Shannon's theory of information was built on the assumption that the information carriers were classical systems, carrying classical messages and moving along well-defined trajectories in spacetime. Its quantum counterpart, quantum Shannon theory, explores scenarios where the messages can be quantum, but their trajectories in spacetime are still classical. Quantum Shannon theory can be regarded as a first quantisation of Shannon's information theory, where the internal state of the information carriers is quantised, but the motional degrees of freedom as classical. In this talk I will discuss a second level of quantisation, where not only the information carriers, but also the path along which information travels can be in a quantum superposition. I will present several examples of this scenario, discussing the different ways in which second-quantised communication protocols can achieve tasks that are impossible in conventional quantum Shannon theory.

Giulio Chiribella is a professor at the Department of Computer Science of The University of Hong Kong, and a visiting professor of the Department of Computer Science of the University of Oxford. He has done pioneering research on quantum causal networks, on the reconstruction of quantum theory, and on the ultimate precision limits of clocks and gyroscopes, for which he was awarded the Hermann Weyl Prize 2010. Before joining the University of Hong Kong, he held faculty positions at Oxford University and Tsinghua University, Beijing. He is a Croucher Senior Research Fellow, a CIFAR-Azrieli Global Scholar, a member of the Standing Committee of the International Colloquia on Group Theoretical Methods in Physics (ICGTMP), Visiting Fellow of Perimeter Institute for Theoretical Physics, Member of the Foundational Questions Institute (FQXi), Fellow of the National Virgilian Academy of Sciences, Letters and Arts (Mantova, Italy), Member of the Editorial Board of Journal of Physics A and of Open Systems and Information Dynamics.