We present a multipartite nonlocal game in which each player must guess the input received by his neighbor. We show that quantum correlations do not perform better than classical ones at this game, for any prior distribution of the inputs. There exist, however, input distributions for which general no-signaling correlations can outperform classical and quantum correlations. Some of the Bell inequalities associated with our construction correspond to facets of the local polytope. Thus our multipartite game identifies parts of the boundary between quantum and postquantum correlations of maximal dimension. These results suggest that quantum correlations might obey a generalization of the usual no-signaling conditions in a multipartite setting.
- BELLS THEOREM