Copenhagen Interpretation of Sleep / Unseen brain?

[Derek Potter]

It doesn't explain why you do. Technically it's why an improper mixed state is a proper one.

I don't understand why we have to have a proper mixed state. What's wrong with an improper mixed state if it does the job of explaining the appearence of outcomes?

 

[atyy]

I don't understand why we have to have a proper mixed state. What's wrong with an improper mixed state if it does the job of explaining the appearence of outcomes?

I don't totally agree with bhobba's way of stating the measurement problem, but I think I understand it. What he means is that if we just have a unitarily evolving wave function, we clearly have no outcomes unless there are some additional assumptions. So the job of any interpretation that solves the measurement problem is to add assumptions that produce the outcome. For example, many worlds adds the assumption that blah, blah, blah ...

 

[Derek Potter]

QUOTE="atyy, post: 5163488, member: 123698"]I don't totally agree with bhobba's way of stating the measurement problem, but I think I understand it. What he means is that if we just have a unitarily evolving wave function, we clearly have no outcomes unless there are some additional assumptions. So the job of any interpretation that solves the measurement problem is to add assumptions that produce the outcome. For example, many worlds adds the assumption that blah, blah, blah ...[/QUOTE]

"Many worlds"? Never heard of it.

I'll put my question another way. Rather than asking how measurement creates a proper mixed state, shouldn't we ask whether it actually does so?

Why do we need outcomes at all? We know that measurements create the appearence of outcomes in the macro world, but the improper mixed state that bhobba referred to (and which does follow from unitary evolution) would, to my simple mind, solve this part of the measurement problem. I don't see the need to insist that the appearence of a mixture must be explained by the mixture being proper. In fact, in the last paper bhobba referred me to, Hensen makes it perfectly clear (section 1.2.3.) that they (case 2 and 3) are indistingishable at the level of observation since they yield the same probabilities. So I'm left asking what role is played by a proper mixed state that cannot be played by an improper one? If decoherence can provide an improper mixed state in which the observer apparently sees a particular outcome, why does this not solve the problem?

edit - Hensen's paper says that it superficially solves the outcome problem (bottom of page 39) but I don't understand the grudging "superficial". Nor the subsequent rejection of the ignorance interpretation.

 

[atyy]

I don't totally agree with bhobba's way of stating the measurement problem, but I think I understand it. What he means is that if we just have a unitarily evolving wave function, we clearly have no outcomes unless there are some additional assumptions. So the job of any interpretation that solves the measurement problem is to add assumptions that produce the outcome. For example, many worlds adds the assumption that blah, blah, blah ...

"Many worlds"? Never heard of it.

I'll put my question another way. Rather than asking how measurement creates a proper mixed state, shouldn't we ask whether it actually does so?

Why do we need outcomes at all? We know that measurements create the appearence of outcomes in the macro world, but the improper mixed state that bhobba referred to (and which does follow from unitary evolution) would, to my simple mind, solve this part of the measurement problem. I don't see the need to insist that the appearence of a mixture must be explained by the mixture being proper. In fact, in the last paper bhobba referred me to, Hensen makes it perfectly clear (section 1.2.3.) that they (case 2 and 3) are indistingishable at the level of observation since they yield the same probabilities. So I'm left asking what role is played by a proper mixed state that cannot be played by an improper one? If decoherence can provide an improper mixed state in which the observer apparently sees a particular outcome, why does this not solve the problem?

edit - Hensen's paper says that it superficially solves the outcome problem (bottom of page 39) but I don't understand the grudging "superficial". Nor the subsequent rejection of the ignorance interpretation.

Can I avoid answering the details by saying that I think I agree with your general point, and I am not totally in agreement with this way of stating the measurement problem as being only the problem of outcomes?

How would you state the measurement problem?

 

[Derek Potter]

:

Can I avoid answering the details by saying that I think I agree with your general point, and I am not totally in agreement with this way of stating the measurement problem as being only the problem of outcomes?
How would you state the measurement problem?

As Schlosshauer seems to feature highly here, I don't see the problem with using his general description:
The problem is, then, how to reconcile the vastness of the Hilbert space of possible states with the observation of a comparatively few “classical” macrosopic states, defined by having a small number of determinate and robust properties such as position and momentum. Why does the world appear classical to us, in spite of its supposed underlying quantum nature, which would, in principle, allow for arbitrary superpositions?
Key phrase here: "appear classical". I don't see the need to presuppose that it actually is classical.
Why do you ask?

 

[atyy]

: As Schlosshauer seems to feature highly here, I don't see the problem with using his general description:
The problem is, then, how to reconcile the vastness of the Hilbert space of possible states with the observation of a comparatively few “classical” macrosopic states, defined by having a small number of determinate and robust properties such as position and momentum. Why does the world appear classical to us, in spite of its supposed underlying quantum nature, which would, in principle, allow for arbitrary superpositions?
Key phrase here: "appear classical". I don't see the need to presuppose that it actually is classical.
Why do you ask?

I'm actually not fond of Schlosshauer's description. I prefer the classic how to have quantum mechanics without a fundamental status for observers. I asked because bhobba was just stating one of Schlosshauer's versions of the measurement problem, and since you were taking him to task about some detail of his version, I was wondering what yours is.

 

[Derek Potter]

I'm actually not fond of Schlosshauer's description. I prefer the classic how to have quantum mechanics without a fundamental status for observers. I asked because bhobba was just stating one of Schlosshauer's versions of the measurement problem, and since you were taking him to task about some detail of his version, I was wondering what yours is.

I don't actually see much of a difference between having QM without a fundamental status for observers and having QM with classical appearence, except that the latter would tolerate ad-hoc postulates, such as the special role of observations, and these need to be eliminated if the measurement problem is not to be trivialised. The implicit aim in both cases is to derive the projection/observer/probability postulate from the state/unitary/Hilbert postulate. Of course the former postulate may be phrased in different ways by different people so we need to make sure we are not trying to prove something that is not needed. Asserting actual collapse of a wavefunction would be overkill.

 

[VALENCIANA]

Well, we don't know where collapse of the wave function occurs. It could be at the detector, or on the more extreme side it could be consciousness. Or we may find we need to modify standard QM to allow for collapse e.g. by gravity.

By 'every object is a wave', I hope you don't mean wave in the classical sense.

 

[VALENCIANA]

What is the accepted interpretation of these two similar related issues:

1) When I am sleeping do my brain and body revert to un-collapsed wave state until and unless seen by a different observer?

2) I *never* have "seen" my brain - have the wave functions of the atoms and cells collapsed?

 

[VALENCIANA]

Do we we know what is exactly the wave function and the collapse (if there actually is a collapse) to differentiate between what happens when we are awake or asleep , or dreaming?
Is dreaming very different from reality?

 

[VALENCIANA]

What I mean is that there shouldn t be any difference between a wave function collapse in the brain and body when we are awake than when we sleep.
From an objective point of view, it should be the same.

 

[ynon]

1977ub: The accepted interpretation? Get a bunch of physicists, doctors, preachers or lawyers together and you get many so called " accepted interpretations". The state of your body or brain is not affected by someone or some thing by simply observing, visual or otherwise. Whatever state it is in is what the observer will observe. Your not having seen your brain is good but it has nothing what so ever to do with any state it may be in.Many try to apply QM behavior to the macroscopic real world events. Nope. You see a fallen tree because it had already fallen. Not visa versa. Cats are never dead and alive. Sometimes they just seem that way. Strilanc nailed it. Welcome fellow new member.

 

[Weinsyein]

Sleep physiology is not in the realm of quantum physics. Turns out, when you are asleep your brain is very active. Your "consciousness" is one of the functions of your brain. Typically, when asleep, you do not have conscious functions. ...

 

[1977ub]

1977ub: The accepted interpretation? Get a bunch of physicists, doctors, preachers or lawyers together and you get many so called " accepted interpretations". The state of your body or brain is not affected by someone or some thing by simply observing, visual or otherwise. Whatever state it is in is what the observer will observe. Your not having seen your brain is good but it has nothing what so ever to do with any state it may be in.Many try to apply QM behavior to the macroscopic real world events. Nope. You see a fallen tree because it had already fallen. Not visa versa. Cats are never dead and alive. Sometimes they just seem that way. Strilanc nailed it. Welcome fellow new member.

As helpfully commonsensical as your response is, what it does not do is address QM > Classical reality transition.
I know that some % of experts do in fact regard consciousness as causing the wavefunction collapse.
Otherwise what initiates a "measurement" ? Why does not a particle's expanding wavefunction not simply interact with the wavefunction nature of particles in the experimental apparatus without ever reducing to a particular position? I gather in MWI there is no collapse - all interactions of particle wavefunctions exist in the multiverse.

https://en.wikipedia.org/wiki/Von_Neumann–Wigner_interpretation
https://en.wikipedia.org/wiki/Measurement_problem

 

[bhobba]

Do we we know what is exactly the wave function and the collapse (if there actually is a collapse) to differentiate between what happens when we are awake or asleep , or dreaming? Is dreaming very different from reality?

Before discussing this one needs to know what a wave function is:
http://www.scottaaronson.com/democritus/lec9.html

Once you do its obvious comments like the above don't even make sense.

Its like asking if how a roulette wheel works and what number comes up depends on if you are dreaming or not - its obvious, and very obvious at that, its got nothing to do with anything.

Thanks
Bill

 

[bhobba]

I know that some % of experts do in fact regard consciousness as causing the wavefunction collapse.

Its a very very small percentage. It originated from an argument Von Neumann made in his highly influential Mathematical Foundations Of Quantum Mechanics. But since then we understand decoherence a lot better and its now realized his argument no longer holds water. Personally I believe the very small percentage that do haven't thought about the issue carefully enough.

Otherwise what initiates a "measurement" ?

Interaction causing entanglement.

Why does not a particle's expanding wavefunction

Wavefunctions do not in general expand - instead they get entangled with the environment.

Thanks
Bill

 

[themaea]

It doesn't explain why you do. Technically it's why an improper mixed state is a proper one.
http://philsci-archive.pitt.edu/5439/1/Decoherence_Essay_arXiv_version.pdf

Thanks
Bill

atyy, bill.. I think there is a mistake inside the paper above.. specifically in section 1.2.3 where:

"However, note that even though 2 = 3, their physical interpretation is not
quite the same. System 2 is in a definite deterministic physical state, whereas
system 3 is part of a composite superposition state. Its physical state is truly
undetermined, as long as no measurement is performed on \part B" of system
3 (that we removed from our control). System 2 is said to be a proper mixture,
versus system 3 which is in a improper mixture. When a measurement
is performed on the discarded part B of system 3, but we are not told of the
outcome (ignorance), system 3 reduces to a proper mixture, and systems 2 and
3 are then physically identical."

The mistake is for system 3 to reduce to a proper mixture.. there is a collapse somewhere.. whereas in system 2.. there is no issue of collapse.. so how can they be physically identical?

 

[bhobba]

The mistake is for system 3 to reduce to a proper mixture.. there is a collapse somewhere.. whereas in system 2.. there is no issue of collapse.. so how can they be physically identical?

Because there is no way observationally to tell the difference.

They are INTERPRETATIONALY different however - remember collapse is an interpretational thing.

Thanks
Bill

 

[atyy]

atyy, bill.. I think there is a mistake inside the paper above.. specifically in section 1.2.3 where:

"However, note that even though 2 = 3, their physical interpretation is not
quite the same. System 2 is in a definite deterministic physical state, whereas
system 3 is part of a composite superposition state. Its physical state is truly
undetermined, as long as no measurement is performed on \part B" of system
3 (that we removed from our control). System 2 is said to be a proper mixture,
versus system 3 which is in a improper mixture. When a measurement
is performed on the discarded part B of system 3, but we are not told of the
outcome (ignorance), system 3 reduces to a proper mixture, and systems 2 and
3 are then physically identical."

The mistake is for system 3 to reduce to a proper mixture.. there is a collapse somewhere.. whereas in system 2.. tere is no issue of collapse.. so how can they be physically identical?

System 2 is already a proper mixture, so you can think of it as already collapsed.

 

[ynon]

1977ub: I like to think my approach to QM is commonsensical though common sense may not always apply to QM at this time. I don't know the transition between QM and classic reality or if there even is one but I don't think consciousness has anything to do with it. The principles of QM were operating many years before consciousness.There should be some transiton I would think.

Think of wave-particle duality. Recently controversial. Experiments " prove it is a particle". Other experiments "prove it is a wave". It could be both and we simply see different views of the same phenomena. For an analogy think of a quarter spinning on a table.You see heads and tails superimposed, the quarter collapses and you see heads or tails. It decided on tails or heads before you observed it as heads or tails. .

.You see a fallen tree laying on the ground, you didnt see it fall. Observation causing it to be fallen means you caused it to fall in the past. Unlikely.However without an observer to hear it fall it would not produce sound because sound is what is heard. A lady was bragging about her new hearing aid. Her friend asked what kind it was. She replied, " 12:30".

A large % of experts do regard consciousness as causing the wavefunction collapse .Some dont. It would explain some things but that is no proof. . Also MWI is just conjecture and is nice for Sci-fi story lines but the fact that it would explain some things isn't much of a proof. There being a God would explain many, many things but is no proof. My humble opinions at this time.

 

[rootone]

A large % of experts do regard consciousness as causing the wavefunction collapse .

Um, source please?

 

[ynon]

rooton: Sorry about that . My source was 1977ub. I incorrectly remembered him saying large % instead of small and didnt notice as I was discounting them altogether anyway. I will double up on the ginko biloba. Works if you remember to take it. I don't believe consciousness causes wave function collapse. .. It is unfortunate that any believe this. Makes for great Sci-fi though.

 

[bhobba]

Think of wave-particle duality. Recently controversial.

Not recently.

It was chucked in the bin in 1926 when Dirac came up with his transformation theory - likely sooner.

Please don't get hung up on this. We spend far too much time here arguing about this point. Its in beginner texts but not advanced ones. If you want to develop a modern understanding of QM forget about it.

Thanks
Bill

 

[Derek Potter]

The mistake is for system 3 to reduce to a proper mixture.. there is a collapse somewhere.. whereas in system 2.. there is no issue of collapse.. so how can they be physically identical?

I think he means they end up the same, not that they are the same from the beginning.

Hensen's mistake, if any, is in System 2 where he glosses over the fact that we choose a state at random from a "reservoir". Remember, this choice is part of the physical preparation of the system, it is not the mathematician's trick of choosing a typical member of an ensemble. In a quantum universe the choice is quantum and thus system 2 is an entanglement of A with the chooser and therefore identical to system 3 which is defined as improper!

As Kirkpatrick says "The proper mixture cannot be created".

I suspect system 2 can be rescued if you postulate wavefunction collapse so that the entanglement is broken. This is exactly what happens to system 3 - the measurement on B is assumed to result in a definite outcome, which implies wavefunction collapse.

I am convinced the distinction between proper and improper mixtures is an artifact that only appears under the assumption of collapse. Since the latter is optional - or as bhobba says, interpretational - it would appear to be a distinction without a difference.

 

[ynon]

Bhobba: I guess I felt the controversy recent because of older texts on the matter I do agree it is best not to get hung up on it though.Funny how people interpret things differently.Is a glass half full or half empty? A car accident can elicit many different but honest versions of the same incident. To me Dirac transformation seemed to validate wave-particle duality.All I have been crudely saying is what Wikipedia says below.For an analogy of the appearances I think of a quarter spinning on a table.You see heads and tails superimposed, the quarter collapses and you see heads or tails.Head or tail, same quarter. Only an analogy of course. .
I see what you mean, we are only talking about apparent aspects as it were. Not true waves or particles. I did know that but didnt specify.. A matter of semantics.
As the Beatles said, " and nothing to be hung about".I am wadeing through the Hilbert space thingy now.. Thank you.

"The term transformation theory refers to a procedure and a "picture" used by P. A. M. Dirac in his early formulation of quantum theory, from around 1927.[1]
(The term further sometimes evokes the wave-particle duality, according to which a particle (a "small" physical object) may display either particle or wave aspects, depending on the observational situation. Or, indeed, a variety of intermediate aspects, as the situation demands.)"Wikipedia

 

[bhobba]

"The term transformation theory refers to a procedure and a "picture" used by P. A. M. Dirac in his early formulation of quantum theory, from around 1927.[1](The term further sometimes evokes the wave-particle duality, according to which a particle (a "small" physical object) may display either particle or wave aspects, depending on the observational situation.

Wikipedia is usually solid - in this case it isn't.

Here is the correct historical context:
http://www.lajpe.org/may08/09_Carlos_Madrid.pdf

The transformation theory shifted QM to the state as the fundamental object - not matrices as in matrix mechanics, or wave as in wave mechanics.

Thanks
Bill

 

[Derek Potter]

Thanks
Boill

New sig, bhobba? :)

 

[ynon]

Bhobba: Thank you. I seek clarification and see why the term wave-particle is outdated. Still in lab at U of H and SWT light appeared to behave like waves or particles whether they were or were not. Maybe wave-appearing / particle-appearing duality would be more appropriate.Is there a word to call this characterist of light that is more succinct than: " MM and WM must always yield the same empirical decisions".?
"
Wikipedia needs your or someones input on this to include a more recent interpretation or definition with what they wrote.

It's still ham no matter how it is sliced. The word " matter" has different meanings depending on the context.Slice is one thing to a butcher and another thing to a golfer. "Pressure" has different meanings to a psychologist or gas station attendant. Define "is" . A defense used by a former president.

 

[bhobba]

Hi Ynon

You will find many threads discussing the issue - it will not be appropriate to rehash them. They tend to be long and simply go around in circles because ideas said in many beginning texts/popularisations are challenged and they are challenged by more advanced material the beginner may not understand the details of, so have to take the word of others.

But if you want to read about it here is a good article:
http://arxiv.org/abs/quant-ph/0609163

Also see our FAQ:
https://www.physicsforums.com/threads/is-light-a-wave-or-a-particle.511178/

Note,, while the paper above specifically states it, please keep in mind what it refers to as a wave is shorthand for wave-fuction, which is different to a wave eg waves are not complex values nor invariant to phase changes.

Here is a much much better foundation for QM than waves particle duality:
http://www.scottaaronson.com/democritus/lec9.html
http://arxiv.org/pdf/quant-ph/0101012.pdf

Thanks
Bill

 

[Feeble Wonk]

I'm actually not fond of Schlosshauer's description. I prefer the classic how to have quantum mechanics without a fundamental status for observers.

I'm not sure how you meant this. Are you saying that "classical" (I'm assuming that the same as "standard") Copenhagen interpretation still places a fundamental status on the role of the observer?