Necessary and sufficient criterion for extremal quantum correlations in the simplest Bell scenario

Abstract

In the study of quantum nonlocality, one obstacle is that the analytical criterion for identifying the boundaries between quantum and postquantum correlations has not yet been given, even in the simplest Bell scenario. We propose a plausible, analytical, necessary and sufficient condition ensuring that a nonlocal quantum correlation in the simplest scenario is an extremal boundary point. Our extremality condition amounts to certifying an information-theoretical quantity; the probability of guessing a measurement outcome of a distant party optimized using any quantum instrument. We show that this quantity can be upper and lower bounded from any correlation in a device-independent way, and we use numerical calculations to confirm that coincidence of the upper and lower bounds appears to be necessary and sufficient for the extremality.

published version, 8 pages, 4 figures

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Cited by in corpus (8)

• Geometry of the quantum set on no-signaling faces
• Self-testing quantum states via nonmaximal violation in Hardy's test of nonlocality
• Device-independent bounds from Cabello's nonlocality argument
• Geometrical self-testing of partially entangled two-qubit states
• Information causality as a tool for bounding the set of quantum correlations
• Extremal Tsirelson inequalities
• (Almost-)Quantum Bell Inequalities and Device-Independent Applications
• NPA Hierarchy and Extremal Criterion in the Simplest Bell Scenario