How can Schrödinger's Cat be both alive and dead?

[Omega0]

Okay, I believe I indeed was sort of confusing. The cat is a macroscopic object. I did agree that quantum entanglement exists but too believe that this exists and is stable with a macroscopic object of billions of particles seems to me more than ridiculous. To state that me as an observer of the box which is macroscopic also is the only observer makes no sense. First: What about the cat? Isn't it an observer? If you can show that also molecules interfere in a quantum mechanical sense - what does it prove? Physics is measuring and finding a theory describing. In some points theory leads to new ideas of measurement to prove a theory. QFT is a good example. Nevertheless, to confuse people in mixing macroscopic and quantum world makes here no sense in my eyes.
I think one should clearly separate the realms of the validity in existing theories - everything else is not science.

 

[Passionflower]

I think one should clearly separate the realms of the validity in existing theories - everything else is not science.

Since in the thought experiment we cannot look into the box then unless we can demonstrate that generally a wave function can collapse without a measurement taking place we simply must assume the cat is in superposition.

That is science, 'to believe it is ridiculous or any other belief about it' is certainly not science.

 

[Omega0]

we simply must assume the cat is in superposition.
That is science

What it scientific in assuming something you can't measure?

 

[Passionflower]

What it scientific in assuming something you can't measure?

That is what we do in QM and very successfully.

 

[Omega0]

That is what we do in QM and very successfully.

Seems I got it wrong! Thought it is a theory based on a rethinking of the measurement process. Are you sure you studied it in detail?

 

[Omega0]

That is what we do in QM and very successfully.

PS: If you feel any uncertainty in your understanding I recommend J.J. Sakurai, "Modern Quantum Mechanics". He explaining the measurement process is a masterpiece in my eyes. Just as a hint. I loved it in my studies.

 

[Passionflower]

Seems I got it wrong! Thought it is a theory based on a rethinking of the measurement process. Are you sure you studied it in detail?

We have a very successful theory about the time evolution of the wave function but we cannot actually measure this just like we cannot measure the state and evolution of the cat but the results of any measurements (using observables) are statistically in accordance with theory.

 

[Omega0]

We have a very successful theory about the time evolution of the wave function but we cannot actually measure this just like we cannot measure the state and evolution of the cat but the results of any measurements (using observables) are statistically in accordance with theory.

So "any measurement" is on a microscopic level, right? You can't find the Eigenstate of the cat but you say that it is determined clearly in the same sense as some atoms are with respect to a quantum entanglement? It is pretty easy, I see... hmmm mightn't it be sort of too easy?
And in the end wrong? If you just say: Well, from our experience this idea holds, the theory works, so just let us expand the theory to the complete universe, to macroscopic bodies, we believe that quantum entanglement now exists for the cat, yeah, let's believe that we have now superpositions of being alive or dead. Is this science? In your eyes?

 

[Passionflower]

So "any measurement" is on a microscopic level, right? You can't find the Eigenstate of the cat but you say that it is determined clearly in the same sense as some atoms are with respect to a quantum entanglement? It is pretty easy, I see... hmmm mightn't it be sort of too easy?
And in the end wrong? If you just say: Well, from our experience this idea holds, the theory works, so just let us expand the theory to the complete universe, to macroscopic bodies, we believe that quantum entanglement now exists for the cat, yeah, let's believe that we have now superpositions of being alive or dead. Is this science? In your eyes?

Yes, we have a theory that works, and unless it is proven by experiments that at a certain scale it no longer works, it should be the prevailing theory.

 

[ZapperZ]

Sometime, a discussion on this forum gets so convoluted, it is difficult to decipher what exactly is the issue here. This appears to be the case here, and I think people are tripping over themselves talking about different things.

Is the issue

(i) the detection of superposition

or is it

(ii) can superposition be detected at the cat/macroscopic level?

Each one of those have different answers. The first one has been discussed ad nauseum in this forum. I had repeatedly mentioned about bonding-antibonding states, the Delft/Stony Brook experiments, etc... etc. There are already many of these types of Schrodinger cat states that have been measured.

http://physicsworld.com/cws/article/news/2815
http://physicsworld.com/cws/article/print/525
http://physicsworld.com/cws/article/news/42019

The second one has also been discussed many times, and the Delft/Stony Brook paper showed the superposition of up to 10^11 particles, which in some scale, is quite macroscopic! The existence of interference experiments with buckyballs and even other larger molecules are clear examples of such huge objects having a superposition of paths. These are not simple experiments, btw, and these are performed under extreme conditions to ensure that all parts of the object are in coherence with each other.

So it is clear, at least to me, that size isn't the issue, but rather the ability to have every part of that object in coherence is the most significant obstacle to observing quantum effects at large scales.

Zz.

 

[Charles Wilson]

Frustrating!
Here's one of the problems: How do we know that the Quantum World maps to the World we live in? If all we have are dials and pointers and screens, then there will ALWAYS be an alternative explanation for what we "observe".

"We opened the box and found the cat was alive AND the poison dispersed". So, did the atom decay or not?
WE DON'T KNOW. The experiment was never about what we could see. That's why a computer screen is as good as - and no worse than - a cat in box. And before you talk of the absurdity of a cat in a box, look at how we used to determine if a woman was pregnant. "Why would a doctor keep a bunch of cute little bunnies? I hope nothing bad happens to them!"

The experiment was about what we could infer from what we assumed was a causal chain from a set of Quantum circumstances.

"Suppose we have an electron..." We are already in a System with this one statement! You write a textbook about Physics. You discuss the Shroedinger Equation and Born's modification. You write that it is very useful and to understand it, you must understand how to normalize the Probability to fit the electron you are examining:
"The Integral from - infinity to + infinity of (Psi) ^2 dx = 1."

This is the normalization condition for finding the electron somewhere along the axis we are observing.

"But the electron has to be SOMEWHERE..." Hence the Integral is set to 1.

That's all Einstein ever needed and we are here denying Einstein and then denying the negation of Einstein.

In short, we continue to argue about the presence of das Noumena within Kantian restrictions and the first person who quotes Hegel loses. We are left with A N Whitehead's criticism of Humean Empiricism: All we can talk about are bees and flowers. There is no "why". All we see are bees landing on flowers. There is nothing else to be said.

[[EDIT: I removed a paragraph sorta' by request. See below.]]

Bell showed that Locality does not provide the results that QM obtains AND QM IS CORRECT.
That's the problem. So how does the QM non-locality map onto a Realistic and/or Local World?

We are only now getting to this examination in Physics.

CW

 

[Omega0]

Yes, we have a theory that works, and unless it is proven by experiments that at a certain scale it no longer works, it should be the prevailing theory.

Good point, you might be right in a sense that a theory which is not wrong in what we know from measurement in small scale might be correct on a bigger scale but this seems to imply that you believe in that this automatically must be valid on bigger scales. So it means that I have to send cats through double slits to measure to find out that on this scale there may be different effects than superposition. In other words: Your believing makes your world complete - but not mine. I am not sure if the theory holds on every scale. I trust in measurement.

 

[ZapperZ]

And on and on. We cannot see, even in principle, Entanglement Correlations. All we have are marks on paper written down from an experiment that flashed red light or green light when a button was pushed. There is no entanglement because marks on paper are not entanglement. The cat cannot be dead and alive but if a Probability Wave is given an OBJECTIVE MEANING then there exists a situation where YOU are dead and alive! "How do you feel?"

This is highly incorrect.

If I have two non-commuting observables, A and B, and [A,B] is not zero, then a measurement of A does NOT collapse anything related to B, and the reverse is also true. So I can easily make some measurement of B, and see if there are particulars of what I measure in which I can detect the effect of A being in a superposition.

This similar concept is what is done in, say, the Delft/Stony Brook experiments. The existence of the coherence energy gap is a DIRECT result of the superposition of the supercurrents! You can verify this by looking at the physics done by Tony Leggett. I really don't need to actually make a measurement of the amount and direction of the current. By not doing that, and measuring something else, I preserved that superposition, and detect its direct effect on another observable.

Zz.

 

[Charles Wilson]

ZapperZ

I have no problem with that! My points are about the development of Thought about QM. I don't doubt QM results. I'm NOT arguing that they are meaningless! That's the point. See my initial post on this on page 1.
The original post was, "I don't understand about Schroedinger's Cat. How can it be both dead and alive?"

Well, if you are looking AT THE CAT, then it cannot be both Dead AND Alive. You can set the experiment so that YOU are seen by others as having to be both dead AND alive. "How do you feel?" For decades, these problems were not dealt with.

Einstein and Bohr went round and round and I think they both missed the action, although I side with Einstein a lot. I don't argue for Local Realism and there are NOW lots of Real Math reasons for denying it, with experiments based on Real Math that give results every time.

My question is still, "How does QM (and non-locality) map onto our perceived World - without the Kantian/Hegelian stuff? By all means, keep posting things that you find!

So, if I still haven't given a coherent answer to what you stated, tell me what I should edit out of my above post and I will be happy to delete or rewrite.

CW

 

[1977ub]

MWI has an infinity of universes where cat is alive, and then a 2nd infinity where they are all dead.

http://en.wikipedia.org/wiki/Many-worlds_interpretation

 

[bhobba]

Since in the thought experiment we cannot look into the box then unless we can demonstrate that generally a wave function can collapse without a measurement taking place we simply must assume the cat is in superposition.

Its not. Long before the vial breaks etc decoherence occurs (evidently a few stray photons or even a single oxygen atom is enough to cause decoherence) and the particle is in an improper mixed state. It is perfectly legitimate to assume the improper mixed state is an actual mixed state meaning the particle really is there prior to detection by the particle detector. That's when the observation occurs - not when the box is opened. Most definitely the cat is not in some weird state of superposition - the particle prior to decoherence - yes - but that occurs very very quickly. All you have to do is assume the improper mixed state is an actual mixed state - no mathematical analysis or observation can prove you wrong and all this weirdness goes away. Other ways to resolve it are via Many Worlds and Decoherent Histories - but to me the easiest and simplest solution is this simple interpretation of decoherence. Why anyone want's to maintain the cat is in some weird state of superposition is beyond me.

Thanks
Bill

 

[bhobba]

First: What about the cat? Isn't it an observer?

Yea - but if its dead it can't really observe anything. However important semantic issue. We have observations in QM which semantically makes people think you must have an observer - in fact in QM an observation is anything that registers in the macro world. The particle detector is where that occurs first and is the observation that collapses the wavefunction - but with decoherence taken into account it is perfectly legitimate to assume, since decoherence would have occurred well before being detected by the particle detector, the particle was there prior to observation. In interpretations that use decoherence that's when the observation occurs and decoherence occurs very very quickly. The exception is Many Worlds when the mixed state of decoherence continues evolving regardless.

Thanks
Bill

 

[bhobba]

So it is clear, at least to me, that size isn't the issue, but rather the ability to have every part of that object in coherence is the most significant obstacle to observing quantum effects at large scales.

Very true - or at least its clear to me as well.

But for a live and dead cat in our normal macro environment as envisioned in this experiment they do not interfere - decoherence is well and truly in force in that situation - and just as an aside it is actually quite hard to show superposition effects for macro objects - but as you point out - correctly - it can be done. At any time the cat is alive or dead (ignoring of course the time it takes the cat to die via the gas) not in some superposition. The 'measurement' and 'collapse' in this thought experiment occurs at the particle detector - not the cat. Thats where the 'weirdness' lies.

Thanks
Bill

 

[1977ub]

Quantum Suicide & Immortality
http://en.wikipedia.org/wiki/Quantum_suicide_and_immortality

 

[Crazymechanic]

As to Zapper for your last post I agree and actually this is the way police has been chasing killers and suspects for many decades , they never try to interfere with the criminal rather they measure what his actions are and stay under the radar so that he wouldn't understand that his being chased.And this all just for the sake of getting enough evidence.
The scientists too try to preserve the original state of things so that they could see the outcomes without disturbing the "main element"

But I would have to argue that it is actually not superposition in the way we want to see it.Now you said that by measuring A you don't have to necessarily destroy B or collapse B wave function.
Ok I can agree to that but just because you haven't interfered with a state that doesn't mean the state hasn't got some properties already to it.AKA just because we haven't or can't see in the "box" without destroying it 's state of things doesn't mean that the state has all the possible outcomes at once.
i think rather QM is like a tiger in the jungle , he lives his own life and nobody knows what is he doing or where he is, now we can search for some indirect clues and judge by those the life of the tiger and his eating and living standards or we can directly approach him and disturb his natural "wave function" and measure a result , either way he has had his own life even when we were not around and now when we are around he just is in a certain given situation and chooses a certain given action and as with tigers so they say with bees you never know what they will do so unless you "measure" you can't be sure of the state their in.

Also I don't like when they say that upon measurement the system has to choose a state to be in but I find that kinda stupid , the atom or system or whatever you call it doesn't have to choose or think or whatever we say it does it just is in a certain state all the time and upon measurement there is a great chance that some interaction can or will occur and it will now be in a different state and that will be the final state that will show the measurement outcome.
The atom or elementary particles are not some self aware things (to our best understanding) that can choose.

Now ok theoretically let's assume we could put objects of billions of atoms in superposition under some extremely tight conditions at laboratory at near absolute zero temperatures now the meaning dead or alive would loose it's meaning because who has seen a living organism able to stay alive at temperatures when particles themselves almoust "freeze" ? :D
And we wouldn't say the state of dead or alive to a copper wire or a old tv set would we?
So to make the experiment is impossible even if we could achieve the right conditions under them the cat would die even before the atom would have ever got the chance to decay.

Now pardon me if I am wrong but currents passing around a loop at almoust absolute zero temperatures is not that perfect of a cat in a box proof it's rather a proof that if you can put particles and atoms in tightly controlled conditions then you can make them stay in a certain state but they are still one state at the time not in all possible sates at once right? Right.

 

[ZapperZ]

Crazymechanic: you are contradicting the content of several published papers that I cited. I suggest you submit a rebuttal to those papers and get them published first, or else what you are trying to do is considered unpublished speculation.

Zz.

 

[DrChinese]

...

But I would have to argue that it is actually not superposition in the way we want to see it.Now you said that by measuring A you don't have to necessarily destroy B or collapse B wave function.
Ok I can agree to that but just because you haven't interfered with a state that doesn't mean the state hasn't got some properties already to it.AKA just because we haven't or can't see in the "box" without destroying it 's state of things doesn't mean that the state has all the possible outcomes at once.

i think rather QM is like a tiger in the jungle , he lives his own life and nobody knows what is he doing or where he is, now we can search for some indirect clues and judge by those the life of the tiger and his eating and living standards or we can directly approach him and disturb his natural "wave function" and measure a result , either way he has had his own life even when we were not around and now when we are around he just is in a certain given situation and chooses a certain given action and as with tigers so they say with bees you never know what they will do so unless you "measure" you can't be sure of the state their in.

...

If you look at your reasoning carefully, you are actually assuming that which you are trying to prove. On the other hand, every single piece of experimental evidence points in the opposite direction.

 

[Crazymechanic]

Hmm okay fair critique, i re read my post one more time as I was writing in the morning a little sleepy but yet I can't find where is all the wrong things that I have said ??

@DrChinese now isn't every one even those who go out and publish a theory assuming what they prove? We all have somekind of a natural bias towards some opinion (not speaking about crackpots here ) all reasonable people do have some assumptions based on some either proven or very likely to happen logic.
Now quantum mechanics so happens to be one of the subfields in physics that is very tied up with assumptions and philosophy actually.because as other forum members before me on this thread pointed out and quit rightly that there are a lot of things we put forward without empirical evidence , sometimes we get the evidence after decades sometimes there is a great chance for us to never get it due to physical laws or the way nature works.

Now call me crazy (which I am actually) but the only thing in my post I could find that would be the object of ZapperZ and DrChinese objection is the fact that I stated that I "believe" that quantum states exist before we even look at them and take a measurement, rather the measurement only collapses the state in which they were and a new one emerges due to the measurement being an interaction in QM.
Now what is so contradicting there ?

 

[DrChinese]

... @DrChinese now isn't every one even those who go out and publish a theory assuming what they prove? ...

No, of course not. And certainly any working assumptions one makes is not an argument in its favor. And throwing out only the evidence that works against your assumption is the first step of a crackpot. You have been around here enough to know that experimental results are given a great deal of weight.

 

[Nugatory]

I "believe" that quantum states exist before we even look at them and take a measurement, rather the measurement only collapses the state in which they were and a new one emerges due to the measurement being an interaction in QM.
Now what is so contradicting there ?

That was at one time a quite respectable position; seeing as how it was at one time Einstein's position, you're in good company .

But would you continue to maintain this position after we've done experiments that yield results that cannot be produced by ANY state that exists before the measurement? The Bell experiments are getting pretty damned convincing these days.

 

[Crazymechanic]

Well yes I do believe empirical evidence is the backbone of physics , ok I guess I'll take another look on the recent papers both linked in this thread or in other sources.As I am not the top person that follows everything quantum mechanical rather the basic rules and the logic or common sense as much as there is any in the case of QM.

So just in case the "up to date" conclusion about the cat in he box or any other state of superposition is that basically the observer made collapse of the system at a given point is also the moment when the system takes a certain shape aka state and before that not only we have no way of knowing what is happening in the "box" but there is a great chance that maybe there is no result in the box and the result become instant and defined in the very moment when there is an observer around to witness ?

 

[Nugatory]

So just in case the "up to date" conclusion about the cat in he box or any other state of superposition is that basically the observer made collapse of the system at a given point is also the moment when the system takes a certain shape aka state and before that not only we have no way of knowing what is happening in the "box" but there is a great chance that maybe there is no result in the box and the result become instant and defined in the very moment when there is an observer around to witness ?

The observer is not needed; the superposition goes away when it interacts with the larger environment around it, as it would with just about any measurement or interaction with any measuring apparatus.

Worth remembering about the Schrodinger's cat thought experiment: Schrodinger invented it as a criticism of the then-standard interpretation of QM. The point of the cat in the box is that something had to be wrong with the way that QM introduced this boundary between the macroscopic/classical world and the microscopic/quantum world.

 

[Crazymechanic]

Well I wasn't actually thinking about the observer as somebody specific , I do know that in QM an observer to collapse a state can be pretty much any interaction that the particle or atom or system encounters in it's way.

But this semantic doesn't change the main though of my previous question which with all respect you didn't answer.

I know the superposition goes away under interaction just as you get dressed whenever you get out on street but the question was is there a state before the collapse before the small subsystems encounters the larger one or so?
is there a chance that a quantum system is at a certain state before it ever encounters something in it's way I do know that there is zero chance of us ever knowing if it had some state prior to the one we measured upon interaction because superposition is basically telling that before the measurement the system can be in either one of the possible states which I objected to as saying that how can something be in many states at once , that was the one of main arguments about this thread in general it was also what I asked and assumed and said and it was also the thing about which ZapperZ and Dr Chinese made me some critique.
@DrChinese well empirical evidence do play a huge role so is there any real physical evidence for superposition other than the mathematical outcomes we get when solving equations in a theory we made about quantum mechanics that is just like most of the physics theories almoust or partly right.
Now I'm not trying to deny basic physics or being a crackpot rather just squeezing the last juice out of this thread to put it to rest

Now I would be honored to hear some opinion from these fellow members also from you Nugatory. :)

 

[BruceW]

What do you mean by "is in a state before collapse" ? Do you mean like (for example) an electron in orbit around the hydrogen having a specific position, even though the position has not been measured? This is a 'hidden variable theory'. And there is nothing wrong with it per se. But as others have probably already said, hidden variable theories are not favoured because many consider them to be a very not useful way to interpret quantum mechanics. And also, some hidden variable theories actually make different predictions to quantum mechanics. But there are hidden variable theories which make the same predictions as standard quantum mechanics (and are therefore an 'interpretation' of quantum mechanics, really).

edit: this is my understanding of it anyway. I was never taught about the interpretations of quantum mechanics, only how to apply it to basic problems. So I am not 100% sure about the definitions of various interpretations.

 

[bhobba]

So just in case the "up to date" conclusion about the cat in he box or any other state of superposition is that basically the observer made collapse of the system at a given point is also the moment when the system takes a certain shape aka state and before that not only we have no way of knowing what is happening in the "box" but there is a great chance that maybe there is no result in the box and the result become instant and defined in the very moment when there is an observer around to witness ?

The 'up to date' conclusion of how an observation causes collapse, or even if it occurs at all, is entirely interpretation dependant. The least favored one these days is that an observer caused it or was required to be around to witness it - it for example makes a mockery of computer science and the objective existence of information in a computer system if taken to an extreme. The last great holdout to that view was probably Wigner but even he changed his mind when he heard about some early work on decoherence by Zurek. The modern champion of it is Hameroff and Penrose:
http://www.quantumconsciousness.org/index.html

But it is very much a minority view.

Thanks
Bill

 

[bhobba]

What do you mean by "is in a state before collapse" ?

I think he means the discontinuous change in state caused by observation.

I was never taught about the interpretations of quantum mechanics, only how to apply it to basic problems. So I am not 100% sure about the definitions of various interpretations.

Probably a wise move of those that designed the courses you learned it from or the books you chose if self taught like me.

The usual issue with interpretation is how to overcome some of the weirdness of the formalism such as between observations the state changes continuously and deterministically but when an observation occurs it changes randomly and discontinuously. The other issue is what Kochen-Specker tells us. It basically means, without other factors taken into account, such as decoherence, the outcome of an observation can't be there prior to observation. Of modern times, while not solving the previous issues to everyone's satisfaction, decoherence has shed a lot of light on it and research is ongoing.

My suggestion to those interested in, or simply want to investigate interpretations, is to get Decoherence and the Quantum-to-Classical Transition by Maximilian Schlosshauer:
https://www.amazon.com/dp/B000SJ155C/?tag=pfamazon01-20

It isn't a book about interpretations per-se but it does examine them quite well in the light of decoherence. And even aside from its application to interpretations its a very interesting area anyway. I have a copy and along with Ballentines book - QM - A Modern Development made a big impact on my understanding of what's going on in QM.

Thanks
Bill

 

[Crazymechanic]

pretty close with your post Bruce.
Well I guess hidden variables or not they are favoured or dismissed rather based on how they work out in terms of equations than what seems logic or not.
just like any other physics theory he language is math.
Actually in QM we have limited capabilities of "seeing" what's going on so I guess we have to rely on math heavily.
it just so happens to be that math is not my best friend around and I rather make my assumptions based on the opinions of people "who know things" or the insiders and my personal common sense and some philosophy.
Well @bhobba the fact that upon measurement the state changes unpredictably is not a problem because the fact that every measurement is also an interaction in QM is fine.It also follow the logic based on what we have seen.The problem as always is with the things we haven't or can't directly or indirectly see or tell.This is the place where people go like "hey opinions" and as in every place some consider their opinion better and etc etc.
So how we find out what happens at the states before measurement I guess we haven't , we just made an opinion and some math and found that happy and good.
Actually I don't care for a certain opinion in QM is not like having a debate about your wifes cooking level.
I just want the truth and if the truth is that we yet don't know then let it be.

@ZapperZ the link you gave """http://physicsworld.com/cws/article/news/2010/mar/18/quantum-effect-spotted-in-a-visible-object"""
it is said there that quote """the team measured the quantum state of the resonator by connecting it electrically to a superconducting quantum bit or "qubit" --connecting it electrically is the key point here I guess.

So basically what they did is they made a supersmall tuning fork with the right materials that would have great qm properties at temperatures almoust absolute zero to see quantum properties undisturbed by any thermal action no mater how small.
But isn't the qubit that is connected electrically even though superconducting at such temperatures isn't the measurement still a state collapse? because even if the temperatures are good to not have any disturbance from outside the qubit itself is the observer in this case.
So how did they came to conclude that the resonator has a excitation and hasn't one at the same time ,I guess they first measured the qubit and it showed no excitation and then measured it again and it showed an excitation probably from some kind of a interaction with the qubit's own electrical impulse or whatever is there so isn't this still just measuring one object at different states but not both in the same time?

Pardon me if I am wrong but this sounds like seeing one is sleeping then coming again in the same way but accidentally making a little noise somewhere on the floor that I;'m not even aware of but which wakes the person up and now I see him awake , and after ten minutes maybe he would fall asleep again.The interaction is always there but without it I would not know if he is asleep or awake.
Ok please comment if you find it worthwhile P.S. Even though philosophy is forbidden on PF it is kinda funny to see that the QM section is one of the sections here where thread end up from some maths to pure philosophy , I think there is a good reason why...
I have seen many long threads here like that some of them even copied out because they were too long to read.

 

[jambaugh]

One problem is in the phrase "superposition of states". Quantum superposition reflects the resolution of a given "state" in a specific basis ("of states"). The "presence" of superposition is in the relationship between the observed system mode and the choice one makes of basis. You can always pick your basis so that there is no superposition. It is like choosing principle axes for the moment of inertia tensor so it becomes diagonal or more aptly resolving a general motion as a "superposition" of horizontal and vertical motions when we resolve a displacement vector in a given basis.

In short don't inadvertently think that "being in a superposition" is a physical property of either the Cat or of an atom. Superpositions arise specifically as a relationship between measurement devices. (e.g. the device measuring position of a particle and the device measuring momentum of a particle.) Superposition then arises when we try to reconcile facts observed from one device with predictions about what will be observed by a complementary device. A definite outcome of one resolves as a superposition of outcomes for the other. Nowhere in that is the system itself in some "weird superposition".

State vectors represent states of knowledge about the system not states of the system! (Orthodox Interpretation.)

 

[f95toli]

In short don't inadvertently think that "being in a superposition" is a physical property of either the Cat or of an atom. Superpositions arise specifically as a relationship between measurement devices. (e.g. the device measuring position of a particle and the device measuring momentum of a particle.)

I sort of agree with this. However, there are plenty of cases where it is -in my view- quite clear what the states that are in a superposition correspond to classically.
An obvious example would be a flux qubit, where the two states correspond to a current flowing clockwise or anti-clockwise.
Another example would be the orignal solid state qubit which was a charge qubit, here the two states correspond to 0 or 1 extra electrons on a mesoscopic island. There are many other cases, mostly from solid state QIP.

The reason or why these examples are -in my view- much more illuminating than examples from atomic physics or optics, is that the states that are put into a superposition also exist classically (if you want your qubit to become a classical system you can just warm it up a bit), whereas there is no such thing as a classical atom or photon.

Hence, any explanation that tries to avoid "quantum weirdness" for solid state QIP devices becomes pretty convoluted.

 

[jambaugh]

I sort of agree with this. However, there are plenty of cases where it is -in my view- quite clear what the states that are in a superposition correspond to classically.
An obvious example would be a flux qubit, where the two states correspond to a current flowing clockwise or anti-clockwise.
Another example [...]

The reason or why these examples are -in my view- much more illuminating than examples from atomic physics or optics, is that the states that are put into a superposition also exist classically (if you want your qubit to become a classical system you can just warm it up a bit), whereas there is no such thing as a classical atom or photon.

Hence, any explanation that tries to avoid "quantum weirdness" for solid state QIP devices becomes pretty convoluted.

I'm not sure I see the issue. Again "in a superposition" is just relative to choice of observables.
A definite spin z-up electron, which we can quite clearly understand in terms of the classical analogue of a rotating mass, is also in a superposition of spin x-"up" and spin-x "down" states. Saying it is "in superposition" or "not" is simply a question of which component is being classically analogized.

Secondly the "quantum weirdness" is imnsho not to be avoided but understood. And that understanding starts with not thinking of "being in a superposition" as if it were some system switch we can turn on or off. I think too many people working in quantum information get caught up in that point. Clearly in a classical computer one wants to be very conscious of the state of the state machine. But that is just the wrong way to think in QM and hence in quantum computing. It is, I think, better to use a communications channel paradigm rather than state machine when invoking e.g. qubits. (The spin of) An electron can be though of as a binary channel able to encode a classical bit in one of a continuum of ways. The quantum comes into play when one is writing in one basis and reading in a different one... and even more fun playing with many qubits which can not only be encoded in many ways but factored into components in many different ways hence we get entanglement phenomena.