Activation of postquantumness in bipartite generalized Einstein-Podolsky-Rosen scenarios

In a standard bipartite Einstein-Podolsky-Rosen (EPR) scenario, Alice and Bob share a system prepared in an entangled state and Alice performs local measurements. One possible generalization of this setup is to allow Bob to also locally process his subsystem. Then correlations generated in such generalized EPR scenarios are examples of nonsignaling bipartite resources, called assemblages, that can exhibit postquantum behavior, i.e., cannot be generated using solely quantum systems. There exist assemblages that, despite being postquantum resources, can only generate quantum correlations in bipartite Bell-type scenarios. Here we present a protocol for activation of postquantumness in bipartite generalized EPR scenarios such as the so-called Bob-with-input, measurement-device-independent, and channel EPR scenarios. By designing a protocol that involves distributing the assemblages in a larger network, we derive tailored Bell inequalities which can be violated beyond their quantum bound in this new setup. Our results show that in all of the above generalized scenarios, the postquantumness of the assemblages can be witnessed at the level of correlations they produce.