Seminario Dottorato 2024/25 - Pietro DE CHECCHI (05.12.2024)

Closed quantum systems are an idealization, their time evolution described by the Schrödinger Equation, i.e. by the action of unitary operators. The physics of a realistic quantum system, on the other hand, is bound to be disturbed by the environment in which it is naturally embedded and with which it inevitably interacts. The dimension of the space needed to fully describe the composite system increases, as one would have to include all, possibly infinite, environments variables, leading to intractable problems. To reduce the system to a smaller subspace of interest and to describe its correct dynamics, many strategies have been developed. These systems have in general non-unitary dynamics and are known as Open Quantum Systems. During the talk, we will introduce some of the main approaches based on various techniques, from dynamical semigroup generators, stochastic unravellings and bottom-up modelling.