  Society relies and depends increasingly on information exchange and
communication. In the quantum world, security and privacy is a built-in feature
for information processing. The essential ingredient for exploiting these
quantum advantages is the resource of entanglement, which can be shared between
two or more parties. The distribution of entanglement over large distances
constitutes a key challenge for current research and development. Due to losses
of the transmitted quantum particles, which typically scale exponentially with
the distance, intermediate quantum repeater stations are needed. Here we show
how to generalise the quantum repeater concept to the multipartite case, by
fully describing large-scale quantum networks, i.e. network nodes and their
long-distance links, in the language of graphs and graph states. This unifying
approach comprises both the distribution of multipartite entanglement across
the network, and the protection against errors via encoding. The correspondence
to graph states also provides a tool for optimising the architecture of quantum
networks.
