How quantum correlations enhance prediction of complementary measurements
Radim Filip, Miroslav Gavenda, Jan Soubusta, Antonín Černoch, Miloslav Dušek · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 2005
If there are correlations between two qubits then the results of the measurement on one of them can help to predict measurement results on the other one. It is an interesting question what can be predicted about the results of two complementary projective measurements on the first qubit. To quantify these predictions the complementary knowledge excesses are used. A non-trivial constraint restricting them is derived. For any mixed state and for arbitrary measurements the knowledge excesses are bounded by a factor depending only on the maximal violation of Bell's inequalities. This result is experimentally verified on two-photon Werner states prepared by means of spontaneous parametric down-conversion.