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Theses and Dissertations

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Articles 1 - 17 of 17

Full-Text Articles in Quantum Physics

Using Superatomic Clusters And Charge Transfer Ligands To Control Electronic Characteristics Of Phosphorene Nanoribbons And Phosphorene Monolayer, Ryan Lambert Jan 2023

Using Superatomic Clusters And Charge Transfer Ligands To Control Electronic Characteristics Of Phosphorene Nanoribbons And Phosphorene Monolayer, Ryan Lambert

Theses and Dissertations

Phosphorene is a two-dimensional electron poor p-type semiconductor with high carrier mobility and great promise for applications in electronics and optoelectronics. As the main theme in this dissertation, the following work represents different investigations of various electronic properties associated with phosphorene. Most notable are the findings on charge transfer doping with metal-chalcogenide superatoms which displays novel control of the two most important properties of a semiconductor – the band gap energy and the nature of carriers. By tuning the width of the gap and p-/n-type character of conduction, we gain control over a material’s capacity to play a certain role …


Determination Of Vortex Locations In A 2x2 Array Of Josephson Junctions For Topological Quantum Computation, Casey L. Kowalski Mar 2022

Determination Of Vortex Locations In A 2x2 Array Of Josephson Junctions For Topological Quantum Computation, Casey L. Kowalski

Theses and Dissertations

A large barrier to practical quantum computation exists in the form of qubit decoherence, which leads to high noise and error when implementing quantum algorithms. A potential solution to this problem is the use of topologically-protected Majorana-based qubits, as their nonlocal nature and unique non-abelian exchange statistics render them virtually immune to decoherence while still allowing the state to be easily manipulated. For such a qubit to be constructed, it is essential to know the locations of the Majorana-hosting vortices in the system. This work presents a solution for the formation locations of vortices in a 2x2 superconducting island array, …


The Exact Factorization Equations For One- And Two-Level Systems, Bart Rosenzweig Jul 2021

The Exact Factorization Equations For One- And Two-Level Systems, Bart Rosenzweig

Theses and Dissertations

Exact Factorization is a framework for studying quantum many-body problems. This decomposes the wavefunctions of such systems into conditional and marginal components. We derive corresponding evolution equations for molecular systems whose conditional electronic subsystems are described by one or two Born-Oppenheimer levels and develop a program for their mathematical study.


Equations Of State For Warm Dense Carbon From Quantum Espresso, Derek J. Schauss Jan 2021

Equations Of State For Warm Dense Carbon From Quantum Espresso, Derek J. Schauss

Theses and Dissertations

Warm dense plasma is the matter that exists, roughly, in the range of 10,000 to 10,000,000 Kelvin and has solid-like densities, typically between 0.1 and 10 grams per centimeter. Warm dense fluids like hydrogen, helium, and carbon are believed to make up the interiors of many planets, white dwarfs, and other stars in our universe. The existence of warm dense matter (WDM) on Earth, however, is very rare, as it can only be created with high-energy sources like a nuclear explosion. In such an event, theoretical and computational models that accurately predict the response of certain materials are thus very …


Ligand Effects On Electronic, Magnetic, And Catalytic Properties Of Clusters And Cluster Assemblies, Dinesh Bista 9288522 Jan 2021

Ligand Effects On Electronic, Magnetic, And Catalytic Properties Of Clusters And Cluster Assemblies, Dinesh Bista 9288522

Theses and Dissertations

Ligands commonly protect metallic clusters against reacting with outside reactants. However, ligands can also be used to control the redox properties enabling the formation of super donors/acceptors that can donate/accept multiple electrons. This thesis focuses on how the ligands can be used to control the electronic and magnetic features of clusters and ligand stabilized cluster-based assemblies, leading to nano pn junctions with directed transport, the possibility of light-harvesting, and catalysts for cross-coupling reactions. The thesis addresses three distinct classes of clusters and their applications. The first class of cluster “metal chalcogen clusters” is the central idea of the thesis focused …


Qwasi: The Quantum Walk Simulator, Warren V. Wilson Aug 2020

Qwasi: The Quantum Walk Simulator, Warren V. Wilson

Theses and Dissertations

As quantum computing continues to evolve, the ability to design and analyze novel quantum algorithms becomes a necessary focus for research. In many instances, the virtues of quantum algorithms only become evident when compared to their classical counterparts, so a study of the former often begins with a consideration of the latter. This is very much the case with quantum walk algorithms, as the success of random walks and their many, varied applications have inspired much interest in quantum correlates. Unfortunately, finding purely algebraic solutions for quantum walks is an elusive endeavor. At best, and when solvable, they require simple …


Solving Combinatorial Optimization Problems Using The Quantum Approximation Optimization Algorithm, Nicholas J. Guerrero Mar 2020

Solving Combinatorial Optimization Problems Using The Quantum Approximation Optimization Algorithm, Nicholas J. Guerrero

Theses and Dissertations

The Quantum Approximation Optimization Algorithm (QAOA) is one of the most promising applications for noisy intermediate-scale quantum machines due to the low number of qubits required as well as the relatively low gate count. Much work has been done on QAOA regarding algorithm implementation and development; less has been done checking how these algorithms actually perform on a real quantum computer. Using the IBM Q Network, several instances of combinatorial optimization problems (the max cut problem and dominating set problem) were implemented into QAOA and analyzed. It was found that only the smallest toy max cut algorithms performed adequately: those …


Sparsity And Weak Supervision In Quantum Machine Learning, Seyran Saeedi Jan 2020

Sparsity And Weak Supervision In Quantum Machine Learning, Seyran Saeedi

Theses and Dissertations

Quantum computing is an interdisciplinary field at the intersection of computer science, mathematics, and physics that studies information processing tasks on a quantum computer. A quantum computer is a device whose operations are governed by the laws of quantum mechanics. As building quantum computers is nearing the era of commercialization and quantum supremacy, it is essential to think of potential applications that we might benefit from. Among many applications of quantum computation, one of the emerging fields is quantum machine learning. We focus on predictive models for binary classification and variants of Support Vector Machines that we expect to be …


Optimization Of Information Storage With Quantum Walks, Gui Zhen Lu Jun 2019

Optimization Of Information Storage With Quantum Walks, Gui Zhen Lu

Theses and Dissertations

A four-vertex quantum graph was analyzed with the objective of storing the highest ampli- tude of an incoming qubit. The procedure included the use of phase shifters to allow the user to store and release information when he or she chooses. Several parameters, such as the phase shift, location of the phase shifter, the size and shape of the binding graph and initial incoming state were varied independently to optimize the storage capacity of the graph.


Nominalization And Interpretation: A Critique Of Global Nominalization Criteria, Jason Alen Dewitt May 2019

Nominalization And Interpretation: A Critique Of Global Nominalization Criteria, Jason Alen Dewitt

Theses and Dissertations

Nominalization is the process which removes abstract objects from our scientific theories. But what makes a proposed nominalization a good or successful one? In the paper “Is It Possible to Nominalize Quantum Mechanics,” Otávio Bueno develops criteria for any successful nominalization. In the present work, I discuss one of these criteria that I call the “interpretation criterion.” It claims that a nominalization of a scientific theory should be neutral with regards to the interpretations of that theory. I argue that the interpretation criterion is problematic, and that it should be replaced with an alternative criterion of nominalization. I first explicate …


An Introduction To Supersymmetric Quantum Mechanics, Vincent R. Siggia Jan 2019

An Introduction To Supersymmetric Quantum Mechanics, Vincent R. Siggia

Theses and Dissertations

In this thesis, the general framework of supersymmetric quantum mechanics and the path integral approach will be presented (as well as the worked out example of the supersymmetric harmonic oscillator). Then the theory will be specialized to the case of supersymmetric quantum mechanics on Riemannian manifolds, which will start from a supersymmetric Lagrangian for the general case and the special case for S2. Afterwards, there will be a discussion on the superfield formalism. Concluding this thesis will be the Hamiltonian formalism followed by the inclusion of deforma- tions by potentials.


Theoretical Studies Of The Structure And Stability Of Metal Chalcogenide Crntem (1≤N≤6, 1≤M≤8) Clusters, Fnu Sweta Prabha Jan 2019

Theoretical Studies Of The Structure And Stability Of Metal Chalcogenide Crntem (1≤N≤6, 1≤M≤8) Clusters, Fnu Sweta Prabha

Theses and Dissertations

In the presented work, first principle studies on electronic structure, stability, and magnetic properties of metal chalcogenide, CrnTem clusters have been carried out within a density functional framework using generalized gradient functions to incorporate the exchange and correlation effects. The energetic and electronic stability was investigated, and it was found that they are not always correlated as seen in the cluster Cr6Te8 which has smaller gap between its HOMO (Highest Occupied Molecular Orbital) and LUMO (Lowest Unoccupied Molecular Orbital) and a high electron affinity of 3.39 eV indicating lower electronic stability whereas higher fragmentation …


Searching For Clean Observables In $B -> D* /Tau- \Bar{\Nu}_{\Tau}$ Decays, Michael D. Williams Jr. Jan 2019

Searching For Clean Observables In $B -> D* /Tau- \Bar{\Nu}_{\Tau}$ Decays, Michael D. Williams Jr.

Theses and Dissertations

In this thesis, the clean angular observables in the $\bar{B} \to D^{*+} \ell^- \bar{\nu}_{\ell}$ angular distribution is studied. Similar angular observables are widely studied in $B \to K^* \mu^+ \mu^-$ decays. We believed that these angular observables may have different sensitivities to different new physics structures.


Beyond Conventional C-Plane Gan-Based Light Emitting Diodes: A Systematic Exploration Of Leds On Semi-Polar Orientations, Morteza Monavarian Jan 2016

Beyond Conventional C-Plane Gan-Based Light Emitting Diodes: A Systematic Exploration Of Leds On Semi-Polar Orientations, Morteza Monavarian

Theses and Dissertations

Despite enormous efforts and investments, the efficiency of InGaN-based green and yellow-green light emitters remains relatively low, and that limits progress in developing full color display, laser diodes, and bright light sources for general lighting. The low efficiency of light emitting devices in the green-to-yellow spectral range, also known as the “Green Gap”, is considered a global concern in the LED industry. The polar c-plane orientation of GaN, which is the mainstay in the LED industry, suffers from polarization-induced separation of electrons and hole wavefunctions (also known as the “quantum confined Stark effect”) and low indium incorporation efficiency that …


Scattering Matrix Elements For The Nonadiabatic Collision B (2PJ) + H2 (1Σ+G, Ν, Ј) ↔ B (2PJ’) + H2 (1Σ+G, Ν’, J’)., Luke A. Barger Dec 2010

Scattering Matrix Elements For The Nonadiabatic Collision B (2PJₐ) + H2 (1Σ+G, Ν, Ј) ↔ B (2PJ’ₐ) + H2 (1Σ+G, Ν’, J’)., Luke A. Barger

Theses and Dissertations

Scattering matrix elements are calculated for the nonadiabatic inelastic collision B (2Pj) + H2 (1Σ+g, ν, ј) ↔ B (2Pj’) + H2 (1Σ+g, ν’, j’). This calculation utilizes the effective potential energy surfaces for this collision generated by Garvin along with a correction to the asymptotic H2 potential. Wavepackets are propagated on these surfaces using a split-operator propagator. This propagation yields correlation functions between reactant and product Møller states which are used to calculate the scattering …


A General Quantum Mechanical Method To Predict Positron Spectroscopy, Paul E. Adamson Sep 2007

A General Quantum Mechanical Method To Predict Positron Spectroscopy, Paul E. Adamson

Theses and Dissertations

The nuclear-electronic orbital (NEO) method was modified and extended to positron systems. NEO - second-order Moeller-Plesset perturbation (MP2) energies and annihilation rates were calculated for the positronium hydride (PsH) system, and the effects of basis set size on correlation energies captured with the NEO-MP2 and NEO-full configuration interaction (FCI) methods are compared and discussed. Equilibrium geometries and vibrational energy levels were computed for the LiX and e+LiX (X = H, F, Cl) systems at the MP2 and NEO-MP2 levels. It was found that anharmonicity plays a significant role, specifically in the differences between the vibrational energy levels of …


Quantum Mechanical Calculations Of Monoxides Of Silicon Carbide Molecules, John W. Roberts Jr. Mar 2003

Quantum Mechanical Calculations Of Monoxides Of Silicon Carbide Molecules, John W. Roberts Jr.

Theses and Dissertations

Modern semiconductor devices are principally made using the element silicon. In recent years, silicon carbide (SiC), with its wide band-gap, high thermal conductivity, and radiation resistance, has shown prospects as a semiconductor material for use in high temperature and radiation environments such as jet engines and satellites. A limiting factor in the performance of many SiC semiconductor components is the presence of lattice defects formed at oxide dielectric junctions during processing. Recent theoretical work has used small quantum mechanical systems embedded in larger molecular mechanics structures to attempt to better understand SiC surfaces and bulk materials and their oxidation. This …