Os efeitos da anisotropia e focalização nos estados gerados pela conversão paramétrica descendente e seu grau de emaranhamento

Abstract

Quantum Mechanics, one of the greatest scientific revolutions, challenged classical determinism with its probabilistic description of natural phenomena. Although its interpretation and scope have sparked intense debates, such as the famous clash between Einstein and Bohr, it has become an essential tool for understanding phenomena observed in Quantum Optics, such as quantum correlations. In this context, the interaction between light and matter offers a rich platform for studying quantum systems, especially with the advances made possible by the invention of lasers in the 1960s. This work focuses exclusively on Spontaneous Parametric Down-Conversion (SPDC), a process in which electromagnetic beams propagate through anisotropic crystals, generating pairs of entangled photons in both discrete and continuous variables. Together with the mathematical framework provided by Fourier Optics, it is possible to describe the generating and resulting electromagnetic fields as superpositions of plane waves, taking into account the existing polarizations, namely ordinary and extraordinary. SPDC, widely used to generate entangled states, enables the investigation and description of how such phenomena arise from the interaction between light and matter. This technique leads to the formation of two beams, and it is possible to observe how these beams are affected by the medium’s anisotropy and, ultimately, to evaluate the degree of entanglement present in these systems using three different methods.