beyond that of classical computation. We study the generation and role of entanglement in the dynamics of spin-1/2 models, both for the design of quantum gates for general-purpose quantum computation and for quantum simulation of interacting spin models. We introduce the neutral atom Mølmer-Sørensen gate, involving rapid adiabatic Rydberg dressing interleaved in a spin-echo sequence. We show its robustness to quasi-static experimental imperfections and favorable scaling with the time-energy scales of Rydberg-mediated entanglement generation. In quantum simulation, we consider critical behavior in quench dynamics of transverse field Ising …

Learning, Optimizing, And Simulating Fermions With Quantum Computers, Andrew Zhao

Physics & Astronomy ETDs

Fermions are fundamental particles which obey seemingly bizarre quantum-mechanical principles, yet constitute all the ordinary matter that we inhabit. As such, their study is heavily motivated from both fundamental and practical incentives. In this dissertation, we will explore how the tools of quantum information and computation can assist us on both of these fronts. We primarily do so through the task of partial state learning: tomographic protocols for acquiring a reduced, but sufficient, classical description of a quantum system. Developing fast methods for partial tomography addresses a critical bottleneck in quantum simulation algorithms, which is a particularly pressing issue for …

A New Effective Gravitational Lensing Approach To Constrain Dark Matter, Birendra Dhanasingham

Physics & Astronomy ETDs

Galaxy-scale strong gravitational lenses offer a unique window into understanding the nature and distribution of dark matter at sub-galactic scales. Beyond the main-lens subhalos, the inclusion of line-of-sight dark matter halos has become essential in lens studies due to their substantial role in perturbing lensed images, making multi-plane lensing a crucial aspect of any lens study. We highlight that these line-of-sight halos appear extended tangentially along the lensing critical line in the effective convergence maps due to the nonlinear nature of multiplane lensing, resulting in a characteristic anisotropic signature in the deflection field. Leveraging tools from large-scale structure analyses, this …

Quantum Computation Using Large Spin Qudits, Sivaprasad Thattupurackal Omanakuttan

Physics & Astronomy ETDs

This dissertation explores quantum computation using qudits encoded into large spins, emphasizing the concept of quantum co-design to harness the unique capabilities of physical platforms for enhanced quantum information processing. First, we delve into the generation of high-fidelity universal gate sets for quantum computation with qudits. Leveraging principles from quantum optimal control, Rydberg physics, and the atomic structure of alkaline-earth atoms, we propose protocols for high-fidelity universal gate sets in the ground state of ⁸⁷Sr with reasonable experimental parameters. Next, we analyze schemes to encode a qubit in the large spin qudits for fault-tolerant quantum computation (FTQC). By comprehending …

A Precise Measurement Of The Lifetime Of B-Mesons, Measurement Of Cp-Violation Parameters Of Bs-Mesons, The Atlas Experiment At The Lhc, And Development Of Silicon Detectors For Future Particle Physics Experiments, Easwar Anand Narayanan

Physics & Astronomy ETDs

A series of connected research projects has been carried out for the purpose of seeking physics phenomena beyond the Standard Model. These consist of a precise measurement of the lifetime of a short-lived b-hadron, the B_d-meson; preparations for measurements of CP-violating parameters in B_s decays; development of triggers that select b-hadron events; development of new instruments for improved precision in detecting fundamental particles; and monitoring and mitigating the effect of radiation on the detectors, which is inescapable in their operating environment. Datasets collected by the ATLAS detector at the Large Hadron Collider (LHC) are used for …

Radio Insights Into Gamma-Ray Mysteries, Seth M. Bruzewski

Physics & Astronomy ETDs

In the time since its launch, the \textit{Fermi Gamma-Ray Space Telescope} has provided new and unparalleled views of the $\gamma$-ray sky, dramatically increasing our understanding of sources of high-energy radiation. During that same time, however, its ``unassociated'' sources have provided a consistent mystery: approximately one third of the modern gamma-ray sky remains completely unaccounted for in other electromagnetic regimes. While some of the fainter sources simply pose challenges in achieving the necessary signal-to-noise ratio, others are well constrained and have resisted traditional investigations for years, and in some cases, for over a decade. Radio astronomy has traditionally been the best …

Modeling Lithographic Quantum Dots And Donors For Quantum Computation And Simulation, Mitchell Ian Brickson

Physics & Astronomy ETDs

Our first focus is on few-hole quantum dots in germanium. We use discontinous Galerkin methods to discretize and solve the equations of a highly detailed k·p model that describes these systems, enabling a better understanding of experimental magnetospectroscopy results. We confirm the expected anisotropy of single-hole g-factors and describe mechanisms by which different orbital states have different g-factors. Building on this, we show that the g-factors in Ge holes are suciently sensitive to details of the device electrostatics that magnetospectroscopy data can be used to make a prediction of the underlying confinement potential. The second focus is on designing quantum …

Understanding The Nature Of Pulsars And Characterizing Propagation Effects Using Pulsar Timing, Pratik Kumar

Physics & Astronomy ETDs

Pulsars are highly magnetized stellar remnants, among the densest known objects, and primarily produce radio emission in the form of lighthouse beams sweeping across the line of sight as a regular train of pulses. Apart from providing tests for matter in high-density regimes, general relativity, and plasma emission; perhaps the most notable characteristic is their applicability as precise astronomical clocks to measure various effects. Pulsar Timing Arrays (PTAs) are galactic scale detectors analogous to ground-based detectors of Gravitational Waves (GWs) like LIGO, with the aim of detecting low-frequency nano-Hz GWs from coalescing binary supermassive black holes. PTAs consist of a …

Application Of Quantum Mechanical Techniques To Optical Waveguide Structures, Stuart Ward

Physics & Astronomy ETDs

The focus of this dissertation is on the application of supersymmetric quantum mechanics to the problem of microbending in optical waveguides and on the analysis of soliton decay due solely to quantum mechanical effects.

The techniques of supersymmetric quantum mechanics are applied to the equation of motion describing light propagation in an optical waveguide which is undergoing microbending. Based on these supersymmetric techniques, given a particular refractive index profile, one may derive a new refractive index profile which results in less loss due to the microbending -- the particular example of the monomial index profile is analyzed in detail. An …

Near- And Far- Field Optical Response Of Ensembles Of Nanostructures, Lauren Zundel

Physics & Astronomy ETDs

The ability of metallic nanostructures to support collective oscillations of their conduction electrons, known as surface plasmons, makes them attractive candidates for a wide range of applications in areas as diverse as cancer therapy, biosensing, and solar energy harvesting. These applications are especially promising for periodic arrays of nanostructures, which can support collective modes known as lattice resonances, and for nanostructures with extreme aspect ratios that give rise to enhanced light-matter interaction. In this Thesis, we employ a coupled dipole model to theoretically explore the lattice resonances supported by complex arrays of nanoparticles containing multiple nanoparticles per unit cell. We …

Rigorous Analysis Of Markov Processes With Applications To Quantum Information, Samuel Edwin Slezak

Physics & Astronomy ETDs

We present a rigorous analysis of the rapid convergence of techniques based on Markov chains for the simulation of thermal quantum systems. We show that a classical computing algorithm called path integral Monte Carlo is capable of simulating thermal states of transverse field Ising models above a threshold temperature by demonstrating the existence of a rapidly mixing Markov chain. We then turn to quantum computing algorithms and show that an idealized version of quantum Metropolis sampling can efficiently simulate systems that satisfy the eigenstate thermalization hypothesis. In a related result, we find a class of stoquastic frustration free Hamiltonians that …

The Quantum Computational Utility Of Symmetry-Protected Topological Order: From Near-Term Advantages To Universal Measurement-Based Quantum Computing, Austin Kevin Daniel

Physics & Astronomy ETDs

Quantum computers offer new avenues to approach difficult problems by taking advantage of the strange and often nonintuitive phenomena present in quantum physics. Though many quantum algorithms are believed or known to outperform the best known classical algorithms, the fundamental mechanism granting them their power remains elusive. In measurement-based quantum computation (MBQC), two key resources have been show to enable universal and provably nonclassical quantum computations, respectively. These are symmetry-protected topological order (SPTO), a notion describing a class of quantum magnets with hidden long-range correlations in their entanglement structure, and quantum contextuality, the fact that a quantum measurement outcome inherently …