Implementing A Self-Corrected Chemical Potential Scheme In Determinant Quantum Monte Carlo Simulations, 2019 University of Tennessee, Knoxville

#### Implementing A Self-Corrected Chemical Potential Scheme In Determinant Quantum Monte Carlo Simulations, Kevin Gordon Kleiner

*University of Tennessee Honors Thesis Projects*

No abstract provided.

Out-Of-Time-Ordered-Correlator Quasiprobabilities Robustly Witness Scrambling, 2019 Chapman University

#### Out-Of-Time-Ordered-Correlator Quasiprobabilities Robustly Witness Scrambling, José Raúl González Alonso, Nicole Yunger Halpern, Justin Dressel

*Mathematics, Physics, and Computer Science Faculty Articles and Research*

Out-of-time-ordered correlators (OTOCs) have received considerable recent attention as qualitative witnesses of information scrambling in many-body quantum systems. Theoretical discussions of OTOCs typically focus on closed systems, raising the question of their suitability as scrambling witnesses in realistic open systems. We demonstrate empirically that the nonclassical negativity of the quasiprobability distribution (QPD) behind the OTOC is a more sensitive witness for scrambling than the OTOC itself. Nonclassical features of the QPD evolve with timescales that are robust with respect to decoherence and are immune to false positives caused by decoherence. To reach this conclusion, we numerically simulate spinchain dynamics and ...

Comparisons Of Performance Between Quantum And Classical Machine Learning, 2019 Southern Methodist University

#### Comparisons Of Performance Between Quantum And Classical Machine Learning, Christopher Havenstein, Damarcus Thomas, Swami Chandrasekaran

*SMU Data Science Review*

In this paper, we present a performance comparison of machine learning algorithms executed on traditional and quantum computers. Quantum computing has potential of achieving incredible results for certain types of problems, and we explore if it can be applied to machine learning. First, we identified quantum machine learning algorithms with reproducible code and had classical machine learning counterparts. Then, we found relevant data sets with which we tested the comparable quantum and classical machine learning algorithm's performance. We evaluated performance with algorithm execution time and accuracy. We found that quantum variational support vector machines in some cases had higher ...

Singularity Resolution In Anisotropic And Black Hole Spacetimes In Loop Quantum Cosmology, 2018 Louisiana State University and Agricultural and Mechanical College

#### Singularity Resolution In Anisotropic And Black Hole Spacetimes In Loop Quantum Cosmology, Sahil Saini

*LSU Doctoral Dissertations*

Loop quantum cosmology (LQC) has in recent years led to successful resolution of singularities in cosmological models while agreeing with general relativity in low curvature limit. Existence of a bounce and the possibility of an effective continuum description closely approximating the quantum evolution have been notable features of this singularity resolution. The effective spacetimes of loop quantized isotropic and Bianchi-I models have been shown to be geodesically complete and free from strong singularities. In this dissertation, we extend these results to effective loop quantized Bianchi-II, Bianchi-IX and Kantowski--Sachs models with arbitrary minimally coupled matter, and also explore the possibility of ...

Computational Spectroscopy Of C-Like Mg Vii, 2018 Atlanta University Center

#### Computational Spectroscopy Of C-Like Mg Vii, Saleh Allehabi

*Electronic Theses & Dissertations Collection for Atlanta University & Clark Atlanta University*

In this thesis, energy levels, lifetimes, oscillator strengths and transition probabilities of Mg VII have been calculated. The Hartree-Fock (HF) and Multiconfiguration Hartree-Fock (MCHF) methods were used in the calculations of these atomic properties. We have included relativistic operators mass correction, spin-orbit interaction, one body Darwin term and spin-other-orbit interaction in the Breit-Pauli Hamiltonian. The configurations, (1s^{2})2s^{2}2p^{2}, 2s2p^{3},2p^{4}, 2s^{2}2p3s, 2s^{2}2p3p,2s2p^{2}(^{4}P)3s and 2s^{2}2p3d which correspond to 52 fine-structure levels, were included in the atomic model for the Mg VII ions. The present ...

Computational Techniques For Scattering Amplitudes, 2018 CUNY New York City College of Technology

#### Computational Techniques For Scattering Amplitudes, Juliano A. Everett

*Publications and Research*

Scattering amplitudes in quantum field theory can be described as the probability of a scattering process to happen within a high energy particle interaction, as well as a bridge between experimental measurements and the prediction of the theory.

In this research project, we explore the Standard Model of Particle Theory, it’s representation in terms of Feynman diagrams and the algebraic formulas associated with each combination.

Using the FeynArts program as a tool for generating Feynman diagrams, we evaluate the expressions of a set of physical processes, and explain why these techniques become necessary to achieve this goal.

Improving The State Selectivity Of Field Ionization With Quantum Control, 2018 Bryn Mawr College

#### Improving The State Selectivity Of Field Ionization With Quantum Control, Vincent C. Gregoric, Jason Bennett, Bianca R. Gualtieri, Ankitha Kannad, Zhimin Cheryl Liu, Zoe A. Rowley, Thomas J. Carroll, Michael W. Noel

*Physics and Astronomy Faculty Publications*

The electron signals from the field ionization of two closely spaced Rydberg states of rubidium-85 are separated using quantum control. In selective field ionization, the state distribution of a collection of Rydberg atoms is measured by ionizing the atoms with a ramped electric field. Generally, atoms in higher energy states ionize at lower fields, so ionized electrons which are detected earlier in time can be correlated with higher energy Rydberg states. However, the resolution of this technique is limited by the Stark effect. As the electric field is increased, the electron encounters numerous avoided Stark level crossings which split the ...

Plasmonic Enhancement Of Photoluminescence And Photobrightening In Cdse Quantum Dots, 2018 University of Arkansas, Fayetteville

#### Plasmonic Enhancement Of Photoluminescence And Photobrightening In Cdse Quantum Dots, David Alan French

*Theses and Dissertations*

Quantum dots are gaining recognition not just in the physics and chemistry community, but in the public eye as well. Quantum dot technologies are now being used in sensors, detectors, and even television displays. By exciting quantum dots with light or electricity, they can be made to emit light, and by altering the quantum dot characteristics the wavelength can be finely tuned. The light emitted can be also be made more intense by an increase in the excitation energy. The excitation light can be increased via plasmonic enhancement, leading to increased luminescence. Aside from the relatively steady-state response, quantum dots ...

Completely Top–Down Hierarchical Structure In Quantum Mechanics, 2018 Chapman University

#### Completely Top–Down Hierarchical Structure In Quantum Mechanics, Yakir Aharonov, Eliahu Cohen, Jeff Tollaksen

*Mathematics, Physics, and Computer Science Faculty Articles and Research*

Can a large system be fully characterized using its subsystems via inductive reasoning? Is it possible to completely reduce the behavior of a complex system to the behavior of its simplest “atoms”? In this paper we answer these questions in the negative for a specific class of systems and measurements. After a general introduction of the topic, we present the main idea with a simple two-particle example, where strong correlations arise between two apparently empty boxes. This leads to surprising effects within atomic and electromagnetic systems. A general construction based on preand postselected ensembles is then suggested, wherein the Nbody ...

Sampling Complexity Of Bosonic Random Walkers On A One-Dimensional Lattice, 2018 University of New Mexico - Main Campus

#### Sampling Complexity Of Bosonic Random Walkers On A One-Dimensional Lattice, Gopikrishnan Muraleedharan, Akimasa Miyake, Ivan Deutsch

*Shared Knowledge Conference*

Computers based quantum logic are believed to solve problems faster and more efficiently than computers based on classical boolean logic. However, a large-scale universal quantum computer with error correction may not be realized in near future. But we can ask the question: can we devise a specific problem that a quantum device can solve faster than current state of the art super computers? One such problem is the so called "Boson Sampling" problem introduced by Aaronson and Arkhipov. The problem is to generate random numbers according to same distribution as the output number configurations of photons in linear optics. It ...

Plasmon-Enhanced Quadrupolar Transitions With Nanostructured Graphene, 2018 University of New Mexico

#### Plasmon-Enhanced Quadrupolar Transitions With Nanostructured Graphene, Stephen Sanders

*Shared Knowledge Conference*

Many important molecules have quadrupolar excitations which occur at much slower rates than the competing dipolar transitions and hence are termed forbidden. In this work, we propose a new approach to enhance quadrupolar transitions using graphene nanostructures. We provide a detailed investigation of the enhanced transition rate in the vicinity of graphene nanoislands and use rigorous computational methods to analyze how this quantity changes with the geometrical and material parameters of the nanoisland. To support these calculations we also provide a semi-analytic approach. Finally, we investigate the performance of arrays of graphene nanoribbons, which constitutes a suitable platform for the ...

The Weak Reality That Makes Quantum Phenomena More Natural: Novel Insights And Experiments, 2018 Chapman University

#### The Weak Reality That Makes Quantum Phenomena More Natural: Novel Insights And Experiments, Yakir Aharonov, Eliahu Cohen, Mordecai Waegell, Avshalom C. Elitzur

*Mathematics, Physics, and Computer Science Faculty Articles and Research*

While quantum reality can be probed through measurements, the Two-State Vector Formalism (TSVF) reveals a subtler reality prevailing between measurements. Under special pre- and post-selections, odd physical values emerge. This unusual picture calls for a deeper study. Instead of the common, wave-based picture of quantum mechanics, we suggest a new, particle-based perspective: Each particle possesses a definite location throughout its evolution, while some of its physical variables (characterized by deterministic operators, some of which obey nonlocal equations of motion) are carried by “mirage particles” accounting for its unique behavior. Within the time interval between pre- and post-selection, the particle gives ...

Beam Theory For Classical And Quantum Nonlinear Optics---Exposing Classical And Quantum Correlations Of Transverse-Spatial Modes, 2018 Louisiana State University and Agricultural and Mechanical College

#### Beam Theory For Classical And Quantum Nonlinear Optics---Exposing Classical And Quantum Correlations Of Transverse-Spatial Modes, Robert Nicholas Lanning

*LSU Doctoral Dissertations*

Optics is arguably the most important branch of physics that has ever been studied. It is not only an essential ingredient of many other branches of physics that we study, it governs how we see, how we measure, and how we communicate in the modern world. And as the world continues to change, so do our tools and resources. In a relatively short amount of time, we have progressed from rudimentary tools that shape the world around us, to tools that harness the fundamental laws of nature. Unsurprisingly, the laws of nature governing optics remain paramount. This is because many ...

Bipartite Quantum Interactions: Entangling And Information Processing Abilities, 2018 Louisiana State University and Agricultural and Mechanical College

#### Bipartite Quantum Interactions: Entangling And Information Processing Abilities, Siddhartha Das

*LSU Doctoral Dissertations*

The aim of this thesis is to advance the theory behind quantum information processing tasks, by deriving fundamental limits on bipartite quantum interactions and dynamics. A bipartite quantum interaction corresponds to an underlying Hamiltonian that governs the physical transformation of a two-body open quantum system. Under such an interaction, the physical transformation of a bipartite quantum system is considered in the presence of a bath, which may be inaccessible to an observer. The goal is to determine entangling abilities of such arbitrary bipartite quantum interactions. Doing so provides fundamental limitations on information processing tasks, including entanglement distillation and secret key ...

Current-Driven Production Of Vortex-Antivortex Pairs In Planar Josephson Junction Arrays And Phase Cracks In Long-Range Order, 2018 Old Dominion University

#### Current-Driven Production Of Vortex-Antivortex Pairs In Planar Josephson Junction Arrays And Phase Cracks In Long-Range Order, Francisco Estellés-Duart, Miguel Ortuño, Andrés M. Somoza, Valerii M. Vinokur, Alex Gurevich

*Physics Faculty Publications*

Proliferation of topological defects like vortices and dislocations plays a key role in the physics of systems with long-range order, particularly, superconductivity and superfluidity in thin films, plasticity of solids, and melting of atomic monolayers. Topological defects are characterized by their topological charge reflecting fundamental symmetries and conservation laws of the system. Conservation of topological charge manifests itself in extreme stability of static topological defects because destruction of a single defect requires overcoming a huge energy barrier proportional to the system size. However, the stability of driven topological defects remains largely unexplored. Here we address this issue and investigate numerically ...

Catalysis Of Stark-Tuned Interactions Between Ultracold Rydberg Atoms, 2018 Old Dominion University

#### Catalysis Of Stark-Tuned Interactions Between Ultracold Rydberg Atoms, A. L. Win, W. D. Williams, Thomas J. Carroll, C. I. Sukenik

*Physics and Astronomy Faculty Publications*

We have experimentally investigated a catalysis effect in the resonant energy transfer between ultracold 85Rb Rydberg atoms. We studied the time dependence of the process, 34p + 34p → 34s + 35s, and observed an enhancement of 34s state population when 34d state atoms are added.We have also performed numerical model simulations, which are in qualitative agreement with experiment and indicate that the enhancement arises from a redistribution of p-state atoms due to the presence of the d-state atoms.

Measuring The Practical Particle-In-A-Box: Orthorhombic Perovskite Nanocrystals, 2018 West Chester University of Pennsylvania

#### Measuring The Practical Particle-In-A-Box: Orthorhombic Perovskite Nanocrystals, Brandon Mitchell, Eric Herrmann, Junhao Lin, Leyre Gomez, Chris De Weerd, Yasufumi Fujiwara, Kazutomo Suenaga, Tom Gregorkiewicz

*Physics*

A connection between condensed matter physics and basic quantum mechanics is demonstrated as we use the fundamental 3D particle-in-a-box model to explain the optical properties of semiconductor nanocrystals, which are substantially modified due to quantum confinement. We also discuss recent advances in the imaging and measurement capabilities of transmission electron microscopy, which have made it possible to directly image single nanocrystals while simultaneously measuring their characteristic absorption energies. We introduce the basic theory of nanocrystals and derive a simplified expression to approximate the optical bandgap energy of an orthorhombic nanocrystal. CsPbBr3 perovskite nanocrystals are used to demonstrate this model due ...

Catalysis Of Stark-Tuned Interactions Between Ultracold Rydberg Atoms, 2018 Old Dominion University

#### Catalysis Of Stark-Tuned Interactions Between Ultracold Rydberg Atoms, A. L. Win, W. D. Williams, T. J. Carroll, C. I. Sukenik

*Physics Faculty Publications*

We have experimentally investigated a catalysis effect in the resonant energy transfer between ultracold ^{85}Rb Rydberg atoms. We studied the time dependence of the process, 34*p* + 34*p* → 34*s* + 35*s*, and observed an enhancement of 34s state population when 34d state atoms are added. We have also performed numerical model simulations, which are in qualitative agreement with experiment and indicate that the enhancement arises from a redistribution of *p*-state atoms due to the presence of the *d*-state atoms.

Charge State Dynamics And Quantum Sensing With Defects In Diamond, 2018 The Graduate Center, City University of New York

#### Charge State Dynamics And Quantum Sensing With Defects In Diamond, Jacob D. Henshaw

*All Dissertations, Theses, and Capstone Projects*

In recent years, defect centers in wide band gap semiconductors such as diamond, have received significant attention. Defects offer great utility as single photon emitters, nanoscale sensors, and quantum memories and registers for quantum computation. Critical to the utility of these defects, is their charge state.

In this dissertation, experiments surrounding the charge state dynamics and the carrier dynamics are performed and analyzed. Extensive studies of the ionization and recombination processes of defects in diamond, specifically, the Nitrogen Vacancy (NV) center, have been performed. Diffusion of ionized charge carriers has been imaged indirectly through the recapture of said carriers by ...

Quantum And Classical Transport Of 2d Electrons In The Presence Of Long And Short Range Disorder, 2018 The Graduate Center, City University of New York

#### Quantum And Classical Transport Of 2d Electrons In The Presence Of Long And Short Range Disorder, Jesse Kanter

*All Dissertations, Theses, and Capstone Projects*

This work focuses on the study of electron transport of 2-D electron gas systems in relation to both fundamental properties of the systems such as disorder and scattering mechanisms, as well as unique magnetoresistance (MR) effects. A large portion of the discussion is built around the use of an in plane magnetic field to vary the ratio between the Zeeman energy between electrons of different spins and the Landau level spacing, creating a tool to control the quantization of the density of states (DOS).

This tool is first used to isolate Quantum Positive Magnetoresistance (QPMR), which grants insight to the ...