Quantum Dissipative Systems
Mostrando 1-12 de 12 artigos, teses e dissertações.
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1. Redes de osciladores dissipativos : o modelo duplicado de Caldeira-Leggett, transferência quase-perfeita de estados e recoerência
In this work we treat firstly what we call the double Caldeira-Leggett model, which consists on the approach to the dynamics of two dissipative harmonic oscillators via Feynman-Vernon theory. We derived and solved the associated master equations in two different situations where i) each oscillator is coupled to its own reservoir and ii) both oscillators are
Publicado em: 2010
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2. Estudo das técnicas de obtenção de Hamiltonianos efetivos em Óptica Quântica
In the Quantum Optics area, the construction of effective hamiltonian is a matter of great importance, since from them we can generate and manipulate quantum states and logical operations. In this work we discuss 3 approximate methods for obtaining such effective hamiltonians: i) adiabatic elimination, ii) method of effective dynamics for oscillating hamilto
Publicado em: 2009
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3. Extended Bell´s Be-ables and Atenuattion × Amplification Competition. / Extensão dos Be-ables de Bell e Competição Atenuação x Amplificação
In the first part of this work we employ the Itô stochastic equation to extend Bells be-able interpretation of quantum mechanics to encompass dissipation, decoherence and quantum-to-classical transition through quantum trajectories. For a particular choice of the source of stochasticity, the one leading to a dissipative Lindblad type correction to the Hamil
Publicado em: 2009
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4. Fases geométricas e invariantes dinâmicos em mecânica quântica
The increasing interest to understand the geometric phases (mainly due to the possi- bility to achieve geometric quantum computation robust against some kind of errors) and the search for new techniques to solve time-dependent problems in Quantum Mechanics, are the topics approached in this thesis. i) Within nowadays technology, it is presented a scheme to c
Publicado em: 2007
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5. Dissipação, termalização e descoerencia via acoplamento caotico / Dissipation, thermalization and decoherence through chaotic coupling
We study here how and under which conditions a chaotic system with only two degrees of freedom can produce irreversible phenomena such as dissipation, thermalization and, from the quantum point of view, decoherence in a simple system coupled to it. In the classical formulation of the problem, we describe analytically the behavior of the energy ux in Linear R
Publicado em: 2006
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6. A study of decoherence processes in solid state qubits / Um estudo sobre processos de descoerencia em qubits de estado solido
Esta tese teve como objetivo estudar processos de perda de coerência quântica, chamados de descoerência, em sistemas de matéria condensada eleitos pela literatura como possíveis implementações do bit quântico (qubit). Esta perda de coerência quântica ocorre devido ao inevitável acoplamento do sistema de interesse com o seu ambiente. Como os estado
Publicado em: 2006
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7. Systems Biology: an information-theoretic-based thermo-statistical approach
Systems Biology (system-level understanding in biological science), from the physical-chemical point of view, is involved with irreversible thermodynamics and nonlinear kinetic theory of open systems which are founded on nonequilibrium statistical mechanics. We describe a modern thermo-statistical approach for dealing with complex systems, in particular biol
Brazilian Journal of Physics. Publicado em: 2004-06
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8. Decoerencia de spin eletronico em pontos quanticos
In the perspective of quantum computation, two levels systems are the best candidates to implement the so called quantum bits. In special, the possibility of growing quantum dots capable of storing one electron makes it plausible to use electronic spin for such devices. Nevertheless, one of the big concerns is the time the electron takes to lose coherence. I
Publicado em: 2003
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9. Aspectos dinamicos de sistemas quanticos abertos
Dynamical aspects of three open quantum systems are examined. In the problem of quantum particle trapping by oscillating fields there is the evidence of movement stabilization and the quadrature-squeezing degradation for the quantum particle, due to the dissipative action of the environment over the particle. In the problem of information transfer occuring i
Publicado em: 1999
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10. Dissipative Properties of Quantum Systems
We consider the dissipative properties of large quantum systems from the point of view of kinetic theory. The existence of a nontrivial collision operator imposes restrictions on the possible collisional invariants of the system. We consider a model in which a discrete level is coupled to a set of quantum states and which, in the limit of a large “volume,�
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11. The second law as a selection principle: The microscopic theory of dissipative processes in quantum systems
The second law of thermodynamics, for quantum systems, is formulated, on the microscopic level. As for classical systems, such a formulation is only possible when specific conditions are satisfied (continuous spectrum, nonvanishing of the collision operator, etc.). The unitary dynamical group can then be mapped into two contractive semigroups, reaching equil
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12. Self-organization in leaky threshold systems: The influence of near-mean field dynamics and its implications for earthquakes, neurobiology, and forecasting
Threshold systems are known to be some of the most important nonlinear self-organizing systems in nature, including networks of earthquake faults, neural networks, superconductors and semiconductors, and the World Wide Web, as well as political, social, and ecological systems. All of these systems have dynamics that are strongly correlated in space and time,
National Academy of Sciences.