Why The Quantum State Only Exists In Our Mind

Dr. David Schmid, Dr. Lídia Del Rio and Hans Busstra explore a metaphysical shift that’s happening in the foundations of physics: the wave function is no longer regarded as something real, but just as a description of what we know about the world. In philosophical terms: the wave function is not ontic, but epistemic. And in more popular terms: the multiverse is science fiction, resting on a too-literal interpretation of a piece of mathematics called the Schrödinger equation. Our previous video with Dr. Del Rio on the Frauchiger-Renner thought experiment: https://www.youtube.com/watch?v=v7kxWT_zI60 Three other 'epistemicists', who’ve just been awarded a prestigious prize in the foundations of physics: https://www.youtube.com/watch?v=NnAj66Z1kNQ Chapters marks 00:00:00 Introduction 00:03:30 — When did it dawn on you that QM is weird? 00:05:54 — The quantum phenomena that still scare David 00:07:53 — How to account for non-locality 00:12:19 — "What are the symbols representing?" 00:15:34 — What is the wavefunction really? 00:17:00 — "The standard view we are taught in the classroom..." 00:19:23 — Classically explaining quantum 00:20:23 — On Wheeler's delayed choice experiment 00:28:38 — How to interpret the delayed choice experiment 00:32:56 — How can a single particle 'know' what's going on at both paths? 00:36:41 — Quantum phenomena that remain weird: contextuality 00:44:38 — What are the viable ontological explanations we have? 00:48:26 — Is there evidence for an epistemic interpretation? 00:52:56 — Understanding epistemic interpretations 00:57:28 — Are we in a new era of physics? 01:00:43 — Lídia on what constitutes measurement 01:04:36 — How relevant are these recent theoretical findings? 01:07:36 — Experiments with AI as an observer? 01:08:36 — David and Lídia on what consciousness is 01:13:51 — Closing thoughts Links to relevant scientific work of Schmid and Del Rio: Why interference phenomena do not capture the essence of quantum theory L Catani, M Leifer, D Schmid, RW Spekkens Quantum 7, 1119 A review and analysis of six extended Wigner's friend arguments D Schmid, Y Yīng, M Leifer arXiv preprint arXiv:2308.16220 Guiding our interpretation of quantum theory by principles of causation and inference D Schmid, Thesis, University of Waterloo https://uwspace.uwaterloo.ca/items/7aed8173-684a-40af-bff5-e625f29fe810 Thought experiments in a quantum computer, Nuriya Nurgalieva, Simon Mathis, Lídia del Rio, Renato Renner: https://arxiv.org/abs/2209.06236 All music licensed under Storyblocks and Soundstripe Stock footage licensed under Storyblocks Images from 'Oppenheimer' under fair use policy. Interview content copyright by Essentia Foundation, 2025 www.essentiafoundation.org