Does Observation Truly Collapse a Wave Function?

[Coldcall]

Hi reilly,

"And we assume, at least in our everyday life, there is a real world out there, quite independent of us. And that assumption has a great track record"

And that's why its probably a good thing that the macroscopic world behaves in that rational objective manner.

However i think its important that science tries to resolve the "measurement problem" even if it confirms materialist's worst nightmares

 

[Maaneli]

Maaneli: Both my and Dave's answer are witihin the Copenhagen interpretation of QM, the paradigm of QM, that is why we are giving the answers that we do. It is not missleading, it is just that we answer within the most accepted interpretation framework - the paradigm. Of course there are more interpretations of QM, but I think the OP (original poster) also asked within the framework of Copenhagen interpretation, hence - our answers will be within that framework too.

There is no evidence that the OP was assuming the Copenhagen interpretation. In fact, many of the questions he's asking are questions that CI cannot even answer. This is why I think it is misleading to talk about wavefunction collapse without qualifying first that you are giving your answer in terms of CI, and that there are other empirically equivalent formulations that don't require any wavefunction collapse to begin with, or that do include collapse, but in a much more rigorous way. Also, what if he's not even familiar with the definitions of and distinctions between CI, GRW, MWI, deBB, and others? Then it's even more misleading to just give a vague answer in terms of CI, without even telling him that it is from the CI and that there are other ways of answering his question which are quite different.

 

[Marty]

Hi, I think the problem of "collapsing" the wave function is rather a physical process of spontaneous emission of a macroscopic wave (say 1dm) function to a local bound atomic state (say 0.5nm). That makes it look like that the electron transfers from a wave to a particle. But it is still a wave at its final state!

All you need is a small component of the initial wave of the bound wave function. Then the electron want to recombine to the lower bound state, and in that process light (or phonon) is emitted. This process is described by QED.

Yes, this is what I mean by looking for a mechanism for the "collapse". In this case, however, it is worthwhile to note that the interaction does not have to be confined to a single atomic orbital...the incoming electron wave can simultaneously excite atomic orbitals distributed across the target, and they will therefore oscillate coherently, causing light to be radiated from the surface. I think we then need to look for a mechanism whereby the distributed electron wave recombines within the target material. But this should happen by normal electron wave interactions, as opposed to any sudden mysterious "collapse" process.

 

[Phrak]

This is why 'observer' is a poor choice of words; it doesn't require consciousness; it merely requires an interaction.

Precisely. And wavefunctions are continually collapsing. It requires some very careful (and only theoretically possible) tinkering to get systems not to collapse. And that tinkering increases in difficulty geometrically with the number of particles, which is why is virtually impossibnle with anyting but a couple of particles at a time.

What interpretation of quantum mechanics attributes a physical collapse to anything but an observer?

Note though, that while the photon may have collapsed the system, there is still a system "wrapped around this one" so to speak. This outer system that includes two things: the original system and the photon. Until that system is collapsed (by another interaction) there are two superposed states this outer system could be in: one where the photon interacted collapsing the system to state (a) and one where the photon interacted and collapsed the system to (b).

This makes no objective sense. A wave is either collapsed or it is not, unless you intend to define collapse as a subjective process, removed a distance from physical actuallity.

 

[Phrak]

There are a several Copenhagen interpretations of quantum mechanics, depending on who you read. Most seem to share in common the interpretation of the wave function as the probability amplitude of a particle. The collapse is a physical process that collapses the probability amplitude.

If anyone can explain how this physical process (collapse) has action on this nonphysical description of possibilites (the wave function) I would sure like hear it.

 

[Fra]

The heart of the matter and why modern interpretations try to eject the observer is because if an observer really is required then we live in a somewhat subjective universe in which obsevers play a central role. It would sort of contradict Copernican reasoning.

I think that "to get rid of the observer" would remove from the scientific ideals. There is no need to give up all order and expect random subjectivity just because one takes the observer view as fundamental. It may be a difficulty, but that's for us to solve, and I think this is more than just interpretations.

The story is somewhat similar in relativity. Every measurement is made relative to an observer, a reference frame. Two observers make different observations. But that does not leave us in random ambigouity, instead relativity comes up with relations between the subjective views.

So while there is freedom to choose observer, the relation between any two observers is not random, because after all they can communicate/interact with each other. This is what generates the relations.

I think the story is somewhat similar in the quantum world. So fundamental observer dependnence of observations, does not IMO imply total chaos.

But I still think that the quantum formalism needs revision, and it's more than just reinterpretations. I even think the observer view is the key to explaining many things. A new locality principle seems to naturally come in the sense that any observer bases his action only upon available information (ie. local information) - this can maybe even be taken as a definition of local. About causality, the sensible thing I see emerging is that it's related to locality in that it's the observers information" or lack thereof that determines his way of choosing questions. So I think the causality lies in the way of reasoning and asking questions, rather than one observation causing another. The overall result is that there is an emergent causality at statistical level.

I also think that when reformulating QM, we need to be more careful about intrinsic and extrinsic constructions. Just like the emission spectrum of systems are constrained, the possible questions a given system can ask are constrained. This means that some paradoxes appear when we ask questions that will in fact never be asked simultaneously from the instrinsic point of view.

I think QM needs revision, but the observer view is central. The question to me isn't how to get rid of it, it's what happens when two contradictory views clash - then I think we get interactions! So this is a possibility, not a pure problem as I see it.

/Fredrik

 

[Coldcall]

Fra,

"I think that "to get rid of the observer" would remove from the scientific ideals"

Yes but that is why other interpretations were theorised. And it's not a coincidence that most of the other interpretations do try to lose the observer as a factor of causation for wave collapse. Many-worlds is a great example of an arguably crazier idea about reality except for one saving grace - it removes any essentiality for an observer's presence. Each and every QM interpretation is a statement of philosophical inclination because the maths always the same. "observers" are the problem for many.

"There is no need to give up all order and expect random subjectivity just because one takes the observer view as fundamental"

I agree. Ther is no contradiction in accepting the observer related qm reality, and the more objective reality we encounter on a daily basis.

My point is that there is a deeper significance to the observer controversy which is based on the implications that perhaps observers play a more central role in the universe than is comfortable for most phycists with classical mindset.

Yes i agree with your thoughts on the similarity of observer status in both qm and Relativity.

"So I think the causality lies in the way of reasoning and asking questions, rather than one observation causing another. The overall result is that there is an emergent causality at statistical level."

Yes that's a very neat concept and i think Henry Stapp has some papers along the lines you allude to above. Ofcourse he believes that everything is conscious and i have my doubts about that; but i favour your idea above with a interrogation-like relationshsip between observer/observed.

I would add to that idea that qm appears a very efficient method for relating information only when it is required, and in neatly discreet values only! Kind of like the rat pecking one of those automatic feeders. It asks for and it gets one pellet.

"I think QM needs revision, but the observer view is central. The question to me isn't how to get rid of it, it's what happens when two contradictory views clash - then I think we get interactions! So this is a possibility, not a pure problem as I see it."

Personally i think we won't get to the bottom of it until we learn more about whether "consciousness" - whatever that means -is the qm causal agent hiding inside the observer :)

 

[dreynaud]

About "Decoherence" I said previously that Serge Reynaud participated to the experiment probing decoherence. I made a mistake : It was in fact Serge Haroche.

Please see the article reporting the experience of observing "real-time" decoherence : http://adsabs.harvard.edu/abs/1996PhRvL..77.4887BTitle : "Observing the Progressive Decoherence of the "Meter'' in a Quantum Measurement"

Authors: Brune, M.; Hagley, E.; Dreyer, J.; Maître, X.; Maali, A.; Wunderlich, C.; Raimond, J. M.; Haroche, S.

Abstract:
A mesoscopic superposition of quantum states involving radiation fields with classically distinct phases was created and its progressive decoherence observed. The experiment involved Rydberg atoms interacting one at a time with a few photon coherent field trapped in a high Q microwave cavity. The mesoscopic superposition was the equivalent of an `` atom+measuring apparatus'' system in which the ``meter'' was pointing simultaneously towards two different directions-a ``Schrödinger cat.'' The decoherence phenomenon transforming this superposition into a statistical mixture was observed while it unfolded, providing a direct insight into a process at the heart of quantum measurement.The pdf scan can be found here : http://www.atomwave.org/rmparticle/ao%20refs/aifm%20refs%20sorted%20by%20topic/decoherence%20refs/BHD96.pdf

 

[Coldcall]

There are a several Copenhagen interpretations of quantum mechanics, depending on who you read. Most seem to share in common the interpretation of the wave function as the probability amplitude of a particle. The collapse is a physical process that collapses the probability amplitude.

If anyone can explain how this physical process (collapse) has action on this nonphysical description of possibilites (the wave function) I would sure like hear it.

Me too

 

[per.sundqvist]

Yes, this is what I mean by looking for a mechanism for the "collapse". In this case, however, it is worthwhile to note that the interaction does not have to be confined to a single atomic orbital...the incoming electron wave can simultaneously excite atomic orbitals distributed across the target, and they will therefore oscillate coherently, causing light to be radiated from the surface. I think we then need to look for a mechanism whereby the distributed electron wave recombines within the target material. But this should happen by normal electron wave interactions, as opposed to any sudden mysterious "collapse" process.

Thats right for the "old" time-dependent Schrödinger equ. But, I think it can go only to one orbital though. The probability Psi(xc)^2 describe a probability of going to "that" atomic orbital. Its a competitive process for a short time, which you perhaps could model with random numbers in a computer.

The formula I gave only give us a hint of what's going on phenomenologically, but explains the Copenhagen interpretation in a nice way. The real thing including creation of light and destruction of incoming wave function and rising of the atomic orbital, is described within QED theory.

 

[QUANTUMQ]

thanks for all the replies theve been ,nice to see the different oppinions.
my questions were in the framework of CI but i would like to hear some of the oppositions to the CI. when reading werner Heisenbergs `physics & philosophy` he dedicated an entire chapter to the subject but ultimatly deemed all opposition as materialists.
also probably one of the most difficult questions there is. how would you personally describe consciousness?

 

[Phrak]

Re copenhagen interp, I said, "If anyone can explain how this physical process (collapse) has action on this nonphysical description of possibilites (the wave function) I would sure like hear it."

Me too

In retrospect it aint gunna happen. It's a utilitarian fiction, for which you are convenienced not to consider the hard questions.

 

[Fra]

Re copenhagen interp, I said, "If anyone can explain how this physical process (collapse) has action on this nonphysical description of possibilites (the wave function) I would sure like hear it."

In retrospect it aint gunna happen. It's a utilitarian fiction, for which you are convenienced not to consider the hard questions.

I am more optimistic. I think it will happen.

This is part of what I'm personally working on but though it's mind-boggling it looks to me very promising. But I think that the mathematics of QM will change too, and the old formalisms will be understood as a special case.

What we need to do is to find the physical basis of the quantum state vector, and the hilbert space it lives in. I think both the state vector and the hilbert space are observer dependent.

Alot of people in game theory treat probability, as a measure of degree of belief. However belief here must not be confused with higher intelligence. I rather think that nature it's contains a natural measure. So given any state of information, it does seem reasonable that there exists a measure on the space of differential changes. I expect here we can define an effective hilbert space. But as I see it the hilbert space is more like a tangent space, and it changes. So the probability space is like a guide on the differential changes.

So I think that what "should be" the state vector, is defined subjectively in the structure of the observer. This is why one can not directly and fully observe the wavefunction conditional on other observers. The only way we make partial observations is by means of interactions, by which we can guess parts of it.

Another component is the "logic of correction". If you have a certain belief, based on your current information. The impact on new information, is that there must be some internal reorganisation that revises your belief. And here clearly, there must be at play some competition. You are combining one piece of information, the prior, with the new observation, what is the intrinsic way of combining them to a new opinion? Clearly this question calls for evolving a logic of correction, since a system that fails to constructivel handle conflicts will not hang around. So I think there is a selection here.

This is often attacked by bayesian logic, but there is more to it than that.

/Fredrik

 

[Coldcall]

thanks for all the replies theve been ,nice to see the different oppinions.
my questions were in the framework of CI but i would like to hear some of the oppositions to the CI. when reading werner Heisenbergs `physics & philosophy` he dedicated an entire chapter to the subject but ultimatly deemed all opposition as materialists.
also probably one of the most difficult questions there is. how would you personally describe consciousness?

Well i think he was right in a sense. Most phycists who obsess about finding some other causal mechanism for wave collapse/decoherence other than the observer are usually materialists. However, materialists are really in a jam because clearly with or without an observer there exists a prior superposition. Materialists if being consistent would need to argue that Schrodinger's cat is actually in a physical state of half-life/half-death before were look in the box.

I really have no idea what "consciousness" is. All i would say is that it if i were investigating a tangible link or common denominator between humans and qm I'd be looking into "subjectivity". If we want to prove for once and for all that observers have some special quality able to act as a causal factor in wave collapse we need to isolate whatever that thing is.

 

[Pythagorean]

Re copenhagen interp, I said, "If anyone can explain how this physical process (collapse) has action on this nonphysical description of possibilites (the wave function) I would sure like hear it."

I'll give this a shot, but I could be mistaken:

Let's say a particle is jiggling around quickly, and you hit it with a photon (that you will receive and analyze with a detector after it bounces off your target particle). The photon must be able to interact with the particle if you want to get any information from it, so it will change the state of the particle (and change it's own state, which you will then analyze to determine how the particles state changed).

But since you have hit the particle with a photon, you (for intance) slowed it down by taking energy from it, so you have collapsed the wave function of it's position (collapsed is a relative term that I would think is based on your instrument resolution, but it basically means the wave function becomes a dirac-delta function and your position is determined more accurately.

The physical process that happened when you collapsed the wave function of the particles position is that you slowed it way down. It's momentum wave function may have become broader in the process (uncertainty principal) but you've made the position of the particle more stable.

 

[Coldcall]

I'll give this a shot, but I could be mistaken:

Let's say a particle is jiggling around quickly, and you hit it with a photon (that you will receive and analyze with a detector after it bounces off your target particle). The photon must be able to interact with the particle if you want to get any information from it, so it will change the state of the particle (and change it's own state, which you will then analyze to determine how the particles state changed).

But since you have hit the particle with a photon, you (for intance) slowed it down by taking energy from it, so you have collapsed the wave function of it's position (collapsed is a relative term that I would think is based on your instrument resolution, but it basically means the wave function becomes a dirac-delta function and your position is determined more accurately.

The physical process that happened when you collapsed the wave function of the particles position is that you slowed it way down. It's momentum wave function may have become broader in the process (uncertainty principal) but you've made the position of the particle more stable.

Do you think that this happens randomly in nature without an observer or scientist firing the photon at the particle? And if so how do we get evidence for it occurring? How do we observer without observing? What a conundrum!

 

[Pythagorean]

Do you think that this happens randomly in nature without an observer or scientist firing the photon at the particle? And if so how do we get evidence for it occurring? How do we observer without observing? What a conundrum!

Yes, I do think it happens in nature. I assume it's random, but you're never sure.

Maybe this thought experiment works to solve the conundrum:

photons from our sun and a distant sun interact on their way to Earth where they are detected by us. The act of detecting them did not affect their prior interaction, but their prior interaction affected how they would be detected, and the detection does affect the photons after detection. (in all the interactions, the photon states are changed of course, or they would not be interactions).

So we've received information from the past, but we haven't affected the past by observing it. We've affected the photons that gave us the information about the past and changed their energy, momentum, and position to find out (to the limited certainty that we can) what their energy, position, and momentum are.

Now if we do this with a whole bunch of photons we begin to collect a more certain picture of the past without altering it.

If you're actually proposing that photons only exist because of our observation, I'll tell you why I think it's silly. Firstly, the word observation has lots of connotations with it, most of which are part of the human imagination (part of a necessary process for storing and utilizing information). The reality of it is, that the only physical meaning behind an observation is interaction. Interactions happen all over the universe, absent of a the human idea of an "observer", but really they're no different from the obsevation. If only our observations affected the events in the universe, then how could we have observed anything in the first place?

If a comet lands in your house and pummels you in your sleep before you wake up, do you not die since you didn't observe it? Do you hang out in limbo until someone else comes along and observes it? Wouldn't we be able to use such a principal to go beyond the limitations (physical laws) of the universe?

 

[Coldcall]

Hi Pythagorean

Good thought experiment.

"So we've received information from the past, but we haven't affected the past by observing it."

There is still some question about whether our observations can actually affect the past. No-one is saying we can travel/communicate backwards in time, but if one considers "Wheelers Delayed Choice" then it implies our "choice" of observations under certain ciricumstances have a backward causal effect. Actually its a facinating experiment:

http://en.wikipedia.org/wiki/Wheeler's_delayed_choice_experiment

"If a comet lands in your house and pummels you in your sleep before you wake up, do you not die since you didn't observe it? Do you hang out in limbo until someone else comes along and observes it? Wouldn't we be able to use such a principal to go beyond the limitations (physical laws) of the universe?"

Yes but you have to remember that we know that quantum weirdness (for want of a better word) mainfests itself very differently or not at all in macrocopic objects. We also have to remember that "entanglement" or Einstein's "spooky action at a distance" is a backward in time effect because for all practical purposes the influence on an entangled particle on its pair is happening at a speed far faster than c.

We also don't know whether entanglement works on a far more fundamental level, in effect entangling all observers and matter in the universe.

 

[QUANTUMQ]

since two particles can be entangled, are the wave functions of these two particles entangled before they collapse? and is a wave function collapse perminent?

 

[Rade]

Why is this topic in 'philosophy' section of the forum ?

 

[peter0302]

Because I think the QM forum moderators are rightfully getting sick of arguments over the interpretive aspects of QM which are not science because they cannot be experimentally tested and make no useful predictions.

 

[Coldcall]

I agree this is the right place for this discussion as the "measurement problem" is clearly foundational from a philosophical point of view.

My personal view is that science lost the right to discuss philosophical concerns once they started trying to pull the wool over people's eyes about the observer controversy.
I take the view that "shut up and claculate" was physics opting out of the deeper implications.

 

[Coldcall]

Because I think the QM forum moderators are rightfully getting sick of arguments over the interpretive aspects of QM which are not science because they cannot be experimentally tested and make no useful predictions.

I agree as i said on the other post; however there is a contradiction at play because even on physics forums we are told there is no more measurement problem due to either MWI or decoherence. Thats just ********. So while i agree that philosophy is the right place for this discussion the physics community cheat on this rule because they then claim one of the other interpretations as being the "right way" to ignore the paradox.

So science is acting like it wants its cake and to eat it as well. If one brings up an interpetation which phycists do not like then they claim one is going off the scope of physics debate, however they bandy about MWI or decoherence as if they have more legitimacy.

So as with qm itself, there is a strange paradox at play within the physics community over interpretations.

 

[peter0302]

It certainly can be a little subjective at times. It all depends on where the discussion is headed. I suggested awhile back a forum dedicated to quantum interpretation, where both scientific and philosophical discussions would be permitted, but I was told that they preferred to use the Philosophy forum for quantum discussions that got too far afield from science.

 

[Coldcall]

It certainly can be a little subjective at times. It all depends on where the discussion is headed. I suggested awhile back a forum dedicated to quantum interpretation, where both scientific and philosophical discussions would be permitted, but I was told that they preferred to use the Philosophy forum for quantum discussions that got too far afield from science.

That's a great idea! I would love such a forum because qm could be the first genuine metaphysical science humans have encountered. And i mean metaphysical in the right way, as in based on sound physics

My view is that speculation is a good thing as long as its based on known facts. using that factual platform speculation is a viable method to reach the next level in understanding nature and reality. Problem is filtering the reasonable from the not so reasonable but physics should be the decider. If something is possible within the known physical contraints then i think its valid.

Unfortunately "what the bleep..." and films like that make it harder to have a sensible discussion on these important issues.

 

[Pythagorean]

"So we've received information from the past, but we haven't affected the past by observing it."

There is still some question about whether our observations can actually affect the past. No-one is saying we can travel/communicate backwards in time, but if one considers "Wheelers Delayed Choice" then it implies our "choice" of observations under certain ciricumstances have a backward causal effect. Actually its a facinating experiment:

http://en.wikipedia.org/wiki/Wheeler's_delayed_choice_experiment

On the quantum level, perhaps (there's still a question of whether or not this is just a restriction on how we observe), but this doesn't have a lot to do with the past as we know it. We can't travel/communicate backwards in time because we experience time very differently than the quantum particle does. In the same way, it's equally difficult to draw serious philosophical conclusions based on quantum physics.

"If a comet lands in your house and pummels you in your sleep before you wake up, do you not die since you didn't observe it? Do you hang out in limbo until someone else comes along and observes it? Wouldn't we be able to use such a principal to go beyond the limitations (physical laws) of the universe?"

Yes but you have to remember that we know that quantum weirdness (for want of a better word) mainfests itself very differently or not at all in macrocopic objects.

This is the point I was making. You previous post:

Do you think that this happens randomly in nature without an observer or scientist firing the photon at the particle? And if so how do we get evidence for it occurring? How do we observer without observing?

The heart of the matter and why modern interpretations try to eject the observer is because if an observer really is required then we live in a somewhat subjective universe in which obsevers play a central role. It would sort of contradict Copernican reasoning.

I would assume 'universe' (the way you're using it) is a macroscopic term.

 

[Coldcall]

Pythagorean,

"On the quantum level, perhaps (there's still a question of whether or not this is just a restriction on how we observe), but this doesn't have a lot to do with the past as we know it. We can't travel/communicate backwards in time because we experience time very differently than the quantum particle does."

Yes i don't think qm has ever suggested a way to carry information backwards in time. However retro-causality is a real phenomenom as demonstrated in Delayed choice, quantum eraser etc...

I agree the question about observership is very hard but we cannot ignore the evidence. We may be able to treat it as an un-intended paradox but to not take it seriously is scientifically regressive in my point of view.

"I would assume 'universe' (the way you're using it) is a macroscopic term."

Yes subjective on a macroscopic level too. However we also have a global reality, which can be seen as the reality we all agree on so it is unchanging - more or less. However new things that no-one may know about come from the subjective un-defined realm and when we discover them they join into the "known" or entangled global reality. So there is actually a subjective-objectivity to it all...if that makes any sense.

 

[QUANTUMQ]

why is there seemingly a lack of interest in the physics world into what subjectivity is when it seems to play a very important role?

 

[f95toli]

Because most physicists that work with QM phenomena belong to the "shut up and calculate" school of thought. People have been discussing various interpretations for several decades now and there hasn't been much progress; mainly because no one has been able to come up with a way to test anything experimentally. Most physicists (including me) simply find the discussion boring and frankly quite pointless.
But at the time we have made HUGE progress when it comes to understanding causes of decoherence, Bell-type tests etc. and this is a VERY active field of research, but most of the issues have nothing to do with philosophy.
To give you a concrete example: the main problem in solid state quantum computing at the moment is the presence of two-level fluctuators in the materials (unpaired electrons and other defects), THEY are what is causing the "wavefunction to collapse" after a few microseconds and by removing them we hope to extend the coherence times by at least a factor of ten, but in in order to achive this you need people who are interested in materials science, not philosophy.
Hence, there are plenty of very technical problems to worry about, and if your goal is to e.g. build a practical quantum computer most philosophical arguments are simply irrelevant.

 

[baywax]

How would we know if a wave function collapsed or not without an observer being present?