Can a conscious observer collapse the probability wave?

[Fredrik]

One has to wonder if there is some slight loss of the interference pattern even in this case, with a gradually increasing loss of interference with increasing sensitivity of the mirror to photon deflection or if there is a threshold value with a binary switch from interference plus no which way detection to no interference plus which way detection?

It has to be the first option, I think. This is similar to the double-slit experiment with C70 molecules that I mentioned, where the pattern gets a little bit messed up when you increase the air pressure a little. In both of these experiments, the problem appears to be that some of the the "quantum weirdness" is moved into the environment, where it's unnoticeable. (Maybe a decoherence expert could explain it better than that. )

 

[Darwin123]

I know very little about QM, so forgive me if this question is a bit difficult to comprehend. I understand that there is some debate about whether a conscious observer is necessary to collapse the wave function. But I was wondering if there was any experimental evidence showing to what degree a conscious observer is actually able to collapse the wave function.

What I mean by this is, as an example, as I understand it, in the double slit experiment it doesn't matter if a device is set up to monitor which slit the particle went through, as long as the information about what the device "saw" is not available to an observer, then the device's observation alone is not sufficient to collapse the wave function. Basically if we turn on the device but do not record the information, then the wave function won't collapse. Turn on a recording device, and the wave function collapses. So is a conscious observer, i.e. a person, a sufficient recording device?

If we set up the double slit experiment so that a person gets a visual indication of which slit the particle went through, and then sees where on the detector the particle was found, is the observer's memory a sufficient recording device. In an experimental setting wouldn't we have to send many thousands of particles through the experiment in order to establish a clear interference, or non-interference pattern? Obviously a person would be unable to remember all the slit and detection information, and lacking that information, what type of pattern should we expect to see? If a mechanical recording device was unable to accurately record the information, wouldn't we expect the interference pattern to remain. Likewise a person might be able to collapse the wave function of one individual particle, but after a large number of particles, shouldn't we expect to see an interference pattern? So even with a person watching, might we not expect an interference pattern in the double slit experiment?

If the conscious observer is the key in collapsing the wave function, then we would expect to see a non-interference pattern, but if the observer is simply a recording device, (and an insufficient one) then wouldn't we still see an interference pattern in the double slit experiment?

To me it seems that the conscious observer is merely a recording device, which is why I ask if there is any experimental evidence indicating that a conscious observer can actually collapse the wave function. Is a conscious observer only able to collapse the wave function of that which they are currently observing, but on a long term scale wouldn't the system revert to a probability wave, as the observer's memory is an unreliable recording device?

As you can tell, I'm confused. Any information that might help me clear this up would be appreciated.

I will answer the question in terms of an interpretation of quantum mechanics called “coherency theory”. The Copenhagen interpretation was an approach to the problem that came before coherency theory. This is the theory that uses the concept of consciousness. However, I think of it as merely a good working model. Not that it still isn't good as a short cut for most measurement problems. However, it has a few internal ambiguities. I am sure you are aware of them.
I am going to ignore the Copenhagen interpretation. Not because it isn't useful sometimes. To be honest, I never understood fully understood the Copenhagen interpretation to begin with.
According to Coherency theory, the measurement process is merely an interaction between two wave systems. The particle properties "emerge" from the wave properties.
The observer does not have to be intelligent or conscious. The observer is the complex system. Complex here means having a lot of degrees of freedom. The observer, like everything else in the universe, has a wave-particle duality. The observer can behave like a large number of particles moving at random velocities, or like a wave function with many quantum numbers that are constantly changing in time. When coupled to another system, it causes a wave front collapse the other system which is merely the result of the interaction.
Sometimes, the phrase measuring instrument is used instead of observer. The idea is the same. The measuring instrument is complex but has certain properties that define a measuring system.
There are some actual experiments that have been done to test "coherency theory".
Here is an article with a link where the investigators examined a beam of C60 molecules emitted from an oven. The molecules were still vibrating because of their high temperature when they were emitted by the oven.
The C60 molecules gave off electromagnetic radiation because of their vibrations. This was called thermal radiation. It probably came close to being a black body spectrum, although I am sure there were line spectra associated with it.
The “observer” was the thermal radiation given off by the C60 molecules. The thermal radiation consisted of thousands of photons per C60 molecule. The thermal radiation waves had thousands of modes with random phases in it. The quantum numbers probably varied randomly in time.
One could have located the atoms using this thermal radiation. Hence, the thermal radiation was effectively a measuring instrument. It was an observer, since the radiation could have been “seen” by a camera. However, there did not have to be an intelligence to observe it. There happened to be an intelligence around (the investigators), but they did not control the thermal radiation. There did not have to be someone with a mind to observe the thermal radiation.
The thermal radiation made the wave function of the C60 molecules collapse just because of the interaction between “EM waves” and “molecular waves”. In theory, the collapse could have been modeled by Schroedingers equation with a Hamiltonian that had thousands of degrees of freedom in it. However, the thermal radiation was so complex that there was no way to do that.
The thermal radiation was not conscious. It was not explicitly designed. It was not manipulated. The thermal radiation was just complex.

http://arxiv.org/pdf/quant-ph/0412003.pdf
“Influence of molecular temperature on the coherence of fullerenes in a near-field interferometer
Abstract
…
This way the heating-dependent reduction of interference contrast can be compared with the predictions of quantum theory. We find that the observed loss of coherence agrees quantitatively with the expected decoherence rate due to the thermal radiation emitted by the hot molecules.”

This reference mentions both the C60 experiments and another series of experiments using superconductivity. Again, thermal waves of Cooper pairs acted as an unconscious “observer”.
http://www.maxschlosshauer.com/publications/DecoherenceExperimentsSchlosshauer.pdf
“Superpositions states and their decoherence have also been observed in superconducting devices whose key variable is charge (or phase), instead of the flux variable _ used in SQUIDs.”

More on C60 experiments.
http://www.univie.ac.at/qfp/publications3/pdffiles/2002-02.pdf
“Interferometry with Macromolecules: Quantum Paradigms Tested in the Mesoscopic World”

A more general treatment of coherency theory
http://opus.kobv.de/ubp/volltexte/2005/135/pdf/henkel.pdf
“Coherence theory of atomic de Broglie waves and electromagnetic near Fields”

 

[drphysica]

No no no the observer dosn't colapse the wave function! It is the "observing" that dose it, ie. the set up of the experiment which causes the colapse of the wf nothing to do with you.

 

[bhobba]

No no no the observer dosn't colapse the wave function! It is the "observing" that dose it, ie. the set up of the experiment which causes the colapse of the wf nothing to do with you.

Yes indeed,

And decoherence even explains how and resolves pretty much all the issues. The only issue left is it does not tell you which state it changes into as a result of an observation - all it gives is probabilities. However it is definitely in that state prior to observation and the observation reveals what it is - the only issue is we cannot predict with certainty what it is.

Thanks
Bill

 

[Meselwulf]

I know very little about QM, so forgive me if this question is a bit difficult to comprehend. I understand that there is some debate about whether a conscious observer is necessary to collapse the wave function. But I was wondering if there was any experimental evidence showing to what degree a conscious observer is actually able to collapse the wave function.

What I mean by this is, as an example, as I understand it, in the double slit experiment it doesn't matter if a device is set up to monitor which slit the particle went through, as long as the information about what the device "saw" is not available to an observer, then the device's observation alone is not sufficient to collapse the wave function. Basically if we turn on the device but do not record the information, then the wave function won't collapse. Turn on a recording device, and the wave function collapses. So is a conscious observer, i.e. a person, a sufficient recording device?

If we set up the double slit experiment so that a person gets a visual indication of which slit the particle went through, and then sees where on the detector the particle was found, is the observer's memory a sufficient recording device. In an experimental setting wouldn't we have to send many thousands of particles through the experiment in order to establish a clear interference, or non-interference pattern? Obviously a person would be unable to remember all the slit and detection information, and lacking that information, what type of pattern should we expect to see? If a mechanical recording device was unable to accurately record the information, wouldn't we expect the interference pattern to remain. Likewise a person might be able to collapse the wave function of one individual particle, but after a large number of particles, shouldn't we expect to see an interference pattern? So even with a person watching, might we not expect an interference pattern in the double slit experiment?

If the conscious observer is the key in collapsing the wave function, then we would expect to see a non-interference pattern, but if the observer is simply a recording device, (and an insufficient one) then wouldn't we still see an interference pattern in the double slit experiment?

To me it seems that the conscious observer is merely a recording device, which is why I ask if there is any experimental evidence indicating that a conscious observer can actually collapse the wave function. Is a conscious observer only able to collapse the wave function of that which they are currently observing, but on a long term scale wouldn't the system revert to a probability wave, as the observer's memory is an unreliable recording device?

As you can tell, I'm confused. Any information that might help me clear this up would be appreciated.

Best not to use the word ''concious''... that kind of implies the idea that consciousness is required to collapse the wave function $$\int_{\Omega} |\psi|^2$$, which is a fallacy. Any kind of observation will collapse a state vector $$<\Psi>$$. Even particles act as observers irrespective of them having no consciousness... A good example of this fallacy is Wigners Friend, you should read up on it.

Another way to put it, is that particles act as observers but the terminology is really called quantum decoherence. If you stick a bunch of particles in a box and leave them long enough, their wave functions couple and become entangled and eventually the will condense into solid objects.

 

[Zmunkz]

Some of this conversation is suffering from a terminological problem. To be clear, we don't actually now if there is a "wave collapse" in reality... Mr. Schroedinger's equation is rather explicit that no wave can evolve from a standard superposition into a collapsed spike. The concept of wave collapse was merely an instrumentalist remedy hand-wavingly introduced by Niels Bohr, but it is not clear exactly how or even if that "event" translates into reality. Considering that the collapse could easily be an instrumental concept rather than a realist one, it's going to be hard to settle in a concrete way what "causes" the collapse. Such are the mysteries of quantum mechanics :-)

 

[Meselwulf]

Some of this conversation is suffering from a terminological problem. To be clear, we don't actually now if there is a "wave collapse" in reality...

There are countless experiments which prove there is a wave function collapse.

The double slit experiment, quantum eraser and decoherence are all examples of wave which collapse.

 

[Zmunkz]

There are countless experiments that demonstrate a measurement of a particle where the math told us there was a wave. I'm trying to separate between the instrumentalist formulation and the realist formulation. According to the math, a wave cannot spontaneously collapse. Obviously it does, because we don't see half of a particle, I'm just saying to talk about the collapse like its something actually happening might be premature. It's quite possibly a side effect of the math we use with no correlation in reality. I'm not saying that for sure either, of course, just putting it out there...

 

[bhobba]

There are countless experiments which prove there is a wave function collapse. The double slit experiment, quantum eraser and decoherence are all examples of wave which collapse.

That is interpretation dependant. The many worlds interpretation has no collapse - all outcomes occur - but we only ever experience one.

I think its mystical nonsense personally but as an interpretation it certainly doesn't require collapse.

Thanks
Bill

 

[bhobba]

There are countless experiments that demonstrate a measurement of a particle where the math told us there was a wave. I'm trying to separate between the instrumentalist formulation and the realist formulation. According to the math, a wave cannot spontaneously collapse. Obviously it does, because we don't see half of a particle, I'm just saying to talk about the collapse like its something actually happening might be premature. It's quite possibly a side effect of the math we use with no correlation in reality. I'm not saying that for sure either, of course, just putting it out there...

First you have to understand what the wave is. Its not a wave in a real sense - its a wave of something called a system state. A system state is a property of a system that tells us the probabilities of possible observational outcomes. In most interpretations it has the same status as the probabilities we assign to the result of flipping a coin. Its simply a theoretical device - not something that exists out there in a real sense. It is of zero concern that it spontaneously changes to another state just as it is of zero concern once you flip a coin the 50-50 probability changes to a dead cert.

There are issues but that not one of them in most interpretations. One issue is exactly how does an observation accomplish this feat - Copenhagen simply assumes it does. Decoherence goes a long way in answering that.

Thanks
Bill

 

[Zmunkz]

Its simply a theoretical device - not something that exists out there in a real sense.

You landed exactly where I was trying to get -- thanks for clarifying the language!

 

[Meselwulf]

That is interpretation dependant. The many worlds interpretation has no collapse - all outcomes occur - but we only ever experience one.

I think its mystical nonsense personally but as an interpretation it certainly doesn't require collapse.

Thanks
Bill

This is true, but the Copenhagen interpretation is the most widely accepted theory in quantum physics today.

Parallel universes have... or I should say, has little experimental back-up .The fact you can disturb a particles wave function is sufficient enough to say that there has been a sudden reduction to the probabilities that they equal 1.

 

[Meselwulf]

You landed exactly where I was trying to get -- thanks for clarifying the language!

Wrong, we have observed the wave function, it is not a mathematical anomaly.

I suggest you read up on the ''Quantum Resonator''. An object small enough but not too small, that we have seen these quantum effects. The wave function is definitely real!

... and physical.

 

[Meselwulf]

First you have to understand what the wave is. Its not a wave in a real sense - its a wave of something called a system state. A system state is a property of a system that tells us the probabilities of possible observational outcomes. In most interpretations it has the same status as the probabilities we assign to the result of flipping a coin. Its simply a theoretical device - not something that exists out there in a real sense. It is of zero concern that it spontaneously changes to another state just as it is of zero concern once you flip a coin the 50-50 probability changes to a dead cert.

There are issues but that not one of them in most interpretations. One issue is exactly how does an observation accomplish this feat - Copenhagen simply assumes it does. Decoherence goes a long way in answering that.

Thanks
Bill

Also, you want to talk about the quantum flip of a coin?

If you flip a coin 100 times, you create slightly over 10^{30} universes. This disturbed Hoyle yet this is in the fact of the rational theory you seem to not be defending very well.

 

[bhobba]

I suggest you read up on the ''Quantum Resonator''. An object small enough but not too small, that we have seen these quantum effects. The wave function is definitely real!

I think a number of people such as Ballentine would disagree. See chapter 9 - Ballentine - Quantum Mechanics - A Modern Development - The Interpretation Of The State Vector - page 239 - where he proves any other view leads to problems. Even bog standard Copenhagen disagrees.

My view is not that fatalistic in that I think a view of a state vector as real can be part of a valid interpretation but it is far from certain such must be. In fact most interpretations like the Ensemble Interpretation or Copenhagen don't buy into its reality. My personal interpretation - being the Ensemble interpretation combined with Decoherence - doesn't either.

Thanks
Bill

 

[bhobba]

Also, you want to talk about the quantum flip of a coin?

If you flip a coin 100 times, you create slightly over 10^{30} universes. This disturbed Hoyle yet this is in the fact of the rational theory you seem to not be defending very well.

I don't want to talk about MW - nor am I defending it - it's pure hokum IMHO for all sorts of reasons. The huge number of universes it requires is one of those reasons - but it does not disprove it. I am simply pointing out it is an interpretation that no generally accepted refutation exists for and it does not require wavefunction collapse.

The coin analogy is also just that - an analogy. The Kochen-Sprecker theorem proves by itself an observation is not like a flip of a coin in that it does not have the property of head or tail prior to observation. However if you take into account decoherence you can say it has the property prior to observation - but that of course requires more work to understand.

Thanks
Bill

 

[bhobba]

Wrong, we have observed the wave function, it is not a mathematical anomaly.

That would be an interesting trick - observing something in QM without requiring an observable - and once you do that Copenhagen, the Ensemble interpretation, and others (not all of course) say the only thing that can be predicted is probabilities and it is the state that tells you that via the usual trace formula Tr(pR) that gives the average - p the state, R the observable.

Thanks
Bill

 

[Meselwulf]

I think a number of people such as Ballentine would disagree. See chapter 9 - Ballentine - Quantum Mechanics - A Modern Development - The Interpretation Of The State Vector - page 239 - where he proves any other view leads to problems. Even bog standard Copenhagen disagrees.

My view is not that fatalistic in that I think a view of a state vector as real can be part of a valid interpretation but it is far from certain such must be. In fact most interpretations like the Ensemble Interpretation or Copenhagen don't buy into its reality. My personal interpretation - being the Ensemble interpretation combined with Decoherence - doesn't either.

Thanks
Bill

To be honest, if he disagree's, he is disagreeing with proven experimental fact. So you can continue to believe in what he says, but he has been proven wrong in his speculations.

Quantum wave function of semi-classical objects have been proven and observed. Please, look up the ''Quantum Resonator.''

 

[Meselwulf]

That would be an interesting trick - observing something in QM without requiring an observable - and once you do that Copenhagen, the Ensemble interpretation, and others (not all of course) say the only thing that can be predicted is probabilities and it is the state that tells you that via the usual trace formula Tr(pR) that gives the average - p the state, R the observable.

Thanks
Bill

The definition of observing something requires there being an observable. There cannot be a logical dispute about that!

 

[bhobba]

The definition of observing something requires there being an observable. There cannot be a logical dispute about that!

Then how do you know via observation a state is real?

Thanks
Bill

 

[Meselwulf]

Then how do you know via observation a state is real?

Thanks
Bill

Is that a real question? The answer is self-explanatory, if you see it, and it exists by testing it experimentally, over and over again, why would one not think it is real?

This is not a rhetorical question. It's a matter of fact. Scientists have a certain proclavity to understanding how real things exist. Observables for instance are represented by Hermitian matrices, spin is an example of such a phenomenon. If spin was not real, we would not be able to measure it and know it was a real artefact of the world.

 

[bhobba]

To be honest, if he disagree's, he is disagreeing with proven experimental fact. So you can continue to believe in what he says, but he has been proven wrong in his speculations. Quantum wave function of semi-classical objects have been proven and observed. Please, look up the ''Quantum Resonator.''

I believe his argument because it is very good - you should acquaint yourself with it. I do believe there are a number of ways to evade it such as MW's but they all seem a bit contrived to me. However to each there own - if you want to believe the state is real - feel free - but just don't say it must be so because quite simply QM does not demand that view - in fact most interpretations I am aware of - the generally trotted out Copenhagen among them - deny it.

Thanks
Bill

 

[bhobba]

Is that a real question? The answer is self-explanatory, if you see it, and it exists by testing it experimentally, over and over again, why would one not think it is real?

This is bog standard basic QM. If you see it you are observing it and hence are subject to collapsing the wave function issue and all other quantum weirdness. If you are not observing it all you can say is it is in a certain state and via the usual trace formula predict probabilities if you were to observe it. The issue here is if the state is real like an electric field or simply a theoretical device - many - probably even most interpretations - do not require its reality.

Thanks
Bill

 

[Meselwulf]

I believe his argument because it is very good - you should acquaint yourself with it. I do believe there are a number of ways to evade it such as MW's but they all seem a bit contrived to me. However to each there own - if you want to believe the state is real - feel free - but just don't say it must be so because quite simply QM does not demand that view - in fact most interpretations I am aware of - the generally trotted out Copenhagen among them - deny it.

Thanks
Bill

Many Worlds interpretation is not sensible for a number of reasons.I won't go over them all, but for the greatest problem concerning it, it surely be can be classed on the league of string theory, M-theory or whatever you wish to call the the five-model string theory.

It's on the same league because, there is actually no way of experimentally-proving it - the universe is what we call, ''intrinsically closed'' or ''self contained'' - usually the latter is used in cosmological terminology. This means anything which happens in anyone universe, must stay within that universe, and whilst it may only seem like a conjecture, it is pivotal that things do not leek between universe because information, just like a Black Hole swallong matter and energy, can never be truly lost.

The basis reason for scientists questioning the possibility of MWI is purely the question ''why do many probabilities show up, when, clearly only one state is ever observed?'' Everette the III then decided well, what if the universe has a wave function itself, which then led him to the idea that maybe all the wave functions in the dynamic universe was determined by playing out the possible events in other universes.

To do so however, the problems which is not even sensible (like tossing a coin 100 and finding you create staggering amount of universes by a series of splittings and merging off our own), it also implied but also not sensible because it cannot be manifestly physical. The reason why is because it actually requires and infinite amount of universes, and infinity doesn't exist in closed universes, in closed universes, everything is finite. So by this reasoning, there can be nothing isomorphic to our universe and besides, our universe has a certain proclavity to abhore infinities in general.

Copenhagen however, has been a true success, from decoherence, observed collapsing of the wave function, the uncertainty principle which is a cornerstone of the Copenhagen Interpretation. Hardly any faults on the top of my head even exist for this Interpretation, but you don't like it and your reasons seem aloof to me.

 

[Meselwulf]

This is bog standard basic QM. If you see it you are observing it and hence are subject to collapsing the wave function issue and all other quantum weirdness. If you are not observing it all you can say is it is in a certain state and via the usual trace formula predict probabilities if you were to observe it. The issue here is if the state is real like an electric field or simply a theoretical device - many - probably even most interpretations - do not require its reality.

Thanks
Bill

When you are not observing it, don't you mean, that it's location is uncertain.

And I don't agree with this:

''The issue here is if the state is real like an electric field or simply a theoretical device - many - probably even most interpretations - do not require its reality.''

It makes no sense. If it is real, then it's real. There can be no question about it, and if you are saying it is real by interpretation, I am not quite sure what is truly meant by that. Interpretations make assertions on what can be measured. If the theory does not match what is measured, either it needs to be adjusted, or scrapped.

 

[bhobba]

If it is real, then it's real. There can be no question about it

Its not that simple. Many many people, Einstein, Bohr, Feynman, Dirac, all sorts of people have debated it and no conclusion has ever been reached. Since QM is a theory about observations when you are not observing it you can if you wish not ascribe any definite property out there to it. The state you think is real simply tells us the probability of the outcome of an observation - nothing more. Unless that outcome is a dead cert (in in the vast majority of cases it isn't) then you can't say it has that property. In principle you can come up with an observation that determines with certainty a pure state and in that sense you might think it real - but then there are so called mixed states that are not like that.

Now since it does not tell us anything between observations its an open question if it has any real property until you observe it. You can think of the state as real if you like - and there is no way to prove you incorrect - or correct for that matter - but if you do then since you think the state is real you need to explain how something real spontaneously changes to something else - or do you believe nature is simply like that?. Although I generally don't like providing the answers to positions I do not agree with it is possible decoherence could do that - but you need to spell it out.

Thanks
Bill

 

[Ken G]

Interpretations make assertions on what can be measured. If the theory does not match what is measured, either it needs to be adjusted, or scrapped.

To expand on what bobba said, I believe you have the meaning of "intepretation" confused with the meaning of a "theory"-- theories make assertions on what can be measured, regardless of interpretation. Interpretations make assertions that cannot be measured or tested in any way-- they make assertions about what is "real", or in some cases, about what is not "real".

The way I like to think about all this is that reality includes whatever apparatus is in place to establish what the reality is. That can be a conscious observer, or other things that play the same role, but it has to be something. A reality that is absent of any apparatus to establish what is real is no kind of reality at all, and we constantly have to use interpretations to "connect the dots" between the elements of the situation that are actually established as real. You can see why what philosophers label "realism" I regard as "unrealism."

 

[Meselwulf]

I see that theories make assertions, but at the same time, one has to make assertions to manifest a theory. Obviously, these assertions and theories are coupled to the direction of the most accurate model which physics at the time. To this day, Copenhagen manages to satisfy both to a much greater degree that MWI.

AS I said, it is on the same league as string theory based models. There is no experimental proof, only assumptions alone based on our mathematics.

 

[Meselwulf]

Its not that simple. Many many people, Einstein, Bohr, Feynman, Dirac, all sorts of people have debated it and no conclusion has ever been reached.
Bill

I can assure you since the Einstein Bohr debates, many things have been resolved. Today our saving grace is that we have experimental evidence that the wave function is in fact real.

I have asked you three times now to look up ''quantum resonator'' it is irrefutable proof it is actually a physical manifestation.

 

[audioloop]

I can assure you since the Einstein Bohr debates, many things have been resolved. Today our saving grace is that we have evidence that the function is in fact real.

is not so easy, read:
(i think that is epistemic i.e. a knowledge representation of reality, not the reality itself).
The quantum state can be interpreted statistically, again
http://physics.stackexchange.com/qu...e-interpreted-statistically-again/36390#36390

Is the wave function, an unreal tool, to partially model a real interaction?
https://www.physicsforums.com/showthread.php?t=619851

The quantum state cannot be interpreted statistically?
https://www.physicsforums.com/showthread.php?t=551554

 

[bhobba]

I can assure you since the Einstein Bohr debates, many things have been resolved. Today our saving grace is that we have experimental evidence that the wave function is in fact real. I have asked you three times now to look up ''quantum resonator'' it is irrefutable proof it is actually a physical manifestation.

I will look it up but please answer me a simple question. Given the mixed state 1/2 |a><a| + 1/2 |b><b| what is the corresponding observable that will tell us it is in that state? And if you can't come up with one why do you think its real?

Added Later:

Looked it up - could not find any article using it as evidence a state is real. Exactly why do you believe it proves it?

Thanks
Bill

 

[Meselwulf]

edit/

 

[Meselwulf]

The wave function is physical. Some authors will say a thing doesn't exist until an observation is made on a system, but if the wave function is real which experimentation seems to suggest, then observation is really not needed to explain this, other than finding an object in a specific place.

 

[Darwin123]

Some of this conversation is suffering from a terminological problem. To be clear, we don't actually now if there is a "wave collapse" in reality... Mr. Schroedinger's equation is rather explicit that no wave can evolve from a standard superposition into a collapsed spike. The concept of wave collapse was merely an instrumentalist remedy hand-wavingly introduced by Niels Bohr, but it is not clear exactly how or even if that "event" translates into reality. Considering that the collapse could easily be an instrumental concept rather than a realist one, it's going to be hard to settle in a concrete way what "causes" the collapse. Such are the mysteries of quantum mechanics :-)

I agree that it is a terminology problem. However, I think that the terminology is slightly clearer in terms of coherency theory than in the Copenhagen interpretation or the mutliworlds interpretation. In terms of coherency, "wave collapse" and "observation" are defined in a very general way. I have in mind a close analogy in terms of synchronously pulsed lasers.
"Wave collapse" isn't much different in my mind from "mode locking". Pulsed lasers can produce wave packets that are less than a picosecond in duration. A synchronously pulsed laser has some property that is modulated with a period equal to the round trip time of the laser cavity. By clipping the tail of the pulse, the wave packet becomes very narrow.
The "observation" in coherency theory is merely the interaction of the measuring device wave with the "system wave". This appears to me very similar to synchronous mode locking. The "system wave" collapses into a wave packet, just due to the interaction. You can't predict exactly when the wave will collapse into a wave packet in a synchronously pulsed laser because the initial wave has an unknown phase. I think this is analogous to the inability to predict the position of the particle after the collapse of the wave function.
"Observation" is a poor word since it implies that there has to be conscious acknowledgment of the results of the interaction. The "observation" is merely a type of nonlinear interaction. Furthermore, "collapse" is a poor word since it implies that the system is no longer a wave after the nonlinear interaction. In actuality, what is left after an observation is a localized wave packet. By Ehrenfests theorem, the wave packet behaves approximately like a classical particle. However, the wave packet will start to disperse soon after forming.
The measuring instrument is never 100% classical in behavior. The Copenhagen interpretation implies that the measuring instrument is somehow behaving like it is made of particles (always) while the system behaves like a wave (until the interaction).
This duality is the source of the logical problem. Our intuition says that everything acts like it is made of classical particles.
Reality says that objects sometimes act like waves and sometimes like particle. This is a problem with intuition, but it is not a problem of logic. The Copenhagen interpretation gives rules that inform us when the system acts like a wave and when it acts like a particle. The logical problems come about when the the rules are not self consistent. If the rules were 100% self consistent, there would never be a logical problem. I don't know if one can say that the rules are 100% self consistent, but the percentage is high.
Coherency theory says that everything acts like a wave, but particle properties "emerge" from the wave properties. So as long as the rules regarding waves are self consistent, the theory is probable. This may be an intuitive problem. However, it is not a logical problem.
I think one of the necessary conditions for a wave being a "measuring instrument" is that it is complex. The wave that is the "classical system" has to have a many degrees of freedom. Obviously, our brains fulfill that condition in excess. So the Copenhagen interpretation may be based on a half truth. The system being examined is interacting with a complex system, which is interacting with complex sensors, which is interacting with complex nerve endings, which is interacting with complex nerves, which is interacting with a complex brain. There is a time delay between each interaction, since the nonlinear interaction has a response time. By the time the chain of interaction has reached from the examined system to the brain, the system has already interacted with a lot of complex systems. So by the time the system interacts with the brain, the wave function of the system has narrowed into a wave packet.
The interaction with our consciousness may be just a milestone rather than a fundamental condition. The real "observation" occurs immediately after the first complex system has caused a wave packet to appear. However, the brain isn't aware of it at that femtosecond. However, subsequent interactions with complex systems narrow the "wave packet" even further. By the time our brain interacts with the system, the "wave packet" is really narrow. So at that point, the system can be considered "classical".
This is just my interpretation. I will now look up some articles on synchronous model locking to support this conjecture.
Here they are. I edited this message in order to add these references. Do the email notifications include later editing?
First, some articles on mode locking laser beams.
http://en.wikipedia.org/wiki/Mode-locking
“Mode-locking is a technique in optics by which a laser can be made to produce pulses of light of extremely short duration, on the order of picoseconds (10−12 s) or femtoseconds (10−15 s).
The basis of the technique is to induce a fixed phase relationship between the modes of the laser's resonant cavity. The laser is then said to be phase-locked or mode-locked. Interference between these modes causes the laser light to be produced as a train of pulses. Depending on the properties of the laser, these pulses may be of extremely brief duration, as short as a few femtoseconds.
…
This process can also be considered in the time domain. The amplitude modulator acts as a weak shutter to the light bouncing between the mirrors of the cavity, attenuating the light when it is "closed", and letting it through when it is "open". If the modulation rate f is synchronised to the cavity round-trip time τ, then a single pulse of light will bounce back and forth in the cavity. The actual strength of the modulation does not have to be large; a modulator that attenuates 1% of the light when "closed" will mode-lock a laser, since the same part of the light is repeatedly attenuated as it traverses the cavity.”

http://www.dmphotonics.com/Autocorrelator/ultrafast.pdf
“Now consider the form of the wave packet output of a model locked laser.” Second, these articles describe model locking effects in systems that aren’t a laser beams.
http://arxiv.org/pdf/cond-mat/0106423.pdf
“In this paper, it is shown that a configuration modulated system described by the
Frenkel-Kontorova model can be locked at an incommensurate phase when the quantum zero point energy is taken into account.”

http://pre.aps.org/abstract/PRE/v75/i3/e036208
“Mode locking of a driven Bose-Einstein condensate”

 

[Meselwulf]

There is no mystery with the Cat Experiment now. Large systems are free from quantum effects. The cat will be dead if the counter releases the gas not a mixture of dead and alive. A cat is a system effected by it's large existence, quantum effects simply don't effect them strong enough to take hold of the inevitable.