Schrödinger cat problem

[Ricardo]

I'd like someone with quantum physics knowledge, which I don't have, to give me an answer, that surely exists, to this question:

If we introduce a recording video camera in the box, with the cat and the randomly activated killing device, after opening it later (and founding either a live or dead cat), would we see in the video recording a cat in an "entangled" alive-dead state?

I think we wouldn,t, we would see either a cat alive all the time or his killing, and the explanation I expect would be that the video camera is a measurement device and the observation "collapsed" the wavelengths...

But...how a delayed observation could collapse the wavelengths at a previous time?

The camera inside the box is an inanimated collection of atoms like the walls of the box and the random killing artifact..it is not an observer...the wavelengths can not "know" that an observer will use it later.

I have the feeling, in my ignorance (I have not advanced physics education) that wiyh macroscopic objects that kind of phenomena do not happen, as we can not produce a difraction pattern in the two slits experiment using big particles, as tennis balls, for example.

 

[Endy0816]

An Observer doesn't need to be a person.

https://en.m.wikipedia.org/wiki/Observer_(quantum_physics).

Real roughly can think of it as by illuminating the cat to record it, our 'cat' wavefunction collapses into a definite state.

[Ricardo]

12 hours ago, Endy0816 said:

An Observer doesn't need to be a person.

https://en.m.wikipedia.org/wiki/Observer_(quantum_physics).

Real roughly can think of it as by illuminating the cat to record it, our 'cat' wavefunction collapses into a definite state.

OK...but just the presence of light is an observation?

In the experiments that show wave behavior of particles, there is light, or, even if they are performed in the dark, there is radiation of the non visible spectrum present, which also could be used for  observation.

Again, I am not a physicist, and of course the idea that I could have found a "flaw" in Quantum Theory, not noticed before by so many geniuses, is absurd.

I just want to know  the experts explanation, which I presume would be a trivial one for them.

Someone wrote in other thread of this fórum that the cat problem was a ironic way to show the absurdeness of QM...I do not think Schrödinger would want that...but perhaps it was a way to ilustrate with a macroscopic image the phenomena of entangled states at microscopic, atomic or subatomic level, where they really take place.

Do the Quantum physicist believe that the entanglement states for complex macroscopic objects like a cat really occur?

Thanks for your answer!

 

[Endy0816]

Typically isolated from everything. I don't think explaining QM is trivial for anyone

Loads of math and really precise definitions. We can at least all take a shot at understanding the last part.

 

They did manage to entangle the state of a couple of diamonds. Not isolated but also incredibly brief.

https://www.scientificamerican.com/article/room-temperature-entanglement/

Article gives a good overview on the issues with traditional entanglement too.

Edited April 2, 2018 by Endy0816

[Bender]

There are several options for your question, depending on the interpretation. I'll give the two most popular ones:

1) manyworld  interpretation: you are entangled with the cat and the camera. When you watch the recording, one version of you sees a living cat, while another version of you sees a dead cat.

2) Copenhagen interpretation: macroscopic objects are never in superposition and Schrodingers cat is a false thought experiment. It remains unclear what exactly constitutes a "macroscopic object", which leads us to the measurement problem.   

On 2/4/2018 at 3:57 AM, Endy0816 said:

They did manage to entangle the state of a couple of diamonds. Not isolated but also incredibly brief.

https://www.scientificamerican.com/article/room-temperature-entanglement/

Article gives a good overview on the issues with traditional entanglement

Interesting. I wonder whether this result does not invalidate the Copenhagen interpretation.

[Carrock]

1 hour ago, Bender said:

2) Copenhagen interpretation: macroscopic objects are never in superposition and Schrodingers cat is a false thought experiment. It remains unclear what exactly constitutes a "macroscopic object", which leads us to the measurement problem.   

There doesn't seem to be any generally accepted definition of the Copenhagen interpretation. This is as good as any. (From https://en.wikipedia.org/wiki/Heisenberg_cut )

Quote

This function, according to quantum theory, consists of a differential equation which determines any future state from the present state of the function... The dividing line between the system to be observed and the measuring apparatus is immediately defined by the nature of the problem but it obviously signifies no discontinuity of the physical process. For this reason there must, within limits, exist complete freedom in choosing the position of the dividing line."^[7]

In other words you could have an atom as the observed system and the rest of the universe as the measurement apparatus.

Or you could have the solar system as the observed system and the rest of the universe as the measurement apparatus. (Voyager 2 would do as an observer.)

 

This seems to me rubbish but it's the best version of the Copenhagen interpretation I'm aware of. Can anyone clearly describe a better one?

[Strange]

On 01/04/2018 at 5:18 PM, Ricardo said:

OK...but just the presence of light is an observation?

Pretty much any interaction with the environment will count as an observation and destroy the superposition (which is one of the things that makes quantum computing so hard).

On 01/04/2018 at 5:18 PM, Ricardo said:

Do the Quantum physicist believe that the entanglement states for complex macroscopic objects like a cat really occur?

Not really, no. The thought experiment was proposed to show how silly the idea is. But has since been used in almost the exact opposite sense.

[studiot]

The point to remember is that the Uncertainty Principle refers to any determination of the values concerned.

This includes, but is not limited to, direct measurement, deduction from other data, calculation of the physical variables involved.

Possibly the simplest way to understand this is to follow the reasoning behing the broadening of a spectral emission line.

Such reasoning is used all the time in Spectroscopy.