Quantum Foundations Podcast

What if quantum particles have no gravity? In this episode of the Quantum Foundations Podcast, Professor Gerard Milburn explains how this radical idea could solve open problems in quantum theory and lead towards a theory of quantum gravity. It comes with extreme consequences for quantum measurements; the formation of black holes; and even the beginning of the universe. From a new understanding of Bell experiments to a cosmological arrow of time, find out if dropping gravity from the equation could be the start of transforming the field of quantum science and technology.

If there really is a quantum reality for every possible outcome of a measurement, then where do measurement probabilities come from? Dr Tony Short at the University of Bristol has used a set of intuitive assumptions to derive probability in a quantum multiverse. In this episode we discuss his motivations for exploring the many-worlds interpretation; what his assumptions are and how they lead to the Born rule for measurement probabilities; and how these ideas fit within the broader landscape of research in quantum foundations, probability and the many-worlds interpretation.

The notion of true quantum nonlocality is absurd. Prof Tim Palmer from the University of Oxford suggests that there is a hidden assumption in standard quantum mechanics, and dropping it will save us from this absurdity. Namely, the reality of counterfactuals: the physics of what could have happened but did not. Inspired by chaos theory and the fractal structure widespread in atmospheric physics, Palmer has developed a new underlying structure for quantum theory, with radical implications for our fundamental principles of quantum physics; the limits of quantum computation; and perhaps even the search for quantum gravity.

What if you could put an observer in superposition on a quantum computer? Dr Will Zeng suggests that this experiment could stretch standard quantum theory so far that it might break — and radically update our understanding of physical reality. However, today's proof-of-principle experiments on quantum computers use single qubits to model observers. Zeng explains how a new programme of research aims to quantify "observer-ness" and conduct experiments with increasingly realistic observers, pushing quantum computers to the limits until they can run actual quantum Artificial General Intelligence experiments.

Our most far-reaching principles of physics are not about what changes, but what stays the same: conservation laws. In this episode of the Quantum Foundations Podcast, Dr Chiara Marletto from the University of Oxford explains how such principles enable discovery of new physical phenomena; their central role in thermodynamics; controversies about how they hold up in quantum mechanics; and how they can be used to formulate results about future theories of physics beyond quantum.