Decoherence of a qubit by non-Gaussian noise at an arbitrary working   point
  The decoherence of a qubit due to a classical non-Gaussian noise with correlation time longer than the decoherence time is discussed for arbitrary working points of the qubit. A method is developed that allows an exact formula for the phase memory functional in the presence of independent random telegraph noise sources to be derived. 
J. Bergli, Y. M. Galperin, and B. L. Altshuler