where H S is the system Hamiltonian, H B is the bath Hamiltonian and H S B is the system-bath interaction. The state of the system is obtained from a partial trace over the combined system and bath: ρ ρ S ( t ) = T r B ( ρ ρ S B ( t ) ) . Reduced dynamics is an equivalent description of the system dynamics utilizing only system operators. Assuming Markov property for the dynamics the basic equation of motion for an open quantum system is the Lindblad equation (GKLS):