Measurement of qutrits
  We proposed the procedure of measuring the unknown state of the three-level system - the qutrit, which was realized as the arbitrary polarization state of the single-mode biphoton field. This procedure is accomplished for the set of the pure states of qutrits; this set is defined by the properties of SU(2) transformations, that are done by the polarization transformers. 
A.V. Burlakov, L.A. Krivitskiy, S.P. Kulik, G.A. Maslennikov, M.V.   Chekhova