  We put forward a dissipative preparation scheme for strongly correlated
photon states. Our approach is based on a two-photon loss mechanism that is
realised via a single four-level atom inside a bimodal optical cavity. Each
elementary two-photon emission event removes one photon out of each of the two
modes. The dark states of this loss mechanism are given by NOON states and
arbitrary superpositions thereof. We find that the steady state of the two
cavity modes exhibits entanglement and for certain parameters, a mixture of two
coherent entangled states is produced. We discuss how the quantum correlations
in the cavity modes and the output fields can be measured.
