Experimental realization of optimal detection strategies for overcomplete states - art. no. 012303

We present the results of generalized measurements of optical polarization designed to provide one of three or four distinct outcomes. This has allowe d us to discriminate between nonorthogonal polarization states with an erro r probability that is close to the minimum allowed by quantum theory. Emplo ying these optimal detection strategies on sets of three (trine) or four (t etrad) equiprobable symmetric nonorthogonal polarization states, we obtain a mutual information that exceeds the maximum value attainable using conven tional (von Neumann) polarization measurements.