Caracterização e evolução de estados quânticos fotônicos e atômicos de muitos níveis

Abstract

The goal of this thesis is to study the generation, characterization and evolution of photonic and atomic quantum states generated by spontaneous parametric down conversion (SPDC) and by a cold atomic beam of rubidium. Photons generated by SPDC are entangled in transversal path after passing through mutiple slits. Two qubit and two qutrit states are generated and their density operator are obtained by minimum quantum state tomography. An discussion about the amount of entanglement and the quality of the experimentally obtained density operator is performed. Through the interaction between a cold atomic beam with a light beam inside a cavity in the quantum electrodynamics regime and in the presence of a external magnetic eld, a superposition of the magnetic sublevels of the ground state of 85Rb is generated detecting a photon with horizontal polarization. Measuring the intensity correlation function by a homodyne process a conditional quantum beat of the ground state superposition is observed. Through a quantum feedback protocol, an study of evolution and how to preserve coherence is done.