Manipulation of states of a degenerate quantum system

We consider the dynamics of an open three-level quantum degenerate system. One of the levels in this system is degenerate. The system interacts with three reservoirs (quantum fields) and a classical external field. We show that nondecaying so-called dark states are generated in this system. Since the interactions of the degenerate level with two different reservoirs are different (correspond to different spaces of dark states), we can describe excitation and manipulations for this kind of states (in particular, observation in spectroscopical experiments). Possible applications of this model in quantum optics, quantum computations, and quantum photosynthesis are discussed.