Necessary and sufficient conditions for Bell violations in one-sided device-independent scenarios

Researchers Marcio M. Taddei, Ranieri V. Neri, and Leandro Aolita, from the  UFRJ have posted a new paper in the arXiv about the interplay between steering and nonlocality. See http://arxiv.org/abs/1603.05247.  A brief description follows.

Quantum steering is an interesting physical effect with both foundational and applied relevance, including important applications within the context of semi-device-independent quantum information. It constitutes, in addition, an intermediate fundamental form of correlation between entanglement and Bell nonlocality. Very recently, a great deal of effort has been devoted to understanding the interplays among the three different forms of quantum nonlocality.

The submitted paper explores the boundary between steering and Bell nonlocality. We derive necessary and sufficient conditions for Bell nonlocal correlations in one-sided device-independent scenarios (one black-box untrusted measurement device + one trusted quantum platform), which are the native framework for steering. Our criterion is flexible in that it can tackle, in a unified way, a very wide range of generic Bell scenarios (arbitrarily many measurement choices for both the black box and the quantum part, as well as arbitrarily many measurement outcomes for the untrusted part). It has, in addition, the built-in advantage that it is expressed in terms of closed-form analytical formulas, requiring neither linear or semi-definite programming nor optimization at all. We believe this is a major improvement over the existing results on the topic.

Our findings constitute a powerful and practical tool for the study of the interplay between EPR steering and Bell nonlocality, with applications expected in the near future.

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