(I would stand by my words with respect to physicists-on-the-street, which is the context I usually talk about, but this was a meeting of experts on foundations.) Apologies for that.īut I’m interested in the claim that most self-professed believers in the Copenhagen interpretation take a purely epistemic view of the wave function. Matt– I’ll agree that my offhand phrasing in the video about why Copenhagen got so much support was certainly not the best I could have given a more sympathetic interpretation. If this had been done in the poll then neo-Copenhagen may well have scored more than 50%, although it is difficult to tell as people were obviously allowed to pick more than one answer.

Nevertheless, the interpretations are all so close in spirit that we should arguably lump them all together as saying roughly the same thing. In particular, they usually clear up the mess that Bohr made by insisting that there must always be some system that is treated classically. made by virtue of the fact that they did not envision macroscopic superpositions or applying quantum theory to the whole universe. They only differ from Copenhagen in that they try to state the position more precisely and they correct some errors that Bohr et. Things like the “information theoretic” interpretation and Quantum Bayesianism are really just modern variants of Copenhagen, and as such I personally call them neo-Copenhagen interpretations. you will see no statement indicating that they thought the wavefunction is real and plenty of staements that indicate they thought it was epistemic. However, if you look into the writings of Bohr, Heisenberg, Pauli et.

It arises because Dirac and von Neumann both thought they were outlining the Copenhagen interpretation when they wrote their famous books and that is where most physicists learned quantum theory from in the early days so this error got repeated in many textbooks. This confusion about Copenhagen is common. The wavefunction, both before and after the measurement, is just a description of our knowledge of the state of the cat and is not a property of the cat itself. On the Copenhagen view, there need be no dramatic transition in the physical properties of Schroedinger’s cat when we look in the box. I can dig up the usual quotes from Bohr to back this up, but I am pretty Bohred of doing that, so I’ll wait to see if someone disagrees with me first. In fact, it is pretty clear that it endorses an epistemic attitude towards the wavefunction, much like the “information theoretical” view described in the video. In contrast, the Copenhagen interpretation does not accept the eigenvalue-eigenstate link.

The conflict between collapse and unitary dynamics is therefore a flat out contradiction on the orthodox view, so the measurement problem shows that the interpretation is inconsistent and should be rejected, despite the fact that we are still teaching it to undergrads. Therefore, on the orthodox view, we have to accept that there is some real physical transformation going on in wavefunction collapse, since the real physical properties of the system change.

This implies that the orthodox interpretation is realist about the wavefunction, since every wavefunction is an eigenstate of some set of observables, and specifying that set is mathematically equivalent to specifying the wavefunction. The main difference is that the orthodox interpretation accepts the eigenvalue-eigenstate link, which says that if a system is in an eigenstate of an observable A then A is a property of the system. That sounds more like the orthodox or Dirac/von-Neumann interpretation, which is the thing that we actually teach to undergraduates. The Copenhagen interpretation is not the thing that you described in the video. Why else would they be at a foundations meeting? I find it very hard to believe that the reason that 42% of the participants at a quantum foundations conference prefer the Copenhagen interpretation is because they haven’t really thought about the foundations of quantum mechanics.

Symbols quantum gis