Experimental realization of a minimal disturbance quantum measurement
  We report the first experimental realization of an ''optimal'' quantum device able to perform a Minimal Disturbance Measurement (MDM) on polarization encoded qubits saturating the theoretical boundary established between the classical knowledge acquired of any input state, i.e. the classical "guess", and the fidelity of the same state after disturbance due to measurement . The device has been physically realized by means of a linear optical qubit manipulation, post-selection measurement and a classical feed-forward process. 
F. Sciarrino, M. Ricci, F. De Martini, R. Filip, and L. Mista Jr