Studies in classical and quantum correlations and their evolution in physical systems

More than a century ago, starting with Michelson, the field of classical coherence has developed rapidly. By studying and uncovering the coherence properties of light, many useful applications were discovered. In modern times, these applications have seen large use in fields like astronomy, where the properties of light can be used to discover stars and determine their radius, for example. Another class of correlations, namely quantum correlations, which were discovered in the beginning of the twentieth century, have gained much attention from the scientific community in the last two decades. In particular, the field of quantum information developed, promising great computational power by using quantum correlations to build computers. Currently, quantum computation is a very active field bringing together physicists, mathematicians, engineers, chemists, and computer scientists to find solutions to the problems encountered in building quantum computers. I consider some classical coherence effects of the degree of cross polarization (DCP) on the Hanbury-Brown Twiss effect, with a specific focus on Gaussian Schell-model beams. I show that the DCP is necessary, in general, to determine the correlations in intensity fluctuations of a beam at two different points. As for quantum correlations, I consider entanglement in realistic systems: one in two-qubit systems, and the other in continuous variable quantum systems. In the former case, when the temperature of the system is finite, entanglement always decays in a finite time. However, in the latter case, entanglement is long-lived, although in the long run it is not of much practical use. Finally, I unravel the relationship between quantum discord and quantum entanglement, as well as quantum discord and entropy for the most general two-qubit systems, and I identify the states that define the boundaries of these relationships.Ph.D