Common misunderstanding of Copenhagen Interpretation of QM
#1
The Copenhagen interpretation (CI), one of the popular interpretations of quantum mechanics (QM), is often used by people to assert evidence towards involvement of "consciousness" in workings of the universe at a very fundamental level. My intent of this thread is to discuss how this is a very very misguided notion arising out of an incorrect understanding of the interpretation.

Firstly it has to be pointed out that CI is not the only interpretation for QM and there are several out there. Its also important to note that none of this interpretations yet have any meaningful contribution to physics per se because they do not offer any new falsifiable testable predictions.

Coming back to CI, one of the primary reason, IMO, that causes the claimed misunderstanding is because of the famous thought experiment Schrodinger's cat.
Schrödinger Wrote:One can even set up quite ridiculous cases. A cat is penned up in a steel chamber, along with the following device (which must be secured against direct interference by the cat): in a Geiger counter, there is a tiny bit of radioactive substance, so small that perhaps in the course of the hour, one of the atoms decays, but also, with equal probability, perhaps none; if it happens, the counter tube discharges, and through a relay releases a hammer that shatters a small flask of hydrocyanic acid. If one has left this entire system to itself for an hour, one would say that the cat still lives if meanwhile no atom has decayed. The psi-function of the entire system would express this by having in it the living and dead cat mixed or smeared out in equal parts. It is typical of these cases that an indeterminacy originally restricted to the atomic domain becomes transformed into macroscopic indeterminacy, which can then be resolved by direct observation. That prevents us from so naively accepting as valid a "blurred model" for representing reality. In itself, it would not embody anything unclear or contradictory. There is a difference between a shaky or out-of-focus photograph and a snapshot of clouds and fog banks.

Its very important to note that this is a hypothetical experiment, and hence the words chosen in its description are very vague and actually incorrect when it comes to actual physics. The biggest error is usage of the word "observation" in the above text. Because of its inherent anthropocentric nature its easy to mistake that CI claims to involve consciousness, associated with the act of observation, in the so called wavefunction collapse.

This is far from truth. CI actually uses the word "measurement" as a cause for wavefunction collapse. And this is not at all in the sense of "human act of measurement". Infact what constitutes measurement, known as measurement problem in quantum mechanics, is an active field of research, but it most certainly doesn't invoke necessity of human involvement.

For example in the double slit experiment the destruction of interference pattern can be achieved via placing particle detectors close to the slits. How CI explains this behavior is that the act of detection by the particle detectors causes a wavefunction collapse of the particle, which makes interference of the wavefunction impossible. This doesn't need any human observation, just presence of the inanimate particle detectors. And their absence always results in formation of the interference pattern on the screen.

In summary CI doesn't offer any positive evidence for involvement of consciousness in fundamental workings of the universe.
[+] 2 users Like Kanad Kanhere's post
Reply
#2
This SciAam article about QBism (Quantum Bayesianism), a recently proposed interpretation of Quantum Mechanics, also outlines how different epistemic stances underlie different QM interpretations and attempts to forestall hijacking by mystics which these interpretations seem prone to.
Can Quantum Bayesianism Fix the Paradoxes of Quantum Mechanics?

Here is an excerpt to serve as a tl;dr version:
Quote:QBism, which combines quantum theory with probability theory, maintains that the wave function has no objective reality.
...
One system—one event—can have as many different wave functions as there are observers. After observers have communicated with one another and modified their private wave functions to account for the newly acquired knowledge, a coherent worldview emerges.
...
The wave function's collapse is just an observer suddenly and discontinuously revising his or her probability assignments based on new information, in the same way that a doctor would revise a cancer patient's prognosis based on a new CT scan. The quantum system hasn't undergone some strange and inexplicable change; the change is in the wave function, which is chosen by the observer to encapsulate the person's expectations.
...
By insisting that the wave function is a subjective property of the observer, rather than an objective property of the (Schrodinger's) cat in the box, QBism eliminates the puzzle. The theory says that of course the cat is either alive or dead (and not both). Sure, its wave function represents a superposition of alive and dead, but a wave function is just a description of the observer's beliefs. Asserting that the cat is truly both alive and dead is akin to a baseball fan saying that the Yankees are stuck in a superposition of both won and lost until he reads the box score. It's an absurdity, a megalomaniac's delusion that one's personal state of mind makes the world come into being.

Some asides and lateral references:
(1) Assertions like David Tong's that we can conclude that we are not living in a simulation simply because chiral fermions cannot be placed in a discrete lattice, need to be examined with the epistemological assumptions therein made explicit. The epistemic stance of Tong's is different from, say, Bohr's, according to which there is no reason to expect every property of a model (built to account for some observations) to be a property of the Universe itself.
(2) The SciAm article provides a quickfire introduction to the classic frequentist-Bayesian debate. To forestall additional misconceptions that the Bayesian approach upholds some kind of 'subjective view of reality', it maybe worth emphasizing at the risk of stating the obvious that it is only the construction of the Bayesian priors (and the updated posterior estimates) that maybe thought of as 'subjective', not the observations themselves which come from the 'real world'.
(3) Many models in computational neuroscience have been inspired by models from statistical physics (eg. Ising Model). In the case of full-scale adoption of Bayesian approaches however, neuroscientists seem to have been earlier adopters than physicists. The inherently context-rich nature of neuroscience problems which motivates the construction of informative priors, and the technical challenges in recording large data-sets of observations demanded by strict frequentist approaches, have contributed in no small measure to this early adoption by neuroscientists.
[+] 1 user Likes arvindiyer's post
Reply
#3
In the below post physicist Sean Carroll talks about a survey among expert physicists etc and calls for more work regarding this issue.
http://www.preposterousuniverse.com/blog...n-physics/

In this video he discusses the same issue while explaining many world interpretation which he accepts.

I don't think it is not primarily a question of empirical investigation but metaphysical what does the reality corresponds to given the following observation. It lies in the intersection between philosophy of physics and quantum mechanics.
Reply
#4
Hi,

I would like to share one very interesting article/research paper I came across two weeks ago. It talks about collapse of wave function and the "observer effect" in collapsing of wave function.

It's titled "Does consciousness really collapse the wave function? : A possible objective biophysical resolution of the measurement problem".

Read/download this article @ http://arxiv.org/pdf/quant-ph/0509042.pdf

The article/research paper is a bit long, only 36 pages.

Thank you smile
Reply
#5
(11-Jun-2013, 06:03 AM)Cosmic Entity Wrote: Hi,

I would like to share one very interesting article/research paper I came across two weeks ago. It talks about collapse of wave function and the "observer effect" in collapsing of wave function.

It's titled "Does consciousness really collapse the wave function? : A possible objective biophysical resolution of the measurement problem".

Read/download this article @ http://arxiv.org/pdf/quant-ph/0509042.pdf

The article/research paper is a bit long, only 36 pages.

Thank you smile

The following is from that paper (not published in any scientific journal I assume) you have in your post.

Quote:The eye as a macroscopic apparatus and its possible role in resolving the
measurement problem

I am not a physicist but my understanding is that the eye (or any inanimate detector) has nothing to do with the wave function collapse. In order to do a measurement you have to shine some light on the experimental set up before the detection can be made by the eye (or any inanimate detector). It is this shining of the light that causes the wave function to collapse. So I really do not understand why this paper is talking about visual pathways in the eye.

Few questions for you. Where is the eye (as a macroscopic apparatus) placed in the experimental set up? And what will happen if a blind eye (visual pathways are irrelevant in the blind eye, right?) is placed at this location instead?

PS: I did not read the paper. Just skimmed through it and stopped when I saw pictures of the eye.
Reply
#6
Observation: I don't think physicists mean by it what you think they mean.
Reply
#7
(11-Jun-2013, 09:03 AM)Captain Mandrake Wrote:
(11-Jun-2013, 06:03 AM)Cosmic Entity Wrote: Hi,

I would like to share one very interesting article/research paper I came across two weeks ago. It talks about collapse of wave function and the "observer effect" in collapsing of wave function.

It's titled "Does consciousness really collapse the wave function? : A possible objective biophysical resolution of the measurement problem".

Read/download this article @ http://arxiv.org/pdf/quant-ph/0509042.pdf

The article/research paper is a bit long, only 36 pages.

Thank you smile

The following is from that paper (not published in any scientific journal I assume) you have in your post.

Quote:The eye as a macroscopic apparatus and its possible role in resolving the
measurement problem

I am not a physicist but my understanding is that the eye (or any inanimate detector) has nothing to do with the wave function collapse. In order to do a measurement you have to shine some light on the experimental set up before the detection can be made by the eye (or any inanimate detector). It is this shining of the light that causes the wave function to collapse. So I really do not understand why this paper is talking about visual pathways in the eye.

Few questions for you. Where is the eye (as a macroscopic apparatus) placed in the experimental set up? And what will happen if a blind eye (visual pathways are irrelevant in the blind eye, right?) is placed at this location instead?

PS: I did not read the paper. Just skimmed through it and stopped when I saw pictures of the eye.

Hi,

I too am not a physicist either. I was not satisfied with the reasons I had read regarding how the presence of conscious observer can change the results in a QM experiments. So while searching for it I came across that document. Day before yesterday I saw the post related to topic here and so I posted it, in a hope that someone with better understanding of the concepts would provide an explanation regarding what exactly is going on.

So probably I am in the same boat as you are in or may be in a lower boat than you are :-). I am sorry I do not haver the answers to your questions.

Thank you smile
Reply
#8
Cosmic Entity,
Thanks for the paper. I skimmed through it and it looks good. I have saved it for detailed reading at a later date. Its a good source to show people that there is lot of other things that the quantum states have to go through before reaching the conscious brain.

(11-Jun-2013, 09:03 AM)Captain Mandrake Wrote: In order to do a measurement you have to shine some light on the experimental set up before the detection can be made by the eye (or any inanimate detector). It is this shining of the light that causes the wave function to collapse. So I really do not understand why this paper is talking about visual pathways in the eye.

Captain Mandrake, there is some validity in your objections. But I want to point out that "shining the light" doesn't necessarily cause a wave collapse. But its true that it does not make much sense to talk about visual pathways.
  • What about other senses?
  • Also there are umpteen other reasons (other than light shining) that might have already caused the collapse.
  • Finally I think the theory completely misses the point that all that eye will collapse is the state of photons that reach the eye, but we are interested in the wave collapse of the source. What I mean is if we do the double split experiment and take a snap of the screen, via some automatic process, then one person looks at the snap while other looks at the screen, as per this paper, its possible for them to observe different results. That seems to contradict our everyday understanding of things.
[+] 2 users Like Kanad Kanhere's post
Reply
#9
Kanad,

Quote:But I want to point out that "shining the light" doesn't necessarily cause a wave collapse.

I have been trying to find out how the detection is actually done. By detection my understanding is that we are trying to figure out where the photon/electron from the double-slit experiment is. In order to do that wouldn't we have to shine some light on the path of photons/electrons and then look at the reflection of the light from these photons/electrons? I assumed that it was this step in the detection process that makes wave function to collapse. I thought that it is irrelevant if there was a human eye or an inanimate detector to pick up the reflected light.

Can you please let me know if and how this understanding is wrong?

PS: Here is nice video by Jim Al Khalili on the double slit experiment.

http://www.youtube.com/watch?v=FW7ynlaF3o4

In the video he shows that when the detector is on we do not get inteference pattern and when it is off there is an interference pattern. Unfortunately he does not explain how the detector works when it is on. Can someome explain how this detector works.
Reply
#10
(12-Jun-2013, 09:40 PM)Captain Mandrake Wrote: I have been trying to find out how the detection is actually done. By detection my understanding is that we are trying to figure out where the photon/electron from the double-slit experiment is. In order to do that wouldn't we have to shine some light on the path of photons/electrons and then look at the reflection of the light from these photons/electrons? I assumed that it was this step in the detection process that makes wave function to collapse. I thought that it is irrelevant if there was a human eye or an inanimate detector to pick up the reflected light.

This part is correct.

(12-Jun-2013, 09:40 PM)Captain Mandrake Wrote: Can you please let me know if and how this understanding is wrong?

I wanted to point out two things
1. Shining light doesn't necessarily cause wavefunction collapse.
I need to collect references for this, but this is from random reading. I don't think if I shine a beam of light on another beam of light, it will cause a wavefunction collapse of either of the beams.

2. Shining light is not the only way wavefunction collapses. There are other ways as well. For example in the double slit experiment when the wavefunction of electron reaches the screen, it collapses so that the electron is seen as a 'dot' on the screen.
Reply
#11
(12-Jun-2013, 11:06 PM)Kanad Kanhere Wrote:
(12-Jun-2013, 09:40 PM)Captain Mandrake Wrote: I have been trying to find out how the detection is actually done. By detection my understanding is that we are trying to figure out where the photon/electron from the double-slit experiment is. In order to do that wouldn't we have to shine some light on the path of photons/electrons and then look at the reflection of the light from these photons/electrons? I assumed that it was this step in the detection process that makes wave function to collapse. I thought that it is irrelevant if there was a human eye or an inanimate detector to pick up the reflected light.

This part is correct.

(12-Jun-2013, 09:40 PM)Captain Mandrake Wrote: Can you please let me know if and how this understanding is wrong?

I wanted to point out two things
1. Shining light doesn't necessarily cause wavefunction collapse.
I need to collect references for this, but this is from random reading. I don't think if I shine a beam of light on another beam of light, it will cause a wavefunction collapse of either of the beams.

2. Shining light is not the only way wavefunction collapses. There are other ways as well. For example in the double slit experiment when the wavefunction of electron reaches the screen, it collapses so that the electron is seen as a 'dot' on the screen.

Thanks for the explanation.

I agree wiith 2). I understand that the wavefunction collapses at the screen and we exactly know where the photon/electron hit the screen as a particle. Similarly when light is shined (shone ??) on the photon/electron before it hits the screen there is a collapse of the wavefunction, ie the location of the photon/electron in transit is identified with some certainty. Based on some casual reading my understanding is that the certainty with which we know the location will also be the extent to which we do not see the interference pattern on the screen. Wonder how the location of the detector with respect to the screen and the slits affects the pattern on the screen.

On 1) I do not understand the two beam thing you are talking about. I will ask some questions after I do some reading.
Reply
#12
DISCLAIMER: I am no expert or professional physicist. My comments are based on my reading of QM.

(12-Jun-2013, 11:48 PM)Captain Mandrake Wrote: I agree wiith 2). I understand that the wavefunction collapses at the screen and we exactly know where the photon/electron hit the screen as a particle. Similarly when light is shined (shone ??) on the photon/electron before it hits the screen there is a collapse of the wavefunction, ie the location of the photon/electron in transit is identified with some certainty. Based on some casual reading my understanding is that the certainty with which we know the location will also be the extent to which we do not see the interference pattern on the screen. Wonder how the location of the detector with respect to the screen and the slits affects the pattern on the screen.

Uncertainty is a fancy word for "spread" of the wavefunction. And its the spread i.e. wave nature, which is what is causing the interference in the first place. Hence uncertainty is most certainly critical in the double-slit behavior that we see.

About the placement of the detector, its very important. This can be observed by just moving the screen very close to the two slits. Interference pattern doesn't occur in that case [refer this experiment]
Reply




Users browsing this thread: 1 Guest(s)