A discrete Darboux-Lax scheme for integrable difference equations

We propose a discrete Darboux-Lax scheme for deriving auto-B"acklund transformations and constructing solutions to quad-graph equations that do not necessarily possess the 3D consistency property. As an illustrative example we use the Adler-Yamilov type system which is related to the nonlinear Schr"odinger (NLS) equation [19]. In particular, we construct an auto-B"acklund transformation for this discrete system, its superposition principle, and we employ them in the construction of the one- and two-soliton solutions of the Adler-Yamilov system.