Unbounded Bell violations for quantum genuine multipartite non-locality

The violations of Bell inequalities by measurements on quantum states give riseto the phenomenon of quantum non-locality and express the advantage of usingquantum resources over classical ones for certain information-theoretic tasks.The relative degree of quantum violations has been well studied in the bipartitescenario and in the multipartite scenario with respect to fully local behaviours.However, the multipartite setting entails a more complex classification in whichdifferent notions on non-locality can be established. In particular, genuine multipartite non-local distributions apprehend truly multipartite effects, given thatthese behaviours cannot be reproduced by bilocal models that allow correlationsamong strict subsets of the parties beyond a local common cause. We show herethat, while in the so-called correlation scenario the relative violation of bilocalBell inequalities by quantum resources is bounded, i.e. it does not grow arbitrarily with the number of inputs, it turns out to be unbounded in the general case.We identify Bell functionals that take the form of non-local games for whichthe ratio of the quantum and bilocal values grows unboundedly as a function ofthe number of inputs and outputs.

Unbounded Bell violations for quantum genuine multipartite non-locality Articles