Under these conditions the dynamical equations of motion become: d d t ρ ρ s = L ρ ρ s , where L is the Liouville superoperator described in terms of the system's Hilbert space, where the reservoirs are described implicitly. Within the formalism of quantum open system, L can take the form of the Gorini-Kossakowski-Sudarshan-Lindblad (GKS-L) Markovian generator or also known just as Lindblad equation . Theories beyond the weak coupling regime have been proposed.