Abstract:
A quantum system is open if it interacts with the external environment. This interaction typically induces dissipation and decoherence on the open system, dynamical effects that cannot be captured by a Schrödinger equation. In order to model them properly, one can adopt two different strategies: either a quantum dissipative dynamics is postulated, based on structural requirements and physical intuition, or the environment is included explicitly in the description and one tries to derive an (approximate) dissipative dynamics for the open system from the global Hamiltonian evolution.
In this talk, I will briefly comment on the first approach, mentioning the well-known GKSL theorem that can be used as a guide to construct phenomenological models, but I will mostly focus on the second approach. In particular, analyzing the prototypical example of a finite-level quantum system interacting with a free Bose gas, I will discuss the main ideas and mathematical tools used to rigorously derive effective open systems dynamics in suitable regimes (e.g. ultrastrong coupling).