Causal Compatibility Inequalities Admitting Quantum Violations in the Triangle Structure

Understand

It has long been recognized that certain quantum correlations are incompatible with particular assumption about classical causal structure.

• Given a causal structure of unknown classicality, the presence of such correlations certifies the nonclassical nature of the causal structure in a device-independent fashion.
• In structures where all parties share a common resource, these nonclassical correlations are also known as nonlocal correlations.
• Any constraint satisfied by all correlations which are classically compatible with a given causal structure defines a causal compatibility criterion.