Physics Commons^™

Combinatorial Algorithms For Perturbation Theory And Application On Quantum Computing, Yudong Cao

Open Access Dissertations

Quantum computing is an emerging area between computer science and physics. Numerous problems in quantum computing involve quantum many-body interactions. This dissertation concerns the problem of simulating arbitrary quantum many-body interactions using realistic two-body interactions. To address this issue, a general class of techniques called perturbative reductions (or perturbative gadgets) is adopted from quantum complexity theory and in this dissertation these techniques are improved for experimental considerations. The idea of perturbative reduction is based on the mathematical machinery of perturbation theory in quantum physics. A central theme of this dissertation is then to analyze the combinatorial structure of the perturbation …

Gravity-Assist Trajectories To Venus, Mars, And The Ice Giants: Mission Design With Human And Robotic Applications, Kyle M. Hughes

Open Access Dissertations

Gravity-assist trajectories to Uranus and Neptune are found (with the allowance of impulsive maneuvers using chemical propulsion) for launch dates ranging from 2024 to 2038 for Uranus and 2020 to 2070 for Neptune. Solutions are found using a patched conic model with analytical ephemeris via the Satellite Tour Design Program (STOUR), originally developed at the Jet Propulsion Laboratory (JPL). Delivered payload mass is computed for all solutions for select launch vehicles, and attractive solutions are identified as those that deliver a specified amount of payload mass into orbit at the target body in minimum time. The best cases for each …

Plasmonic Devices Based On Transparent Conducting Oxides For Near Infrared Applications, Kim Jongbum

Open Access Dissertations

In the past decade, there have been many breakthroughs in the field of plasmonics and nanophotonics that have enabled optical devices with unprecedented functionalities. Even though remarkable demonstration of at photonic devices has been reported, constituent materials are limited to the noble metals such as gold (Au) and silver (Ag) due to their abundance of free electrons which enable the support of plasmon resonances in the visible range. With the strong demand for extension of the optical range of plasmonic applications, it is now a necessity to explore and develop alternative materials which can overcome intrinsic issues of noble metals …

Dynamic Holography In Semiconductors And Biomedical Optics, Hao Sun

Open Access Dissertations

Three-dimensional scanning and display are rapidly-advancing new technologies with important commercial drivers such as 3D printing and remote imaging for big data applications. Holography is a natural approach to recording and displaying three-dimensional information because it uses phase-sensitive interferometry to record interference patterns when a reference beam encounters coherent light arriving from an object. The 3D information is contained in the values of wave optics. Holography is a broad field that goes beyond recording and displaying. For instance, holographic optical elements, which take advantage of holographic imaging principles, perform the functions of lenses, gratings or mirrors. Holographic interferometry is also …

Wave Propagation And Imaging In Structured Optical Media, Zun Huang

Open Access Dissertations

Structured optical media, usually characterized by periodic patterns of inhomogeneities in bulk materials, provide a new approach to ultimate control of wave propagation with possible practical applications: from distributed feedback lasers by diffraction gratings, to highly nonlinear performance for super-continuum generation, to fiber-optic telecommunications by microstructured photonic crystal fibers, to invisibility cloaking, to super-resolution imaging with metamaterials etc.

In particular, structured optical media allow to manipulate the wave propagation and dispersion. In this thesis, we focus on engineering the propagation phase dispersion by modulating the compositions and dimensions of the periodic elements. By tailoring the dispersion in momentum space, we …

Nanophotonics For Dark Materials, Filters, And Optical Magnetism, Mengren Man

Open Access Dissertations

Research on nanophotonic structures for three application areas is described, a near perfect optical absorber based on a graphene/dielectric stack, an ultraviolet bandpass filter formed with an aluminum/dielectric stack, and structures exhibiting homogenizable magnetic properties at infrared frequencies. The graphene stack can be treated as a effective, homogenized medium that can be designed to reflect little light and absorb an astoundingly high amount per unit thickness, making it an ideal dark material and providing a new avenue for photonic devices based on two-dimensional materials. Another material stack arrangement with thin layers of metal and insulator forms a multi-cavity filter that …

Exploring Spin-Transfer-Torque Devices And Memristors For Logic And Memory Applications, Zoha Pajouhi

Open Access Dissertations

As scaling CMOS devices is approaching its physical limits, researchers have begun exploring newer devices and architectures to replace CMOS.

Due to their non-volatility and high density, Spin Transfer Torque (STT) devices are among the most prominent candidates for logic and memory applications. In this research, we first considered a new logic style called All Spin Logic (ASL). Despite its advantages, ASL consumes a large amount of static power; thus, several optimizations can be performed to address this issue. We developed a systematic methodology to perform the optimizations to ensure stable operation of ASL.

Second, we investigated reliable design of …

Students' Reasoning With Haptic Technologies: A Qualitative Study In The Electromagnetism Domain, Sadhana Balachandran

Open Access Theses

With abundant applications in the medical training and entertainment industry, haptic technology is slowly making its way into the realm of science education, particularly in conveying abstract and non-visible concepts. Electric field is one such abstract concept. Past studies have shown that learning concepts such as electric fields in a traditional classroom can be quite challenging since students have a hard time visualizing the phenomena and applying its effects to reason. Furthermore, these concepts are the building blocks for more complex concepts such as matter and molecular interactions. Visuo-haptic devices provide a great platform to enable students to visualize and …

Particle Modeling Of Non-Equilibrium Field Emission Driven Rf Microplasmas, Siva Sashank Tholeti

Open Access Dissertations

Non-equilibrium microplasmas at atmospheric pressures have been investigated for active flow control, micropropulsion and electronic display applications to name a few. The operational voltages for these microplasmas are on the order of kilovolts. When the electric field at the electrodes reaches GV/m or tens of GV/m either due to reduced interelectrode spacing and surface irregularities or due to carefully designed nanostructures on the electrodes, quantum processes such as field emission and field ionization come into effect. These can potentially reduce the operational voltages of microplasma devices by an order of magnitude. Due to the rarefied and non-equilibrium nature of these …

Tailoring Optical And Plasmon Resonances In Core-Shell And Core-Multishell Nanowires, Sarath Ramadurgam

Open Access Dissertations

Semiconductor nanowires (NWs) are sub-wavelength structures which exhibit strong optical (Mie) resonances in the visible range. In addition to such optical resonances, the localized surface plasmon resonances (LSPR) in metal and semiconductor (or dielectric) based core-shell (CS) and core-multishell (CMS) NWs can be tailored to achieve novel negative-index metamaterials (NIM), extreme absorbers, invisibility cloaks and sensors. Particularly, in this dissertation, the versatility of CS and CMS NWs for the design of negative-index metamaterials in the visible range and, plasmonic light harvesting in ultrathin photocatalyst layers for water splitting are studied.

Utilizing the LSPR in the metal layer and the magnetic …

Dropwise Condensation Dynamics In Humid Air, Julian Eduardo Castillo Chaco

Open Access Theses

Dropwise condensation of atmospheric water vapor is important in multiple practical engineering applications. The roles of environmental factors and surface morphology/chemistry on the condensation dynamics need to be better understood to enable efficient water-harvesting, dehumidication, and other psychrometric processes. Systems and surfaces that promote faster condensation rates and self-shedding of condensate droplets could lead to improved mass transfer rates and higher water yields in harvesting applications. The thesis presents the design and construction of an experimental facility that allows visualization of the condensation process as a function of relative humidity. Dropwise condensation experiments are performed on a vertically oriented, hydrophobic …

Optical Position Sensing In Free Space Optical Communication, Muhammad Salman Bashir

Open Access Theses

In this thesis the performance of three estimators, (center of gravity, template matching and maximum likelihood (MLE)) to estimate the center of the beam on a photoemissive receiver array in a Free Space Optics (FSO) system, is compared in terms of mean square error. Simulations have been conducted in Matlab by generating a two dimensional nonhomogeneous Poisson process, and, mean square error is computed for three estimators. The cases of continuous and discrete arrays are also considered for various levels of signal-to-noise (SNR) ratio. Simulations have shown that the MLE gives the least mean squared error and especially performs significantly …

Feasibility Analysis Of Large Length-Scale Thermocapillary Flow Experiment For The International Space Station, Samantha Jean Alberts

Open Access Theses

The investigation of microgravity fluid dynamics emerged out of necessity with the advent of space exploration. In particular, capillary research took a leap forward in the 1960s with regards to liquid settling and interfacial dynamics. Due to inherent temperature variations in large spacecraft liquid systems, such as fuel tanks, forces develop on gas-liquid interfaces which induce thermocapillary flows. To date, thermocapillary flows have been studied in small, idealized research geometries usually under terrestrial conditions. The 1 to 3m lengths in current and future large tanks and hardware are designed based on hardware rather than research, which leaves spaceflight systems designers …

Drift-Flux Correlation Development For Two-Phase Flow In Rod Bundles, Collin M. Clark

Open Access Theses

A rod bundle drift-flux correlation is developed with intended application across a wide range of two-phase flow conditions. Special consideration is made for fluid flow mechanisms at low liquid velocity and low pressure conditions. In these instances, gravitational forces from the density difference of the associated fluid phases are more significant. Secondary flow patterns may develop as a result and a drift-flux correlation would need to make appropriate adjustments. Earlier correlations may have increased error at these conditions if they have been formulated with respect to relatively higher pressures or flow rates. In the present work, area-average void fraction data …

Nanoscale Semiconductor Materials And Devices Employing Hybrid 1d And 2d Structures For Tunable Electronic And Photonic Applications, Suprem Ranjan Das

Open Access Dissertations

Das, Suprem R. Ph.D., Purdue University, December 2013. Nanoscale Semiconductor Materials and Devices employing Hybrid 1D and 2D structures for Tunable Electronic and Photonic Applications. Major Professor: Dr. David B. Janes.

Continued miniaturization of microelectronic devices over past decades has brought the device feature size towards the physical limit. Likewise, enormous `waste energy' in the form of self-heating in almost all of the electronic and optoelectronic devices needs an `energy-efficient low power' and `high performance' material as well as device with alternate geometry. III-V semiconductors are proven to be one of the alternate systems of materials for various applications including …

Atomistic Simulation Of Plasma Interaction With Plasma Facing Components In Fusion Reactors, Xue Yang

Open Access Dissertations

The interaction between plasma and fusion relevant materials is one of the critical issues in successfully using those materials in Tokamak reactors. This research uses molecular dynamics, kinetic Monte Carlo and binary collision approximation methods to model fusion relevant material bombarded by energetic particles to investigate retention, deposition, sputtering, erosion, blistering effects, diffusion, and so on.

The deuterium bombardment of monocrystalline tungsten was modeled by LAMMPS code using Tersoff type interatomic potential. The deuterium trapping rate, implantation depth, and stopping time in 600-2000 K tungsten bombarded by 5-100 eV deuterium atoms were simulated. Irradiated monocrystalline tungsten became amorphous prior to …

Applicability Of Continuum Fracture Mechanics In Atomistic Systems, Shao-Huan Cheng

Open Access Dissertations

By quantitating the amplitude of the unbounded stress, the continuum fracture mechanics defines the stress intensity factor K to characterize the stress and displacement fields in the vicinity of the crack tip, thereby developing the relation between the stress singularity and surface energy (energy release rate G). This G-K relation, assigning physical meaning to the stress intensity factor, makes these two fracture parameters widely used in predicting the onset of crack propagation. However, due to the discrete nature of the atomistic structures without stress singularity, there might be discrepancy between the failure prediction and the reality of nanostructured materials. Defining …

Quantum Computing With Steady State Spin Currents, Brian Matthew Sutton

Open Access Theses

Many approaches to quantum computing use spatially confined qubits in the presence of dynamic fields to perform computation. These approaches are contrasted with proposals using mobile qubits in the presence of static fields. In this thesis, steady state quantum computing using mobile electrons is explored using numerical modeling. Firstly, a foundational introduction to the case of spatially confined qubits embodied via quantum dots is provided. A collection of universal gates implemented with dynamic fields is described using simulations. These gates are combined to implement a five-qubit Grover search to provide further insight on the time-dependent field approach. Secondly, the quantum …