The closeting of secrets

Fri 3 February 2023

Lady Mitchell Hall

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.

Cost: Free