Comment by codethief
5 hours ago
> Actually this is true whichever interpretation you take
In the Copenhagen interpretation the collapse of the wave function explicitly violates unitarity (and thus reversibility).
5 hours ago
> Actually this is true whichever interpretation you take
In the Copenhagen interpretation the collapse of the wave function explicitly violates unitarity (and thus reversibility).
(This is way beyond my area of expertise so excuse me that this might be a stupid idea.)
I assume the following happens: while a (small) subsystem is in "pure state" (in quantum coherence), no information flows out of this subsystem. Then, when measuring, information flows out and other information flows in, which disturbs the pure state. This collapses of the wave function (quantum decoherence). For all practical purposes, it looks like quantum decoherence is irreversible, but technically this could still be reversible; it's just that the subsystem (that is in coherence) got much, much larger. Sure, for all practical purposes it's then irreversible, but for us most of physics anyway looks irreversible (eg. black holes).
Yes, I think that's a stance many physicists take these days. Unfortunately, it's not verifiable. And we also don't have any clue how gravity (which does become relevant at our scales) would fit into this picture.
The problem is that the larger subsystem includes an observer in a superposition of states of observing different measured values. And we never observe this. Copenhagen interpretation doesn't deal with this at all. It just states this empirical fact.
So if I understand correctly, you are saying the observer doesn't feel like he is in a superposition (multiple states at once). Sure: I agree that observers never experience being in a superposition.
But don't think that necessarily means we are in a Many-Worlds. I rather think that we don't have enough knowledge in this area. Assuming we live in a simulation, an alternative explanation would be, that unlikely branches are not further simulated to save energy. And in this case, superposition is just branch prediction :-)