Network science is a new and rapidly evolving branch of research that has hitherto aimed to
characterise classical networks observed in nature and society. In contrast, radically different
concepts apply for quantum systems, which can exhibit much stronger correlations than those
possible for any classical system. What does quantum bring to networks?
There are multiple possibilities for quantum aspects to appear within network formalisms, and there
is a sizeable body of literature discussing individual aspects of connected quantum systems. A
commonly discussed setting is one in which a network consists of quantum nodes, connected via
classical channels which carry quantum information. More intriguingly, settings may be envisaged
within which the entire network can be quantum-mechanical, including superpositions of nodes and
superpositions of links, leading to superpositions of network topology. Network with such properties
have no known (classical) graph that can describe its underlying structure, and might exhibit
radically different properties.
The aim of our project is to provide a unified formalism for quantum effects in networks and to
underpin this framework with clearly targeted measurement schemes. We will furthermore examine
the properties of model constituents of quantum networks in order to provide first experimental
bounds for the physical properties of such networks.
Beyond fundamental advances, we expect several practical implications to result from this project,
especially at the physical interface between classical and quantum networks. Security enhancement
provided by quantum schemes, such as quantum key distribution, is a well-known application. The
formal framework developed in this project will allow us, for example, to examine whether quantum
schemes can be used to enhance other aspects of network performance, or whether quantum
measurements can be used to determine network properties more efficiently than cla