Disagreement with Schrodinger's Cat

[PatrickO]

Schrodinger's Cat, according to The Complete Idiots Guide to Theories of The Universe, Is essentially an experiment which states that a cat that is in a box with a vial of poison, is both dead and alive, because we don't know whether or not it IS living unless we look into the box. In this scenario we wouldn't be looking into the box.

 

It's used as an example for wave particle duality, and I personally think it's a bad example and shouldn't be referenced.

 

Here's my reasoning:

 

According to SC (abbreviated for ease) we do NOT know whether or not the cat is alive. But according to WPD (wave particle duality) we DO know that light is both a wave and a particle at the same time.

 

Shouldn't there be a better example for this?

[Strange]

It is important to realise that Schroedinger proposed the cat thought experiment (you talk about it as if it were a real thing!) to show how ridiculous the Copenhagen interpretation of quantum mechanics is. It was not really supposed to make sense and probably isn't physically realistic.

 

So, yes, I'm sure there are better examples. Ones taken from real life, perhaps, where we have shown quantum superposition in the lab.

 

And note that wave-particle duality is a completely different thing. It is just a (rather misleading) way of describing the properties of quantum particles.

Edited October 19, 2016 by Strange

[Delta1212]

Schrodinger's Cat, according to The Complete Idiots Guide to Theories of The Universe, Is essentially an experiment which states that a cat that is in a box with a vial of poison, is both dead and alive, because we don't know whether or not it IS living unless we look into the box. In this scenario we wouldn't be looking into the box.

 

It's used as an example for wave particle duality, and I personally think it's a bad example and shouldn't be referenced.

 

Here's my reasoning:

 

According to SC (abbreviated for ease) we do NOT know whether or not the cat is alive. But according to WPD (wave particle duality) we DO know that light is both a wave and a particle at the same time.

 

Shouldn't there be a better example for this?

It's used as an example of quantum superposition of states, rather than wave-particle duality.

[Sensei]

Shouldn't there be a better example for this?

For me, Schrodinger's Cat experiment,

is example of randomness at quantum level.

You don't know whether something happened or not happened, until you look, perform measurement.

But if you do perform measurement, you destroy initial (unknown) state, and it's irreversible.

If you look at object, photons emitted/reflected by object are absorbed, changed to excited electrons/particles, excited atoms, excited nucleus, in eye or electronic detector, and gone from system under observation.

[Carrock]

I think of Schrödinger's cat as an illustration of the problem of defining measurement.

 

Consider someone in a large sealed box with a small box containing the unfortunate cat.

 

She opens the cat box and finds the cat definitely alive or definitely dead.

 

Has the cat's vitality been measured?

 

Until the large box is eventually opened anyone outside the large box still has to describe the cat as in a live/dead superposition.

[added]

One superposition of the woman found the cat dead but when the large box is opened the cat may be alive, with a woman who has no memory of the cat being dead.

Edited October 19, 2016 by Carrock

[PatrickO]

I think of Schrödinger's cat as an illustration of the problem of defining measurement.

 

Consider someone in a large sealed box with a small box containing the unfortunate cat.

 

She opens the cat box and finds the cat definitely alive or definitely dead.

 

Has the cat's vitality been measured?

 

Until the large box is eventually opened anyone outside the large box still has to describe the cat as in a live/dead superposition.

[added]

One superposition of the woman found the cat dead but when the large box is opened the cat may be alive, with a woman who has no memory of the cat being dead.

That definitely cleared things up

 

Thank you!

[PeterWB]

Schrödinger objected to the Copenhagen Interpretation's definition of his wave function as the probability of an electron, or other quantum object, being in a particular position or state, and that it was in all positions/states at the same time until measured/observed, when the function collapsed to a single definite position/state.

Unfortunately he could not come up with an alternative "physical" interpretation of what the wave function represented, and he also missed the biggest flaw in the Copenhagen Interpretation(CI):

- The CI is based on a Classical (i.e. pre quantum) definition of an observer as a Human being.

 

Quantum Mechanics was born out of subatomic physics, where electrons and protons, etc, are so small that they they are not "seeable" in the way we understand this. The only way to "see" an atom, electron, photon, etc, is to "bounce another particle off it", i.e. have it interact with another quantum object so that information is exchanged. e.g. a photon being absorbed by a dye molecule in a light sensitive cell in the retina of our eye (the photons energy changes the shape of the molecule, revealing a enzyme site which starts the process of triggering a neurone, etc, etc, which eventually leads to sight.).

Thus a quantum observation or measurment does not involve a human being, but instead is an interaction which changes the state of the thing being observed ( even if the interaction occurs in the retina of our eye, rather than in a camera or piece of laboratory equipment). Therefore it is not the involvement of a human observer which changes the state of the observed particle as claimed by CI.

 

This points to a second flaw in the Copenhagen Interpretation - There can be multiple human observers of a single measurement/observation, which can occur at different times.

This is illustrated by Baryon's post where the first human observer was also in a box and subject to being "observed" by a second human observer.

Edited October 23, 2016 by PeterWB

[Daecon]

The thought experiment implies that a Human has to be the observer, but why isn't the cat considered an observer? What would be the smallest thing that could be considered an observer?

Edited October 23, 2016 by Daecon

[Carrock]

Welcome to scienceforums PeterWB.

The thought experiment implies that a Human has to be the observer, but why isn't the cat considered an observer? What would be the smallest thing that could be considered an observer?

It's a near infinite regress. I ignored the cat beyond describing it as 'unfortunate' since I didn't want to argue about whether or not it could be regarded as an honorary human observer.

See below...

Schrödinger objected to the Copenhagen Interpretation's definition of his wave function as the probability of an electron, or other quantum object, being in a particular position or state, and that it was in all positions/states at the same time until measured/observed, when the function collapsed to a single definite position/state.

Unfortunately he could not come up with an alternative "physical" interpretation of what the wave function represented, and he also missed the biggest flaw in the Copenhagen Interpretation(CI):
- The CI is based on a Classical (i.e. pre quantum) definition of an observer as a Human being.

No it isn't.

There is/was no constraint on the intelligence or size of the observer in the maths on which the Copenhagen Interpretation and all the other differently unsatisfactory interpretations are based.

The idea that an observer has to be human and the alternative idea that a human (or a cat) is too large to make a "quantum observation or measurment" are precisely what is addressed in the Schrödinger's cat thought experiment.

Where is the cutoff? Derive it from quantum mechanics.

If humans can't make a "quantum observation or measurment" then they can't tell whether the cat is alive or dead when they open the box since they would be observing indirectly whether or not the radioactive atom decayed and killed the cat.

Quantum Mechanics was born out of subatomic physics, where electrons and protons, etc, are so small that they they are not "seeable" in the way we understand this. The only way to "see" an atom, electron, photon, etc, is to "bounce another particle off it", i.e. have it interact with another quantum object so that information is exchanged. e.g. a photon being absorbed by a dye molecule in a light sensitive cell in the retina of our eye (the photons energy changes the shape of the molecule, revealing a enzyme site which starts the process of triggering a neurone, etc, etc, which eventually leads to sight.).

Thus a quantum observation or measurment does not involve a human being, but instead is an interaction which changes the state of the thing being observer ( even if the interaction occurs in the retina of our eye, rather than in a camera or piece of laboratory equipment). Therefore it is not the involvement of a human observer which changes the state of the observed particle as claimed by CI.

This points to a second flaw in the Copenhagen Interpretation - There can be multiple human observers of a single measurement/observation, which can occur at different times.
This is illustrated by Baron's post where the first human observer was also in a box and subject to being "observed" by a second human observer.

Am I Baron?

Every interpretation is differently dubious.

There can be multiple human observers of a single measurement/observation, which can occur at different times.

...and have different superposed results. Once everyone has 'observed' the cat, they all agree it is definitely alive or dead.

I don't see this as a flaw.

It's possible to imagine everything described in my OP enclosed in an even larger box (such as the multiverse) waiting for, er, an outside observer to observe them and collapse the superposition of (dead cat and observers) and (live cat and observers).

Getting weird results isn't enough to discredit a theory or interpretation or thought experiment if nothing better is available.

e.g. spooky action at a distance.

[J.C.MacSwell]

I think of Schrödinger's cat as an illustration of the problem of defining measurement.

 

Consider someone in a large sealed box with a small box containing the unfortunate cat.

 

She opens the cat box and finds the cat definitely alive or definitely dead.

 

Has the cat's vitality been measured?

 

Until the large box is eventually opened anyone outside the large box still has to describe the cat as in a live/dead superposition.

[added]

One superposition of the woman found the cat dead but when the large box is opened the cat may be alive, with a woman who has no memory of the cat being dead.

Eugene Wigner had similar thoughts...

 

https://en.wikipedia.org/wiki/Wigner%27s_friend

[Carrock]

Eugene Wigner had similar thoughts...

 

https://en.wikipedia.org/wiki/Wigner's_friend

Interesting but...

This article needs additional citations for verification.

and

Wigner designed the experiment to illustrate his belief that consciousness is necessary to the quantum mechanical measurement process.

From this ref, Wigner seems to associate unknown physics with consciousness; it reminds me of earlier researchers trying to weigh the soul by measuring weight before and after death.

 

Similarly Roger Penrose quoted in the same Wiki:(Couldn't access the original text.)

For there is nothing in the formalism of quantum mechanics that demands that a state of consciousness cannot involve the simultaneous perception of a live and a dead cat.

I wasn't aware of Penrose and Wigner's alleged contributions earlier; they certainly support this:

 

The CI is based on a Classical (i.e. pre quantum) definition of an observer as a Human being.

I reject that version of CI.

[PeterWB]

 

I reject that version of CI.

 

I was not aware that there were multiple versions of the Copenhagen Interpretation.

 

 

Eugene Wigner had similar thoughts...

 

https://en.wikipedia.org/wiki/Wigner%27s_friend

 

The maths makes me wonder if it might be possible to design an experiment to test when the superposition ends.

Maybe a variation on the Bell's Theorem experiment, where entangled particles in a superposition are measured, then a second measurement is made before the first result is seen by the experimenter (This assumes that a new superposition is not created automatically after the first measurement).

 

If the second measurement showed that there was still a superposition, this would support the intelligent observer version of CI.

If not, maybe science writers will eventually stop asking "Can the universe exist without a human observer" (not that we can observe the universe - all we can observe are photons and cosmic rays).

[Strange]

That sounds a little like the "delayed quantum eraser" experiment.

https://en.wikipedia.org/wiki/Delayed_choice_quantum_eraser

[Carrock]

 

I reject that version of CI.

I was not aware that there were multiple versions of the Copenhagen Interpretation.

 

From https://en.wikipedia.org/wiki/Copenhagen_interpretation#Current_status_of_the_term

Current status of the term

According to an opponent of the Copenhagen interpretation, John G. Cramer, "Despite an extensive literature which refers to, discusses, and criticizes the Copenhagen interpretation of quantum mechanics, nowhere does there seem to be any concise statement which defines the full Copenhagen interpretation."

 

Eugene Wigner had similar thoughts...

 

https://en.wikipedia.org/wiki/Wigner's_friend

The maths makes me wonder if it might be possible to design an experiment to test when the superposition ends.

Maybe a variation on the Bell's Theorem experiment, where entangled particles in a superposition are measured, then a second measurement is made before the first result is seen by the experimenter (This assumes that a new superposition is not created automatically after the first measurement).

 

If the second measurement showed that there was still a superposition, this would support the intelligent observer version of CI.

If not, maybe science writers will eventually stop asking "Can the universe exist without a human observer" (not that we can observe the universe - all we can observe are photons and cosmic rays).

 

That sounds a little like the "delayed quantum eraser" experiment.

https://en.wikipedia.org/wiki/Delayed_choice_quantum_eraser

Also, without a good theory to test, any experiment will only rule out a few possibilities.

[Country Boy]

For me, Schrodinger's Cat experiment,

is example of randomness at quantum level.

It is intended to be more than that. Its purpose is to show that randomness, at the quantum level, can have macro, non-quantum level, effects.

You don't know whether something happened or not happened, until you look, perform measurement.

But if you do perform measurement, you destroy initial (unknown) state, and it's irreversible.

If you look at object, photons emitted/reflected by object are absorbed, changed to excited electrons/particles, excited atoms, excited nucleus, in eye or electronic detector, and gone from system under observation.

[Carrock]

[The Schrodinger's Cat experiment's] purpose is to show that randomness, at the quantum level, can have macro, non-quantum level, effects.

Where is the split?

 

Perhaps Heisenberg's cut?

In quantum mechanics, a Heisenberg cut is the hypothetical interface between quantum events and an observer's information, knowledge, or conscious awareness. Below the cut everything is governed by the wave function; above the cut a classical description is used.... 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.

I don't think there's any way to have detectable macroscopic non-quantum effects without requiring a suitable observer subject to unknown physics.

 

Cats might not be regarded as suitable observers.

[Ophiolite]

Cats might not be regarded as suitable observers.

Indeed. Even when they know they are dead they won't share the information with humans.

[Sensei]

Indeed. Even when they know they are dead they won't share the information with humans.

 

Cat meows. If cat not meows for a long time, cat is certainly dead..

Edited November 7, 2016 by Sensei

[DrP]

What happens when you stroke this pussy? This is a new thought experiment that I am going to contemplate for a bit.