  Light harvesting processes are often computationally studied from a
time-dependent viewpoint, in line with ultrafast coherent spectroscopy
experiments. Yet, natural processes take place in the presence of incoherent
light, which induces a stationary state. Such stationary states can be
described using the eigenbasis of the molecular Hamiltonian, but for realistic
systems a full diagonalization is prohibitively expensive. We propose three
efficient computational approaches to obtaining the stationary state that
circumvent system Hamiltonian diagonalization. The connection between the
incoherent perturbations, decoherence, and Kraus operators is established.
