Project level: Honours, PhD

Quantum information has developed in the last decades into a broad field, offering several promising applications for future technology and deep insights into the foundations of physics.

Very recently, first steps have been made in the direction of theoretically characterising and experimentally manipulating causal relations between quantum systems from an information-theoretical perspective. The motivations are two-fold: from a foundational perspective, it is expected that the notion of definite, classical causal structure would not survive in a theory where gravity, and thus space-time, are subject to quantum effects. More practically, it has been proposed that quantum causal relations can also be realised in laboratory experiments and that they can provide advantage for several tasks, such as computation and communication complexity.

As this is a very new field, it still needs development of basic tools and exemplary protocols. To name but a few possibilities:

  • how does indefinite causal structure affect the possibility of communicating classical or quantum information?
  • Discrimination of causal structure: Given a set of events and some prior information about their causal relations, what are the optimal protocols for inferring the causal structure?
  • Teleportation of causal structure: is it possible to exploit “entangled causal relations” to effectively teleport an unknown causal structure from a set of events to another?
  • Information measures on indefinite causal structure: what are meaningful ways to quantify information encoded in systems with indefinite causal structure? Is it possible to quantify information about the causal structure itself?

The aim of the project is to develop some of these tools, having in mind potential applications to information-theoretical tasks, quantum technologies, or foundational questions.

Project members

Dr Fabio Costa

Honorary Senior Research Fellow
School of Mathematics and Physics