Shortcuts to relaxation in open quantum systems

In quantum computing, one of the problems to face has always been to reduce the effects of the coupling between the system of interest and the external environment. New researches, however, have innovatively addressed the problem, using the environment and its interaction with the system as an effective tool for the generation of quantum states. One can wonder if it is possible to speed up the approach of open quantum systems towards stationarity through protocols that go by the name of "Shortcuts to Relaxation". The first chapter introduces the theory of open quantum systems by providing the reader with the mathematical tools to understand the work developed afterward. In particular, I introduce the formalism of the master equations used to describe the dynamics of these systems. The second chapter introduces the protocol called Shortcut to Equilibration (STE), which consists in manipulating some parameters of the Hamiltonians, thus modifying the interaction between the system and the external bath. In this way, the protocol reduces the natural relaxation time of the system. In the third chapter, I introduce the so-called Unitary Priming protocol (UP), which consists in applying an optimal unitary transformation to the initial state of the system before the temporal evolution, to cancel the overlap with the slowest decay modes, exponentially accelerating the rate of relaxation. In the fourth chapter, I present an original protocol that combines the previous two, showing that the relaxation is further accelerated with respect to applying them individually. In the conclusions, I summarize the main results obtained, demonstrating that such protocols can effectively accelerate the dynamics of an open quantum system