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 (module, the efficiency loophole).