Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 22 for “"macroscopic quantum"”.
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Macroscopic quantum tunneling in superconducting nanowire devices
Macroscopic quantum tunneling is a process by which a macroscopic object, rather than a single electron, tunnels between two macroscopically distinct quantum states. In this dissertation, we will present the study of macroscopic quantum tunneling of phase-slips in superconducting devices, including …
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Thermal activation and macroscopic quantum phenomena in superconducting devices
… to both thermal activation over the barrier and macroscopic quantum tunneling through the barrier. The measurements were performed for a variety of device parameters, corresponding to different shapes of the potential barrier. We find strong evidence for macroscopic quantum tunneling in both one …
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Some problems on macroscopic quantum phenomena and josephson junctions
… two parts. In the' first part, the theory of quantum dynamics of a general particle in fermionic heat baths is considerd. In contrast to the existing work in the literature, we employ a path. integral formalism with fermions being treated in Grassmann algebra. Working on this formalism, we are …
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Holographic Superfluids and Solitons
… is perhaps one of the most remarkable observed macroscopic quantum effect. Superfluidity appears when a macroscopic number of particles occupies a single quantum state. Using modern experimental techniques one dark solitons) and vortices. There is a large literature on theoretical work studying …
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Boson Josephson Junctions based on Exciton-Polariton Condensates
… treatise on the Josephson effect in dilute quantum gases of excitons and exciton-polaritons. An exciton is a kind of elementary excitation in semiconductors, which, through strong coupling with photons, can form a light-matter hybrid particle called an exciton-polariton. Similar to …
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Effects of interactions on correlation, thermalization, and transport of exciton-polaritons
… are hybrid quasiparticles in a semiconductor quantum-well microcavity that exhibit both light-matter and matter-matter interactions. Polaritons have the effective mass inherited from the ultralight cavity photon mass, which sets polariton transport phenomena to be photon-like and allows …
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Dissipative processes in superconducting nanodevices: nanowire-resonators, shunted nanowires, and graphene proximity junctions
… insulator transition (SIT), the observation of macroscopic quantum behavior such as quantum phase slips (QPS), and the potential use of nanowires as qubits. Superconducting coplanar microwave waveguide resonators have also become a popular way of studying superconducting junctions and qubits, as …
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Resonant readout of a superconducting persistent current qubit
… rank among the best candidates for realizing a quantum computer. While the coherent control of quantum dynamics has been demonstrated in these solid-state, macroscopic quantum systems, a major challenge has been to increase the coherence times for these qubits. With an objective to reduce the …
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Observation of nonlinear tunneling of a Bose-Einstein condensate in a single Josephson junction
… In our experiment, the required overlap of two macroscopic wavefunctions is provided by loading a BEC into an optical double well potential. It is realized by a superposition of a one-dimensional optical lattice with a focused laser beam optical dipole trap. The tunneling dynamics between the …
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Microwave Spectroscopy and Transport Measurements of Andreev Bound States in Superconductor – Semiconductor Josephson Junctions
… junctions is governed by a combination of the macroscopic quantum coherence of superconducting systems and the mesoscopic physics inherent to semiconducting devices and Andreev bound states are the microscopic states which mediate transport through these junctions. In this thesis a series of …
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Fabrication and measurement of a niobium persistent current qubit
… them prime candidates for the implementation of quantum computing. This doctoral thesis details the study of a niobium Josephson junction circuit for quantum computing applications. The thesis covers two main areas: 1) the fabrication of sub-micron niobium Josephson junction devices using a …
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Exotic Phenomena Emerging from Localized Multipolar Degrees of Freedom
… matter systems offers the opportunity for exotic macroscopic quantum phenomena. Multipolar moments, higher order generalizations of the familiar dipole, present a unique avenue for the discovery of a variety of exotic and novel phases of matter. These anisotropic charge and magnetization densities …
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Probing quantum phase slips in superconducting nanowires modified using high bias voltage pulses
Quantum phase slips (QPS) or the macroscopic quantum tunneling (MQT) of a nanowire’s order parameter through an activation energy barrier have remained the subject of intense debate for many years. They are expected to occur at low enough temperature where thermally activated phase slips (TAPS) …
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Resistive transition and protection of LHC supenconduction cables and magnets
Superconductivity and superfluidity are macroscopic quantum-effects that are used in technology. One of the most important applications of superconductivity is the design of strong magnets, which guide particles at very high energies in circular accelerators. In the Large Hadron Collider (LHC), …
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Novel ground states of Bose-condensed gases
… (BEC) provide a novel tool for the study of macroscopic quantum phenomena and condensed matter systems. Two of the recent frontiers, quantized vortices and ultracold molecules, are the subject of this thesis. The formation of highly-ordered vortex lattices in a Bose-condensed gas has been …
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Broadband single and multimode quantum light generation using optical nonlinearities
… fields of physics to bridge the classical and quantum realms. To our best understanding, our world is governed by the laws of quantum mechanics, but some of its most interesting features - such as the ability to morph uncertainty and noise - are washed out when system sizes become too large. …
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Using imperfect semiconductor systems for unique identification
… of semiconductor devices by measuring a macroscopic quantum property of the system. The variations in these quantum properties are amplified by the existence of such atomic‐scale imperfections, meaning these devices would be the hardest possible system to clone, use the least resources …
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Correlated exciton dynamics in semiconductor nanostructures
… of correlated exciton states in gallium arsenide quantum wells. With the aid of theoretical models, 2D spectra of quantum wells revealed clear contributions of Coulomb correlations to the exciton dynamics. Time and power dependent properties of the 2D spectra indicate several mechanisms for …
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Two-state systems with non-Markovian thermal and squeezed quantum noise inputs
The effect of quantum noise on the two-state system is studied in the context of (i) coherent quantum tunnelling in a double-well system subject to low temperature quantum noise, and (ii) the two-level atom subject to finite bandwidth squeezed noise. Our approach to these problems is based on the …
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