Quantum Phase Transitions
Mostrando 1-12 de 26 artigos, teses e dissertações.
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1. Characterization of CBD-CdS Doped with Some Rare Earths III (Eu3+,Ce3+) as Function of Synthesis Time
Rare earths (Europium, cerium)-doped CdS nanofilms are prepared using the growth technique chemical bath deposition (CBD) at the reservoir temperature of 70±2°C varying the synthesis time in a wide range. For the rare earths doped CdS nanofilms the synthesis time was ranged from 80 to 135 min. The rare earths molar concentration was in the range 0.0≤x≤
Mat. Res.. Publicado em: 01/02/2018
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2. Termalização e correlações quânticas nos contextos de sistemas quânticos abertos e cadeias de spins
In this thesis, we study the behavior of Quantum Discord in the contexts of open quantum systems and spin chains. Furthermore, we investigate the thermalization process of a spin chain due to interaction with the environment. First, we present a review on the concept of quantum correlation, beginning with the first ideas on non-locality, and leading to the m
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 11/01/2013
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3. Study of quantum effects in condensed matter thermodynamics : phase transitions at finite temperature / Estudo de efeitos quânticos na termodinâmica da matéria condensada : transições de fase a temperatura finita
Neste trabalho apresentaremos a extensão dos métodos adiabatic switching (AS), reversible scaling (RS) e integração dinâmica de Clausius-Clapeyron (d-CCI) para o formalismo de integral de tragetória. Desenvolvemos programas de Monte Carlo de integrais de trajetória (PIMC) para implementar esses métodos a fim de incluir efeitos quânticos nos cálculo
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 22/06/2012
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4. Geometria e simetrias do emaranhamento
In the present work we present a geometric method to identify and measure the degree of entanglement of a two-qubit state. It is based on writing a map of the system state, from a non-unitary transformation. By introducing new parameters for such 4X4 matrix, the product of eigenvalues, two by two, acquire the form of squared 4D distances, having a Minkowski
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 20/05/2011
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5. Efeitos da aperiodicidade sobre as transições quânticas em cadeias XY / Effects of aperiodicity on the quantum transitions in XY chains
Neste trabalho realizo uma adaptação do método de Ma, Dasgupta e Hu para o estudo e caracterização das transições de fase quânticas, induzidas por um campo transverso, em cadeias XY de spins 1/2, unidimensionais e aperiódicas, no espírito da adaptação correspondente para cadeias XXZ. O presente trabalho determina de forma analítica uma série de
Publicado em: 2011
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6. Transições de fase hádron-quark em estrelas de nêutrons
Recent advances on the field of high energy physics have enabled the study of matter under extreme conditions and, in this context, new states of matter are being discovered and speculated upon. Among these hypothetical states of matter is the one of deconfined quarks in high densities and/or temperatures. An environment with extreme densities and low temper
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 2011
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7. Cálculo de la concurrencia para el modelo de Heisenberg
The concurrence is a quantity that allows us to measure the entanglement of a quantum system and can be calculated from the reduced density matrix. In this paper we show explicitly how to calculate the concurrence for a finite chain of spins s =1/2 described by the anisotropic Heisenberg model. We show that for finite chains the concurrence has a maximum at
Revista Brasileira de Ensino de Física. Publicado em: 2010-09
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8. Classical and quantum correlations under decoherence / Correlações clássicas e quânticas sob decoerência
Recently, in the context of discrete variables, the existence of quantum correlations that are more general than entanglement was identified. We may conjecture that these correlations are a very important resource in quantum information science and in some areas of physics. However, this fragile resource is quickly destroyed by the decoherence process. In th
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 26/08/2009
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9. Quantum entanglement in a many-body system exhibiting multiple quantum phase transitions
We investigate the quantum entanglement-related features of the many-body model of Plastino and Moszkowski [N. Cimento 47 (1978) 470]. This is an exactly solvable N-body, SU2 two-level model exhibiting several quantum phase transitions. We show that these transitions happen to be also entanglement-transitions associated with different many-body Dicke states.
Brazilian Journal of Physics. Publicado em: 2009-08
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10. Emaranhamento e estados de produto de matrizes em transições de fase quanticas / Entanglement and matrix product states in quantum phase transitions
This thesis attempts to contribute to the understanding of possible connections between Quantum Information and Condensed Matter theories, a new field of research in broad development. Specifically, we investigated the role of entanglement, or quantumcorrelations, in continuous quantum phase transitions. While the importance of the first in the theory of Qua
Publicado em: 2008
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11. Estudos do transporte de partÃculas brownianas interagentes e de transiÃÃes de fases em modelos de spin quÃnticos
Nesta Tese, sÃo investigados dois temas de interesse atual, o transporte de partÃculas brownianas interagentes e as transiÃÃes de fase em sistemas magnÃticos quÃnticos. No primeiro, o transporte de partÃculas brownianas interagentes sujeitas a um potencial de substrato do tipo catraca foi investigado numericamente atravÃs da dinÃmica de Langevin. Me
Publicado em: 2008
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12. Disappearance of squeezed back-to-back correlations: a new signal of hadron freeze-out from a supercooled quark gluon plasma
We briefly discuss four different possible types of transitions from quark to hadronic matter and their characteristic signatures in terms of correlations. We also highlight the effects arising from mass modification of hadrons in hot and dense hadronic matter, as well as their quantum statistical consequences: the appearance of squeezed quantum states and t
Brazilian Journal of Physics. Publicado em: 2007-09