Regarding consciousness causing wavefunction collapse

[ModusPwnd]

Why doesn't it work? You just described one possible outcome and then say it doesn't work...

Or the presence of the detector at the slits changes the wave function so that no interference is produced.

Right, I included that possibility in my post (right after where you quoted me). If the detector alone changes the wave function so that no interference pattern is produced then consciousness is not required.

I'm confused because it looks like you describe that consciousness is not required then simply state it doesn't work (that is, we don't know if consciousness is required) .

 

[Nugatory]

I want to understand this better but I don't quite follow.

Case A: No detector at the slit and we see an interference pattern.
Case B: Detector with conscious observation at the slit and we do not see an interference pattern.

Now remove the conscious observation of the detector at the slit, but leave the detector on.
Case C: Detector without conscious observation at the slit. If we see an interference pattern then the consciousness is required to collapse. If we do not see an interference pattern then consciousness is not required to collapse the function. This logic does not follow?

In case C we do not see an interference pattern (and most if not all experiments have been case C not case B), but that does not lead to the conclusion that consciousness is not required to collapse the wave function. The problem is that we still have to look at the experimental results to see ("see" is your word not mine!) if there is an interference pattern, so we haven't disproved the hypothesis that the recording device was in a superposition of interference pattern and no interference pattern until it collapsed when us conscious observers looked at it.

That hypothesis is somewhat absurd, and it is no part of the modern formulation of quantum mechanics in which consciousness is irrelevant to collapse, but is not disproved by this experiment; there is no experiment that could even in principle disprove it.

 

[ModusPwnd]

In case C we do not see an interference pattern (and most if not all experiments have been case C not case B), but that does not lead to the conclusion that consciousness is not required to collapse the wave function. The problem is that we still have to look at the experimental results to see ("see" is your word not mine!) if there is an interference pattern, so we haven't disproved the hypothesis that the recording device was in a superposition of interference pattern and no interference pattern until it collapsed when us conscious observers looked at it.

By "it" do you mean the screen or the recording device? In Case C we don't look at the recording device, we look at the screen. In Case A we look at the screen and see an interference pattern. Only in Case B do we look at the recording device.

 

[PeterDonis]

I included that possibility in my post

Sorry, I see now I was a little unclear in my response. You are assuming that QM allows for the possibility that an interference pattern can be observed with detectors at the slits. It doesn't. On any interpretation of QM, if there are detectors at the slits then no interference pattern will be observed. So you can't use this experiment to distinguish between a "consciousness is required for collapse" interpretation and a "consciousness is not required for collapse" interpretation; to do that, the two interpretations would have to make different predictions, and they don't.

 

[ModusPwnd]

On any interpretation of QM, if there are detectors at the slits then no interference pattern will be observed.

Yes, that is what I went into this assuming. To me this statement looks like an affirmation that consciousness is not required. After all, the detector is not conscious.

So you can't use this experiment to distinguish between a "consciousness is required for collapse" interpretation and a "consciousness is not required for collapse" interpretation; to do that, the two interpretations would have to make different predictions, and they don't.

They don't? In my Case C I gave two different predictions. Prediction 1: If consciousness is required the detector alone will not collapse the wave function at the slit and we will see interference pattern at the screen. Prediction 2: If consciousness is not required then the detector alone will collapse the wave function at the slit and we will not see an interference pattern at the screen.
Nugatory said " the recording device was in a superposition of interference pattern and no interference pattern until it collapsed when us conscious observers looked at it." I don't follow yet, but I suspect this is where my thinking is incorrect.

 

[PeterDonis]

To me this statement looks like an affirmation that consciousness is not required.

No, it isn't, because there is no need to assume that the wave function collapses at the detector in order to derive the prediction that, with detectors present at the slits, no interference pattern will be observed. That's why I stressed that this is a prediction of QM for any interpretation; that includes no collapse interpretations like the MWI.

 

[Lord Jestocost]

I want to understand this better but I don't quite follow.

Case A: No detector at the slit and we see an interference pattern.
Case B: Detector with conscious observation at the slit and we do not see an interference pattern.

Now remove the conscious observation of the detector at the slit, but leave the detector on.
Case C: Detector without conscious observation at the slit. If we see an interference pattern then the consciousness is required to collapse. If we do not see an interference pattern then consciousness is not required to collapse the function. This logic does not follow?

Following Feynman: "Nature does not know what you are looking at, and she behaves the way she is going to behave whether you bother to take down the data or not."

Whether you read out the detectors or not, it doesn't matter. Have a look at chapter 3-2, "The Feynman Lectures on Physics, Volume III"

 

[ModusPwnd]

No, it isn't, because there is no need to assume that the wave function collapses at the detector in order to derive the prediction that, with detectors present at the slits, no interference pattern will be observed. That's why I stressed that this is a prediction of QM for any interpretation; that includes no collapse interpretations like the MWI.

Thanks for bearing with me. I'm sorry, but I still don't get it.

Im not versed in MWI, but I do understand it produces the same results as other interpretations. I can forget the idea of a collapsing wave function. Still, the detector does something - right? Otherwise Case A and Case B would produce the same result at the screen. The difference between Case A and Case B is the detector and conscious observer at the slit. We hold everything else constant in the experiment and thus determine that is the inclusion of the detector and conscious observer at the slit that prevents the interference pattern. Now we can take it a step further and perform the experiment without the conscious observer and see what we get.

Following Feynman: "Nature does not know what you are looking at, and she behaves the way she is going to behave whether you bother to take down the data or not."

Whether you read out the detectors or not, it doesn't matter. Have a look at chapter 3-2, "The Feynman Lectures on Physics, Volume III"

Thanks for the reference, I will check that out. I have to say though, each of your sentences look like definite affirmations that consciousness is not required to destroy the interference pattern. (That is to say, consciousness is not required to count as an "observation".) If I don't read the detectors, consciousness isn't involved in the observation.

 

[PeterDonis]

the detector does something - right?

Yes.

The difference between Case A and Case B is the detector and conscious observer at the slit.

There is no need to invoke a conscious observer at the slit to derive the difference in predictions. That's my point. So your case B includes an extra specification--the conscious observer at the slit--that is irrelevant to deriving the prediction for that case.

consciousness is not required to count as an "observation".

That depends on how you define an "observation". That term is an ordinary language term and is not precise. You can define it so that a detector that is not looked at by any conscious observer counts as an "observation", or you can define it so that only a conscious observer looking at something counts as an "observation". But this difference in definition is not about physics; it's about the use of ordinary language words.

 

[ModusPwnd]

I define "observation" as something that affects the wavefunction such that an interference pattern is not produced.

There is no need to invoke a conscious observer at the slit to derive the difference in predictions. That's my point. So your case B includes an extra specification--the conscious observer at the slit--that is irrelevant to deriving the prediction for that case.

Again, that looks like a clear statement that consciousness is not required to be an observation or collapse the wavefunction or whatever you want to call destroying the interference pattern. lol Oh well, this is why I'm not smart enough to be a physicist.

 

[PeterDonis]

I define "observation" as something that affects the wavefunction such that an interference pattern is not produced.

Ok, but you need to understand that not everybody uses this definition. Again, "observation" is an ordinary language term. Your definition links this term to actual stuff in the physical model, which is good if you want to discuss physics. But not everybody wants to use the term "observation" for that purpose.

Again, that looks like a clear statement that consciousness is not required to be an observation or collapse the wavefunction or whatever you want to call destroying the interference pattern.

Now you're throwing together two different things. You defined "be an observation" as "something that affects the wavefunction such that an interference pattern is not produced". This refers, as I said above, the actual stuff in the physical model--stuff that affects the wavefunction.

However, "collapse the wavefunction" does not refer to anything in the physical model. It's an interpretation. You can describe the same physical model--the same math--without ever using the term "collapse" at all (e.g., using the MWI). So by your definition of "observation", "collapse the wavefunction" is not even the same kind of thing as an observation.

So you have taken what looks to you like a "clear statement" and made it into a muddle of two different things. The first amounts to saying that consciousness does not appear anywhere in the physical model--the math of QM doesn't invoke consciousness anywhere to explain what happens to the wavefunction. That's true (and is basically what I've been saying).

But the second thing is a statement about an interpretation--a version of the collapse interpretation in which "collapse" only happens when a conscious observer looks at something. This has nothing to do with the actual physical model, because "collapse" doesn't appear anywhere in that model, any more than consciousness does. I haven't said anything at all about whether that interpretation is "right" or not; I personally don't even think that's a meaningful question.

 

[Lord Jestocost]

Thanks for bearing with me. I'm sorry, but I still don't get it.

Thanks for the reference, I will check that out. I have to say though, each of your sentences look like definite affirmations that consciousness is not required to destroy the interference pattern. (That is to say, consciousness is not required to count as an "observation".) If I don't read the detectors, consciousness isn't involved in the observation.

Maybe, you have misunderstood me. I am not talking about the role of consciousness in connection with quantum physics. I am merely talking about the quantum mechanical formalism as a calculational recipe to predict the probabilities of macroscopic outcomes when, e.g., performing “double-slit experiments with detectors present at the slits”.

EDIT: To my mind, the quantum enigma is, to quote A.J. Leggett: “Basically, the quantum measurement paradox is that most interpretations of QM at the microscopic level do not allow definite outcomes to be realized, whereas at the level of our human consciousness it seems a matter of direct experience that such outcomes occur….” (A. J. Leggett, “The Quantum Measurement Problem”, Science 307, 871 (2005))

 

[vanhees71]

Again, there is no consciousness needed for anything to collapse (despite the fact that I don't believe in the religion of collapse at all). The point is that if you want to have which-way information you need to somehow prepare the photons going through the slits such that they carry the information through which slit they came, and this destroys the interference pattern. One way is to use initially linearly polarized photons (say in $x$ direction) then you put quarter-wave plates in each of the slit one oriented $45^{\circ}$ and one $-45^{\circ}$ relative to the $x$ direction. Then the photons going through slit 1 are left- and the ones going through slit 2 are right-handed polarized. In adding the amplitudes for the photons going through either slit and taking the modulus squared you'll get no interference term because the two polarization degrees of freedom are exactly orthogonal to each other, and thus by measuring the polarization you can precisely know through which slit each photon came. There's no consciousness necessary to make the interference pattern vanishing but just the appropriate preparation procedure such that the photons cary the which-way information.

Quantum theory is sometimes a bit counter-intuitive, because our everyday experience is trained on our interaction with macroscopic bodies which behave (according to quantum statistics!) classical. You don't need esoterics but just quantum theory to understand the behavior of microscopic entities, and in physics you don't need to find a proper definition of consciousness, which in my opinion is impossible to get anyway.

 

[entropy1]

Consciousness might play a role for else no one could verify the measurement. However, if the natural laws governing the experiment are dreamt up by the observer, there is no reason they should be constant, which they appear to be. Furthermore, if the natural laws are dreamt up by the observer, anything could be dreamt up by the observer. By avoiding this standpoint, we can admit that the laws of nature determine the measurement. However, again, the conscious observer can't be taken out of the equation. Still, then you have: "who is it?"

 

[bhobba]

“Basically, the quantum measurement paradox is that most interpretations of QM at the microscopic level do not allow definite outcomes to be realized, whereas at the level of our human consciousness it seems a matter of direct experience that such outcomes occur….” (A. J. Leggett, “The Quantum Measurement Problem”, Science 307, 871 (2005))

This is the sort of thing that gets me.

Now Leggert is a professor of physics so of course you have to give some weight to what he says.

But also as a professor of physics he knows, as well as most physicists do, that the modern theory of quantum observations resolves that ie why we in everyday experience only have definite outcomes ie the quantum world is hidden - and there is even a standard textbook on it:
https://www.amazon.com/dp/3540357734/?tag=pfamazon01-20

Now there are some issues left to be resolved, and if you want to discuss them start a new thread and me and others will be only to happy to tell them to you - as Leggert should have done rather than the, at best, half truth he did say - at worse an actual falsehood.

Thanks
Bill

 

[Lord Jestocost]

...Now there are some issues left to be resolved, and if you want to discuss them start a new thread and me and others will be only to happy to tell them to you - as Leggert should have done rather than the, at best, half truth he did say - at worse an actual falsehood.Bill

With all due respect, as I don't get the point there is no need to start a new thread.

 

[bhobba]

With all due respect, as I don't get the point there is no need to start a new thread.

Scratching head. What don't you get about the fact he is wrong? Its not a matter of opinion - its standard textbook stuff - I even gave the textbook. We know very well why the brain perceives specific outcomes - its because the world around us is classical and much progress has been made in understanding why. There are some remaining issues, but this is not the correct thread to discuss it. Just as an example even more fundamental than our brains registering specific outcomes is why to we get any outcomes at all. That's a legit problem - technically its how an improper state becomes a proper one. It goes way beyond the consciousness thing although those into it will probably find a way to invoke it.

Thanks
Bill

 

[StevieTNZ]

What don't you get about the fact he is wrong?

Wrong about what?

 

[Lord Jestocost]

...What don't you get about the fact he is wrong?...

What facts about what?

 

[bhobba]

What facts about what?

I carefully explained it.

One more time - he said 'whereas at the level of our human consciousness it seems a matter of direct experience that such outcomes occur'

This is because the world around us is classical and, with a few caveats, we know why that is.

If you don't get it when it's that clear -

Thanks
Bill

 

[bhobba]

Wrong about what?

The same as above. The reason our brain perceives single outcomes is because that's how the world around us actually is. QM at the atomic level is different - but we know why these days that is.

I know you think consciousness is involved in that, but such is very backwater these day for good reason. Yes its still a legit interpretation, but far from the only one.

Thanks
Bill

 

[PeterDonis]

This thread has run its course and is now closed.