Dottorato in FISICA

Titolo della tesi: Diverse Applications of the Quantum Walk model in Quantum Information: a theoretical and experimental analysis in the optical framework

Quantum Walks have been drawing a great deal of attention in the last thirty years, after their first definition and rigorous formulation. The analysis of the many possible variations of their behavior has delivered a plethora of solutions and platforms for many fields of investigation. The range of applications of the Quantum Walk model spans from the development of quantum algorithms, to the modeling and simulation of systems of the most diverse nature, such as solid state or biological ones. In general, it has helped developing a well-established model for quantum (or coherent) propagation phenomena, useful both inside and outside physics, and featuring a wide applicability to quantum information tasks. The great success of Quantum Walks as a framework for the analysis and steering of physical systems or for the design of efficient protocols resides in a general underlying idea: the dynamical study of a system may provide more insights about it than a static measurement of its features. The present thesis revolves around this concept: we can use dynamical methods, Quantum Walk-based for instance, both to study and control quantum systems. We focus on the study of disordered Quantum Walks, in order to get a better understanding of the influence of Quantum Walk disordered dynamics over non-classical correlations and quantum information propagating through a network. Then, we generalize this dynamical approach to Quantum Information processing, reporting on a quantum receiver for Quantum State Discrimination featuring a time-multiplexing structure; we investigate the potential of the corresponding Quantum Walk-inspired protocol, through the development and realization of experimental protocols characterized by increasing complexity. In the end, we also address an attempt to employ a dynamical approach to the problem of Entanglement Distribution, describing a protocol that relies on the interaction of the nodes of a network with a "walker", an always separable carrier system. We review such manifold matter recognizing the presence of a common denominator, being the ubiquitous quest for dynamical theoretical and experimental approaches, and showcasing the capabilities of optics as a flexible and powerful experimental framework for fundamental investigation as well as for technological application.