  Quantum networks connect and supply a large number of nodes with multi-party
quantum resources for secure communication, networked quantum computing and
distributed sensing. As these networks grow in size, certification tools will
be required to answer questions regarding their properties. In this work we
demonstrate a general method to guarantee that certain correlations cannot be
generated in a given quantum network. We apply quantum inflation methods to
data obtained in quantum group encryption experiments, guaranteeing the
impossibility of producing the observed results in networks with fewer optical
elements. Our results pave the way for scalable methods of obtaining
device-independent guarantees on the network structure underlying multipartite
quantum protocols.
