Now a new paper on Von Neumann's book, the Compton-Simon experiment and the collapse hypothesis blames him for collapse of the wave function.
Few things in physics have caused so much hand-wringing as von Neumann's collapse hypothesis. Unable to derive it mathematically, von Neumann attributed it to interaction with the observer's brain! Few physicists agreed, but tweaks of von Neumann's measurement theory did not lead to collapse, and Shimony and Brown proved theorems establishing `the insolubility of the quantum measurement problem'. Many different `interpretations' of quantum mechanics were put forward, none gained a consensus, and some scholars suggested that the foundations of quantum mechanics were flawed to begin with. Yet, in the last ninety years, no-one looked into now von Neumann had arrived at his collapse hypothesis!I don't know about this experiment, but collapse of the wave function is observed. Not directly, as the wave function is not directly observed, but measurements do put systems into eigenstates that determine future measurements.
Von Neumann based his argument on the experiment of Compton and Simon. But, by comparing readings from von Neumann's book and the Compton-Simon paper, we find that the experiment provides no evidence for the collapse hypothesis; von Neumann had misread it completely!
This is textbook quantum mechanics.
Believers of many-worlds theory do not want to accept it, as they believe that the wave function splits into a collapsed version that we see, and other pieces in parallel universes that cannot be seen. So they are always complaining about the collapse, as they think it is unfairly discriminating against other universes.
Regardless, we see the collapse in our universe, and we are all indebted to von Neumann for figuring this out.
The paper has some amusing anecdotes about his memory, and this:
When von Neumann’s seminal book appeared in English, Wigner told Abner Shimony: “I have learned much about quantum the- ory from Johnny, but the material in his Chapter Six Johnny learnt all from me”.So maybe the credit/blame for collapse should go to Eugene Wigner? He supposedly once said that a dog's consciousness could collapse a wave function.