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.

You’ve heard of cryptography. Perhaps quantum cryptography too. Maybe even post-quantum cryptography. But what about *quantum post-quantum cryptography*?! When this came up in conversation with Oxford Computer Scientist Matthew Gray recently, I’d never heard of it. I wanted to know more, so I invited him for a podcast. Turns out, there’s a whole world of layers to unravel linking quantum and cryptography — or even multiple worlds… In this discussion, we dip into those, and how this all relates to “metacomplexity” problems: the hardness of figuring out the hardness of a problem. Listen to this episode if you want to experience your perception of how quantum computing meets cryptography shift from monochrome to technicolour, as we push cryptography to its limits through the lens of fundamental assumptions about computation, quantum physics and reality.

What if time isn’t fundamental — but emerges from quantum mechanics itself? In this episode, Dr Simone Rijavec explains how a timeless quantum universe can still give rise to the illusion of time flowing. We unpack the Wheeler–DeWitt equation, the Page–Wootters model of relational time, and how these ideas connect to the multiverse and quantum gravity. Dr Rijavec is a postdoctoral researcher at Tel Aviv University and former PhD researcher at the University of Oxford.

From the Big Bang puzzles to testing if the early universe was quantum entangled — physicist Dr Aditya Iyer, from the University of Oxford, explains how quantum phenomena are key to understanding cosmology, gravity and even how it's possible we exist at all.

What if we don't need quantum mechanics to express the key properties of quantum information? Join me for a deep-dive into the Constructor Theory of information with Dr Chiara Marletto, Research Fellow at the University of Oxford.   Constructor Theory is a research programme proposed by Prof. David Deutsch in 2012, and further developed by Deutsch and Marletto, and collaborators, since then. The theory aims to unify various strands of physics, and solve open problems — and the key motivation and starting point is a new conception of the laws of physics surrounding information.   In this podcast, we discuss what constructor theory is; how it expresses laws about classical and quantum information; applications to e.g. tests of quantum gravity and quantum field theory; the role of locality and subsystems in the testability of physics; and taking fundamental physics back to the roots of the early days of quantum information theory.

In this episode of the Quantum Foundations Podcast, I'm joined by Professor Vlatko Vedral from the University of Oxford. We discuss modern and historic experimental proposals for testing quantum gravity. Get ready to dive deep into understanding what different proposals would *really* tell us about the nature of quantum gravity, and what problems we're up against to reconcile quantum mechanics and general relativity. All from the modern perspective of quantum information theory.

I interview Dr Andrea Di Biagio, who is a postdoctoral research fellow at IQOQI Vienna. We discuss Andrea's journey through interpretations of quantum theory, including QBism, Relational Quantum Mechanics, Everettian Quantum Theory and Wigner's friend. These topics have been subjects of Andrea's past and active research, including work with Prof. Carlo Rovelli.

I interview Dr Sam Kuypers, who is a postdoctoral research fellow at the Université de Montréal. We discuss the many-worlds interpretation of quantum mechanics, also known as Everettian quantum theory, which has been the subject of Sam's research including work together with Prof. David Deutsch.

I interview Dr Nick Ormrod, who recently completed his DPhil at the University of Oxford and is now a post-doctoral research fellow at the Perimeter Institute in Canada. We discuss the new interpretation of quantum theory that Nick has been working on during his DPhil, with Prof. Jonathan Barrett. The key idea is that reality emerges from causal structures.

Dr. Nicetu Tibau Vidal explains how we can keep both locality and realism within standard quantum mechanics. However, we need to update our understanding of the physical properties of a particle that really exist — with important implications for the nature of reality.