Physics Commons^™

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 …

Applications Of Quantum Optics: From The Quantum Internet To Analogue Gravity, Anthony Brady

LSU Doctoral Dissertations

The aim of this thesis is to highlight applications of quantum optics in two very distinct fields: space-based quantum communication and the Hawking effect in analogue gravity. Regarding the former: We simulate and analyze a constellation of satellites, equipped with entangled photon-pair sources, which provide on-demand entanglement distribution ser- vices to terrestrial receiver stations. Satellite services are especially relevant for long-distance quantum-communication scenarios, as the loss in satellite-based schemes scales more favor- ably with distance than in optical fibers or in atmospheric links, though establishing quantum resources in the space-domain is expensive. We thus develop an optimization technique which balances …

Smart Quantum Technologies Using Photons, Narayan Bhusal

LSU Doctoral Dissertations

The technologies utilizing quantum states of light have been in the spotlight for the last two decades. In this regard, quantum metrology, quantum imaging, quantum-optical communication are some of the important applications that exploit fascinating quantum properties like quantum superposition, quantum correlations, and nonclassical photon statistics. However, the state-of-art technologies operating at the single-photon level are not robust enough to truly realize a reliable quantum-photonic technology.

In Chapter 1, I present a historical account of photon-based technologies. Furthermore, I discuss recent efforts and encouraging developments in the field of quantum-photonic technologies, and major challenges for the experimental realization of reliable …

Towards A General Framework For Practical Quantum Network Protocols, Sumeet Khatri

LSU Doctoral Dissertations

The quantum internet is one of the frontiers of quantum information science. It will revolutionize the way we communicate and do other tasks, and it will allow for tasks that are not possible using the current, classical internet. The backbone of a quantum internet is entanglement distributed globally in order to allow for such novel applications to be performed over long distances. Experimental progress is currently being made to realize quantum networks on a small scale, but much theoretical work is still needed in order to understand how best to distribute entanglement and to guide the realization of large-scale quantum …

Adsorption And Reconfiguration Of Amphiphiles At Silica-Water Interfaces: Role Of Electrostatic Interactions, Van Der Waals Forces And Hydrogen Bonds, Yao Wu

LSU Doctoral Dissertations

The ability to explore and predict metastable structures of hybrid self-assemblies is of central importance for the next generation of advanced materials with novel properties. As compared to their thermodynamically stable forms, the kinetically stabilized materials show improved functionality potentially over their stable counterparts. The self-assembly processes usually originate from weak intermolecular interactions, involving a dynamic competition between attractive and repulsive interactions. These weak forces, including van der Waals (vdW), electrostatic interaction and the hydrogen bonding (H-bonding), can be tuned by external stimuli, e.g., confinement, temperature and ionization, and consequently driving hybrid materials into different configurations. It is challenging to …

A Study Of 26al(P, Γ)27si With The Silicon Array For Branching Ratio Experiments (Sabre), Erin Courtney Good

LSU Doctoral Dissertations

The observation of the radioisotope ²⁶Al is an indicator of ongoing nucleosynthesis in the Galaxy due to its short lifetime (t_1/2 = 7.2 × 10⁵ yr) on Galactic timescales. It is thought to be synthesized in several different environments in our Galaxy, one of which is in classical novae. Classical novae are stellar explosions that occur on the surface of a white dwarf in a binary system with a main sequence star. The isotopic production resulting from the nucleosynthesis that drives these explosions can be modeled with the input of nuclear reaction rates. In recent years, many …

Modeling Anatomic Changes For Adaptive Radiotherapy In Locally Advanced Lung Cancer Patient Population, James Alexander Kavanaugh

LSU Doctoral Dissertations

Anatomic changes occurring mid-treatment for patients undergoing radiation therapy for locally advanced lung cancer can degrade the quality of the intended treatment plan. These changes include tumor regression, geometric misalignment, and lung density changes (atelectasis and pleural effusion), and are visible on the daily 3D cone beam CT (CBCT). To maintain the intended treatment quality, adaptive radiotherapy (ART) can be employed to modify the treatment plan to account for these anatomic changes. However, the evaluation on when to adapt is currently completed manually by the treating clinicians, resulting in a subjective and inconsistent application. To address these limitations, a series …

Quantum Criticality In Strongly Correlated Electron Systems, Samuel Obadiah Kellar

LSU Doctoral Dissertations

The study of the Hubbard model in three dimensions contains a variety of phases dependent upon the chosen parameters. This thesis shows that there is the indication of a zero temperature phase transition at a finite doping. The Hubbard model has been used to identify a similar quantum critical point in two dimensions. The presented results continue these investigations. The system demonstrates a strange metal phase at finite temperature which cannot be described in term of the conventional Fermi liquid. While there have been extensive studies over the past three decades for such materials in two dimensions, there are few …

Identifying Structure Transitions Using Machine Learning Methods, Nicholas Walker

LSU Doctoral Dissertations

Methodologies from data science and machine learning, both new and old, provide an exciting opportunity to investigate physical systems using extremely expressive statistical modeling techniques. Physical transitions are of particular interest, as they are accompanied by pattern changes in the configurations of the systems. Detecting and characterizing pattern changes in data happens to be a particular strength of statistical modeling in data science, especially with the highly expressive and flexible neural network models that have become increasingly computationally accessible in recent years through performance improvements in both hardware and algorithmic implementations. Conceptually, the machine learning approach can be regarded as …

Accurate Tracking Of Position And Dose During Vmat Based On Vmat-Ct, Xiaodong Zhao

LSU Doctoral Dissertations

Purpose: Local tomography reconstruction is achievable with EPID images acquired during VMAT and was named as VMAT-CT. However, it did not gain popularity due to multiple limitations and technical challenges. The goal of this study was to extend VMAT-CT concept, generate complete 3D or 4D CT images and dose, track and adapt VMAT plan based on updated images and dose.

Methods: We considered collimator angle and removed blurred areas in EPID images for VMAT-CT reconstruction to reduce artifacts and improve image quality. VMAT-CT+ images were generated by fusing VMAT-CT and planning CT using rigid or deformable registration. For 4D SBRT …

On Characterizing Quantum Processes And Detectors, Kevin Valson Jacob

LSU Doctoral Dissertations

In 2009, physicists at the National Institute of Standards and Technology in Colorado, Boulder developed what could arguable be called the first rudimentary quantum computer [1]. The past decade has seen unprecedented improvements in quantum information science culminating in the demonstration of quantum supremacy --- that quantum computers can solve problems that are impractical to be solved on the best supercomputers [2]. This remarkable progress necessitates the development of techniques to characterize the quantum devices that are being developed. In my thesis, I will focus on such devices that manipulate and detect light.

In Chapter 1, I will introduce the …

Limitations On Protecting Information Against Quantum Adversaries, Eneet Kaur

LSU Doctoral Dissertations

The aim of this thesis is to understand the fundamental limitations on secret key distillation in various settings of quantum key distribution. We first consider quantum steering, which is a resource for one-sided device-independent quantum key distribution. We introduce a conditional mutual information based quantifier for quantum steering, which we call intrinsic steerability. Next, we consider quantum non-locality, which is a resource for device-independent quantum key distribution. In this context, we introduce a quantifier, intrinsic non-locality, which is a monotone in the resource theory of Bell non-locality. Both these quantities are inspired by intrinsic information and squashed entanglement and are …

X-Ray Interferometry Without Analyzer For Breast Ct Application, A Simulation Study, Jingzhu Xu

LSU Doctoral Dissertations

We investigated a novel analyzer-less X-ray interferometer with a spatially modulated phase-grating (MPG) which produces three types of images (attenuation image, phase image and scatter image) for Breast computed tomography (CT). The system provides the three complimentary X-ray images with the goals of limiting the dose to the object and achieving similar attenuation image sensitivity as a standard absorption-only Breast CT. The MPG system features an X-ray source, a source-grating, a single phase-grating, and a detector. No analyzer grating is necessary, compared to other geometries such as Talbot-Lau X-ray interferometry (TLXI). Thus, there is a ~2 times improvement in X-ray …

Comprehensive Investigation Of Radiation Techniques For Whole Breast And Post-Mastectomy Irradiations, Yibo Xie

LSU Doctoral Dissertations

Purpose: The purpose of this dissertation is to compare treatment outcomes and cost-effectiveness of various radiotherapy techniques for post-mastectomy radiotherapy (PMRT) and whole breast radiotherapy (WBRT) patients.

Methods: Treatment planning comparison of standard volumetric modulated arc therapy (STD-VMAT), multiple arc VMAT (MA-VMAT), non-coplanar VMAT (NC-VMAT), intensity modulated radiotherapy (IMRT), helical tomotherapy (HT), mixed beam therapy and proton therapy was performed for 9 PMRT patients, and cost-effectiveness of those PMRT techniques compared to standard of care (SOC) were evaluated using a Markov model. Treatment planning comparison of SOC, field-in-field (FIF), hybrid IMRT, full IMRT, STD-VMAT, MA-VMAT and NC-VMAT was performed …

Novel Photon-Detector Models For Enhanced Quantum Information Processing, Elisha Siddiqui

LSU Doctoral Dissertations

This work is devoted to the development of novel photon-detector models at room temperature using quantum optics elements. This work comprises of two photon-number-resolving detector (PNRD) models, and the application of PNRD in LIDAR. The first model is based on using a two-mode squeezing device to resolve photon number at room temperature. In this model we study the average intensity-intensity correlations signal at the output of a two-mode squeezing device with |N> and |α> as the two input modes. We show that the input photon-number can be resolved from the average intensity-intensity correlations. In particular, we show jumps in the …

Investigation Of Complex Magnetic Phenomena In Spinel Femn2o4, Mnfe2o4, And Nife2o4, Roshan Kumar Nepal

LSU Doctoral Dissertations

Frustrated magnetic systems, where all spin interactions cannot be simultaneously satisfied, have continued to attract interest due to a plethora of novel magnetic states that emerge in them due to frustration and their potential technological applications. Spinel oxides AB₂O₄, where A and B are metal ions) are an excellent testing ground for the exploration of frustrated magnetism. This dissertation presents the experimental investigation of complex magnetic phenomena in the spinel oxides FeMn₂O₄, MnFe₂O₄, and NiFe₂O₄.

FeMn₂O₄ and MnFe₂O_{4 …}

Examining Interaction Effects In 2d Fermi Gases Using Renormalization Group Theory, Sri Laalitya Uppalapati

LSU Doctoral Dissertations

We use the Renormalization Group (RG) method within the perturbation theory framework to study properties of a balanced, two-dimensional Fermi gas with short-range, attractive interactions in non-superfluid (normal) phase. We find that the RG method allows for the evaluation of logarithmic corrections to Equations of State in various regimes of density and temperature. We present two calculations using RG with perturbation theory. The first being a simplified RG scheme with an interpolation of crossover between RG flow in different regimes. The second calculation features a rigorous derivation whereby the Green's function within a standard perturbation theory is renormalized to derive …

Calibration Transients In Ligo Detectors, Thomas Daniel Abbott

LSU Doctoral Dissertations

This dissertation describes a novel method of analyzing fluctuations in the time-dependent calibration models of the LIGO interferometers to estimate their effect on strain reconstruction for gravitational-wave detections. The time-dependence of the calibration model of each detector is tracked with a set of parameters which are continuously measured while the interferometers are operating. These parameters track slow variations in the sensing function of the detectors as well as the actuators that hold the detectors in an operational state. The time-dependent parameter data during the second observation run (O2 [November 30, 2016 16:00 UTC to August 25, 2017 22:00:00 UTC]) and …

Vibrational And Electronic Structure Of Environmentally Persistent Free Radicals Formed On Metal Oxide Nanoclusters And Single-Crystal Surfaces, Nadra Ibrahim Sakr

LSU Doctoral Dissertations

We have studied the morphology and electronic structure of transition metal oxides (TMOs) nanoparticles and single-crystal surfaces which are known to be active for the formation of environmentally persistent free radicals (EPFRs) from organic precursors. We have also investigated the effect of simulated solar irradiation on the formed EPFRs.

First, we examined the change in the vibrational and structural properties of TiO₂, ZnO, CuO, and Fe₂O₃ nanoparticles due to phenol adsorption at high temperature and thus EPFR formation on the surface of these TMOs. The paramagnetic signal observed by electron paramagnetic resonance (EPR) indicates the …

Stellar Nucleosynthesis: Direct Measurement Of The Neutron-Capture Cross Sections Of Stable Germanium Isotopes And Design Of A Next Generation Ion Trap For The Study Of Beta-Delayed Neutron Emission, Alexander Laminack

LSU Doctoral Dissertations

Knowledge of stellar nuclear reaction rates is critical to understanding the cosmic origins of the abundances of elements. In order to determine these reaction rates, accurate measurements of nuclear cross sections are needed. This thesis presents the results of an experiment to directly measure the neutron capture cross sections of 70-Ge, 72-Ge, 74-Ge, and 76-Ge. These measurements were performed at the Los Alamos Neutron Science CEnter (LANSCE) using the Detector for Advanced Neutron Capture Experiments (DANCE). This is the first direct measurement for many of these isotopes across the neutron energy spectrum of 10 eV to 1 MeV using the …

Measurements Of The 16c + 12c And 16c + 13c Fusion Cross Sections With Implications For Astrophysics, Ashley Ann Hood

LSU Doctoral Dissertations

The fusion of neutron-rich nuclei is of interest to nuclear astrophysics and nuclear structure. X-ray superbursts are powered by runaway thermonuclear burning deep inside of a neutron star, where heating from the pycnonuclear fusion of neutron-rich isotopes is an important heat source. Experimental measurements of fusion cross sections of neutron-rich isotopes have provided insights regarding nucleon transfer and nuclear structure properties affecting fusion. Recently, the ¹⁵C + ¹²C total fusion cross section was measured using a ¹⁵C beam produced by the in-flight beam production facility, which is part of the Argonne Tandem LINAC Accelerator System (ATLAS) at …

High Power And Optomechanics In Advanced Ligo Detectors, Terra Christine Hardwick

LSU Doctoral Dissertations

In September 2015, a new era of astronomy began with the first direct detection of grav- itational waves from a binary black hole coalescence. The event was captured by the Laser Interferometer Gravitational-wave Observatory, comprised of two long-baseline interferometers, one in Livingston, LA and one in Hanford, WA. At the time of the first detection, the interferometers were part way through an upgrade to an advanced configuration and were operating with a strain sensitivity of just better than 10⁻²³/Hz^1/2 around 100Hz. The full Advanced LIGO design calls for sensitivity of a few parts in 10⁻²⁴/Hz …

Alpha Capture Reaction Rates For Nucleosynthesis Within An Ab Initio Framework, Alison Constance Dreyfuss

LSU Doctoral Dissertations

Clustering in nuclear systems has broad impacts on all phases of stellar burning, and plays a significant role in our understanding of nucleosynthesis, or how and where nuclei are produced in the universe. The role of alpha particles in particular is extremely important for nuclear astrophysics: ⁴He was one of the earliest elements produced in the Big Bang, it is one of the most abundant elements in the universe, and helium burning -- in particular, the triple-alpha process -- is one of the most important ``engines'' in stars. To better understand nucleosynthesis and stellar burning, then, it is important …

Electromagnetic Sum Rules And Response Functions From The Symmetry-Adapted No-Core Shell Model, Robert Byron Baker

LSU Doctoral Dissertations

Recent developments in ab initio nuclear structure have provided us with a variety of many-body methods capable of describing nuclei into the medium-mass region of the chart of nuclides. One of these, the symmetry-adapted no-core shell model (SA-NCSM), capitalizes on inherent symmetries of the nucleus and is uniquely suited to examine the underlying physics of dynamical quantities, such as the response function.

We examine the applicability of the SA-NCSM to calculations of these quantities and assess the quality of its inputs by calculating electromagnetic sum rules and response functions with the Lanczos sum rule method and Lanczos response function method, …

Stray Radiation Dose From X-Ray And Proton Beam Radiation Therapies, Christopher William Schneider

LSU Doctoral Dissertations

The growing population of cancer survivors at risk of radiation induced side-effects is a public health concern. These side-effects include serious conditions such as second cancers, the majority of which occur outside of the primary treatment volume. Radiotherapy treatment planning systems systematically underestimate the dose to tissues out-of-field. Attempts to predict and reduce the risks of radiogenic side effects require accurate and personalized knowledge of the out-of-field radiation dose to patients. The long-term goal of this research is to provide clinical and research tools necessary to reduce the risk of radiotherapy side effects and improve the health outcomes of radiotherapy …

Nonlinear Optical Studies Of Bulk And Thin Film Complex Materials, Joel E. Taylor

LSU Doctoral Dissertations

Nonlinear optical studies of bulk and thin film materials provide a vast playground for physical and dynamical characterization. In this thesis, we have implemented experimental methods to probe novel phase transitions in single crystals using rotational anisotropic second harmonic generation (RASHG) and carrier dynamics in thin films with time-resolved pump-probe reflectivity. Furthermore, a novel low temperature ultra-high vacuum system coupled to nonlinear optics has been developed to extend lab capabilities. Doping (Bi_1-xSb_x)₂Se₃ with antimony, the surface electronic reconstruction near x=80% was identified with RASHG by deviations in the six-fold and three-fold polarization anisotropic …

Application Of X-Ray Grating Interferometry To Polymer/Flame Retardant Blends In Additive Manufacturing, Omoefe Joy Kio

LSU Doctoral Dissertations

X-ray grating interferometry is a nondestructive tool for visualizing the internal structures of samples. Image contrast can be generated from the absorption of X-rays, the change in phase of the beam and small-angle X-ray scattering (dark-field). The attenuation and differential phase data obtained complement each other to give the internal composition of a material and large-scale structural information. The dark-field signal reveals sub-pixel structural detail usually invisible to the attenuation and phase probe, with the potential to highlight size distribution detail in a fashion faster than conventional small-angle scattering techniques. This work applies X-ray grating interferometry to the study of …

Framework For Algorithmically Optimizing Longitudinal Health Outcomes: Examples In Cancer Radiotherapy And Occupational Radiation Protection, Lydia Joyce Wilson

LSU Doctoral Dissertations

Background: Advancements in the treatment of non-infectious disease have enabled survival rates to steadily increase in recent decades (e.g., diabetes, heart disease, and cancer). Epidemiological studies have revealed that the treatments for these diseases can have life-threatening and/or life–altering effects. Thus, realizing the full beneficial potential of advanced treatments necessitates new tools to algorithmically consider all major components of the health outcome, including benefit and detriment. The goal of this dissertation was to develop a framework for improving projected health outcomes following planned radiation exposures in consideration of all beneficial and detrimental, early and late, and fatal and non-fatal …

Optimization Of Quantum Optical Metrology Systems, Nicholas Michael Studer

LSU Doctoral Dissertations

It can be said that all of humanity's efforts can be understood as a problem of optimization. We each have a natural sense of what is ``good'' or ``bad'' and thus our actions tend towards maximizing -- or optimizing -- some notion of good and minimizing those things we perceive as bad or undesirable.

Within the sciences, the greatest form of good is knowledge. It is this pursuit of knowledge that leads to not only life-saving innovations and technology, but also to furthering our understanding of our natural world and driving our philosophical pursuits.

The principle method of obtaining knowledge …

Precision Of Parameter Estimation In Quantum Metrology, Chenglong You

LSU Doctoral Dissertations

The fundamental precision limit of an interferometer is crucial since it bounds the best possible sensitivity one could achieve using such a device. This thesis will focus on several different interferometers and try to give the ultimate precision bounds by carefully counting all the resources used in the interferometers.

The thesis begins with the basics of the quantum state of light. The fundamentals of quantum metrology are also reviewed and discussed. More specifically, the terminology of classical and quantum Cram\'er-Rao bound and classical and quantum Fisher information are introduced.

Chapter 3 discusses the conclusive precision bounds in two-mode interferometer such …