Schroedinger's cat is always dead

In the Copenhagen interpretation, the wavefunction is not a physical entity. It has the same sort of ontological status as a probability distribution. It is not itself a probability distribution, but it is the mathematical object from which probability distributions are derived. And it also has this in common with probability distributions, that when new information about the world is obtained, you have to update it.

It sounds like you're saying the wavefunction represents our uncertainty. My impression is that you know more about grand theories of physics than I do; but I'm confident that the wavefunction does not represent mere uncertainty. Entanglement, the double-slit experiment, the uncertainty principle, etc., can't be explained by uncertainty.

At least, not in the sense that everyone is assuming, according to which the wavefunction is a real thing.

"Everyone" is assuming no such thing.

Look: I did NOT CLAIM THAT CONSCIOUSNESS COLLAPSES THE WAVEFUNCTION. Just READ the post. I am not going to explain it again. It is VERY CLEAR that it is presenting TWO alternatives, ONE of which is that consciousness collapses the waveform.

Almost everyone simply chooses one of the two alternatives, and says, "That's impossible!".

Please stop doing that. In general. This is the nature of the post: You have only 2 obvious alternatives, and BOTH of them are impossible.

I am NOT proposing a solution. I am NOT saying that the cat is always dead. I am pointing out that there is no currently viable solution.

If you can't resolve the situation BY PICKING ONE OF THE TWO ALTERNATIVES - NOT by dismissing one and ignoring the other - you should change your downvote to an upvote.

Note:Mitchell Porter is very smart, and did not actually say that I said that consciousness collapses the waveform.

Typo.

I'm going to add my comment reply (below) to the post, in response to your question.

My guess is that the Copenhagen interpretation isn't supposed to talk about what your beliefs are; it's just supposed to talk about entanglement of waveforms. So Schroedinger's beliefs about whether the cat is alive or dead don't matter.

But I've heard people talk about such situation as if Schroedinger's belief that the cat was alive or dead was important. Especially in connection with the idea that a waveform only truly collapses when an observation is made by a conscious agent.

If you don't say that only conscious agents can collapse waveforms, then you have to agree that something in the box collapses the waveform as seen from inside the box, while it's still uncollapsed to Schroedinger. And Schroedinger's opening the box collapses that waveform for him; but it is still uncollapsed for someone outside the room.

But if you do say that only conscious agents can collapse waveforms, then it's something about their mental processes that does the collapsing. This could mean their beliefs matter. And then, the cat is always dead.

The whole business seems murky and mysterious to me, and I hope for some enlightenment. And if it is not enlightening, it can at least be entertaining.

If interacting with another subatomic particle were sufficient to collapse a waveform, then you couldn't prepare two particles in an entangled state. But entangled particles are regularly prepared in the lab, so your conjecture seems to have been refuted.

I think the best bet for a collapse interpretation of quantum mechanics is some form of spontaneous collapse theory, like GRW.

Right - but that's part of the point of the post. You read the post, and then reasoned your way from its beginning, to its halfway point.

The post is not claiming that the cat is always dead.

Actually, this would be like the case where you shine a light in the two-slit experiment to see which slit the electron passes through, but the light is dim enough that it won't interact with the electron every time. You get the sum of an interference pattern and a classical double Gaussian in that case.

In the experiment you suggest, the experimenter's wavefunction would be the sum of one where the cat is dead and the experimenter observes a 1, and one in which the experimenter observes a 0 and the cat remains in dead-alive superposition from the observer's perspective. (That is, the weighted sum of a factorizable wavefunction with a non-factorizable one.)

But then on observing a 0 the cat would still be in a superposition of states.

Exactly.

I'm pretty sure it's meant to be literal. Also, that it's not proven.

Schrödinger's cat is a thought experiment. The cat is supposed to be real in the experiment. The experiment is supposed to be seen as silly.

People can reason through the math at the level of particles and logically there should be no reason why the same quantum logic wouldn't apply to larger systems. So if a bunch of particles can be entangled and if on observation (unrelated to consciousness) the wavefunction collapses (and thereby fully determines reality) then the same should be able to happen with a particle and a more complex system, such as a real live cat. After all, what is a cat except for a bunch of particles? This means the cat is literally both alive and dead until the superposition resolves.

The problem is that philosophers have sometimes abused this apparent paradox (both alive and dead!?) as some sort of Deep Mystery of quantum physics. It's not a deep mystery at all. It's just something that illustrates that if you take the Copenhagen interpretation literally then you have to bite the bullet and admit that a cat (or a human, etc) can be both alive and dead at the same time. Not just seemingly so, but actually so in reality. As that's the only thing that's consistent with the small scale quantum experiments. Schrödinger came up with this thought experiment because he realized the implications of the Copenhagen interpretation and concluded the implications were absurd.

If you're not willing to bite that bullet (and most quantum physicists nowadays aren't) then you have to look at other possibilities. For instance that the world splits and that in one world the cat is alive and in the other the cat is dead. In one world you'll observe the cat being alive and in the other world you observe the cat as dead. Both worlds are equally real and in both worlds you have the sensation of being in the only real world.

(I only have an elementary understanding of QM)

Once, the Copenhagen really was an interpretation. As physicists shied away from the mysticism of the founders, they refused to admit their deviation and redefined the Copenhagen interpretation to be what you say.

The idea of the non-collapsed waveform is that there are two systems that haven't interacted; and each is indeterminate to the other until they interact.

But you can have any number of nested systems, each of which may or may not have interacted with the system it is contained in. If the cat in the box can be in an indeterminate state to Schroedinger, then Schroedinger and the cat can be in an indeterminate state to someone out in the hallway. Whether Schroedinger has opened the box or not.

The Copenhagen interpretation doesn't admit of the possibility that every waveform is either collapsed or not collapsed. If that were the case, every atom's waveform would always collapse as soon as it interacted with another atom!

It can only be collapsed with respect to some observer. UNLESS you make the stipulation that only very special observers, like conscious agents, can collapse a waveform.

See comment above to Mitchell. Read the post. It is NOT claiming what you think it is claiming.

I don't understand how all you people can read the post and think that it's claiming that the cat is always dead. The title is a lead-in. You don't read the title and then stop thinking.