Determine the full power of information causality

Determine the full power of the information causality principle, including whether it imposes constraints beyond macroscopic locality at leading order in the vanishing-capacity limit in the simplest Bell scenario.

Background

The paper proves that generalized information causality exactly recovers the macroscopic-locality/Tsirelson–Landau–Masanes boundary in the simplest bipartite Bell scenario and is strictly stronger than macroscopic locality at nonzero channel capacity. It therefore leaves unresolved how much additional constraining power information causality has beyond the demonstrated results.

The authors specifically ask whether another communication protocol can produce constraints beyond macroscopic locality already in the leading-order, vanishing-capacity regime. Resolving this would clarify whether the strength observed at finite channel capacity can also appear in the asymptotic low-capacity limit.

References

The full power of IC is still unknown, even in the simplest Bell scenario. Can a different protocol yield constraints beyond ML already at leading order in the vanishing-capacity limit?

— Information Causality Characterizes the Set of Quantum Correlations in the Simplest Bell Scenario  (2609.10508 - Gachechiladze et al., 9 Sep 2026) in Section Discussion

Whether almost-quantum correlations satisfy generalized IC remains unresolved.

— Information Causality Characterizes the Set of Quantum Correlations in the Simplest Bell Scenario  (2609.10508 - Gachechiladze et al., 9 Sep 2026) in Section Discussion

The full power of IC is still unknown, even in the simplest Bell scenario. Can a different protocol yield constraints beyond ML already at leading order in the vanishing-capacity limit? Does the recovery of ML through optimized communication channel extend to more general bipartite Bell scenarios? Can almost-quantum correlations violate generalized IC, either in the simplest Bell scenario or in a larger one?

— Information Causality Characterizes the Set of Quantum Correlations in the Simplest Bell Scenario  (2609.10508 - Gachechiladze et al., 9 Sep 2026) in Section Discussion