Experimental investigation of a coherent quantum measurement of the   degree of polarization of a single mode light beam
  A novel method for the direct measurement of the degree of polarization is described. It is one of the first practical implementations of a coherent quantum measurement, the projection on the singlet state. Our first results demonstrate the successful operation of the method. However, due to the nonlinear crystals used presently, its application is limited to spectral widths larger than ~8nm. 
Matthieu Legre, Mark Wegmuller, Nicolas Gisin (Group of Applied   Physics, University of Geneva, Switzerland)