Ladder Proof of Nonlocality without Inequalities: Theoretical and Experimental Results

We show how a previous demonstration of nonlocality without inequalities for two spin-half particles can be improved so that a greater proportion of the pairs are shown to be subject to a contradiction with local realism. This is achieved by considering more settings of the apparatus at each end. Also, we report on an experimental realization employing a tunable source of polarization entangled photons. The experimental results violate locality (modulo, the efficiency loophole). copyright 1997 The American Physical Society