  In a recent paper, Buscemi and al. defined a notion of clean positive
operator valued measures (POVMs). We here characterize which POVMs are clean in
some class that we call quasi-qubit POVMs, namely POVMs whose elements are all
rank-one or full-rank. We give an algorithm to check whether a given
quasi-qubit POVM satisfies to this condition. We describe explicitely all the
POVMs that are clean for the qubit. On the way we give a sufficient condition
for a general POVM to be clean.
