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 268 for “"quantum systems"”.
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Quantum Systems Simulator
Thesis (M.Eng. and S.B.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science; and, (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2000.
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Low-dimensional quantum systems
We study low-dimensional quantum systems with analytical and computational methods. Firstly, the one-dimensional extended t-V model of fermions with interactions of finite range is investigated. The model exhibits a phase transition between liquid and insulating regimes. We use various analytical …
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Controlling open quantum systems
… techniques) of new methods for controlling open quantum systems. First, methods that improve coherent control through the use of both strong control fields and detailed knowledge of the system's Hamiltonian are demonstrated. With the aid of numerical search methods, pulsed irradiation schemes are …
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Decoherence in infinite quantum systems
… wird die Zeitentwicklung des betrachteten Systems irreversibel, und diese Irreversibilität ist in der Lage, klassische Effekte dynamisch zu erzeugen. Genauer gesprochen bewirkt die Wechselwirkung eine starke Verschränkung zwischen System und Umgebung, welche Phasenfaktoren zwischen Vektoren …
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Eigenfunctions in chaotic quantum systems
The structure of wavefunctions of quantum systems strongly depends on the underlying classical dynamics. In this text a selection of articles on eigenfunctions in systems with fully chaotic dynamics and systems with a mixed phase space is summarized. Of particular interest are statistical …
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Analytic representation of quantum systems
Finite quantum systems with d-dimension Hilbert space, where position x and momentum p take values in Zd(the integers modulo d) are studied. An analytic representation of finite quantum systems, using Theta function is considered. The analytic function has exactly d zeros. The d paths of these …
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Control of open quantum systems
… techniques of new methods for controlling open quantum systems. First, methods that improve coherent control through the use of both strong control fields and detailed knowledge of the subsystem's Hamiltonian are demonstrated. With the aid of numerical search methods, pulsed irradiation schemes …
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CHARACTERIZATION AND ENGINEERING OF QUANTUM SYSTEMS
… the exceptional results and developments that quantum mechanics, in combination with information theory, has developed in recent decades. This thesis is part of this line of research, with the scope of providing new results regarding quantum sensing and quantum control. Firstly, the need for …
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TENSOR NETWORKS FOR OPEN QUANTUM SYSTEMS
Is it possible to efficiently simulate a quantum physical system on a classical computer? The computational resources needed to manipulate quantum many-body states typically scale exponentially in the number of their constituents, making the simulation very difficult or outright impossible even at …
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Coupled quantum systems in inflationary cosmology.
… in this thesis describe applications of quantum field theory in a time dependent background. Two distinct problems are addressed in the framework of inflationary cosmology. The strict predictions of inflation are mostly in agreement with the Cosmic Microwave Background observations. In …
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RECOVERY AND RECONSTRUCTION IN QUANTUM SYSTEMS
Quantum systems are prone to noises. Accordingly, many techniques are developed tocancel the action of a quantum operation, or to protect the quantum information against the noises. In this dissertation, I discuss two such schemes, namely the recovery channel and the quantum error correction, and …
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Dissipative Quantum Systems and Flow Equations
This work investigates dissipative quantum systems by means of Flow Equations for Hamiltonians. We start with the Spin-Boson Model including one bosonic mode. The Flow Equation results for the ground-state energy and for the transformation of the Pauli spin matrices are compared with the …
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Group integrals in chaotic quantum systems
We derive a recursion formula for a class of group integrals both in ordinary space and in superspace. These group integrals represent the generalization of Bessel functions to matrix and supermatrix spaces. Thereby we derive exact expressions for the one and two--point eigenvalue correlator of a …
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Entanglement entropy in integrable quantum systems
… we compute the entanglement of various systems. Using the celebrated “replica trick” we compute the entanglement entropy of non unitary systems using integrable tools in continuum and discrete models. In particular, in the first article we generalise the method described in the seventh …
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Dynamical Aspects of Topological Quantum Systems
… encoded within the ground states of many-body quantum systems. In this thesis, we discuss how novel phenomena associated with topological phases can arise in systems that are driven out of equilibrium or coupled to their surroundings, which are not described by ground state physics. Firstly, we …
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Markovian transport through few-level quantum systems
In der vorliegenden Dissertation wird der Markov’sche quantenmechanische Mastergleichungsansatz benutzt, um die Transporteigenschaften unterschiedlicher experimenteller Aufbauten zu untersuchen. Motiviert durch die Suche nach möglichen physikalischen Implementierungen die Quanteneigenschaften für …
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Some aspects of measurement of quantum systems
… incorrect, measurement on otherwise closed quantum systems with two eigenstates. Previous work has set up a model for this situation, and showed the existence of 'telegraphing', in which the state of the system changes very little over extended periods of time before switching to the …
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Semiclassical hybrid dynamics for open quantum systems
… extended in order to be capable of treating open quantum systems considering finite baths. The corresponding phenomena, i.e. decoherence and dissipation, are investigated for various scenarios.
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Enforcing nonclassicality in medium-scale quantum systems
… <br/><br/>The first aspect is macroscopic quantumness, a field which considers the properties of macroscopic superpositions. The various measures of macroscopicity are reviewed. An optomechanical system is described which enables us to study nonclassicality in macroscopic mechanical …
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Studies of Integrable One-Dimensional Quantum Systems
In this thesis, I use the Bethe Ansatz (BA) to study various one-dimensional models. I first go through some background on the BA (both the coordinate and algebraic forms). I start the study by using the BA to compare bound state occurrences between the 2-particle XXZ, Bose–Hubbard, and Fermi– …
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