  We develop an SU(2)-invariant approach to the depolarization of quantum
systems as the effect of random unitary SU(2) transformations. From it we
derive an SU(2)-invariant Markovian master equation. This is applied to several
quantum states examining whether nonclassical states are more sensible to
depolarization than the classical ones. Furthermore, we show that this
depolarization model provides a nontrivial generalization of depolarization
channels to states of arbitrary dimension.
