QBism: this changes everything

Originally posted on Wed, 05/22/2013

This month’s Scientific American has an article on Quantum Bayesianism, a re-formulation of quantum mechanics in terms of probability. Apparently physicists hadn’t been using Bayesian statistics in their formulas, and that’s the reason for all the quantum paradoxes. Particle/wave duality? A wave is just a probability of a particle being somewhere; no more, no less. It is so straightforward that my only question is: why hasn’t this been the standard interpretation since the 1930s? This is so much more simple an explanation than the other interpretations.

Here is how Schrödinger’s Cat is viewed in different interpretations of quantum mechanics:

  • Copenhagen: the cat is simultaneously dead and alive, in a quantum superposition which includes both states.
  • Multiple Universes: an infinite number of universes are created, and the cat is dead in half of them.
  • Quantum Bayesianism: the cat is either dead or alive, you just don’t know which.

I think it’s clear which interpretation is both simplest and most intuitive.