Quantum and Super-quantum enhancements to two-sender, two-receiver channels

We study the consequences of ‘super-quantum non-local correlations’ as represented by the PR-box model of Popescu and Röhrlich, and show PR-boxes can enhance the capacity of noisy interference channels between two senders and two receivers. PR-box correlations violate Bell/CHSH inequalities and are thus stronger – more non-local – than quantum mechanics; yet weak enough to respect special relativity in prohibiting faster-than-light communication. Understanding their power will yield insight into the non-locality of quantum mechanics. We exhibit two proof-of-concept channels: first, we show a channel between two sender-receiver pairs where the senders are not allowed to communicate, for which a shared super-quantum bit (a PR-box) allows perfect communication. This feat is not achievable with the best classical (senders share no resources) or quantum entanglement-assisted (senders share entanglement) strategies. Second, we demonstrate a class of channels for which a tunable parameter ǫ achieves a double separation of capacities; for some range of ǫ, the super-quantum assisted strategy does better than the entanglement-assisted strategy, which in turn does better than the classical one.