Redes de osciladores dissipativos: o modelo duplicado de Caldeira-Leggett, transferência quase-perfeita de estados e recoerência

• Ano de defesa: 2010
• Autor(a) principal: Cacheffo, Alexandre
• Orientador(a): Moussa, Miled Hassan Youssef
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de São Carlos
• Programa de Pós-Graduação: Programa de Pós-Graduação em Física - PPGF
• País: BR
• Palavras-chave em Português: Mecânica quântica; Decoerência (Decoherence); Redes de osciladores quânticos; Integrais de trajetórias; Transferência e recorrência de estados quânticos; Recoerência
• Área do conhecimento CNPq: CIENCIAS EXATAS E DA TERRA::FISICA
• Link de acesso: https://repositorio.ufscar.br/handle/20.500.14289/4922

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 coupled to the same reservoir. Finally we analyzed the decoherence process of entangled states prepared in both oscillators. Next, we treat the problem of quasi-perfect state transfer (QPST) in networks of dissipative harmonic oscillators. In this context, we have presented two different protocols for QPST: the first based in the detuning between the frequencies of the emitter and receiver oscillators regarding that of the transmitter oscillators and the second consisting in the use of what we call a decoherence quasi-free subspace (DQFS). To this end, we derived the regime of parameters enabling the emergence of DQFS. In both protocols we verified that QPST processes occur by means of a mechanism, similar to the tunneling effect, i. e., the excitations of the state to be transferred populate only virtually the transmission channel. Finally, regarding quantum open systems, we present the phenomenon that we call spontaneous recoherence of states. Through this phenomenon, we verified that the reservoir only shuffle the information of the system, instead of erasing it. The password to retrieve the original information consists of the knowledge of the initial state itself and its associated pure basis