Physics Commons^™

All-Optical Probes Of Particle-Like Charge Migration Dynamics, Kyle A. Hamer

LSU Doctoral Dissertations

Particle-like charge migration (CM) is the coherent, back-and-forth motion of a positively-charged electron hole along the backbone of a molecule following a sudden ionization. CM in small molecules generally occurs on an Angstrom (10^-10 m) spatial scale and an attosecond (10^-18 s) timescale. I use time-dependent density-functional theory (TDDFT) to simulate CM modes in organic molecules, and to explore all-optical probes of this attosecond electron dynamics using high-harmonic spectroscopy (HHS). By leveraging my results from previous studies of two-center interferences in carbon dichalcogens, in which I separated the harmonic signal into contributions from individual Kohn-Sham orbitals, I first …

Modeling And Numerical Analysis Of The Cholesteric Landau-De Gennes Model, Andrew L. Hicks

LSU Doctoral Dissertations

This thesis gives an analysis of modeling and numerical issues in the Landau-de Gennes (LdG) model of nematic liquid crystals (LCs) with cholesteric effects. We derive various time-step restrictions for a (weighted) $L^2$ gradient flow scheme to be energy decreasing. Furthermore, we prove a mesh size restriction, for finite element discretizations, that is critical to avoid spurious numerical artifacts in discrete minimizers that is not well-known in the LC literature, particularly when simulating cholesteric LCs that exhibit ``twist''. Furthermore, we perform a computational exploration of the model and present several numerical simulations in 3-D, on both slab geometries and spherical …

Characterizing And Mitigating Transient Noise In Ligo Observatories For Gravitational Wave Detection, Jane Glanzer

LSU Doctoral Dissertations

The existence of gravitational waves is predicted by Albert Einstein's Theory of General Relativity. Commonly referred to as "ripples in spacetime", these waves are generated by some of the most violent and energetic processes in the universe. Despite their theoretical prediction over a century ago, it wasn't until 2015 that the Advanced LIGO (aLIGO) interferometers in Hanford, WA and Livingston, LA directly detected gravitational waves for the first time, confirming Einstein's theory and ushering in a new era of astrophysics.

Detecting gravitational waves requires incredible precision. Because of the extreme sensitivity required, it is possible for the gravitational wave data …

Entanglement In The Hawking Effect: From Astrophysical To Optical Black Holes, Dimitrios Kranas

LSU Doctoral Dissertations

The Hawking effect is an exciting physical prediction lying at the intersection of the two most successful theories of the past century, namely, Einstein’s theory of relativity and quantum mechanics. In this dissertation, we put special emphasis on the quantum aspects of the Hawking process encoded in the entanglement shared by the emitted fluxes of created quanta. In particular, we employ sharp tools from quantum information theory to quantify the entanglement produced by the Hawking effect throughout the black hole evaporation process. Our framework allows us to extend previous calculations of entanglement to a larger set of cases, for instance, …

Adaptive Quantum Information Processing In Non-Equilibrium Environments, Arshag Danageozian

LSU Doctoral Dissertations

Solid state and condensed matter systems, such as diamond impurities, superconductors, quantum dots, and ion traps, constitute important physical platforms for various applications in quantum information processing (QIP). However, it has consistently been shown that all such modern platforms suffer from non-equilibrium behavior on timescales that are relevant for many important QIP tasks. The causes range from intrinsic non-equilibrium dynamics (e.g. in diamond) to the presence of various impurities with their own internal dynamics (e.g. in superconductors and quantum dots) or variations in the control fields used to stabilize the quantum matter (e.g. in ion traps). When reserving degrees of …

A Menagerie Of Symmetry Testing Quantum Algorithms, Margarite Lynn Laborde

LSU Doctoral Dissertations

In Chapter 1, we establish the mathematical background used throughout this thesis. We review concepts from group and representation theory. We further establish fundamental concepts from quantum information. This will allow us to then define the different notions of symmetry necessary in the following chapters. In Chapter 2, we investigate Hamiltonian symmetries. We propose quantum algorithms capable of testing whether a Hamiltonian exhibits symmetry with respect to a group. Furthermore, we show that this algorithm is that this algorithm is DQC1-Complete. Finally, we execute one of our symmetry-testing algorithms on existing quantum computers for simple examples. In Chapter 3, we …

Nanosecond Infrared Laser Ablation Dynamics, Achala Priyadarshani Deenamulla Kankanamalage

LSU Doctoral Dissertations

Laser ablation dynamics encompasses studies of fundamental physical processes of mid infrared laser ablation. Understanding the mechanisms of IR laser desorption and ionization can lead to improvements in laser ablation-based techniques and expansion of their applications. Control of material removal ensures both accuracy and precision of the laser ablation-based techniques. The laser ablation mechanism in the studied wavelength region, is a process of water vaporization and photothermal disruption of tissue. Glycerol was used as the ablation target to establish the methods. Experiments were first aimed at developing methods to monitor material removal during ablation using a 2.94 µm wavelength mid-IR …

Measurement Of Near-Threshold Proton Branching Ratios In 31s Important For Novae, Sudarsan Balakrishnan

LSU Doctoral Dissertations

Classical novae are stellar explosions that contribute to the nucleosynthesis of isotopes on the proton-rich side of the valley of stability up to ⁴⁰Ca. In ONe novae, the incompletely understood reaction rate of ³⁰P(p,γ)³¹S is known to strongly influence the production rate of several stable isotopes such as ³⁰Si, ³¹P, and ^32,33,34S. A precise measurement of this reaction rate has several potential implications towards matching astrophysical observables to the physical composition of the nova site -- the observed elemental abundance ratios of O/S and S/Al have been suggested as useful `thermometers' to gauge …

Sers Platform For Single Fiber Endoscopic Probes, Debsmita Biswas

LSU Doctoral Dissertations

Molecular detection techniques have huge potential in clinical environments. In addition to many other molecular detection techniques, endoscopic Raman spectroscopy has great ability in terms of minimal invasiveness and real-time spectra acquisition. However, Raman Effect is low in sensitivity, limiting the application. Surface-Enhanced Raman Scattering (SERS), addresses this limitation. SERS brings rough nano-metallic surfaces in contact with specimen molecules which enormously enhances Raman signals. This provides Raman spectroscopy with immense capabilities for diverse fields of applications.

Generally, in clinical probe applications, the spectrometer is brought near the target molecules for detection. Typically, optical fibers are used to couple spectrometers to …

Compilation Optimizations To Enhance Resilience Of Big Data Programs And Quantum Processors, Travis D. Lecompte

LSU Doctoral Dissertations

Modern computers can experience a variety of transient errors due to the surrounding environment, known as soft faults. Although the frequency of these faults is low enough to not be noticeable on personal computers, they become a considerable concern during large-scale distributed computations or systems in more vulnerable environments like satellites. These faults occur as a bit flip of some value in a register, operation, or memory during execution. They surface as either program crashes, hangs, or silent data corruption (SDC), each of which can waste time, money, and resources. Hardware methods, such as shielding or error correcting memory (ECM), …

Controlling Electro-Magnetic Functionality Of Ruthenates By Heterostructure Design, Zeeshan Ali

LSU Doctoral Dissertations

Perovskite oxides (ABO₃) show wide range of functionalities originating from interplay of structural, spin, charge, and orbital degrees of freedoms. The bulk perovskite structure could be controlled via conventional chemical substitution, though exploiting heterostructure engineering novel ground states could be observed which otherwise are absent in bulk. In this thesis, the interest is to explore the electro-magnetic phenomena as complex oxides are confined in heterostructures.

I first investigate electromagnetic properties of ultrathin epitaxial ruthenate: SrRuO₃ (SRO); spatially confined between SrTiO₃ (STO) i.e., STO⁵-SROⁿ-STO⁵ with n = 1- and 2-unit cells. It …

Experimental Investigation Of The Physical Properties Of Irmsnn (M = 1, 3 And N = 2, 4, 7), Smita Speer

LSU Doctoral Dissertations

Exploration of transition metal stannides, formed from a combination of transition metals (T) and Sn, has resulted in the discovery a variety of materials with interesting physical properties, which is in part due to the complexity of interactions that can occur between the T-d orbitals and Sn-p orbitals. There have been observations of (extremely) large magnetoresistance [1-4], topological flat and nearly flat bands [5-7], superconducting behavior in 2D and 3D systems [5, 8-11], ultrahigh carrier mobility [12-13], and more attributed to d-p orbital mixing in such systems. This dissertation will address the effects of T-Sn interactions …

Characterization Of Electrophoretic Deposited Zinc Oxide Nanopartices For The Fabrication Of Next-Generation Nanoscale Electronic Applications, Fawwaz Abduh A. Hazzazi

LSU Doctoral Dissertations

Several reports state that it is crucial to analyze nanoscale semiconductor materials and devices with potential benefits to meet the need for next-generation nanoelectronics, bio, and nanosensors. The progress in the electronics field is as significant now, with modern technology constantly evolving and a greater focus on more efficient robust optoelectronic applications. This dissertation focuses on the study and examination of the practicality of Electrophoretic Deposition (EPD) of zinc oxide (ZnO) nanoparticles (NPs) for use in semiconductor applications.

The feasibility of several synthesized electrolytes, with and without surfactants and APTES surface functionalization, is discussed. The primary objective of this study …

Surpassing The Standard Quantum Limit Using An Optical Spring, Torrey Cullen

LSU Doctoral Dissertations

In 1916, Albert Einstein predicted the existence of gravitational waves based on his new theory of general relativity. He predicted an accelerating mass with a non-zero quadrupole moment would emit energy in the form of gravitational waves. Often referred to as ripples in space-time, gravitational waves are extremely small by the time reach Earth, potentially having traveled hundreds of megaparsecs. It is common for these ripples in space-time to stretch and squeeze matter 1000 times smaller than the width of a proton.
Laser interferometer observatories were first built in the 1990s in the US and Europe, and as sensitivity improvements …

Tuning Properties Of Topological Insulators: An Ab-Initio Approach, Karunya Shailesh Shirali

LSU Doctoral Dissertations

This thesis develops a first-principles based approach to explore the tuning of topological properties of the tetradymite topological insulators. We begin by setting up a framework to systematically obtain the bulk and surface properties of topological insulators, treating the structural and electronic properties on an equal footing. We determine a consistent method for including the van der Waals interactions, which are responsible for the weak coupling between sets of atomic layers in this family of layered materials, which is important in obtaining accurate structural properties. We obtain close agreement with experimental values for both the bulk and surface states.

To …

Advanced Communication And Sensing Protocols Using Twisted Light And Engineered Quantum Statistics, Michelle L. Lollie

LSU Doctoral Dissertations

Advanced performance of modern technology at a fundamental physical level is driving new innovations in communication, sensing capability, and information processing. Key to this improvement is the ability to harness the power of physical phenomena at the quantum mechanical level, where light and light-matter interactions produce technological advancement not realizable by classical means. Theoretical investigation into quantum computing, sensing capability beyond classical limits, and quantum information has prompted experimental work to bring state-of-the-art quantum systems to the forefront for commercial use. This dissertation contributes to the latter portion of the work. A set of preliminaries is included highlighting pertinent physical …

New Aspects Of Optical Coherence And Their Potential For Quantum Technologies, Nathaniel Robert Miller

LSU Doctoral Dissertations

Currently, optical technology impacts most of our lives, from light used in scientific measurement to the fiber optic cables that makeup the backbone of the internet. However, as our current optical infrastructure grows, we discover that these technologies are not limitless. Astronomers find themselves unable resolve stars that are too close to one another. Meanwhile, the internet is always under threat as our computer technology improves and more complex ways to break encryption emerge, threatening our personal information and infrastructure. However, our current optical technology functions on classical principles, and can be easily improved by incorporating our knowledge of quantum …

Computational Study Of The Reactions Of Heteroatomic Compounds On Ceo2, Suman Bhasker Ranganath

LSU Doctoral Dissertations

The mechanisms of ambient-temperature reactions of heteroatomic compounds catalyzed by ceria (CeO₂), an archetypical reducible oxide, for enzyme mimetics, environmental protection, and chemical synthesis are investigated in this dissertation using theoretical methods. CeO₂ is modeled with thermodynamically stable low-index surfaces exposed by commonly studied ceria thin films and nano particles. To understand phosphatase-like dephosphorylation activity, stable adsorption states and surface reactions of model phosphates are examined. Binding of the central P-atom to surface lattice oxygen (O_latt) supplemented by phosphoryl O-Ce interaction is the only stable adsorption state for the un-dissociated molecule. Deprotonation of phosphate monoesters, …

Deformed No-Core Shell Model And Symplectic Effective Field Theory, David Kekejian

LSU Doctoral Dissertations

Most nuclei are deformed! This simple fact has been established since Bohr and Mot- telson, and successfully demonstrated from first principles by nuclear structure calculations carried out using the ab-initio Symmetry-Adapted No-Core Shell Model (SA-NCSM) us- ing realistic interactions. This simple fact has been the main driver towards understanding the underlying physics; namely, that symplectic symmetry describes deformation and is a dominant symmetry in all nuclei independent of A (nucleon number) and of the realistic interaction used. These two simple observations laid the foundation of this thesis work to explore the applications of symplectic symmetry towards defining a deformed symplectic …

Droplet-Based Fuel Property Measurements, Wanjun Dang

LSU Doctoral Dissertations

Ongoing work to find renewable biofuels to function as drop-in replacements or blending components with gasoline has identified a large number of fuel candidates. Given the vast number of potential biomass-derived fuel molecules and limited sample sizes, screening tools are required to down-select candidate fuels having desired physical properties to ensure good engine performance. This work investigates approaches for rapid screening of candidate fuels using micro-liter sample sizes targeting four properties -- surface tension, viscosity, heat of vaporization (HOV), and vapor pressure. Measurement techniques for fuel properties are developed based on unit phenomena for liquid fuel droplets including droplet oscillation …

Limits On Parameter Estimation Of Quantum Channels, Vishal Katariya

LSU Doctoral Dissertations

The aim of this thesis is to develop a theoretical framework to study parameter estimation of quantum channels. We begin by describing the classical task of parameter estimation that we build upon. In its most basic form, parameter estimation is the task of obtaining an estimate of an unknown parameter from some experimental data. This experimental data can be seen as a number of samples of a parameterized probability distribution. In general, the goal of such a task is to obtain an estimate of the unknown parameter while minimizing its error.

We study the task of estimating unknown parameters which …

Interface-Induced Lattice Structure And Magnetism In Ultrathin Transition Metal Oxide Trilayers, David Howe

LSU Doctoral Dissertations

The study of magnetism has been a rich playground in condensed matter physics due to the multiple mechanisms capable of producing the effect and its relationship to multiple characteristics of a material. Transition metal oxides (TMOs) have been of particular interest for ongoing research into magnetic phenomenon due to the abundance of interesting physical phenomena found in member systems such as colossal magnetoresistance, skyrmion formation, and interface-driven 2D electron gases. Thin films introduce an additional thickness-dependent element, where reduction below a critical thickness eliminates the magnetic coherence of a system and FM order is lost. The atomic structure of these …

Electromagnetic Transitions And Beta Decays In Nuclei From The Ab Initio Symmetry-Adapted No-Core Shell Model, Grigor Sargsyan

LSU Doctoral Dissertations

Nuclear physics today is a diverse field, involving research that extends from the minus- cule scales of neutrons and protons to the colossal dimensions of astrophysical objects in the universe. And since the ab initio methods in nuclear physics use realistic internucleon interactions, nuclear modeling has gained predictive capabilities that enable us to probe ever more deeply into the fundamental nature of matter. One of these models – the symmetry- adapted no-core shell model (SA-NCSM) – is capable of reaching the medium-mass region of the chart of the nuclides, by exploiting the emergent symmetries of nuclei, and is therefore well-suited …

Effects Of Structure, Crystallographic Orientation, And Dimensionality On Emergent Properties Of Transition Metal Oxide Thin Films, Prahald Siwakoti

LSU Doctoral Dissertations

SrRuO₃ is the only example of ferromagnetic perovskite oxide of a 4d transition metal, wherein the electron -electron correlation is still relevant while the heavier 4d ion (Ru) gives it a larger spin-orbit coupling strength which makes it an interesting material to study. In this thesis, we present our investigation of the structure and properties of SrRuO₃ thin films of varying thickness grown on [001] and [111] crystallographic orientation of the SrTiO3 substrate. For SrRuO₃(001), we present microscopically the presence of 90◦ in-plane rotated structural domains that are identified by the difference in octahedral rotations and …

Simulation Of Compound Flood Events In Low-Gradient Coastal Watershed, Felix Luis Santiago-Collazo

LSU Doctoral Dissertations

Low-gradient coastal watersheds are susceptible to flooding caused by various flows such as rainfall, tides, and storm surge. Compound flooding occurs when at least two of these mechanisms happen simultaneously or in close succession. Different inundation models, observed data, and/or a combination of these are coupled through varying techniques involving one-way, loosely, tightly, or fully coupled approaches to assess compound flooding. This study presents a one-dimensional (1-D), fully coupled compound inundation model based on the Shallow Water equations. This model approach simultaneously simulates the free water surface variations in the ocean domain (i.e., tide and storm surge modeling), rainfall-runoff in …

A Generalized, Modular Approach To Treating Moving Tumors With Ion Beams, Michelle Jennifer Lis

LSU Doctoral Dissertations

Despite advancements in cancer therapy, certain indications continue to have a poor prognosis, including cancers of the thorax. Existing methods for treating moving tumors with carbon ions have shown promise, but require technologically complex facilities and still have inherent limitations to mitigating tumor motion. The goal of this dissertation was to develop and test a safe, portable, and modular motion-synchronized dose delivery system (M-DDS) and its peripheral components as a framework for studying motion mitigation with ion beams.

We designed and integrated a motion-synchronized radiotherapy approach, called multi-phase 4D delivery (MP4D), as modular units of a clinical dose delivery system. …

Optomechanical Quantum Entanglement, Kahlil Y. Dixon

LSU Doctoral Dissertations

As classical technology approaches its limits, exploration of quantum technologies is critical. Quantum optics will be the basis of various cutting-edge research and applications in quantum technology. In particular, quantum optics quite efficacious when applied to quantum networks and the quantum internet. Quantum Optomechanics, a subfield of quantum optics, contains some novel methods for entanglement generation. These entanglement production methods exploit the noise re-encoding process, which is most often associated with creating unwanted phase noise in optical circuits. Using the adapted two-photon formalism and experimental results, we simulate (in an experimentally viable parameter space) optomechanical entanglement generation experiments. These simulations …

Identification And Reduction Of Scattered Light Noise In Ligo, Siddharth Soni

LSU Doctoral Dissertations

We ushered into a new era of gravitational wave astronomy in 2015 when Advanced LIGO gravitational wave detectors in Livingston, Louisiana and Hanford, Washington observed a gravitational wave signal from the merger of binary black holes. The first detected GW150914 was a part of first Observing run (O1) and since then there have been a total of 3 Observing runs. Advanced Virgo detector in Cascina, Italy joined the efforts in the third Observing run (O3) which spanned from April 1, 2019, to March 27, 2020. It was split into O3a and O3b with a month long break between them, during …

Energy-Constrained Distinguishability Measures For Assessing Performance In Quantum Information Processing, Kunal Sharma

LSU Doctoral Dissertations

The aim of this thesis is to develop a framework for assessing performance in quantum information processing with continuous variables. In particular, we focus on quantifying the fundamental limitations on communication and computation over bosonic Gaussian systems. Due to their infinite-dimensional structure, we make a realistic assumption of energy constraints on the input states of continuous-variable (CV) quantum operations. Our first contribution is to show that energy-constrained distinguishability measures can be used to establish tight upper bounds on the communication capacities of phase-insensitive, bosonic Gaussian channels -- thermal, amplifier, and additive-noise channels. We then prove that an optimal Gaussian input …

Majorana Quasiparticles In Topological Material Interfaces, David Alspaugh

LSU Doctoral Dissertations

In this dissertation we analyze how Majorana quasiparticles found on material interfaces of both topological insulators (TIs) and topological superconductors (TSCs) are affected by imperfections within their local environment. While these quasiparticles are predicted to be critical for the construction of quantum computers, they are typically modeled only under pristine conditions. Thus, although quantum computers may require the spatial manipulation of Majorana quasiparticles, these topological material interfaces are commonly studied in static contexts and their response to manipulation remains an open question. We first demonstrate that interface potentials on the topological insulator Bi₂Se₃ can enable the emergence …