Relational Quantum Mechanics

Schrödinger's cat

A bit less nervous?

Richard Feynman wrote: “We have always had a great deal of difficulty understanding the world view that quantum mechanics represents. At least I do, because I’m an old enough man that I haven’t got to the point that this stuff is obvious to me. Okay, I still get nervous with it ... You know how it always is, every new idea, it takes a generation or two until it becomes obvious that there’s no real problem. I cannot define the real problem, therefore I suspect there’s no real problem, but I’m not sure there’s no real problem” (Simulating Physics with Computers, 1981).

I'm studying the article "Relational Quantum Mechanics" by Carlo Rovelli (search the internet for: arXiv: quant-ph/9609002). Carlo Rovelli is an Italian theoretical physicist and writer that works in the field of Quantum Gravity, where he is among the founders of the Loop Quantum Gravity theory.

In this article Rovelli provides an interpretation of Quantum Mechanics that I didn't know and it just seems to make sense! This is the first time I see a chance to understand what nature is telling us with the laws of Quantum Mechanics. Rovelli's critics of the physical meaning of the mysterious wave function is in my opinion illuminating. His work is based on the analysis of the famous problem of Wigner's friend (the third person problem) and on the concept of Everett's relative status. The interpretation of the theory makes use of the concept of Shannon information.

The consequences of the relational interpretation is that properties of quantum systems have no absolute meaning but they must be always characterized with respect to other physical systems. It turns out that Relational QM is compatible with realism in the sense that there is a world outside our mind, which exists independently from us, but is incompatible with realism in a stronger sense that it is possible (at last in principle) to list all the features of the world as we can do in classical mechanics.

Work in progress. I’m studying again (starting from The Theoretical Minimum) Quantum Mechanics(*), but I'm a bit less nervous now.

(*) https://theoreticalminimum.com/courses/quantum-mechanics/2012/winter