Self-testing of genuine multipartite non-local and non-maximally entangled states

Self-testing enables the characterization of quantum systems with minimal assumptions their internal working. As such it represents the strongest form of certification for quantum systems. In the existing self-testing literature, self-testing states which are not maximally entangled, but exhibit genuine multipartite nonlocality, have remained an open problem. This is particularly important because, for many-body systems, genuine multipartite nonlocality has been recognized as the strongest form of multipartite quantum correlation. In this work, we present a Hardy-like paradox for scenarios involving arbitrary number of parties. This paradox is a tool for detecting genuine multipartite nonlocality, allowing for the specific identification and self-testing of states that defy the paradox's limits the most, which turn out to be non-maximally multipartite entangled states. While recent results [{{S}upi\'c et al., Nature Physics, 2023}] suggest network self-testing as a means to self-test all quantum states, here we operate within the standard self-testing framework to self-test genuine multipartite non-local and non-maximally entangled states.