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.