Current Search: Mucciolo, Eduardo (x)
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 Title
 INSULATORINSULATOR CONTACT CHARGING AS A FUNCTION OF PRESSURE.
 Creator

Hogue, Michael, Mucciolo, Eduardo, University of Central Florida
 Abstract / Description

Metal – metal and to an extent metal – insulator contact or triboelectric charging are well known phenomena with good theoretical understanding of the charge exchange mechanism. However, insulator – insulator charging is not as well understood. Theoretical and experimental research has been performed that shows that the surface charge on an insulator after triboelectric charging with another insulator is rapidly dissipated with lowered atmospheric pressure. This pressure...
Show moreMetal – metal and to an extent metal – insulator contact or triboelectric charging are well known phenomena with good theoretical understanding of the charge exchange mechanism. However, insulator – insulator charging is not as well understood. Theoretical and experimental research has been performed that shows that the surface charge on an insulator after triboelectric charging with another insulator is rapidly dissipated with lowered atmospheric pressure. This pressure discharge is consistent with surface ions being evaporated off the surface once their vapor pressure falls below the saturation vapor pressure. A twophase equilibrium model based on an ideal gas of singly charged ions in equilibrium with a submonolayer adsorbed film was developed to describe the pressure dependence of the surface charge on an insulator. The resulting charge density equation is an electrostatic version of the Langmuir isotherm for adsorbed surface particles, which describes well the experimental observations.
Show less  Date Issued
 2005
 Identifier
 CFE0000755, ucf:46592
 Format
 Document (PDF)
 PURL
 http://purl.flvc.org/ucf/fd/CFE0000755
 Title
 DECOHERENCE IN QUANTUM DOT CHARGE QUBITS: THE ROLE OFELECTROMAGNETIC FLUCTUATIONS.
 Creator

McCracken, James, Mucciolo, Eduardo, University of Central Florida
 Abstract / Description

Lateral semiconductor quantum dot structures have been proposed as an effective quantum bit (qubit) for quantum computation. A single excess electron with the freedom to move between two capacitively coupled quantum dots creates a `pseudo'spin system with the same qubit behavior as the more natural two level system of a single electron spin. The excess electron in the double dot system is restricted to one of the two dots, thereby creating two separate and distinct states (usually referred...
Show moreLateral semiconductor quantum dot structures have been proposed as an effective quantum bit (qubit) for quantum computation. A single excess electron with the freedom to move between two capacitively coupled quantum dots creates a `pseudo'spin system with the same qubit behavior as the more natural two level system of a single electron spin. The excess electron in the double dot system is restricted to one of the two dots, thereby creating two separate and distinct states (usually referred to as L> and R>). The benefit of these charge qubits lie in the relative ease with which they can be manipulated and created. Experiments have been performed in this area and have shown controllable coherent oscillations and thus efficient singlequbit operations. However, the decoherence rates observed in the experiments is still quite high, making double dot charge qubits not very appealing for largescale implementations. The following work describes the effect of the electromagnetic (EM) environment of the double quantum dot system on the decoherence of the charge state. Sources of decoherence in similar systems have been extensively investigated before and this paper follows a close theoretical framework to previous work done in the area. The effect of the EM environment can been seen in the calculations discussed below, although it is clear that the decoherence seen in experiments cannot be fully explained by the voltage fluctuations as they are investigated here. The limitations of the calculations are discussed and improvements are suggested.
Show less  Date Issued
 2006
 Identifier
 CFE0001167, ucf:46850
 Format
 Document (PDF)
 PURL
 http://purl.flvc.org/ucf/fd/CFE0001167
 Title
 AN IMPROVED TIGHTBINDING MODEL FOR PHOSPHORENE.
 Creator

DeLello, Kursti, Mucciolo, Eduardo, University of Central Florida
 Abstract / Description

The intent of this thesis is to improve upon previously proposed tightbinding models for one dimensional black phosphorus, or phosphorene. Previous models offer only a qualitative analysis of the band structure of phosphorene, and fail to fully realize critical elements in the electronic band structure necessary for transport calculations. In this work we propose an improved tightbinding model for phosphorene by including up to eight nearestneighbor interactions. The efficacy of the model...
Show moreThe intent of this thesis is to improve upon previously proposed tightbinding models for one dimensional black phosphorus, or phosphorene. Previous models offer only a qualitative analysis of the band structure of phosphorene, and fail to fully realize critical elements in the electronic band structure necessary for transport calculations. In this work we propose an improved tightbinding model for phosphorene by including up to eight nearestneighbor interactions. The efficacy of the model is verified by comparison with DFTHSE06 calculations, and the anisotropy of the effective masses in the armchair and zigzag directions is considered.
Show less  Date Issued
 2016
 Identifier
 CFH2000023, ucf:45597
 Format
 Document (PDF)
 PURL
 http://purl.flvc.org/ucf/fd/CFH2000023
 Title
 DECOHERENCE IN SEMICONDUCTOR SOLIDSTATE QUANTUM COMPUTERS.
 Creator

Valente, Diego, Mucciolo, Eduardo, University of Central Florida
 Abstract / Description

In this dissertation we discuss decoherence in charge qubits formed by multiple lateral quantum dots in the framework of the spinboson model and the BornMarkov approximation. We consider the intrinsic decoherence caused by the coupling to bulk phonon modes and electromagnetic environmental fluctuations. In the case of decoherence caused by phonon coupling, two distinct quantum dot configurations are studied and proposed as setups that mitigate its nocive effects : (i) Three quantum dots in...
Show moreIn this dissertation we discuss decoherence in charge qubits formed by multiple lateral quantum dots in the framework of the spinboson model and the BornMarkov approximation. We consider the intrinsic decoherence caused by the coupling to bulk phonon modes and electromagnetic environmental fluctuations. In the case of decoherence caused by phonon coupling, two distinct quantum dot configurations are studied and proposed as setups that mitigate its nocive effects : (i) Three quantum dots in a ring geometry with one excess electron in total and (ii) arrays of quantum dots where the computational basis states form multipole charge configurations. For the threedot qubit, we demonstrate the possibility of performing one and twoqubit operations by solely tuning gate voltages. Compared to a previous proposal involving a linear threedot spin qubit, the threedot charge qubit allows for less overhead on twoqubit operations. For small interdot tunnel amplitudes, the threedot qubits have Q factors much higher than those obtained for doubledot systems. The highmultipole dot configurations also show a substantial decrease in decoherence at low operation frequencies when compared to the doubledot qubit. We also discuss decoherence due to electromagnetic fluctuations in charge qubits formed by two lateral quantum dots. We use effective circuit models to evaluate correlations of voltage fluctuations in the qubit setup. These correlations allows us to estimate energy (T1) and phase (T2) relaxation times of the the qubit system. We also discuss the dependence the quality factor Q shows with respect to parameters of the setup, such as temperature and capacitive coupling between the electrodes.
Show less  Date Issued
 2009
 Identifier
 CFE0002961, ucf:47959
 Format
 Document (PDF)
 PURL
 http://purl.flvc.org/ucf/fd/CFE0002961
 Title
 Practical Dynamic Transactional Data Structures.
 Creator

Laborde, Pierre, Dechev, Damian, Leavens, Gary, Turgut, Damla, Mucciolo, Eduardo, University of Central Florida
 Abstract / Description

Multicore programming presents the challenge of synchronizing multiple threads.Traditionally, mutual exclusion locks are used to limit access to a shared resource to a single thread at a time.Whether this lock is applied to an entire data structure, or only a single element, the pitfalls of lockbased programming persist.Deadlock, livelock, starvation, and priority inversion are some of the hazards of lockbased programming that can be avoided by using nonblocking techniques.Nonblocking...
Show moreMulticore programming presents the challenge of synchronizing multiple threads.Traditionally, mutual exclusion locks are used to limit access to a shared resource to a single thread at a time.Whether this lock is applied to an entire data structure, or only a single element, the pitfalls of lockbased programming persist.Deadlock, livelock, starvation, and priority inversion are some of the hazards of lockbased programming that can be avoided by using nonblocking techniques.Nonblocking data structures allow scalable and threadsafe access to shared data by guaranteeing, at least, systemwide progress.In this work, we present the first waitfree hash map which allows a large number of threads to concurrently insert, get, and remove information.Waitfreedom means that all threads make progress in a finite amount of time  an attribute that can be critical in realtime environments.We only use atomic operations that are provided by the hardware; therefore, our hash map can be utilized by a variety of dataintensive applications including those within the domains of embedded systems and supercomputers.The challenges of providing this guarantee make the design and implementation of waitfree objects difficult.As such, there are few waitfree data structures described in the literature; in particular, there are no waitfree hash maps.It often becomes necessary to sacrifice performance in order to achieve waitfreedom.However, our experimental evaluation shows that our hash map design is, on average, 7 times faster than a traditional blocking design.Our solution outperforms the best available alternative nonblocking designs in a large majority of cases, typically by a factor of 15 or higher.The main drawback of nonblocking data structures is that only one linearizable operation can be executed by each thread, at any one time.To overcome this limitation we present a framework for developing dynamic transactional data containers.Transactional containers are those that execute a sequence of operations atomically and in such a way that concurrent transactions appear to take effect in some sequential order.We take an existing algorithm that transforms nonblocking sets into static transactional versions (LFTT), and we modify it to support maps.We implement a nonblocking transactional hash map using this new approach.We continue to build on LFTT by implementing a lockfree vector using a methodology to allow LFTT to be compatible with nonlinked data structures.A static transaction requires all operands and operations to be specified at compiletime, and no code may be executed between transactions.These limitations render static transactions impractical for most use cases.We modify LFTT to support dynamic transactions, and we enhance it with additional features.Dynamic transactions allow operands to be specified at runtime rather than compiletime, and threads can execute code between the data structure operations of a transaction.We build a framework for transforming nonblocking containers into dynamic transactional data structures, called Dynamic Transactional Transformation (DTT), and provide a library of novel transactional containers.Our library provides the waitfree progress guarantee and supports transactions among multiple data structures, whereas previous work on data structure transactions has been limited to operating on a single container.Our approach is 3 times faster than software transactional memory, and its performance matches its lockfree transactional counterpart.
Show less  Date Issued
 2018
 Identifier
 CFE0007215, ucf:52212
 Format
 Document (PDF)
 PURL
 http://purl.flvc.org/ucf/fd/CFE0007215
 Title
 Spin Pumping in Lateral Double Quantum Dot Systems.
 Creator

Pelton, Sabine, Mucciolo, Eduardo, Ishigami, Marsahir, Leuenberger, Michael, University of Central Florida
 Abstract / Description

Electron transport in single lateral quantum dot (QD) and parallel lateral doublequantum dot (DQD) systems is modeled using semiclassical rate equations. The Zeemaneffect, in conjunction with resonant tunneling, is used to select the spin of electronsinvolved in transport. We show adiabatic spin pumping by periodic variation of thesystems' confining parameters, namely the quantum point contacts (QPCs) dictating theboundaries of the dots, and the gate voltage applied to each dot. The...
Show moreElectron transport in single lateral quantum dot (QD) and parallel lateral doublequantum dot (DQD) systems is modeled using semiclassical rate equations. The Zeemaneffect, in conjunction with resonant tunneling, is used to select the spin of electronsinvolved in transport. We show adiabatic spin pumping by periodic variation of thesystems' confining parameters, namely the quantum point contacts (QPCs) dictating theboundaries of the dots, and the gate voltage applied to each dot. The limitations ofadiabatic spin pumping are subsequently examined by counting the average spin pumpedper cycle when frequency and interdot capacitance are adjusted.
Show less  Date Issued
 2012
 Identifier
 CFE0004334, ucf:49435
 Format
 Document (PDF)
 PURL
 http://purl.flvc.org/ucf/fd/CFE0004334
 Title
 Characterizing Exoplanet Atmospheres: From Lightcurve Observations to RadiativeTransfer Modeling.
 Creator

Cubillos Vallejos, Patricio, Harrington, Joseph, Mucciolo, Eduardo, Campins, Humberto, Fortney, Jonathan, University of Central Florida
 Abstract / Description

Multiwavelength transit and secondaryeclipse lightcurve observations are some of the most powerful techniques to probe the thermochemical properties of exoplanets. Although the large planettostar brightness contrast and few available spectral bands produce data with low signaltonoise ratios, a Bayesian approach can robustly reveal what constraints we can set, without overinterpreting the data. Here I performed an endtoend analysis of transiting exoplanet data. I analyzed space...
Show moreMultiwavelength transit and secondaryeclipse lightcurve observations are some of the most powerful techniques to probe the thermochemical properties of exoplanets. Although the large planettostar brightness contrast and few available spectral bands produce data with low signaltonoise ratios, a Bayesian approach can robustly reveal what constraints we can set, without overinterpreting the data. Here I performed an endtoend analysis of transiting exoplanet data. I analyzed spacetelescope data for three planets to characterize their atmospheres and refine their orbits, investigated correlated noise estimators, and contributed to the development of the respective dataanalysis pipelines. Chapters 2 and 3 describe the Photometry for Orbits, Eclipses and Transits (POET) pipeline to model Spitzer Space Telescope light curves. I analyzed secondaryeclipse observations of the Jupitersized planets WASP8b and TrES1, determining their dayside thermal emission in the infrared spectrum. The emission data of WASP8b indicated no thermal inversion, and an anomalously high 3.6 micron brightness. Standard solarabundance models, with or without a thermal inversion, can fit the thermal emission from TrES1 well. Chapter 4 describes the most commonly used correlatednoise estimators for exoplanet lightcurve modeling, and assesses their applicability and limitations to estimate parameters uncertainties. I show that the residualpermutation method is unsound for estimating parameter uncertainties. The timeaveraging and the waveletbased likelihood methods improve the uncertainty estimations, being within 20  50% of the expected value. Chapter 5 describes the opensource Bayesian Atmospheric Radiative Transfer (BART) code to characterize exoplanet atmospheres. BART combines a thermochemicalequilibrium code, a onedimensional linebyline radiativetransfer code, and the Multicore Markovchain Monte Carlo statistical module to constrains the atmospheric temperature and chemicalabundance profiles of exoplanets. I applied the BART code to the Hubble and Spitzer Space Telescope transit observations of the Neptunesized planet HATP11b. BART finds an atmosphere enhanced in heavy elements, constraining the water abundance to ~100 times that of the solar abundance.
Show less  Date Issued
 2015
 Identifier
 CFE0005935, ucf:50838
 Format
 Document (PDF)
 PURL
 http://purl.flvc.org/ucf/fd/CFE0005935
 Title
 Experiments in Graphene and Plasmonics.
 Creator

Smith, Christian, Ishigami, Masa, Peale, Robert, Mucciolo, Eduardo, Chanda, Debashis, University of Central Florida
 Abstract / Description

Graphene nanoribbons, graphene based optical sensors, and grating based plasmonics are explored experimentally. Graphene nanoribbons exhibit highly insulating states that may allow for graphene based digital applications. We investigate the sensitivity of these states to local charged impurities in ultra high vacuum. We look into the possibility of isolating twodimensional films of HBN and BSCCO, and test for any interesting phenomena. We also assess graphene's applicability for optical...
Show moreGraphene nanoribbons, graphene based optical sensors, and grating based plasmonics are explored experimentally. Graphene nanoribbons exhibit highly insulating states that may allow for graphene based digital applications. We investigate the sensitivity of these states to local charged impurities in ultra high vacuum. We look into the possibility of isolating twodimensional films of HBN and BSCCO, and test for any interesting phenomena. We also assess graphene's applicability for optical sensing by implementing a new style of spectral detector. Utilizing surface plasmon excitations nearby a graphene fieldeffect transistor we are able to produce a detector with wavelength sensitivity and selectivity in the visible range. Finally, we study another plasmonic phenomenon, and observe the resonant enhancement of diffraction into a symmetryprohibited order in silver gratings.
Show less  Date Issued
 2014
 Identifier
 CFE0005887, ucf:50874
 Format
 Document (PDF)
 PURL
 http://purl.flvc.org/ucf/fd/CFE0005887
 Title
 Resource Management in Largescale Systems.
 Creator

Paya, Ashkan, Marinescu, Dan, Wocjan, Pawel, Bassiouni, Mostafa, Mucciolo, Eduardo, University of Central Florida
 Abstract / Description

The focus of this thesis is resource management in largescale systems. Our primary concerns are energy management and practical principles for selforganization and selfmanagement. The main contributions of our work are:1. Models. We proposed several models for different aspects of resource management, e.g., energyaware load balancing and application scaling for the cloud ecosystem, hierarchical architecture model for selforganizing and selfmanageable systems and a new cloud delivery...
Show moreThe focus of this thesis is resource management in largescale systems. Our primary concerns are energy management and practical principles for selforganization and selfmanagement. The main contributions of our work are:1. Models. We proposed several models for different aspects of resource management, e.g., energyaware load balancing and application scaling for the cloud ecosystem, hierarchical architecture model for selforganizing and selfmanageable systems and a new cloud delivery model based on auctiondriven selforganization approach.2. Algorithms. We also proposed several different algorithms for the models described above. Algorithms such as coalition formation, combinatorial auctions and clustering algorithm for scalefree organizations of scalefree networks.3. Evaluation. Eventually we conducted different evaluations for the proposed models and algorithms in order to verify them. All the simulations reported in this thesis had been carried out on different instances and services of Amazon Web Services (AWS).All of these modules will be discussed in detail in the following chapters respectively.
Show less  Date Issued
 2015
 Identifier
 CFE0005862, ucf:50913
 Format
 Document (PDF)
 PURL
 http://purl.flvc.org/ucf/fd/CFE0005862
 Title
 The Design, Implementation, and Refinement of WaitFree Algorithms and Containers.
 Creator

Feldman, Steven, Dechev, Damian, Heinrich, Mark, Orooji, Ali, Mucciolo, Eduardo, University of Central Florida
 Abstract / Description

My research has been on the development of concurrent algorithms for shared memory systems that provide guarantees of progress.Research into such algorithms is important to developers implementing applications on mission critical and time sensitive systems.These guarantees of progress provide safety properties and freedom from many hazards, such as deadlock, livelock, and thread starvation.In addition to the safety concerns, the finegrained synchronization used in implementing these...
Show moreMy research has been on the development of concurrent algorithms for shared memory systems that provide guarantees of progress.Research into such algorithms is important to developers implementing applications on mission critical and time sensitive systems.These guarantees of progress provide safety properties and freedom from many hazards, such as deadlock, livelock, and thread starvation.In addition to the safety concerns, the finegrained synchronization used in implementing these algorithms promises to provide scalable performance in massively parallel systems.My research has resulted in the development of waitfree versions of the stack, hash map, ring buffer, vector, and a multiword compareandswap algorithms.Through this experience, I have learned and developed new techniques and methodologies for implementing nonblocking and waitfree algorithms.I have worked with and refined existing techniques to improve their practicality and applicability.In the creation of the aforementioned algorithms, I have developed an association model for use with descriptorbased operations.This model, originally developed for the multiword compareandswap algorithm, has been applied to the design of the vector and ring buffer algorithms.To unify these algorithms and techniques, I have released Tervel, a waitfree library of common algorithms and containers.This library includes a framework that simplifies and improves the design of nonblocking algorithms.I have reimplemented several algorithms using this framework and the resulting implementation exhibits less code duplication and fewer perceivable states.When reimplementing algorithms, I have adapted their Application Programming Interface (API) specification to remove ambiguity and nondeterministic behavior found when using a sequential API in a concurrent environment.To improve the performance of my algorithm implementations, I extended OVIS's Lightweight Distributed Metric Service (LDMS)'s data collection and transport system to support performance monitoring using perf_event and PAPI libraries.These libraries have provided me with deeper insights into the behavior of my algorithms, and I was able to use these insights to improve the design and performance of my algorithms.
Show less  Date Issued
 2015
 Identifier
 CFE0005946, ucf:50813
 Format
 Document (PDF)
 PURL
 http://purl.flvc.org/ucf/fd/CFE0005946
 Title
 Photon Statistics in Disordered Lattices.
 Creator

Kondakci, Hasan, Saleh, Bahaa, Abouraddy, Ayman, Christodoulides, Demetrios, Mucciolo, Eduardo, University of Central Florida
 Abstract / Description

Propagation of coherent waves through disordered media, whether optical, acoustic, or radio waves, results in a spatially redistributed random intensity pattern known as speckle  a statistical phenomenon. The subject of this dissertation is the statistics of monochromatic coherent light traversing disordered photonic lattices and its dependence on the disorder class, the level of disorder and the excitation configuration at the input. Throughout the dissertation, two disorder classes are...
Show morePropagation of coherent waves through disordered media, whether optical, acoustic, or radio waves, results in a spatially redistributed random intensity pattern known as speckle  a statistical phenomenon. The subject of this dissertation is the statistics of monochromatic coherent light traversing disordered photonic lattices and its dependence on the disorder class, the level of disorder and the excitation configuration at the input. Throughout the dissertation, two disorder classes are considered, namely, diagonal and offdiagonal disorders. The latter exhibits disorderimmune chiral symmetry  the appearance of the eigenmodes in skewsymmetric pairs and the corresponding eigenvalues in opposite signs. When a disordered photonic lattice, an array of evanescently coupled waveguides, is illuminated with an extended coherent optical field, discrete speckle develops. Numerical simulations and analytical modeling reveal that discrete speckle shows a set of surprising features, that are qualitatively indistinguishable in both disorder classes. First, the fingerprint of transverse Anderson localization  associated with disordered lattices, is exhibited in the narrowing of the spatial coherence function. Second, the transverse coherence length (or speckle grain size) freezes upon propagation. Third, the axial coherence depth is independent of the axial position, thereby resulting in a coherence voxel of fixed volume independently of position.When a single lattice site is coherently excited, I discovered that a thermalization gap emerges for light propagating in disordered lattices endowed with disorderimmune chiral symmetry. In these systems, the span of subthermal photon statistics is inaccessible to the input coherent light, which  once the steady state is reached  always emerges with superthermal statistics no matter how small the disorder level. An independent constraint of the input field for the chiral symmetry to be activated and the gap to be observed is formulated. This unique feature enables a new form of photonstatistics interferometry: by exciting two lattice sites with a variable relative phase, as in a traditional twopath interferometer, the excitationsymmetry of the chiral mode pairs is judiciously broken and interferometric control over the photon statistics is exercised, spanning subthermal and superthermal regimes. By considering an ensemble of disorder realizations, this phenomenon is demonstrated experimentally: a deterministic tuning of the intensity fluctuations while the mean intensity remains constant.Finally, I examined the statistics of the emerging light in two different lattice topologies: linear and ring lattices. I showed that the topology dictates the light statistics in the offdiagonal case: for evensited ring and linear lattices, the electromagnetic field evolves into a single quadrature component, so that the field takes discrete phase values and is noncircular in the complex plane. As a consequence, the statistics become superthermal. For oddsited ring lattices, the field becomes random in both quadratures resulting in subthermal statistics. However, this effect is suppressed due to the transverse localization of light in lattices with high disorder. In the diagonal case, the lattice topology does not play a role and the transmitted field always acquires random components in both quadratures, hence the phase distribution is uniform in the steady state.
Show less  Date Issued
 2015
 Identifier
 CFE0005968, ucf:50786
 Format
 Document (PDF)
 PURL
 http://purl.flvc.org/ucf/fd/CFE0005968
 Title
 Solving Constraint Satisfaction Problems with Matrix Product States.
 Creator

Pelton, Sabine, Mucciolo, Eduardo, Ishigami, Masa, Leuenberger, Michael, University of Central Florida
 Abstract / Description

In the past decade, Matrix Product State (MPS) algorithms have emerged as an efficient method of modeling some manybody quantum spin systems. Since spin system Hamiltonians can be considered constraint satisfaction problems (CSPs), it follows that MPS should provide a versatile framework for studying a variety of general CSPs. In this thesis, we apply MPS to two types of CSP. First, use MPS to simulate adiabatic quantum computation (AQC), where the target Hamiltonians are instances of a...
Show moreIn the past decade, Matrix Product State (MPS) algorithms have emerged as an efficient method of modeling some manybody quantum spin systems. Since spin system Hamiltonians can be considered constraint satisfaction problems (CSPs), it follows that MPS should provide a versatile framework for studying a variety of general CSPs. In this thesis, we apply MPS to two types of CSP. First, use MPS to simulate adiabatic quantum computation (AQC), where the target Hamiltonians are instances of a fully connected, random Ising spin glass. Results of the simulations help shed light on why AQC fails for some optimization problems. We then present the novel application of a modified MPS algorithm to classical Boolean satisfiability problems, specifically kSAT and max kSAT. By construction, the algorithm also counts solutions to a given Boolean formula (\#SAT). For easy satisfiable instances, the method is more expensive than other existing algorithms; however, for hard and unsatisfiable instances, the method succeeds in finding satisfying assignments where other algorithms fail to converge.
Show less  Date Issued
 2017
 Identifier
 CFE0006902, ucf:51713
 Format
 Document (PDF)
 PURL
 http://purl.flvc.org/ucf/fd/CFE0006902
 Title
 Electronic transport properties of carbon nanotubes: the impact of atomic charged impurities.
 Creator

Tsuchikawa, Ryuichi, Ishigami, Masa, Mucciolo, Eduardo, Peale, Robert, Masunov, Artem, University of Central Florida
 Abstract / Description

Even changing one atom in nanoscale materials is expected to alter their properties due to their small physical sizes. Such sensitivity can be utilized to modify materials' properties from bottom up and is essential for the utility of nanoscale materials. As such, the impact of extrinsic atomic adsorbates was measured on pristine graphene and a network of carbon nanotubes using atomic hydrogen, cesium atoms, and dye molecules. In order to further quantify such an atomic influence, the...
Show moreEven changing one atom in nanoscale materials is expected to alter their properties due to their small physical sizes. Such sensitivity can be utilized to modify materials' properties from bottom up and is essential for the utility of nanoscale materials. As such, the impact of extrinsic atomic adsorbates was measured on pristine graphene and a network of carbon nanotubes using atomic hydrogen, cesium atoms, and dye molecules. In order to further quantify such an atomic influence, the resistance induced by a single potassium atom on metallic and semiconducting carbon nanotubes was measured for the first time. Carbon nanotubes are sensitive to adsorbates due to their high surfacetovolume ratio. The resistance arising from the presence of extrinsic impurity atoms depends on the types of nanotubes. Metallic carbon nanotubes are resilient to a longranged, Coulomblike potential, whereas semiconducting carbon nanotubes are susceptible to these impurities. The difference in the scattering strength originates from the chirality of carbon nanotubes, which defines their unique electronic properties. This difference had not directly measured experimentally because of the issue of contact resistance, the difficulty of chirality identification, and the uncertainty in the number of impurity atoms introduced on carbon nanotubes.We synthesized atomically clean, long ((>)100 ?m) carbon nanotubes, and their chirality was identified by Rayleigh scattering spectroscopy. We introduced potassium atoms on the nanotubes to impose a longrange, Coulomb potential and measured the change in resistivity, excluding the contact resistance, by plotting the resistance as a function of the carbon nanotube length. The flux of potassium atoms coming onto the nanotubes was monitored by quartz crystal microbalance, and the scattering strength of a single potassium atom was deduced from the change in resistivity and the density of potassium atoms on the nanotubes. We found that the scattering strength of potassium atoms on semiconducting nanotubes depends on the charge carrier type (holes or electrons). Metallic nanotubes were found to be less affected by the presence of potassium atoms than semiconducting nanotubes, but the scattering strength showed a large dependence on Fermi energy. These experimental results were compared to theoretical simulations, and we found a good agreement with the experiments. Our findings provide crucial information for the application of carbon nanotubes for electronic devices, such as transistors and sensors.
Show less  Date Issued
 2015
 Identifier
 CFE0005729, ucf:50078
 Format
 Document (PDF)
 PURL
 http://purl.flvc.org/ucf/fd/CFE0005729
 Title
 THEORETICAL AND NUMERICAL STUDIES OF PHASE TRANSITIONS AND ERROR THRESHOLDS IN TOPOLOGICAL QUANTUM MEMORIES.
 Creator

Jouzdani, Pejman, Mucciolo, Eduardo, Chang, Zenghu, Leuenberger, Michael, Abouraddy, Ayman, University of Central Florida
 Abstract / Description

This dissertation is the collection of a progressive research on the topic of topological quantum computation and information with the focus on the error threshold of the wellknown models such as the unpaired Majorana, the toric code, and the planar code.We study the basics of quantum computation and quantum information, and in particular quantum error correction. Quantum error correction provides a tool for enhancing the quantum computation fidelity in the noisy environment of a real world....
Show moreThis dissertation is the collection of a progressive research on the topic of topological quantum computation and information with the focus on the error threshold of the wellknown models such as the unpaired Majorana, the toric code, and the planar code.We study the basics of quantum computation and quantum information, and in particular quantum error correction. Quantum error correction provides a tool for enhancing the quantum computation fidelity in the noisy environment of a real world. We begin with a brief introduction to stabilizer codes. The stabilizer formalism of the theory of quantum error correction gives a welldefined description of quantum codes that is used throughout this dissertation. Then, we turn our attention to a quite new subject, namely, topological quantum codes. Topological quantum codes take advantage of the topological characteristics of a physical manybody system. The physical manybody systems studied in the context of topological quantum codes are of two essential natures: they either have intrinsic interaction that selfcorrects errors, or are actively corrected to be maintainedin a desired quantum state. Examples of the former are the toric code and the unpaired Majorana, while an example for the latter is the surface code.A brief introduction and history of topological phenomena in condensed matter is provided. The unpaired Majorana and the Kitaev toy model are briefly explained. Later we introduce a spin model that maps onto the Kitaev toy model through a sequence of transformations. We show how this model is robust and tolerates local perturbations. The research on this topic, at the time of writing this dissertation, is still incomplete and only preliminary results are represented.As another example of passive error correcting codes with intrinsic Hamiltonian, the toric code is introduced. We also analyze the dynamics of the errors in the toric code known as anyons. We show numerically how the addition of disorder to the physical system underlying the toric code slows down the dynamics of the anyons. We go further and numerically analyze the presence of timedependent noise and the consequent delocalization of localized errors.The main portion of this dissertation is dedicated to the surface code. We study the surface code coupled to a noninteracting bosonic bath. We show how the interaction between the code and the bosonic bath can effectively induce correlated errors. These correlated errors may be corrected up to some extend. The extension beyond which quantum error correction seems impossible is the error threshold of the code. This threshold is analyzed by mapping the effective correlated error model onto a statistical model. We then study the phase transition in the statistical model. The analysis is in two parts. First, we carry out derivation of the effective correlated model, its mapping onto a statistical model, and perform an exact numerical analysis. Second, we employ a Monte Carlo method to extend the numerical analysis to large system size.We also tackle the problem of surface code with correlated and singlequbit errors by an exact mapping onto a twodimensional Ising model with boundary fields. We show how the phase transition point in one model, the Ising model, coincides with the intrinsic error threshold of the other model, the surface code.
Show less  Date Issued
 2014
 Identifier
 CFE0005512, ucf:50314
 Format
 Document (PDF)
 PURL
 http://purl.flvc.org/ucf/fd/CFE0005512
 Title
 Nanoplasmonics In Twodimensional Dirac and Threedimensional Metallic Nanostructure Systems.
 Creator

Safaei, Alireza, Chanda, Debashis, Leuenberger, Michael, Mucciolo, Eduardo, Tetard, Laurene, Zhai, Lei, University of Central Florida
 Abstract / Description

Surface plasmons are collective oscillation of electrons which are coupled to the incident electric field. Excitation of surface plasmon is a route to engineer the behavior of light in nanometer length scale and amplifying the lightmatter interaction. This interaction is an outcome of nearfield enhancement close to the metal surface which leads to plasmon damping through radiative decay to outgoing photons and nonradiative decay inside and on the surface of the material to create an...
Show moreSurface plasmons are collective oscillation of electrons which are coupled to the incident electric field. Excitation of surface plasmon is a route to engineer the behavior of light in nanometer length scale and amplifying the lightmatter interaction. This interaction is an outcome of nearfield enhancement close to the metal surface which leads to plasmon damping through radiative decay to outgoing photons and nonradiative decay inside and on the surface of the material to create an electronhole pair via interband or intraband Landau damping. Plasmonics in Dirac systems such as graphene show novel features due to massless electrons and holes around the Dirac cones. Linear band structure of Dirac materials in the lowmomentum limit gives rise to the unprecedented optical and electrical properties. Electronical tunability of the plasmon resonance frequency through applying a gate voltage, highly confined electric field, and low plasmon damping are the other special propoerties of the Dirac plasmons. In this work, I will summarize the theoretical and experimental aspects of the electrostatical tunable systems made from monolayer graphene working in midinfrared regime. I will demonstrate how a cavitycoupled nanopatterned graphene excites Dirac plasmons and enhances the lightmatter interaction. The resonance frequency of the Dirac plasmons is tunable by applying a gate voltage. I will show how different gatedielectrics, and the external conditions like the polarization and angle of incident light affect on the optical response of the nanostructure systems. I will then show the application of these nanodevices in infrared detection at room temperature by using plasmonassisted hot carriers generation. An asymmetric nanopatterned graphene shows a high responsivity at room temperature which is unprecedented. At the end, I will demonstrate the properties of surface plasmons on 3D noble metals and its applications in lightfunneling, photodetection, and lightfocusing.
Show less  Date Issued
 2019
 Identifier
 CFE0007904, ucf:52746
 Format
 Document (PDF)
 PURL
 http://purl.flvc.org/ucf/fd/CFE0007904
 Title
 Light Matter Interaction in Single Molecule Magnets.
 Creator

Cebulka, Rebecca, Del Barco, Enrique, Klemm, Richard, Mucciolo, Eduardo, Luis, Fernando, University of Central Florida
 Abstract / Description

This dissertation includes a series of experimental realizations which focus on studying the coupling between photons and singlemolecule magnets (SMMs) in both the weak and strong coupling regimes. In the weak coupling regime, the aim is to achieve coherent control over the time evolution of the spin of SMMs while applying rapid microwave pulses at subKelvin temperatures, where polarization of the spin bath may be achieved without large magnetic fields, allowing the suppression of dipolar...
Show moreThis dissertation includes a series of experimental realizations which focus on studying the coupling between photons and singlemolecule magnets (SMMs) in both the weak and strong coupling regimes. In the weak coupling regime, the aim is to achieve coherent control over the time evolution of the spin of SMMs while applying rapid microwave pulses at subKelvin temperatures, where polarization of the spin bath may be achieved without large magnetic fields, allowing the suppression of dipolar dephasing. The continuing results of this experiment will be to provide a window into fundamental sources of decoherence in singlecrystal SMMs in an energy range not thoroughly investigated. We expect that these conditions would allow us to study the quantum dynamics of the spins as governed by the intrinsic molecular magnetic anisotropy, which should give rise to nonwelldefined Rabi oscillations of the spin state, including metastable precessional spin states. In the strong coupling regime, high quality factor superconducting CPW resonators have been designed and fabricated to investigate the vacuum Rabi splitting between a photon and the SMM spin. The proposed setup will permit measurements of coherent collective coupling between molecular spins and a low number of photons, ideally down to a single photon. This experiment may ultimately provide the opportunity for reaching the strong coupling regime with a single spin. Finally, this thesis also documents a research study into the impact of servicelearning methodology on students' depth of learning and critical thinking skills during a novel nanoscale science and technology course offered in the UCF Physics Dept. The overall learning of students was assessed and results clearly showed improvement in both multiple choice pre/posttests and critical reflection papers. We associate this improvement at least partially to the servicelearning experience.
Show less  Date Issued
 2019
 Identifier
 CFE0007442, ucf:52728
 Format
 Document (PDF)
 PURL
 http://purl.flvc.org/ucf/fd/CFE0007442
 Title
 Electronic, Optical, and Magnetic Properties of Graphene and SingleLayer Transition Metal Dichalcogenides in the Presence of Defects.
 Creator

Khan, Mahtab, Leuenberger, Michael, Mucciolo, Eduardo, Saha, Haripada, Tetard, Laurene, Schoenfeld, Winston, University of Central Florida
 Abstract / Description

Twodimensional (2D) materials, such as graphene and singlelayer (SL) transition metal dichalcogenides (TMDCs), have attracted a lot of attention due to their fascinating electronic and optical properties. Graphene was the first 2D material that has successfully been exfoliated from bulk graphite in 2004. In graphene, charge carriers interacting with the honeycomb lattice of carbonatoms of graphene to appear as massless Dirac fermions. Massless quasiparticles with linear dispersion are also...
Show moreTwodimensional (2D) materials, such as graphene and singlelayer (SL) transition metal dichalcogenides (TMDCs), have attracted a lot of attention due to their fascinating electronic and optical properties. Graphene was the first 2D material that has successfully been exfoliated from bulk graphite in 2004. In graphene, charge carriers interacting with the honeycomb lattice of carbonatoms of graphene to appear as massless Dirac fermions. Massless quasiparticles with linear dispersion are also observed in surface states of 3D topological insulators and quantum Hall edgestates. My first project deals with the twodimensional HongOuMandel (HOM) type interferenceexperiment for massless Dirac fermions in graphene and 3D topological insulators. Since masslessDirac fermions exhibit linear dispersion, similar to photons in vacuum, they can be used to observethe HOM interference intensity pattern as a function of the delay time between two massless Dirac fermions. My further projects and the major part of this dissertation deal with singlelayer (SL) transition metal dichalcogenides (TMDCs), such as MoS$_2$, WS$_2$, MoSe$_2$ and WSe$_2$, which have recently emerged as a new family of twodimensional (2D) materials with great interest, not only from the fundamental point of view, but also because of their potential application to ultrathin electronic and optoelectronic devices. In contrast to graphene, SL TMDCs are direct band semiconductors and exhibit large intrinsic spinorbit coupling (SOC), originating from the d orbitals of transition metal atoms. Waferscale production of SL TMDCs is required for industrial applications. It has been shown that artificially grown samples of SL TMDCs through various experimental techniques, such as physical vapor deposition (PVD), chemical vapor deposition (CVD), and molecular beam epitaxy (MBE), are not perfect, instead certain type of imperfections such as point defects are always found to be present in the grown samples. Defects compromise the crystallinity of the sample, which results in reduced carrier mobility and deteriorated optical efficiency. However, defects are not always unwanted; in fact, defects can play an important role in tailoring electronic, optical, and magnetic properties of materials. Using Density functional theory we investigate the impact of point defects on the electronic, optical, and magnetic properties of SL TMDCs. First, we show that certain vacancy defects lead to localized defect states, which in turn give rise to sharp transitions in inplane and outofplane optical susceptibilities of SL TMDCs. Secondly, we show that a naturally occurring antisite defect Mo$_S$ in PVD grown MoS$_2$ is magnetic in nature with a magneticmoment of 2$\mu_B$, and remarkably exhibit an exceptionally large atomic scale magnetic anisotropy energy (MAE) of ~ 500 eV. Both magnetic moment and MAE can be tuned by shifting the position of the Fermi level which can be achieved either by gate voltage or by chemical doping. Thirdly, we argue that the antisite defect Se$_W$ in WSe$_2$ leads to long lived localized excited states, which can explain the observed single quantum emitters in CVD grown WSe$_2$ samples, with potential application to quantum cryptography.
Show less  Date Issued
 2018
 Identifier
 CFE0007030, ucf:52047
 Format
 Document (PDF)
 PURL
 http://purl.flvc.org/ucf/fd/CFE0007030
 Title
 Mathematical Foundations of Adaptive Quantum Processing.
 Creator

Bonior, Daniel, Mucciolo, Eduardo, Martin, Keye, Argenti, Luca, Shivamoggi, Bhimsen, Marinescu, Dan, University of Central Florida
 Abstract / Description

Quantum information has the potential to revolutionize the way we store, process, transfer and acquire information [1,14,15,21,37]. In particular, quantum information offers exciting new approaches to secure communication, computation and sensing. However, in order to realize such technologies, we must first understand the effect that environmental noise has on a quantum system. This dissertation builds upon recent studies that have explored the underlying structure of quantum information and...
Show moreQuantum information has the potential to revolutionize the way we store, process, transfer and acquire information [1,14,15,21,37]. In particular, quantum information offers exciting new approaches to secure communication, computation and sensing. However, in order to realize such technologies, we must first understand the effect that environmental noise has on a quantum system. This dissertation builds upon recent studies that have explored the underlying structure of quantum information and the effects of qubit channels in quantum communication protocols.This work is divided into five main chapters, with Chapter 1 being a brief introduction to quantum information. We then begin Chapter 2 by defining the error function for our qubit communication protocols. From there we explore the properties of our error functions and the topological space that they form. In Chapter 3 we consider the newly patented process Adaptive Quantum Information Processing, patent number US9838141 B2; originally outlined by Martin in [23]. We restate the adaptive scheme and exemplify its application through the Prepare and Send Protocol and Quantum Key Distribution. Applying our results from Chapter 2, we obtain an expression for the adaptability of unital channels in these two protocols and classify the channels that admit the most improvement. We dedicate Chapter 4 to the derivation of gravitational noise, and show that in certain circumstances gravity results in a channel that can be maximally improved in Adaptive QKD [3,14,16]. Lastly, we study the set of error functions through the lens of domain theory. Domain theory is a subset of mathematics that was developed in order to rigorously formalize computations. The first four chapters are all consequences of past discoveries in the mathematical structure of quantum channels. In Chapter 5 we characterize the set of error functions through domain theory, extending the mathematical foundations of quantum information. [12,18,20, 22, 23,25].
Show less  Date Issued
 2018
 Identifier
 CFE0007313, ucf:52124
 Format
 Document (PDF)
 PURL
 http://purl.flvc.org/ucf/fd/CFE0007313
 Title
 The Power of Quantum Walk: Insights, Implementation, and Applications.
 Creator

Chiang, ChenFu, Wocjan, Pawel, Marinescu, Dan, Dechev, Damian, Mucciolo, Eduardo, University of Central Florida
 Abstract / Description

In this thesis, I investigate quantum walks in quantum computing from threeaspects: the insights, the implementation, and the applications. Quantum walks are the quantum analogue of classical random walks. For the insights of quantum walks, I list and explain the required components for quantizing a classical random walk into a quantum walk. The components are, for instance, Markov chains, quantum phase estimation, and quantum spectrum theorem. I then demonstrate how the product of two...
Show moreIn this thesis, I investigate quantum walks in quantum computing from threeaspects: the insights, the implementation, and the applications. Quantum walks are the quantum analogue of classical random walks. For the insights of quantum walks, I list and explain the required components for quantizing a classical random walk into a quantum walk. The components are, for instance, Markov chains, quantum phase estimation, and quantum spectrum theorem. I then demonstrate how the product of two reflections in the walk operator provides a quadratic speedup, in comparison to the classical counterpart. For the implementation of quantum walks, I show the construction of an efficient circuit for realizing one single step of the quantum walk operator. Furthermore, I devise a more succinct circuit to approximately implement quantum phase estimation with constant precision controlled phase shift operators. From an implementation perspective, efficient circuits are always desirable because the realization of a phase shift operator with high precision would be a costly task and a critical obstacle. For the applications of quantum walks, I apply the quantum walk technique along with other fundamental quantum techniques, such as phase estimation, to solve the partition function problem. However, there might be some scenario in which the speedup of spectral gap is insignificant. In a situation like that that,I provide an amplitude amplificationbased approach to prepare the thermal Gibbs state. Such an approach is useful when the spectral gap is extremely small. Finally, I further investigate and explore the effect of noise (perturbation)on the performance of quantum walks.
Show less  Date Issued
 2011
 Identifier
 CFE0004094, ucf:49148
 Format
 Document (PDF)
 PURL
 http://purl.flvc.org/ucf/fd/CFE0004094
 Title
 Quantum Algorithms for: Quantum Phase Estimation, Approximation of the Tutte Polynomial and Blackbox Structures.
 Creator

Ahmadi Abhari, Seyed Hamed, Brennan, Joseph, Mucciolo, Eduardo, Li, Xin, Marinescu, Dan, University of Central Florida
 Abstract / Description

In this dissertation, we investigate three different problems in the field of Quantum computation. First, we discuss the quantum complexity of evaluating the Tutte polynomial of a planar graph. Furthermore, we devise a new quantum algorithm for approximating the phase of a unitary matrix. Finally, we provide quantum tools that can be utilized to extract the structure of blackbox modules and algebras. While quantum phase estimation (QPE) is at the core of many quantum algorithms known to date...
Show moreIn this dissertation, we investigate three different problems in the field of Quantum computation. First, we discuss the quantum complexity of evaluating the Tutte polynomial of a planar graph. Furthermore, we devise a new quantum algorithm for approximating the phase of a unitary matrix. Finally, we provide quantum tools that can be utilized to extract the structure of blackbox modules and algebras. While quantum phase estimation (QPE) is at the core of many quantum algorithms known to date, its physical implementation (algorithms based on quantum Fourier transform (QFT)) is highly constrained by the requirement of highprecision controlled phase shift operators, which remain difficult to realize. In the second part of this dissertation, we introduce an alternative approach to approximately implement QPE with arbitrary constantprecision controlled phase shift operators.The new quantum algorithm bridges the gap between QPE algorithms based on QFT and Kitaev's original approach. For approximating the eigenphase precise to the nth bit, Kitaev's original approach does not require any controlled phase shift operator. In contrast, QPE algorithms based on QFT or approximate QFT require controlled phase shift operators with precision of at least Pi/2n. The new approach fills the gap and requires only arbitrary constantprecision controlled phase shift operators. From a physical implementation viewpoint, the new algorithm outperforms Kitaev's approach.The other problem we investigate relates to approximating the Tutte polynomial. We show that the problem of approximately evaluating the Tutte polynomial of triangular graphs at the points (q,1/q) of the Tutte plane is BQPcomplete for (most) roots of unity q. We also consider circular graphs and show that the problem of approximately evaluating the Tutte polynomial of these graphs at a point is DQC1complete and at some points is in BQP.To show that these problems can be solved by a quantum computer, we rely on the relation of the Tutte polynomial of a planar G graph with the Jones and HOMFLY polynomial of the alternating link D(G) given by the medial graph of G. In the case of our graphs the corresponding links are equal to the plat and trace closures of braids. It is known how to evaluate the Jones and HOMFLY polynomial for closures of braids.To establish the hardness results, we use the property that the images of the generators of the braid group under the irreducible JonesWenzl representations of the Hecke algebra have finite order. We show that for each braid we can efficiently construct a braid such that the evaluation of the Jones and HOMFLY polynomials of their closures at a fixed root of unity leads to the same value and that the closures of the resulting braid are alternating links.The final part of the dissertation focuses on finding the structure of a blackbox module or algebra. Suppose we are given blackbox access to a finite module M or algebra over a finite ring R and a list of generators for M and R. We show how to find a linear basis and structure constants for M in quantum poly (logM) time. This generalizes a recent quantum algorithm of Arvind et al. which finds a basis representation for rings. We then show that our algorithm is a useful primitive allowing quantum computer to determine the structure of a finite associative algebra as a direct sum of simple algebras. Moreover, it solves a wide variety of problems regarding finite modules and rings. Although our quantum algorithm is based on Abelian Fourier transforms, it solves problems regarding the multiplicative structure of modules and algebras, which need not be commutative. Examples include finding the intersection and quotient of two modules, finding the additive and multiplicative identities in a module, computing the order of an module, solving linear equations over modules, deciding whether an ideal is maximal, finding annihilators, and testing the injectivity and surjectivity of ring homomorphisms. These problems appear to be exponentially hard classically.
Show less  Date Issued
 2012
 Identifier
 CFE0004239, ucf:49526
 Format
 Document (PDF)
 PURL
 http://purl.flvc.org/ucf/fd/CFE0004239