From enigmas in physics to a structural version of idealism

Our first-person perspective is primary, the external world emergent, argues physicist and member of the Austrian Academy of Sciences, Dr. Markus Müller, in his presentation during Essentia Foundation’s 2020 online work conference. A follow-up interview with Dr. Müller, expanding on the topics of his presentation, is also available. [I'm posting the interview in the next post - Sci]

Dr. Müller is Group Leader at the Institute for Quantum Optics and Quantum Information in Vienna, Austria, and a member of the Austrian Academy of Sciences. He is also a Visiting Fellow at the Perimeter Institute for Theoretical Physics, in Waterloo, Canada. Prior to these appointments, Dr. Müller has been an Assistant Professor and Canada Research Chair in the Foundations of Physics at the University of Western Ontario in London, Canada. He received his doctorate from the Berlin University of Technology in 2007, with a thesis titled Quantum Kolmogorov Complexity and the Quantum Turing Machine, under the supervision of Prof. Ruedi Seiler. Dr. Müller has over 50 technical publications to his name, and is a member of Essentia Foundation‘s Academic Advisory Board.

An interview with physicist Dr. Markus Müller

An obvious way out—for which I argue—is to give up the container view altogether, at least fundamentally. For some reason, this seems to be psychologically difficult. Hence, if the quantum puzzles were the only ones we encounter in physics or philosophy, then one might well choose to be a Bohmian or an Everettian and enjoy the resulting psychological comfort. But as I argue in my work, there are many more challenges to this container view than just quantum mechanics; for example, the puzzles and thought experiments that I have mentioned in my talk, which arguably render the container view methodologically inadequate. I believe that there is something important about our world and our place in it that we have so far failed to grasp.

Given the puzzles of quantum mechanics, the many-worlds view that you have mentioned in your question aims at telling a coherent story about the quantum world in terms of this container or stage play view. Does this Everettian interpretation succeed in doing so? Yes, absolutely! But the problem is that you can make every worldview consistent with modern physics if you stretch it far enough. Do you dislike the idea of many worlds and would like to hold on to a single-world classical picture? Then pick Bohmian mechanics! Do you prefer to abandon any notion of randomness altogether? Then pick ‘t Hooft’s superdeterministic cellular-automaton interpretation! Pick whatever you like—the experimental predictions will be identical, and nobody can prove you wrong.

Given this situation, I think that the only reliable way to understand what we can really learn from QM—what it tells us about the world—is to disregard interpretations and look at actual scientific practice. There, we find that quantum states are nothing but our calculational tool to determine probabilities of measurement outcomes—and all we ever see are these outcomes. And it turns out that these probabilities have surprising properties. For example, they violate Bell’s inequalities. The simplest logical conclusion to me is to see this as a hint that the world is, first, fundamentally probabilistic in some sense, and second, that we cannot consistently regard the outcomes of our measurements as predetermined in any way that would deserve this name.

Law without law: from observer states to physics via algorithmic information theory

Markus P. Mueller

According to our current conception of physics, any valid physical theory is supposed to describe the objective evolution of a unique external world. However, this condition is challenged by quantum theory, which suggests that physical systems should not always be understood as having objective properties which are simply revealed by measurement. Furthermore, as argued below, several other conceptual puzzles in the foundations of physics and related fields point to limitations of our current perspective and motivate the exploration of an alternative: to start with the first-person (the observer) rather than the third-person perspective (the world). In this work, I propose a rigorous approach of this kind on the basis of algorithmic information theory. It is based on a single postulate: that universal induction determines the chances of what any observer sees next. That is, instead of a world or physical laws, it is the local state of the observer alone that determines those probabilities. Surprisingly, despite its solipsistic foundation, I show that the resulting theory recovers many features of our established physical worldview: it predicts that it appears to observers as if there was an external world that evolves according to simple, computable, probabilistic laws. In contrast to the standard view, objective reality is not assumed on this approach but rather provably emerges as an asymptotic statistical phenomenon. The resulting theory dissolves puzzles like cosmology's Boltzmann brain problem, makes concrete predictions for thought experiments like the computer simulation of agents, and suggests novel phenomena such as "probabilistic zombies" governed by observer-dependent probabilistic chances. It also suggests that some basic phenomena of quantum theory (Bell inequality violation and no-signalling) might be understood as consequences of this framework.