Schrodinger's Cat vs. The Principle of Explosion

[jason_m]

onsider the following link:

http://en.wikipedia.org/wiki/Principle_of_explosion

Now, consider Schrodinger's Cat. Does this not imply the following statements?

- A) The cat is alive before the box is opened.
- B) The cat is not alive before the box is opened.

Aren't both of these statements supposedly true?

Now, consider the following proof based on the principle of explosion:

1) The cat is not alive before the box is opened or Santa Claus exists. (From A))
2) The cat is alive.
3) Santa Claus exists (because 2) contradicts A) and 1) must be true - just like the Wikipedia link states).

Therefore, is the principle of explosion wrong or is something wrong with the notion of Schrodinger's Cat? (Or something else?)

Jason

 

[HallsofIvy]

No, it does NOT imply the two statements you give. What it implies is that the cat is in an "indeterminate" state of "neither alive nor dead" but some combination of the two.

 

[jason_m]

I'm not a physics major. I'm a philosophy major studying logic and have only read about quantum physics in my spare time. That's why I wondered... Is that okay with you? Is it the lack of face-to-face communication and therefore I'm misinterpreting you, or is it for some strange reason a touchy subject...

 

[phinds]

This is a physics forum, not a philosophy forum. People tend to give straight-forward, factual, answers to questions (as Halls did in this case). There is no "touchiness" involved, just the possibility that you don't like the answer.

 

[jason_m]

This is a physics forum, not a philosophy forum. People tend to give straight-forward, factual, answers to questions (as Halls did in this case). There is no "touchiness" involved, just the possibility that you don't like the answer.

If it's not meant to be helpful, then why should I cooperate? (Of course, I realize that maybe it was meant to be helpful and I am misinterpreting him/her...)

 

[D H]

Now, consider Schrodinger's Cat. Does this not imply the following statements?

- A) The cat is alive before the box is opened.
- B) The cat is not alive before the box is opened.

Aren't both of these statements supposedly true?

Nope. It means you don't know what has transpired until you open the box.

You have ascribed a local variable that remains hidden until the box is opened. There are no local hidden variables. Bell's Theorem. There are *lots* of threads on Bell's Theorem in this forum.

 

[phinds]

If it's not meant to be helpful, then why should I cooperate? (Of course, I realize that maybe it was meant to be helpful and I am misinterpreting him/her...)

Halls provided a succinct and accurate/correct answer to your question. I cannot imagine how he could have been more helpful.

 

[jason_m]

Halls provided a succinct and accurate/correct answer to your question. I cannot imagine how he could have been more helpful.

Then let's just chalk it up to the fact that Internet communication can be misleading...

 

[DennisN]

jason_m, Schrödinger's cat is just a thought experiment, designed to illustrate some counterintuitive issues in quantum mechanics;

• superposition ("dead and alive cat") before measurement
• measurement (that a superposition - "dead and alive cat" - will be observed as either "dead or alive cat" after a measurement).

Schrödinger's cat is nowadays often presented in various introductions to quantum mechanics. In my opinion you will get more meat out of the double-slit experiment(s), as it brings you more face to face with quantum mechanics.

 

[audioloop]

Then let's just chalk it up to the fact that Internet communication can be misleading...

no, the thing, goes beyond science, philosophy, go to the root of existence, but some people argues "well it coincides with observation, empirical method and so on" but observation rest on concepts and i ask, what are concepts ? concepts that sustain physics, philosophy any thing that you can think, logics etc.
then, is a thin ice, that can break any moment..

 

[phinds]

no, the thing, go beyond science, philosophy, go to the root of existence, but some people argues "well it coincides with observation, empirical method and so on" but observation rest on concepts and i ask, what are concepts ? concepts that sustain physics, philosophy any thing that you can think, logics etc.
then, is a thin ice, that can break any moment.


.

I can't make any sense at all of this statement. What is your point? What are you saying?

 

[audioloop]

This is a physics forum, not a philosophy forum. People tend to give straight-forward, factual, answers to questions (as Halls did in this case). There is no "touchiness" involved, just the possibility that you don't like the answer.

what is a FACT ?


.

 

[USeptim]

How can the cat be in a mixed state? Can a hidrogen atom be partially in the S1 state and partially in the P(2,1) state?

In that case one would think when in the S1 state it can be transfer a quantity of energy smaller than the 10.2 eV ( the energy to go from S1 to P(2,1) ) because you can "partially" put the atom in P(2,1) which is false.

That's false not because of the photon but because of the electron. Photons are the manifestation of the interaction between EM and matter but it's just EM what travels, there is nothing like the mass that can help you to say "this region of EM field it's a photon"... but in fact this is another subject of debate...

In brief, I think the Schrödiger cat paradox just means that before we open the box, we only have statistical knowledge about what's inside the box.

 

[Maui]

what is a FACT ?


.

Quantumness that's no longer coherent?

 

[Crazymechanic]

Ok let's be real no cat has ever been dead and alive altogether , the cat either lives until the box is opened or dies at some given exact time and is dead when we open the box , it' s not about the cat not about the box , it's rather about our lack of knowing when that happens , or I should say lack of a way to even get that answer without disturbing the outcome.

There could be chances to open up the box and see the cat being dead already which would rather indicate that the particle has decayed sometime ago and the only way to conclude that would be to make an autopsy of the cats dead body to tell an approximate time of death.Then there are chances of decaying the particle while opening the box which kills the cat , and then there are chances that nothing bad happens and the kitty ends up ok.Which one will happen in a given situation is a casino bet.
Further opinions are 100% philosophical , spiritual etc as there are no more ways of knowing the answer as nature forbids it. Why who knows , God , Buddha , nobody a matter of opinion , well I have my own and I think its right but then again many of us do so I am not going to endorse that here. :)

 

[DrChinese]

In brief, I think the Schrödiger cat paradox just means that before we open the box, we only have statistical knowledge about what's inside the box.

The point of the paradox is to indicate the opposite. There is a state called superposition which is neither this nor that for a quantum system. If such were not the case, Bell tests would yield different experimental results. (As well as many other things.)

 

[ZapperZ]

The problem with threads and questions in this topic is that people tend to mix many different aspects of QM and confusing them to be one. I see in this thread alone, the mixing up of the concept of "superposition", "realism", and "contextuality". And no, I am NOT doing philosophy either because these concepts are also defined in physics and there are experiments that are testing such things (which is why it is NOT philosophy).

There have been several papers in the Noteworthy Papers thread in the General Physics forum that have dealt with such issues:

https://www.physicsforums.com/showpost.php?p=4351057&postcount=157
https://www.physicsforums.com/showpost.php?p=4129344&postcount=155
https://www.physicsforums.com/showpost.php?p=3372804&postcount=139
https://www.physicsforums.com/showpost.php?p=2288402&postcount=86

It is confusing when different concepts are mixed in, and this often cause the responses to go in all different directions.

If the issue is the idea of superposition, which is what I believe it is, I've highlighted, numerous times, the Delft/Stony Brook paper (do a search on PF) and also Tony Leggett's treatise on this. It is one of the strongest demonstration of this principle.

Zz.

 

[dauto]

If it's not meant to be helpful, then why should I cooperate? (Of course, I realize that maybe it was meant to be helpful and I am misinterpreting him/her...)

Instead of doing something useful and trying to understand the answer given, you are wasting time debating the useless point of whether or not the topic is a touchy one. - Clearly an philosophy major...

 

[Crazymechanic]

I don' t think @dauto there was any need to feel superior to a philosophy major , doesn't seem you yourself would be the next Einstein, clearly a response like that doesn't indicate you being any better than the OP with his misunderstanding.

As to the the OP and what Zapper said already , we need to have distinction between different terminology.
There is the principle of superposition , clearly no doubt about it, but a macro object like a cat or for the sake of an argument any object you can touch is not in and cannot be in a superposition let alone because of the surrounding medium that ti normally is in.
Millions of atoms , room temperature etc.
In the case of Schroedingers cat it is more the fact that we cannot know the outcome without a high chance of making it a certain way when doing the " peek" in the box , just because when it comes down to a few radioactive atoms or whatnot measuring is also interacting and vice versa.
The atom knows very well in what position it was before we saw it being in a different one but ofcourse that is an abstraction as it would imply an atom to be conscious which is not the case.

To add just a little bit of philosophy to this our lack of determining the result without disturbing it rather comes from the fact that we are conscious creatures but we also are a macro being in other words we can only interact with macro object , nobody sees an atom directly that why we need " tools" special ones to look into the quantum world and these tools are also the ones which interact and disturb the quantum world.
If atoms would be humans then we could very well see in what state each one of us is in at a given moment.But that just a side note.

 

[bhobba]

The problem with threads and questions in this topic is that people tend to mix many different aspects of QM and confusing them to be one. I see in this thread alone, the mixing up of the concept of "superposition", "realism", and "contextuality". And no, I am NOT doing philosophy either because these concepts are also defined in physics and there are experiments that are testing such things (which is why it is NOT philosophy).

Right on.

People get very confused about Schrodinger's Cat I think largely because of populist gibberish like What The Bleep Do We Know Anyway.

Copenhagen, the interpretation that was the most prevalent when Schrodinger's Cat was proposed, assumes the existence of a commonsense classical world out there independent of observation exactly like is assumed in classical physics. It assumes we know about quantum systems via 'marks' left in that classical world - that are called observations, measurements etc. QM is a theory about such 'marks'. In Copenhagen the solution to Schrodinger's Cat is trivial, utterly trivial. Quantum effects make their appearance here in the classical world at the particle detector. It either detects a particle or not - nothing weird at all going on from that point on. The cat is alive or dead when you open the box, or even if you don't open the box - consciousness is not involved to collapse anything.

So what is its importance - why is Schrodinger's Cat considered a valid tool to help elucidate issues with QM? Its not what you usually read in the popular press. Its simply this - the classical world that Copenhagen assumes is composed of quantum stuff. So how does a theory that assumes the existence of something the theory itself should explain actually accomplish this feat and explain it. We need a fully quantum theory of measurement. That's the issue.

Since then a lot of work has been done on just that and decoherence has shed a lot of light on the issue - but it does not resolve it to everyone's satisfaction - it's hotly debated.

If you want to understand the issues check out:
http://philsci-archive.pitt.edu/5439/1/Decoherence_Essay_arXiv_version.pdf

I hold to the ignorance ensemble interpretation. I won't defend it because it usually ends up in a heated debate. Instead I urge the OP to go through the paper and form his own opinion.

Doing this will give you a correct understanding of the issue - which unfortunately popular accounts will not give you - and even some under graduate texts like Griffith skirt around what's really going on, instead concentrating on how to solve problems.

If you really want to understand QM, I mean really understand it, the book to get is Ballentine - QM - A Modern Development:
https://www.amazon.com/dp/9810241054/?tag=pfamazon01-20
http://www-dft.ts.infn.it/~resta/fismat/ballentine.pdf

Thanks
Bill

 

[dauto]

The atom knows very well in what position it was before we saw it being in a different one but of course that is an abstraction as it would imply an atom to be conscious which is not the case.

No, it doesn't, and that's the point. If you think the atom "knows" its position before the measurement, you don't understand quantum mechanics. Bell's inequality was designed to test this very point and experimental results confirm that, indeed, the atom doesn't "know" its own position before it is measured.

 

[dauto]

As I understand the question, this thread is not supposed to be about interpretations of Quantum Mechanics. It is about whether quantum mechanics states that the cat might in principle (forget about the inpracticality of creating a macroscopic superposition for a moment) be alive and not alive at the same time, triggering the Explosion theorem. The answer of course must be no. So what gives? Quantum mechanics is actually stating that a live cat and a dead cat are not opposites. They are in fact perpendicular to each other in a space of possible states that is more than one dimensional. That space has other possible states besides dead or alive, and those states will have non-zero components in both the dead and the alive direction making both things partially true at the same time. Opening the box changes the state forcing the cat to be either dead or alive. Is that weird? Sure... But who cares? experiments have confirmed this fundamental aspect of Quantum Mechanics at every turn, and experiments beat philosophy any day of the week.

 

[DennisN]

As I understand the question, this thread is not supposed to be about interpretations of Quantum Mechanics. It is about whether quantum mechanics states that the cat might in principle (forget about the inpracticality of creating a macroscopic superposition for a moment) be alive and not alive at the same time, triggering the Explosion theorem.

That's my impression of the original post #1 too. My impression was that the OP was asking about the concept of quantum superposition. And it sure would be good to get some feedback from the OP, so we do not end up talking to ourselves about interpretations. There are plenty of other threads for that, and plenty more will come; that's a safe prediction I can make without using any equation .

 

[D H]

So what gives?

Nothing.

By way of analogy, general relativity shows that the universe is markedly non-Euclidean. Did this disprove Euclidean geometry? Of course not. Back on topic, did experiments that show that Schrodinger's cat paradox is valid suddenly cause every logical (and illogical) thought by mankind to suddenly become false and true at the same time? Of course not.

That reality motivates developments in mathematics and logic does not mean that new developments/observations in science can falsify old mathematics and logic. That's not how mathematics and logic work. Euclid's geometry and Aristotle's logic are still quite valid, despite developments by modern physics.

 

[Maui]

As I understand the question, this thread is not supposed to be about interpretations of Quantum Mechanics. It is about whether quantum mechanics states that the cat might in principle (forget about the inpracticality of creating a macroscopic superposition for a moment) be alive and not alive at the same time, triggering the Explosion theorem. The answer of course must be no. So what gives?

Why would that be a 'no'? How else are we to view what we observe but as quantum fields(and matter as excitations of same fields)? The standard model got recently re-confirmed with the evidence of the Higgs boson and there really is no other understanding of reality and the experimental evidence in that respect is overwhelming(to say the least). As has been noted in other threads, decoherence alone does not adequatelly explain single outcomes and hence all single-state objects, incl. cats. If anything, the statement 'all matter is constantly in a state of superposition' fits better the theoretical framework and there are no known conflicts except maybe someone's prejudices. Whereas the statement - 'all matter is never in a state of superposition' is in contradiction with both theory and experiment.

Edit: There is one resolution to this impasse and it's well known among the physicists - it's called the MWI. Many a physicist adhere to it for that reason alone.

 

[Crazymechanic]

Also I would like to point out that this philosophy vs science /experiments stuff is kinda stupid , I don't think people with academic diplomas or just common sense should fall into such stupidity or maybe a diploma doesn't make one intellectual at the same time which is the case most of the time.

Just because some people like to use philosophy or science for what it should not be used for doesn't make one or the other valid or invalid.
Science is science and it deals with physical phenomenon that can be either replicated or observed or some that can be only theorized.
Philosophy deals with other stuff , sometimes they overlay most of the times they take their different roads , comparing them or denying the one or the other feeling that the one is somehow superior is childish stupidity.Looking from this perspective maybe let' s abandon every arts , poetry, theater etc just because the things mentioned there are not real most of the time they are pure emotions which some feel and some don't so let' s consider that as not being valid , now that would be stupid wouldn't it ?

Ok back to the topic @dauto yes I agree that the atom before measurement is in a indefinite state which follows from the fact that you can make many measurements and the outcomes will be different for the same exact situation.But can you really say that the atoms itself doesn't know what state he is in at any given moment ? Well we have no way of knowing that that's for sure , even the physical surrounding aka other atoms have no way of knowing it because if they could then that wouldn't be a superposition anymore as decoherence would have happened but even when the atom is all alone under these special conditions does it really is undefined ? Well maybe we can say so because there is no so called frame of reference for that atom until it has made it's interaction.
Ok but if really what you say is true then if the conditions would be right physical objects could change their whole being and structure and somehow this is not the case well we know why because any macro object has too many atoms for such a situation to occur.

The thing is I just somehow feel that even though the experiments show us this outcome which I don't deny , there is something lacking in the way we interpret them as you know that whatever a real physical experiment may show the interpretation from the conscious observer is just as important.

 

[dauto]

Why would that be a 'no'? How else are we to view what we observe but as quantum fields(and matter as excitations of same fields)? The standard model got recently re-confirmed with the evidence of the Higgs boson and there really is no other understanding of reality and the experimental evidence in that respect is overwhelming(to say the least). As has been noted in other threads, decoherence alone does not adequatelly explain single outcomes and hence all single-state objects, incl. cats. If anything, the statement 'all matter is constantly in a state of superposition' fits better the theoretical framework and there are no known conflicts except maybe someone's prejudices. Whereas the statement - 'all matter is never in a state of superposition' is in contradiction with both theory and experiment.

Edit: There is one resolution to this impasse and it's well known among the physicists - it's called the MWI. Many a physicist adhere to it for that reason alone.

You misunderstand me. I'm not denying Quantum Mechanics. I'm explaining it. The answer must be no because the explosion theorem unleashes all sorts on inconsistencies. But alas Quantum Mechanics does not trigger the explosion theorem, despite appearance.

 

[dauto]

Crazymechanic says

Also I would like to point out that this philosophy vs science /experiments stuff is kinda stupid , I don't think people with academic diplomas or just common sense should fall into such stupidity or maybe a diploma doesn't make one intellectual at the same time which is the case most of the time.

Just because some people like to use philosophy or science for what it should not be used for doesn't make one or the other valid or invalid.
Science is science and it deals with physical phenomenon that can be either replicated or observed or some that can be only theorized.
Philosophy deals with other stuff , sometimes they overlay most of the times they take their different roads , comparing them or denying the one or the other feeling that the one is somehow superior is childish stupidity.Looking from this perspective maybe let' s abandon every arts , poetry, theater etc just because the things mentioned there are not real most of the time they are pure emotions which some feel and some don't so let' s consider that as not being valid , now that would be stupid wouldn't it ?

and I hear "Blah, Blah, Blah..." ;-)

Ok back to the topic

Yes, please

@dauto yes I agree that the atom before measurement is in a indefinite state which follows from the fact that you can make many measurements and the outcomes will be different for the same exact situation.But can you really say that the atoms itself doesn't know what state he is in at any given moment ? Well we have no way of knowing that that's for sure , even the physical surrounding aka other atoms have no way of knowing it because if they could then that wouldn't be a superposition anymore as decoherence would have happened but even when the atom is all alone under these special conditions does it really is undefined ? Well maybe we can say so because there is no so called frame of reference for that atom until it has made it's interaction.

You're mistaken here. The whole point of Bell's inequality was to show that that question CAN be answered experimentally - And it has.

Ok but if really what you say is true then if the conditions would be right physical objects could change their whole being and structure and somehow this is not the case

Yes, it is. look up radioactive decay

well we know why because any macro object has too many atoms for such a situation to occur.

That's just a matter of impracticality (which I set aside in my post) - not impossibility.

The thing is I just somehow feel that even though the experiments show us this outcome which I don't deny , there is something lacking in the way we interpret them as you know that whatever a real physical experiment may show the interpretation from the conscious observer is just as important.

I hear you. You are not alone man. Einstein himself expressed similar feelings. But he also failed to figure out any alternative explanations, and by now we have already past the point of no return in that matter mainly due to the aforementioned Bell's inequality.

 

[Crazymechanic]

" ' " and I hear "Blah, Blah, Blah..." ;-)" " "

The fact that you are " hearing" strange voices while " reading" what I wrote tells me that you might be in a superposition of two sates from which one is an intellectual commentator (I suppose rather hope) and the other being an ignorant individual who happens to have a need for a doctors visit. :D

Why do you put radioactive decay into this subject ? Surely it is not what I meant to say and yes I do understand what I am talking about.Radioactive decay has to do with pretty physical fundamental forces and large nucleus being unstable etc.

I mentioned that a every day object like a cat or whatnot could easily be transformed if we could achieve the superposition of so many atoms alltogether, transforming something in such a way sure is very different than transforming a material due to atomic decay , surely a living creature like a human consists much of water , hydrogen being a very usual component of the universe , haven' t heard a hydrogen decay for a while ...

The point is I'm not trying to speculate or put forward my personal opinion as I see you have already did that with yours on the " anything other than physics" thing all I want to say is that if what you say (not the Bell part but the part which you add yourself) is really true then we could shape the universe and anything in it in like a million different ways given the fact that we would need to achieve these special conditions for macro objects of billions of atoms.

But that sparks a further question if the atom which is in superposition doesn't know himself in what state he is prior to measurement then how would a million atoms of unknown states choose the right ones to form a real and definite creature or object not some kind of a video card artifact?
measuring one or few atoms in superposition is one thing but imagine a whole bunch of them ...

 

[dauto]

" ' " and I hear "Blah, Blah, Blah..." ;-)" " "

The fact that you are " hearing" strange voices while " reading" what I wrote tells me that you might be in a superposition of two sates from which one is an intellectual commentator (I suppose rather hope) and the other being an ignorant individual who happens to have a need for a doctors visit. :D

You can relax. All teasing statements in previous posts were intended as tongue-in-cheek

Why do you put radioactive decay into this subject ? Surely it is not what I meant to say and yes I do understand what I am talking about.Radioactive decay has to do with pretty physical fundamental forces and large nucleus being unstable etc.

The radioactive decay is an example of an object changing its own state. I though that's what you were talking about.

I mentioned that a every day object like a cat or whatnot could easily be transformed if we could achieve the superposition of so many atoms alltogether, transforming something in such a way sure is very different than transforming a material due to atomic decay , surely a living creature like a human consists much of water , hydrogen being a very usual component of the universe , haven' t heard a hydrogen decay for a while ...

Again, the difference between the superposition of a macroscopic object - a cat, and the superposition of a microscopic object - a decaying atom, is a matter of practicality. but I set practicality aside from the get go.

The point is I'm not trying to speculate or put forward my personal opinion as I see you have already did that with yours on the " anything other than physics" thing all I want to say is that if what you say (not the Bell part but the part which you add yourself) is really true then we could shape the universe and anything in it in like a million different ways given the fact that we would need to achieve these special conditions for macro objects of billions of atoms.

I have no idea what you're trying to say here :-(

But that sparks a further question if the atom which is in superposition doesn't know himself in what state he is prior to measurement then how would a million atoms of unknown states choose the right ones to form a real and definite creature or object not some kind of a video card artifact?
measuring one or few atoms in superposition is one thing but imagine a whole bunch of them ...

To be clear - The atom has a definite state, but that state is a superposition of different states which will lead to different possible outcomes. The atom has no prior knowledge of which of the possible outcomes will be realized. So when you measure the position of the atom its state must change to conform with the newly acquired knowledge about that experiment. That means the atom did not known its own position before the measurement was taken.

 

[Crazymechanic]

Thanks dauto but I'm already relaxed , the only time I got a little " amazed" was when you said that rephrasing let' s throw out anything else than just a few numbers. :D

Well actually it' s not so much of a disagreement here as I just didn' t understand you from the beginning but now I think I do.
Yes the atom indeed cannot know what it's going to turn out upon measurement just as you can only have a slight prediction about how your children will turn out before you have them or how your wife will turn out before you marry her.So yes an atom before a measurement is somehow a half complete set.

The thing you referred to that you don't understand was meant about if we could make a superpositioned cat then upon measurement would it be a cat anymore because if we speak about the fact that an atom takes a certain state upon measurement then if we could do this to a whole animal the question then becomes not so much alive or dead but would it still be a cat ?
See what i mean?

 

[dauto]

I understand it better now though I don't see why wouldn't it be a cat. A dead cat is still a cat, I assume, and so is a live cat. A superposition of both is probably still a cat. But now we are really talking about philosophy, I think.

 

[USeptim]

The point of the paradox is to indicate the opposite. There is a state called superposition which is neither this nor that for a quantum system. If such were not the case, Bell tests would yield different experimental results. (As well as many other things.)

What it's more ashtonishing from Bell's test is that Alice and Bob spins remain oposite after the collapse, because in some way the collapse of A affects on B instantaneouslly. This is well described on Wikipedia.

http://en.wikipedia.org/wiki/Bell's_inequality

Anyway, this means that we have a mixed state between two particles but I cannot see clearly that this is the same that having just one particle in two states, as the cat paradox tells.

 

[dauto]

The particle really isn't in two states. It is in a single well defined state that happens to be a superposition of two other single well defined states.

 

[Crazymechanic]

well yes the ca can be only dead or alive when we are speaking about one atom decaying due to whatever makes it decay.
What I meant was a whole cat (every atom in a cat) put on superposition like that quantum experiment where they put many atoms in such a state.
Now when you measure all those atoms they turn out various different ways (states) and you cannot predict with certainty the outcome , that why I asked will it then be a cat anymore ?