Emerging dynamics and its application in attempts to model a quantum measurement process

Quantum theory is undoubtedly a successful physics theory: it is consistent, its mathematical formalism is well founded and the laws that govern the small scale phenomena are, mostly, well described by quantum theory. However, in our daily lives we do not experience quantum phenomena. Classical physics is well enough to describe the daily world. In this thesis we use quantum information theory tools, particularly quantum channels, to contribute to the search for an answer to the question: what is the real role/importance of the impossibility of accessing all the degrees of freedom of a quantum system to emergence of the effective, "classical", realm and, parallel, the "death" of quantum features? Such impossibility is translated mathematically via a coarse-graining quantum channel. We start by developing a framework to investigate what kinds of dynamics emerge when one does not have full access to the degrees of freedom of a given system. As an application of the developed general framework, we present attempts to model a quantum measurement process: a system to be measured consisting of a qubit in a superposition interacts with a measuring apparatus consisting of a spin coherent state (first attempt) and a N qubit state (second attempt). Looking at the emerging, effective description of the apparatus, we were able to recover the superposition coefficients of the system (in both attempts). In the first attempt, we were also able to visualize the death of quantum correlations between system and apparatus and the creation of classical ones. In the second, we managed to observe the death of quantum coherences in the apparatus’ effective state, obtained through the coarse-graining action. A situation akin to decoherence, although it was not necessary to evoke any interaction with the surrounding environment.