Schrödinger's cat question

[leonid.ge]

TL;DR

In Schrödinger's cat thought experiment, am I right to say that the cat and the the atom are not truly entangled at the start?

So if the the room is large and the cat starts walking away from the atom, the probability of the decayed atom influencing the cat decreases...

When entangled particles are created, say a pair of electrons with opposite spins, they are truly entangled even when taken far apart.
So would it not be better for this thought experiment to use two cats which hug each other in outer space. At some stage the cats get angry and push each other apart and fly away from each other. So if we let them fly for a long time and suppose the vacuum is perfect and they don't emit or receive any radiation, both cats are still entangled, and measuring their spins when they are 10 light years away will produce correlating results.

 

[PeroK]

TL;DR Summary: In Schrödinger's cat thought experiment, am I right to say that the cat and the the atom are not truly entangled at the start?

So if the the room is large and the cat starts walking away from the atom, the probability of the decayed atom influencing the cat decreases...

When entangled particles are created, say a pair of electrons with opposite spins, they are truly entangled even when taken far apart.
So would it not be better for this thought experiment to use two cats which hug each other in outer space. At some stage the cats get angry and push each other apart and fly away from each other. So if we let them fly for a long time and suppose the vacuum is perfect and they don't emit or receive any radiation, both cats are still entangled, and measuring their spins when they are 10 light years away will produce correlating results.

I think you've missed the point of the thought experiment.

 

[leonid.ge]

Thanks!

 

[Nugatory]

So would it not be better for this thought experiment to use two cats….

The point of the thought experiment was to show that something was wrong with the then current (mid 1920s) understanding of QM - the math seemed to lead to the clearly incorrect result that we would end up with a cat that was neither dead nor alive.

You may be confusing this issue with the altogether-unrelated question of spin-entangled particles.

 

[weirdoguy]

The point of the thought experiment

Which is also missed by most of popularisations, and unfortunately a lot of physicists.

 

[bhobba]

Which is also missed by most of popularisations, and unfortunately a lot of physicists.

Indeed.

We now know the real issue is how the classical world of everyday experience emerges. Once the chain in the thought experiment is commonsense classical, there is no issue, and that occurs prior to the detector. After that, there is no mystery.

To be fair, it is a good thought experiment introducing entanglement for those learning QM.

The modern understanding of how the ordinary world emerges has advanced a lot since the 1920s:
https://www.sciencenews.org/blog/context/gell-mann-hartle-spin-quantum-narrative-about-reality

Thanks
Bill

 

[pines-demon]

There is a big gap on why the Schrödinger cat is interesting vs what is intended by popular physics.

How each community uses the Schrödinger cat:

• Schrödinger (original): to show that quantum mechanics is absurd
• Popular physics: to introduce superposition (this is possibly one of the worse thought experiments for that)
• Actual physicists: to discuss decoherence (this requires understanding at least undergrad physics).

The popular physics route is very bad because Schrödinger's cat taken in its most simplified form is not different than a coin flip in terms of outcomes. With this experiment alone, you cannot use it to explain why it is different than uncertainty of a coin flip because the only basis in which you can measure is the live/dead basis.