The observing self
I’m tickled to read that physicists at Oxford are inventing experiments to explore more closely the nature of the wave function. I am not as convinced as some that different interpretations of quantum mechanics are entirely equivalent. In my view, the large problem with the Copenhagen interpretation is that it relies on leaving the notion of observer undefined and assigning him a role different from other physical systems. No other theory of physics does that. In Newtonian mechanics, in general relativity, in classical electrodymics, the observer of an experiment is subject to the same rules of the theory as anything else. And so, can be anything from a collection of physicists to a stripchart plotter or a patch if photosensitive dye.
That’s not so in the Copenhagen interpretation. A stripchart plotter can be made entangled with other quantum systems, putting it into a superposition of states, cohering like that until a real observer comes along and causes the wave function to collapse. The not-yet-collapsed nature of that superposition is important to subsequent events. That is how quantum computing works — by modifying qubits that are in a superposition of states, not to be collapsed until the answer is read. Physicists, of course, count as observers. A patch of dye or stripchart plotter, not so much. Cats? Well, that is the point of Schrödinger’s gedanken. I wonder if his critique would have seemed sharper had he posited an undergraduate rather than a cat?