However, this is an idealization of the dynamics which is unavoidably subjects to noise raising from couplings to other degrees of freedom, which are often referred to as the environment. The theory of open quantum system concerns with the dynamics of relatively small quantum system coupled to a second system (the environment), that is typically considered very large, such as phonons in crystal, a gas of particles, or a beam of photons. The coupling to the environment induce energy dissipation and decoherence processes on the quantum system and are responsible for the emergence of irreversibility. Our group develop methods and tools to describe the dynamics of open quantum system in the weak and strong system-environment coupling regimes and for open system driven by time-dependent Hamiltonians.