Which causal structures might support a quantum-classical gap?

Understand

A causal scenario is a graph that describes the cause and effect relationships between all relevant variables in an experiment.

• A scenario is deemed `not interesting' if there is no device-independent way to distinguish the predictions of classical physics from any generalised probabilistic theory (including quantum mechanics).
• Conversely, an interesting scenario is one in which there exists a gap between the predictions of different operational probabilistic theories, as occurs for example in Bell-type experiments.
• Henson, Lal and Pusey (HLP) recently proposed a sufficient condition for a causal scenario to not be interesting.