The definition and properties of information may seem to be fundamental features of the world that are independent of how particles, fields and space-time behave. In fact, though, information is fundamentally physical and twentieth century physics has radically changed our understanding of its nature and properties. Einstein’s relativity theories tell us that information cannot travel faster than the speed of light in vacuum. Quantum theory tells us that the information carried by microscopic systems is qualitatively different from the familiar ``classical’’ information with which we presently communicate and compute: for example, quantum information cannot be copied. These realisations have led to new applications and emerging new technologies, including relativistic quantum cryptography and new forms of quantum communication and computation in space-time. This lecture will illustrate several ways in which physics-based cryptography and communication allow otherwise unachievable forms of security and flexibility, including guaranteeing a fair coin toss for mistrustful parties, making and later revealing secret predictions that carry a guaranteed time stamp, and secure forms of money that emulate quantum particles by following multiple paths and recombining to solve otherwise insoluble trading problems. We will also ask how confident we should be that we now fully understand how information is carried and processed in nature, and whether new physics discoveries might yet change our understanding and lead to further technological advances.

Adrian Kent is Professor of Quantum Physics at the Department of Applied Mathematics and Theoretical Physics, University of Cambridge, a Fellow of Wolfson College and Director of Studies in Mathematics at Darwin College. He is also a Distinguished Visiting Research Chair at Perimeter Institute for Theoretical Physics, Fellow of the UK Institute of Physics, Founder Member of the Foundational Questions Institute and Charter Honorary Fellow of the John Bell Institute for the Foundations of Physics. Adrian’s research interests include the nature of physical reality, fundamental tests of quantum theory and its relationship to gravity, the properties of quantum information in space-time, and applications of fundamental physics to new forms of quantum and relativistic cryptography, communication and computation.