Study of the dynamics of quantum brownian particles

Author(s)

Oscar Salomon Duarte Muñoz

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Física Gleb Wataghin
• Defense date: 2011-12-12

Examining board members

Amir Ordacgi Caldeira; Kyoko Furuya; José Antonio Roversi; Thiago Rodrigues de Oliveira; Frederico Borges de Brito

• Advisor: Amir Ordacgi Caldeira

Abstract

We use the system-plus-reservoir model to study the dynamics of a system of two particles that interact with a heat bath in thermal equilibrium. We analyze the effects, for the two particle case, of a direct generalization of the usual model for one brownian particle. We particularly call for attention to the fundamental role of the counterterm in order to obtain the proper dynamics in the classical limit. We use an extension of the bath of oscillators capable of inducing an effective coupling between the brownian particles depending on the choice made to the spectral function of the oscillators components of the bath. The coupling is non-linear in the variables of interest and an exponential dependence is imposed in order to guarantee the translational invariance of the model. The quantum dynamics is studied through the reduce density operator of the two particles. We obtain the evolution of the reduce density operator for two systems of interest: the first one is composed by two free particles initially prepared in a gaussian state and the second one is composed by two harmonic oscillators prepared initially in a non-gaussian state formed by superposition of gaussian packets. The environment in uence is observed through the evolution of entanglement. Our model provides a criterion of distance for identifying in which cases a common environment can induce entanglement. Three regimes are found: the short distance regime, equivalent to a bilinear system-reservoir coupling, the long distance regime in which the particles act like coupled to independent reservoirs and the intermediate regime suitable for the coexistence between decoherence and induced-entanglement (AU)

• FAPESP's process: 06/04356-0 - Study of many Brownian particles dynamics
• Grantee: Oscar Salomón Duarte Muñoz
• Support Opportunities: Scholarships in Brazil - Doctorate