Noise models for superoperators in the chord representation

We study many-qubit generalizations of quantum noise channels that can be written as an incoherent sum of translations in phase space, for which the chord representation results specially useful. Physical descriptions in terms of the spectral properties of the superoperator and the action in phase space are provided. A very natural description of decoherence leading to a preferred basis is achieved with diffusion along a phase space line. The numerical advantages of using the chord representation are illustrated in the case of coarse-graining noise.