Qubit quantum channels: A characteristic function approach

A characterization of qubit quantum channels is introduced. In analogy to what happens in the context of bosonic channels we exploit the possibility of representing the states of the system in terms of characteristic function. The latter are functions of noncommuting variables (Grassmann variables) and are defined in terms of generalized displacement operators. In this context we introduce the set of Gaussian channels and show that they share similar properties with the corresponding bosonic counterpart.