Schrodinger's Cat. What say you?

[HappySkeptic]

I think the question is does the probability function collapse for different, non-communicating observers at different times?

Imagine it is not the cat but you in the box.   The probability function of your being alive collapses the moment the thing that determines your life and death executes it’s decision.  But if you have no means of communicating the outcome of this collapse to an outside observer, would the outside observer continue to perceive the box as if you were both alive and dead inside?

The box has to be an impossible box for the thought experiment to work.  It cannot leak information about the state of the cat outside the box.

But you are right.  If it was a person in the box, is one human "consciousness" enough to collapse the wavefunction for all observers?  How about cat consciousness?

The reason for the absurd cat thought experiment is that there is nowhere in Quantum Mechanics for collapse to happen.  When two particles interact they form a superposition.  When those two interact with another two, the four are in superposition, and so on, up and including cats.

In any QM experiment, there is a System Under Test (SUT), and there is the external environment.  When the SUT is not entangled with the environment, we can show that the expectation values for measured values are quantum.  When the SUT becomes entangled with the environment, decoherence theory tells us that the expectation values of the SUT then become classical.

However, the SUT can theoretically be any size, including a cat and the equipment to kill it, so if there were such an impossible box that didn't leak quantum information about the state of the cat, Schroedinger's cat should be quantum reality.  However, if true, then the whole of the universe could be an SUT, and in a state of superposition, with no single history, past, or future.  This is the collapse problem.

It is possible that real collapse happens at some level of entropy, or that gravity or some non-linearity in the math causes collapse.  Unfortunately, these may require breaking energy conservation laws (though that might not be as big a problem as it sounds.  Dark energy?)

QM is a shit-show, but one one that is completely verified up to our current ability to do so.  We just still don't understand collapse.