Thoughts on Schrödinger's cat.

[Shilla]

I am quite confused... A cat cannot be alive and dead at the same time, essentially what Schrödinger was trying to prove.. A state can collapse without a conscious observer. How did so many people misinterpret his thought experiment? Or am I missing something here? 

[Bufofrog]

It is an analogy.  Cats are not really alive and dead at the same time.  

[Eise]

AFAIK Schrödinger only used his cat for demonstrating the absurdity of quantum physics. 'Absurd' in the meaning, 'we cannot grasp it with our daily notions'.

Today most physicists assume that any interaction with the superposition of 'the radioactive atom has decayed' and 'the radioactive atom has not decayed', is like a measurement. So consciousness is not needed.

[Shilla]

1 minute ago, Bufofrog said:

It is an analogy.  Cats are not really alive and dead at the same time.  

But really, didn't people on quantum physics say that quantum particles can reach a collapsed state from their superposition when a conscious observer observes... He was trying to prove them wrong with his thought experiment... That it cannot apply in the real world.. So as opposed to the theory of the cat being both dead and alive until the box is opened, he's saying that it has already reached a collapsed state without the observer having to open the box. People are thinking his thought experiment proves otherwise.. It's not just an analogy...

[Eise]

12 minutes ago, Shilla said:

A cat cannot be alive and dead at the same time

But I do hope you can accept that quantum particles can be in two states at the same time, because that is fundamental to quantum physics

[Strange]

15 minutes ago, Shilla said:

I am quite confused... A cat cannot be alive and dead at the same time, essentially what Schrödinger was trying to prove.. A state can collapse without a conscious observer. How did so many people misinterpret his thought experiment? Or am I missing something here? 

Schroedinger was trying to point out how strange and unintuitive quantum theory is. He was not trying to prove a cat can be alive and dead at the same time.

3 minutes ago, Shilla said:

But really, didn't people on quantum physics say that quantum particles can reach a collapsed state from their superposition when a conscious observer observes...

It doesn't require a conscious observer. An "observer" just means that the particle (or system) interacts with the environment.

[Bufofrog]

Just now, Eise said:

But I do hope you can accept that quantum particles can be in two states at the same time, because that is fundamental to quantum physics

Of course.  Just pointing out the obvious; cats aren't quantum parrticles.

[Shilla]

1 minute ago, Strange said:

Schroedinger was trying to point out how strange and unintuitive quantum theory is. He was not trying to prove a cat can be alive and dead at the same time.

Yeah I get that.. That's what I said... A cat cannot be alive and dead at the same time: In other words, Schrödinger was trying to prove that a cat cannot be alive and dead at the same time.. 

3 minutes ago, Eise said:

But I do hope you can accept that quantum particles can be in two states at the same time, because that is fundamental to quantum physics

Yep.. I know that, a state of superposition..

[Eise]

2 minutes ago, Shilla said:

Schrödinger was trying to prove that a cat cannot be alive and dead at the same time.. 

I don't think Schrödinger was very interested in cats. He wanted to show to what absurdities the Copenhagen interpretation leads, if you assume that it is consciousness that collapses the wave function. But be aware that quantum experimenters get bigger and bigger objects in superposition. Just not in a simple "Schrödinger's cat way".

[studiot]

14 minutes ago, Shilla said:

But really, didn't people on quantum physics say that quantum particles can reach a collapsed state from their superposition when a conscious observer observes... He was trying to prove them wrong with his thought experiment... That it cannot apply in the real world.. So as opposed to the theory of the cat being both dead and alive until the box is opened, he's saying that it has already reached a collapsed state without the observer having to open the box. People are thinking his thought experiment proves otherwise.. It's not just an analogy...

I guarantee that if the box is not opened for 200 years after the cat is placed in it, said cat will be very dead.

Interpretation.

Time of cat being definitely dead and motionless + 200 years (very exact)

Time of decease uncertainly with very inexact uncertainty of 200 years.

Exactly as predicted by both QM and Classical M.

Edited July 29, 2020 by studiot

[Shilla]

10 minutes ago, Eise said:

But be aware that quantum experimenters get bigger and bigger objects in superposition. Just not in a simple "Schrödinger's cat way".

Oh, mind telling me what they got into a state of superposition bigger than a quantum particle? This is interesting..

[Strange]

1 minute ago, Shilla said:

Oh, mind telling me what they got into a state of superposition bigger than a quantum particle? This is interesting..

First google result: https://www.nature.com/articles/news.2010.130

[swansont]

 

Quote

I don't think Schrödinger was very interested in cats. 

It was his wife's cat

 

 

[Strange]

2 minutes ago, swansont said:

It was his wife's cat

Another example of the Law of Eponymy: https://en.wikipedia.org/wiki/Stigler's_law_of_eponymy

[swansont]

32 minutes ago, Strange said:

Another example of the Law of Eponymy: https://en.wikipedia.org/wiki/Stigler's_law_of_eponymy

Which didn't originate with Stigler, of course

[Eise]

37 minutes ago, Shilla said:

Oh, mind telling me what they got into a state of superposition bigger than a quantum particle? This is interesting..

Buckyballs. (C₆₀, i.e. a kind of soccer ball with 60 C atoms). And even more:

Quote

• Researchers test the quantum superposition principle at a massive scale like never before.
• They illustrated the delocalization of the massive molecules containing 40,000 neutrons, electrons, and protons. 
• Up to 2,000 atoms remained in two places at once for 7 milliseconds – a new record of quantum superposition. 

But the experiments are difficult, because even the tiniest disturbance would destroy the superposition.

[Markus Hanke]

3 hours ago, Eise said:

I don't think Schrödinger was very interested in cats.

Schrödinger hated cats  He was very much a dog person, which is why he came up with such a cruel thought experiment...
Besides - my own cat definitely exists on both sides of the door simultaneously, as it is impossible to keep her out of the kitchen.

3 hours ago, Shilla said:

A cat cannot be alive and dead at the same time

Indeed. And that’s the crucial point - the cat should be in a state of superposition, but when we look at it, it never is. And this is true for any observation we make, be it on a quantum system, or on something macroscopic - we never observe any superpositions, only definite outcomes. So how does the system prior to observation, which demonstrably is in a state of superposition, get to take on precisely one definite state when we look at it? This is essentially what is called the ‘measurement problem’.

[Sensei]

4 hours ago, Strange said:

Schroedinger was trying to point out how strange and unintuitive quantum theory is.

IMHO Schroedinger was trying to point out that quantum theory is probabilistic. There is nothing unintuitive and strange in randomness. Lack of randomness would mean absolute determinism i.e. events would always go one way at precisely defined moments. That would be damn boring Universe. Like playing chess always one fixed way.

 

[Strange]

1 hour ago, Sensei said:

IMHO Schroedinger was trying to point out that quantum theory is probabilistic.

Nope. It is very obviously about superposition.

[Sensei]

1 hour ago, Strange said:

Nope. It is very obviously about superposition.

In an experiment with a cat, a radioactive atom is used that decays at a random moment.

[Strange]

36 minutes ago, Sensei said:

In an experiment with a cat, a radioactive atom is used that decays at a random moment.

But that is not the important part. 

[lagrangian]

Isn't systems collapsing by themselves a big problem in quantum computing? It doesn't depend only on an observer right? It collapses by itself all the time.

Awesome that they were able to maintain superposition of a 2000 atom system for 7 ms.

[Strange]

10 minutes ago, lagrangian said:

Isn't systems collapsing by themselves a big problem in quantum computing? It doesn't depend only on an observer right? It collapses by itself all the time.

Good point. 

[swansont]

14 minutes ago, lagrangian said:

Isn't systems collapsing by themselves a big problem in quantum computing? It doesn't depend only on an observer right? It collapses by itself all the time.

Awesome that they were able to maintain superposition of a 2000 atom system for 7 ms.

That is in support Schrödinger’s point, but OTOH the demarcation line of systems behaving in a QM fashion moves toward larger systems as people gain expertise and the equipment gets better.

[Don410]

Wouldn’t the cat be an observer that collapses the system? At least if it’s awake? 

Edited August 11, 2020 by Don410