Copenhagen & Many Worlds Falsified?

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Professor John Cramer, author of the transactional interpretation of QM, recently gave a talk at Boskone, the famous science fiction con, that sugggests a new experiment may be about to falsify the predictions of the Copenhagen and Many Worlds interpretations(and also decoherence and Consistent Histories). Not surprisingly, since Cramer is giving the talk, the transactional interpretation is NOT falsified by the experiment.

Here's the Power Point presentation from the talk
 
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selfAdjoint said:
Professor John Cramer, author of the transactional interpretation of QM, recently gave a talk at Boskone, the famous science fiction con, that sugggests a new experiment may be about to falsify the predictions of the Copenhagen and Many Worlds interpretations(and also decoherence and Consistent Histories). Not surprisingly, since Cramer is giving the talk, the transactional interpretation is NOT falsified by the experiment.

Here's the Power Point presentation from the talk

It would have been nice if he had included an exact reference to the Afshar experiment, especially since his whole argument rests solely on the validity of its result.

It is also strange that he argued that his theory of TI of QM and the formalism of QM both are consistent with the Afshar experiment, but CI and MW aren't. I find it strange because both CI and MW are BASED on the formalism of QM, i.e. they are not separate from it. So how he came up with the conclusion that they offer a result that differ from the QM formalism itself is puzzling. This is because if that is true, then one can LOGICALLY falsify both interpretations without having to do any experiment.

Zz.
 
Read the presentation again, note his distinction between an interpretation and a model, and also the different responses to Afshar's wire grid. It seems that in spite of the mantra about the equivalence of the interpretations there is indeed a difference, and that the difference is testable. At any rate, if this is not so, the negation needs to be supported.
 
Apparently, Afshar gave a talk at Texas A&M yesterday on a forthcoming paper: Violation of Bohr's principle of complementarity in an optical "which-way" experiment. I could not locate much on him.

Unless the HUP is shown to be violated, I am not sure how an experiment is going to detect differences between competing interpretations. Maybe the answer is in the powerpoint from Cramer. But I would object to drawing a distinction between a model and an interpretation. Either way, we are dealing with "scientific theory" regardless of what you call it.
 
I am not familiar with Ashfar's experiment, but there is certainly a difference between the predictions of Many-Worlds and the orthodox von-Neumann approach to quantum mechanics. I will not discuss Copenhagen here, because it probably has enough variants to evade any experimental test you might propose.

In the orthodox approach, wavefunction collapse is postulated to happen when you make a measurement. Whether this collapse is a real physical process, or just an updating of the information represented by the wavefunction is deliberately not addressed. However, if we can agree that some particular physical process constitutes a measurement, then we should not be able to recover the original superposition after the measurement has taken place.

In contrast, Many-Worlds postulates no-collapse, so we should be able to undo a measurement if we can control a sufficiently large number of degrees of freedom of the quantum system, apparatus, environment, etc.

The difficulty of testing this is to actually agree on what constitutes a measurement. Different interpretations can evade the predictions of many proposed experimental tests can by defining the notion of measurement differently. I suspect that a similar issues might arise in the analysis of Ashfar's experiment, but I have to look at it in more detail before I make any further comment.

Proponents of different interpretations have got very good at making it look like their point of view is the only reasonable one to take. Therefore, I would advise people to take Cramer's view with a pinch of salt until the implications of the experiment have been fully debated. It is worth noting that Copenhagen, Many-Worlds and the transactional interpretation are not the only options on the market and I don't think that the dividing line between theory and interpretation can be made as clear as he thinks it is.
 
Obviously, I'm not the only one who has never heard of this experiment till now. Considering that I troll most of the major physics journals regularly (daily?), I'm quite curious as to where this result was published. Considering the implication of the experiment, such measurement would qualify to be considered for publication in "The Big 3" of physics journals. If it wasn't, why? [.. and all the usual warning bells typically would go off here - can we say "cold fusion"?]

If anyone can find the citation to this experiment, pass it along. Thanks!

Zz.
 
It appears that this result has not been published yet - nor is it available as a preprint. I imagine that it is in the process of being written up. Ashfar has just been giving a few seminars about the result to selected audiences and this is apparently how Cramer knows about it. We will have to wait until the paper appears to make any sensible comments. I hope he posts it to arXiv/quant-ph soon.
 
I was just about to post a topic about this, but lucky for me I searched the forum first. Anyways...

It is also strange that he argued that his theory of TI of QM and the formalism of QM both are consistent with the Afshar experiment, but CI and MW aren't. I find it strange because both CI and MW are BASED on the formalism of QM, i.e. they are not separate from it. So how he came up with the conclusion that they offer a result that differ from the QM formalism itself is puzzling. This is because if that is true, then one can LOGICALLY falsify both interpretations without having to do any experiment.

I'll quote from my source:
"It has been widely accepted that the rival interpretations of quantum mechanics, e.g., the Copenhagen Interpretation, the Many-Worlds Interpretation, and my father John Cramer's Transactional Interpretation, cannot be distinguished or falsified by experiment, because the experimental predictions come from the formalism that all such interpretations describe. However, the Afshar Experiment demonstrates in an interaction-free way that there is a loophole in this logic: if the interpretation is inconsistent with the formalism, then it can be falsified. In particular, the Afshar Experiment falsifies the Copenhagen Interpretation, which requires the absence of interference in a particle-type measurement. It also falsifies the Many-Worlds Interpretation which tells us to expect no interference between "worlds" that are physically distinguishable, e.g., that correspond to the photon's measured passage through one pinhole or the other." http://www.kathryncramer.com/wblog/archives/000530.html
 
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RageSk8 said:
I was just about to post a topic about this, but lucky for me I searched the forum first. Anyways...



I'll quote from my source:
"It has been widely accepted that the rival interpretations of quantum mechanics, e.g., the Copenhagen Interpretation, the Many-Worlds Interpretation, and my father John Cramer's Transactional Interpretation, cannot be distinguished or falsified by experiment, because the experimental predictions come from the formalism that all such interpretations describe. However, the Afshar Experiment demonstrates in an interaction-free way that there is a loophole in this logic: if the interpretation is inconsistent with the formalism, then it can be falsified. In particular, the Afshar Experiment falsifies the Copenhagen Interpretation, which requires the absence of interference in a particle-type measurement. It also falsifies the Many-Worlds Interpretation which tells us to expect no interference between "worlds" that are physically distinguishable, e.g., that correspond to the photon's measured passage through one pinhole or the other." http://www.kathryncramer.com/wblog/archives/000530.html

The blog did not indicate two things: (1) that there's no references to the Afshar experiment and (2) that it is having problems in the refereeing stage. In fact, unconfirmed reports have indicated that the Afshar experiment report that was uploaded to the e-print archive was removed, something that is unheard of for arXiv.

http://groups.yahoo.com/group/undernetphysics/message/907

Zz.
 
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  • #10
I see that this thread hasn't been moving for quite some time. Nor has it been read much, lately, either. So, I'll post what I have to say only in brief.


This is how I see the situation:

1) The reported results of the Afshar experiment are just what the quantum formalism predicts.

2) The type of thinking that Cramer employs - in the name of "Copenhagen" - in order to arrive at a conclusion which contradicts the Afshar results is, in fact, a manner of thought which the Copenhagen Interpretation itself deems invalid.

3) This manner of thought results from taking a rather extreme point of view regarding a notion which must be invoked in any typical discussion of a Wheeler-Delayed-Choice scenario. This type of thinking is inconsistent with the quantum formalism.
 
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  • #11
Afshar Setup

The following summary of the Afshar experiment may prove helpful.

--------------------------

Afshar experimental arrangement:

A beam of light of fixed wavelength from a coherent source is incident upon the following sequential arrangement:

- double-slit [1, 2]
- wire gird [WG]
- lens [L]
- particle detectors [1' ,2']

See diagram.

--------------------------

Some details:

1) The wire grid WG consists of wires placed at the positions of the (would-be) interference minima (for a screen placed at that distance from the double-slit).

2) The lens L is such that rays from slit 1 (2), in the absence of any obstacles, will be focused at detector 1' (2').

3) With only one slit open, and WG in place, the detector experiences a 6% loss relative to the setup with no WG. WG is therefore said to have 6% opacity.

--------------------------

Summary of reported results:

a) No WG + both slits open --> no loss;

b) WG + only one slit open --> 6% loss;

c) WG + both slits open --> < 0.1% loss.

--------------------------

Conclusion:

Since the results of c) are very nearly the same as those of a) and, on the other hand, appreciably different from those of b), the situation in c) must be that of "wave-like" behavior (i.e. the quantum system interacts with both slits, and not just one slit). That is to say, two waves are propagating, one from each slit, and in the vicinity of WG these waves overlap and interfere to produce minima at the locations of the wires in WG. For this reason, WG is essentially transparent to the incident beam.
 

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  • #12
Eye_in_the_Sky said:
Summary of reported results:

a) No WG + both slits open --> no loss;

b) WG + only one slit open --> 6% loss;

c) WG + both slits open --> < 0.1% loss.

Thanks for supplying this information.

It doesn't seen so weird to me. There must be a lot of experimental setups which demonstrate the wave nature of light. For example, you can insert a polarizer lens between 2 other polarizer lenses, and at the proper angles get more light from 3 than from 2. This loosely compares to the Afshar setup, which also gets more light with 2 slits than with 1.

Do you have any idea how Afshar concludes this separates one QM interpretation from another? I cannot picture how the formalisms would yield anything but identical predictions.
 
  • #13
DrChinese said:
Do you have any idea how Afshar concludes this separates one QM interpretation from another? I cannot picture how the formalisms would yield anything but identical predictions.

I think it's fair to say that, in the literal sense, by definition, an "interpretation of a formalism" is something necessarily consistent with that formalism. Of course, in the process of formulating such an interpretation, one could err in some way, and consequently, end up with something which does, in fact, contradict the formalism. Regarding this, I would use the expression "the interpretation fails" in order to indicate that the said interpretation is inconsistent with the formalism.


With the above in mind, what Afshar and Cramer have claimed[*] regarding "Copenhagen" and "Many Worlds" amounts to the following:

These interpretations fail on account of certain unwitting implications which contradict the quantum formalism.

That is to say, Afshar and Cramer claim that the authors of these interpretations have unintentionally "stepped out of line" with the quantum formalism, making assertions which, when given the proper consideration, turn out to have implications which contradict the formalism itself.[**]
_____________________


[*] This is only one of two parts of their claim. The other part is that these interpretations fail in relation to what the experimental facts happen to be (whence the significance of the Afshar results).

[**] Does the content of this post serve to dispel the strangeness about which ZapperZ wrote (in the second post of this thread)?


ZapperZ said:
It is also strange that he argued that his theory of TI of QM and the formalism of QM both are consistent with the Afshar experiment, but CI and MW aren't. I find it strange because both CI and MW are BASED on the formalism of QM, i.e. they are not separate from it. So how he came up with the conclusion that they offer a result that differ from the QM formalism itself is puzzling. This is because if that is true, then one can LOGICALLY falsify both interpretations without having to do any experiment.
 
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  • #14
Something is bothering me in what I wrote above ... in things like:

Eye_in_the_Sky said:
... These interpretations fail on account of certain unwitting implications which contradict the quantum formalism.

... making assertions which ... have implications which contradict the formalism itself.
How can one calculate what the formalism predicts, unless, at least at some level and to some degree, one employs an interpretation to "guide" that calculation?

------------------------

I think it would be better to skip all of the generalizations and go right to the unambiguous particulars of what Cramer purports to be implied by "Copenhagen" and "Many Worlds". Doing that will certainly clear things up.
 
  • #15
Cramer, in the name of "Copenhagen"

Let us now establish the particulars of Cramer's argument in relation to the Copenhagen Interpretation.

--------------------------------------

Two Measurement Options:

Take a look at the diagram. It shows a modification of the Afshar setup in which the wire grid WG has been removed. For this setup, consider the following two measurement options:

(a) Before light can reach the lens, at a screen labeled
sigma1, measure an interference pattern;

(b) After light has passed through the lens, at a screen
labeled sigma2, measure two distinct, separate images,
situated at 1' and 2'.

--------------------------------------

Cramer's Rendition:

Here is what Cramer has to say, in the name of "Copenhagen", regarding these two options (see diagram):

(C-a) Measure at sigma1, the interference pattern, giving the
wavelength and the momentum of the photon;

(C-b) Measure at sigma2, which slit the particle passed
through, giving its position.

--------------------------------------

Complementarity:

By statements (C-a) and (C-b), Cramer purports that, according to the Copenhagen Interpretation, the following is true:

P1: Options (a) and (b) are experiments which measure complementary attributes of the quantum system.

--------------------------------------

Argument for (C-b):

Cramer's statement (C-b) regarding option (b) is built upon the following type of argument:

P2: A photon arriving at 1' (2') must have passed through slit 1 (2) and not 2 (1). Therefore, a measurement at sigma2 corresponds to a "determination" of which slit the photon went through.

Since this type of argument serves as a basis for Cramer's statement (C-b) concerning (b), and (C-b) itself is said in the name of "Copenhagen", it must be that the precise sense in which an argument like P2 eventually leads to Cramer's (C-b) is seen by Cramer to be deemed valid by the Copenhagen Interpretation.

--------------------------------------

Cramer's Conclusion:

In a final step, the wire grid WG is put back into the arrangement of (b) to give, once again, the Afshar setup. With all of the above in mind, Cramer then concludes - in the name of "Copenhagen" - regarding the Afshar experiment (see diagram):

The measurement-type forces particle-like
behavior, so there should be no interference, and
no minima ...

This statement makes the intended meaning of Cramer's (C-b) absolutely clear. That intended meaning is equivalent to the following proposition:

P3: In option (b), the measurement performed at sigma2 is physically equivalent to a nondemolition measurement which takes place at the site of the slits and determines which slit the photon passes through.

To repeat, according to Cramer, P3 (like the propositions P1 and P2 above) is deemed correct by "Copenhagen".
 

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  • #16
So did this experiment ever get published?
 
  • #17
Eye_in_the_Sky said:
P2: A photon arriving at 1' (2') must have passed through slit 1 (2) and not 2 (1). Therefore, a measurement at sigma2 corresponds to a "determination" of which slit the photon went through.

I can accept this, but how does Afshar's setup determine that photon's momentum when, excluding those points barred by the wires, it could have passed through the lens at any other point with varying probability?
 
  • #18
This has gotten into Newscientist as well. I can't claim to be an expert, but I am not convinced.

P2: A photon arriving at 1' (2') must have passed through slit 1 (2) and not 2 (1). Therefore, a measurement at sigma2 corresponds to a "determination" of which slit the photon went through.
Why must a photon arriving at 1' (2') have passed through slit 1 (2)?
 
  • #19
P2: A photon arriving at 1' (2') must have passed through slit 1 (2) and not 2 (1). Therefore, a measurement at sigma2 corresponds to a "determination" of which slit the photon went through.

Tony Wagstaff said:
I can accept this, but how does Afshar's setup determine that photon's momentum when, excluding those points barred by the wires, it could have passed through the lens at any other point with varying probability?
The Afshar setup doesn't determine the photon's momentum (... except for the magnitude, in that a lens with such-and-so index of refraction focuses the light as it does (... but this information, like that of the alleged "position measurement", is only retrodictive)).

However, in order for Cramer to make his point, there is no need for a momentum determination.

And what is Cramer's point? His point (erroneously made!) is:

According to the Copenhagen Interpretation, proposition P3 is true.
P3: In option (b), the measurement performed at sigma2 is physically equivalent to a nondemolition measurement which takes place at the site of the slits and determines which slit the photon passes through.
--------------------------------

FZ+ said:
This has gotten into Newscientist as well. I can't claim to be an expert, but I am not convinced.

... Why must a photon arriving at 1' (2') have passed through slit 1 (2)?
The Copenhagenist is not convinced either. Here is his response:

Proposition P2 is a "valid" statement in the following sense: Given that a photon has arrived at 1' (2'), then if a nondemolition measurement had been performed at the site of the slits, the photon would have been found to pass through slit 1 (2). However, in the absence of the actual performance of such a measurement, it is in general incorrect to say that, on account of our "knowing" what the result of such a measurement would have been, the quantum phenomena will be the same as those obtained when the measurement is in fact performed. That it is incorrect to say so follows from Bohr's "Principle of Nonseparability".

In fact, with a bit of reflection on the two "measurement options", we see that they are not at all "complementary". They were:

Two Measurement Options:

(a) Before light can reach the lens, at a screen labeled
sigma1, measure an interference pattern;

(b) After light has passed through the lens, at a screen
labeled sigma2, measure two distinct, separate images,
situated at 1' and 2'.
Option (a) is consistent with a "wave picture" but not a "particle picture", whereas, option (b), on the other hand, is consistent with both a "wave picture" and a "particle picture". The two options are therefore not complementary.

All of this P2-like thinking is due to a "playing" of "Wheel-er's Game of Delayed Choice of Fortune".
 
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  • #20
RageSk8 said:
It also falsifies the Many-Worlds Interpretation which tells us to expect no interference between "worlds" that are physically distinguishable, e.g., that correspond to the photon's measured passage through one pinhole or the other."

Is that really what the MWI tells us? I thought it wasn't.

I think the claim that the MWI is inconsistent with the formalism of QM is rather strange, because essentially MWI is what happens when you take the formalism literally (it says there's a wave function, and nothing else).

It looks to me like what has actually been falsified, if anything, is the standard strawman version of MWI that has world-splitting as a fundamental physical process. Am I correct?
 
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  • #21
Ontoplankton said:
It looks to me like what has actually been falsified ...
Cramer's claim itself is FALSE - CI and MWI have not been falsified, neither in relation to the QM formalism nor with respect to the experimental facts.
 
  • #22
I've read your posts now, and I think I see what you're saying.

If I understand correctly, Cramer is saying that at the first plane (sigma_1), a measurement takes place (if you're a Copenhagenist) or a world-splitting takes place (if you're an Everettist). But this isn't what the interpretations themselves say: MWI says world-splitting only takes place later, when there's decoherence, and Copenhagen says measurement only takes place later (at the second plane, or at the observer). Have I got that correct?

If I do have this correct, then it looks like a pretty basic misunderstanding to me (at least of MWI, don't know about what Copenhagen proponents usually say about where measurement happens), and I like how Cramer weasels out of the possibility that he has misunderstood or misrepresented the interpretations in advance:

However, quantum interpretational theorists are fairly slippery characters. It remains to be seen if they will find some way to save their pet interpretations.

On the other hand, I'm in doubt that I've understood this, because he also says decoherence and consistent histories have been falsified.
 
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  • #23
Thanks, Eye in the Sky, that's basically what I thought.
 
  • #24
Ontoplankton said:
If I understand correctly, Cramer is saying that at the first plane (sigma_1), a measurement takes place (if you're a Copenhagenist) ...
Yes. (I would only change the wording of "a measurement takes place" to "the equivalent of a measurement takes place".)


... or a world-splitting takes place (if you're an Everettist) ...
Yes.


... But this isn't what the interpretations themselves say: MWI says world-splitting only takes place later, when there's decoherence, and Copenhagen says measurement only takes place later (at the second plane, or at the observer). Have I got that correct?
Yes (… but I am unable to confirm the part about "decoherence" in MWI (because in my (more basic) understanding of MWI, all I have is that a "world-splitting" in MWI occurs wherever/whenever a "measurement" happens in Copenhagen)).


If I do have this correct, then it looks like a pretty basic misunderstanding to me ...
Yet, somehow not "basic" enough to have fooled more than one competent physicist.


On the other hand, I'm in doubt that I've understood this ...
Don't doubt it! Retrodiction (i.e. the utilization of present information or ideas to infer or explain a past event or state of affairs) in QM can be real tricky.


... because he also says decoherence and consistent histories have been falsified.
All it means is that Cramer finds it easier to not err in TI than in all of the other interpretations when it comes to "retrodiction".
 
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  • #25
Eye_in_the_Sky, thanks for your explanation;

I found another good explanation of what is going on here, in the comment by 'Aaron'.
 
  • #26
So the claim that a measurement at sigma2 corresponds to a "determination" of which slit the photon went through, is no stronger than EPR's claim that given two "paired" particles S1 and S2, a position measurement on S1 "determines" the position of S2.
Bohr, by contrast, insisted that we can only infer from a position measurement on S1 what the position of S2 would be if we measured it. If we measure S2's momentum instead then we disturb the system sufficiently to nullify the inference.
In Afshar's experiment, what would we need to do similarly to nullify the claim that a measurement at sigma2 "determines" which slit the photon went through?
 
  • #27
Locrian said:
So did this experiment ever get published?

Ashfar will publish a paper soon. There is a pretty good summary article on it in New Scientist this week but it will be interesting to see the paper. Here's a short quote from the NS article;

Afshar admits that, in the end, he is unsure what his experiment means in detail for quantum theory. "We are back at the fork in the road encountered by Bohr and Einstein, and avoided entirely due to Bohr's ingenious complementarity," he says.

But we've still got a wave that's a particle, and a particle that's a wave. What are we to make of that? Well, Afshar says, there are two choices. The first is to shrug your shoulders and concede that human logic and language will never explain what is going on. The second option is to conclude that the particle phenomenon isn't really there, and to use the wave picture for the entire experiment. In this interpretation, the interference pattern and which-way information are not logically inconsistent - the waves do go through both slits, while the "image" each detector sees corresponds to light waves from only one of the pinholes.

Afshar believes the second option is the simpler and better choice, which leaves a big question: is there any such thing as a photon?

The photon detectors in Afshar's experiment "click" when they detect a photon. But if there is no photon, what are they seeing? It comes down to the interpretation of Einstein's photoelectric effect, the experiment that "proved" the existence of the photon - and won him the 1921 Nobel prize. Afshar says the American physicist Willis Lamb and others have explained these particle-like clicks as a result of the interaction of unquantised electromagnetic waves and quantised matter particles in the detector. So although Einstein was right to doubt Bohr's complementarity, he was "right for the wrong reasons", Afshar says. "In order to declare Einstein the winner of the Bohr-Einstein debate, we must take back his Nobel prize. We have no other choice but to declare the idea of Einstein's photon dead."

I rekon its quite exciting myself. Apparently he has another experiment planned which he believes "could resolve the light quantisation issue once and for all"
 
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  • #28
Tony Wagstaff said:
So the claim that a measurement at sigma2 corresponds to a "determination" of which slit the photon went through, is no stronger than EPR's claim that given two "paired" particles S1 and S2, a position measurement on S1 "determines" the position of S2.
To this, I would like to add: not only is it "no stronger", but it is "definitively weaker". That is to say, the degree of "determination" in the sigma2-measurement is less than that which occurs in the EPR scenario. Specifically, in the language of "collapse", the sigma2-measurement does not "induce" a "collapse" at the slits, whereas in the EPR scenario, the measurement upon S1 does "induce" a "collapse" with regard to S2.

To put it another way, in the simga2-measurement scenario (see diagram), the two cases of "no, we do not perform a measurement at the slits" and "yes, we do perform a measurement at the slits" are physically distinct; that is, by introducing a suitably chosen identical "element" into each of these cases, we find that each case will exhibit distinct quantum phenomena. For the EPR, scenario, on the other hand, there is no such "element" which can be introduced into each of the cases ("no, we do not perform the position-measurement on S2", and "yes, we do perform the position-measurement on S2") that will distinguish between the them.


... what would we need to do similarly to nullify the claim that a measurement at sigma2 "determines" which slit the photon went through?
... Tony, I will have to address the remainder of your post at another time. For, at this particular moment, there is some subtlety which evades me.
 
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  • #29
The results of Afshars single-photon experiement are now in and confirm his earlier resulsts. Bye bye CI ...

And here's an article by Cramer which may be of interest ---> http://www.analogsf.com/0409/altview2.shtml
 
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  • #30
SimonA said:
The results of Afshars single-photon experiement are now in and confirm his earlier resulsts. Bye bye CI ...

And here's an article by Cramer which may be of interest ---> http://www.analogsf.com/0409/altview2.shtml

"confirm by his earlier results<sp>"?

You're forgetting that OTHER people will confirm his results, not him!

Secondly, at the bottom of that article, the manuscript was only recently submitted to PRL (July 2004). It is anything but a done deal, and anyone who has tried to publish anything in PRL would know this (you can get up to FOUR referees reviewing your paper).

Thirdly, as mentioned above, even if it appears in a peer-reviewed journal, it will then finally be presented to the physics community and be tested, questioned, and prodded. The road to being an accepted observation, ideas, etc. in physics can be a very long, arduous, and tedious process.

I wouldn't put a bet on the apparent "death" of CI if I were you.

Zz.
 
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  • #31
ZapperZ said:
"confirm by his earlier results<sp>"?

You're forgetting that OTHER people will confirm his results, not him!

Secondly, at the bottom of that article, the manuscript was only recently submitted to PRL (July 2004). It is anything but a done deal, and anyone who has tried to publish anything in PRL would know this (you can get up to FOUR referees reviewing your paper).

Thirdly, as mentioned above, even if it appears in a peer-reviewed journal, it will then finally be presented to the physics community and be tested, questioned, and prodded. The road to being an accepted observation, ideas, etc. in physics can be a very long, arduous, and tedious process.

I wouldn't put a bet on the apparent "death" of CI if I were you.

Okay provisionally confirmed the results of his previous study all pending peer review - if you'd prefer :-)

Someone will surely find plasters for CI but but it does seem to be limping quite badly...

Simon
 
  • #32
SimonA said:
And here's an article by Cramer which may be of interest ---> http://www.analogsf.com/0409/altview2.shtml

Here he goes again:

John Cramer said:
I predict that a new generation of "Quantum Lawyers" will begin to populate the physics literature with arguments challenging what "is" is and claming that the wounded interpretations never said that interference should be completely absent in a quantum which-way measurement.

That's because, as far as I can tell, MWI never did say that, at least not in its more recent versions (see here, here, ...). I'm sure something similar is true for Copenhagen.

Unless there's something I've missed, Cramer is attacking strawmen to sell his transactional interpretation. That's a nasty thing to do, IMHO.
 
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  • #33
SimonA said:
Okay provisionally confirmed the results of his previous study all pending peer review - if you'd prefer :-)

Er.. what previous study?

As far as I know, this IS the only study. The brouhaha so far has been on this one, which from what I understand, was put on ArXiv, and then retracted. So now it has officially been submitted for peer-review publication. He hasn't verified anything previously in print.

Zz.
 
  • #34
ZapperZ said:
Er.. what previous study?

As far as I know, this IS the only study. The brouhaha so far has been on this one, which from what I understand, was put on ArXiv, and then retracted. So now it has officially been submitted for peer-review publication. He hasn't verified anything previously in print.

As far as I know nothing has been published (and been peer reviewed) by Afshar on this yet. Obviously science requires that for good reason but at the end of the day all of us interested in science should be interested in anything which potentially advances our understanding surely ?

The study mentioned in the article I linked and the one being discussed here was first done by Afshar last year and then repeated by him at Harvard. His team have just done a new experiment at very low light intensity using a detector that can detect the arrival of a single quantum of light. I'm no quantum physicist but Afshar seems convinced this has proven that the CI is inconsistent with the quantum formalism.

I doubt it will include anything from this latest experiement but for those in the US Afshar will be on NPR's Science Friday program tonight.

For those of us elsewhere there will be a live broadcast of the program here;

http://sciencefriday.com/streaming.html

More details here ---> http://www.sciencefriday.com/pages/2004/Jul/hour2_073004.html

Simon
 
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  • #35
Is not the essential feature of this result that, although the Copenhagen Interpretation says a photon and a particle can be observed either as a wave or a particle, depending on the experiment, but NOT at the same time, the Ashfar experiment seems to show that they are both simultaneously?
 
  • #36
Yes Garth - although Afshar is going even further and suggesting that the only quantisation that's occurring is in the particles of the emmiter (and detector). Cramer went with this when he used the Hanbury-Brown-Twiss effect in his 1986 paper.

To me (and I'm just talking crazy ideas here..) this suggests that's because the particles that make the emmiter require a certain level of energy spread across them before their orbital shells are full and they release it as a quanta of energy. So this is in some ways a packet because of how its released but its nature is very much wave like and passes through both slits. The only way I could think of explaining the wave nature is if there were waves on the surface of the ZPF. Another possibility is that it is an actual particle (i.e. there is something in light that is by nature unit like) but its infinitisimally lower in 'density' (wrong word but can't think of another more appropriate) than the ZPF and so just hovers at the surface (this would apply to all "massless" 'particles' such as EM). Thus the wave is like its wake in the ZPF but it doesn't actually rise out of it and so doesn't hit the walls between the slits. But that's another discussion :-)

If anyone missed the Afshar interview its available here ---> http://www.npr.org/features/feature.php?wfId=3804795

(You may have to be on Media Player 9 ---> http://www.microsoft.com/windows/windowsmedia/9series/player.aspx for it to work...

Simon
 
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  • #37
Many of you people have basically got your knickers twisted because you've believed the false interpretation that water is bucket like :smile:
 
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  • #38
SimonA said:
Many of you people have basically got your knickers twisted because you've believed the false interpretation that water is bucket like :smile:

Or maybe we're not as guillable as you are. For example:

The study mentioned in the article I linked and the one being discussed here was first done by Afshar last year and then repeated by him at Harvard. His team have just done a new experiment at very low light intensity using a detector that can detect the arrival of a single quantum of light. I'm no quantum physicist but Afshar seems convinced this has proven that the CI is inconsistent with the quantum formalism.

If there is such a thing as a photon detector that has 100% quantum efficiency, we would NEVER have a detection loophole in an EPR-type experiment. The fact is that we DON'T (and there is still the possibility of a detection loophole in EPR-type experiments).

I find that this discussion is rather moot, and premature, considering that the ACTUAL publication isn't out yet. I thought we have already learned the lessons from all the brouhaha surrounding Pon and Fleishmann's "cold fusion" paper.

Zz.
 
  • #39
ZapperZ said:
Or maybe we're not as guillable as you are.


I'm not the one hanging on an interpretation that nature is only determined when I decide how I want to set my experiment up. You call me gullible because new evidence has been suggested that supports my view that CI was for gullible people. I don't have a problem with the formalism, I have a problem with this observer dependent interpretation that has led to wacky new age theories. But then again I have some time for some of Bohm's ideas and they have resulted in the same kind of thing :-)




For example:

If there is such a thing as a photon detector that has 100% quantum efficiency, we would NEVER have a detection loophole in an EPR-type experiment. The fact is that we DON'T (and there is still the possibility of a detection loophole in EPR-type experiments).


So we have to admit we're just scratching the surface at present ? If so I agree...


I find that this discussion is rather moot, and premature, considering that the ACTUAL publication isn't out yet. I thought we have already learned the lessons from all the brouhaha surrounding Pon and Fleishmann's "cold fusion" paper.

Well I think Afshars results are significant enough (unless he's blatantly lying or the "experimenter effect" is of massive significance), to consider CI does not agree with the formalism. And I'm prepared to speculate on that just as the peer reviewers will be when they read his paper.

Simon
 
  • #40
SimonA said:
To me this suggests that's because the particles that make the emmiter require a certain level of energy spread across them before their orbital shells are full and they release it as a quanta of energy. So this is in some ways a packet because of how its released but its nature is very much wave like and passes through both slits.
Simon
Does this result therefore simply endorse the Schrodinger coordinate representation in which particles/photons are wave packets of energy? Particles have also inertial mass whereas photons do not.
 
  • #41
Garth said:
Does this result therefore simply endorse the Schrodinger coordinate representation in which particles/photons are wave packets of energy? Particles have also inertial mass whereas photons do not.

I took the liberty of editing my post there slightly (was late at night!) but I would be more interested in thinking about "what is mass ?". Standard theory would say its to do with how much the quarks 'jitter about'. Relativity says its the amount the particle stretches space-time. And you could even speculate about inertia being the result of all particles retaining a kind of remnant of entanglement from the big bang.

But I find some of the ideas of people like Bernhard Haisch to be very interesting in making progress towards some kind of explanation with a more sound epistemology. This article gets to some of these issues on the second page ---> http://www.science-spirit.org/articles/Articledetail.cfm?article_ID=126

Simon
 
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  • #42
Well there's another "matter is illusion" idea from the more professionally connected physicsts, that mass is just an interaction with a Higgs field. The standard model says that three particles, the weak force bosons, get mass that way, and the speculation is that when all the chips are down, all particle mass will come that way.

But it has been pointed out that most of the mass in our world comes from protons and neutrons, and most of their mass comes, not from the quarks that are their "matter particles" but from the binding energy of the massless gluons that hold them together.
 
  • #43
SimonA said:
I'm not the one hanging on an interpretation that nature is only determined when I decide how I want to set my experiment up. You call me gullible because new evidence has been suggested that supports my view that CI was for gullible people. I don't have a problem with the formalism, I have a problem with this observer dependent interpretation that has led to wacky new age theories. But then again I have some time for some of Bohm's ideas and they have resulted in the same kind of thing :-)

I'm sorry, but where exactly did I say that I'm for one interpretation over another? Just because I question the validity (and interpretation) of this experiement somehow automatically, by default, made me someone who is in favor of CI?

As an experimentalist, I have no patience for such dogma, nor would I ever want to dictate what Nature wants to do. I've encountered way too many instances where such insistance (mainly by theorists) crumble spectacularly. If Nature does end up with an "observer dependent interpretation", so be it. It appears that you have already dictated what Nature should and should not be, simply based on a matter of taste.

Well I think Afshars results are significant enough (unless he's blatantly lying or the "experimenter effect" is of massive significance), to consider CI does not agree with the formalism. And I'm prepared to speculate on that just as the peer reviewers will be when they read his paper.

Call me silly, but I'd rather hold judgement until I actually see the full paper. Obviously, this criteria appears rather trivial on here.

Zz.
 
  • #44
SimonA said:
I'm not the one hanging on an interpretation ...

ZapperZ said:
... where exactly did I say that I'm for one interpretation over another? Just because I question the validity ... [of the claim that "CI is not a tenable interpretation of QM"] ... somehow automatically, by default, [that] made me someone who is in favor of CI?
Hey ... ditto for me! ... I'm with ZapperZ on this one.

With all due respect, SimonA, do not presume that one's defense of CI on this matter is on account of a belief that "CI is the correct explanation of the underlying reality behind QM". One's defending of CI may only be on account of one's belief that "CI is not in conflict with the Afshar results".

By the "Afshar results" I mean:

Eye_in_the_Sky said:
Summary of reported results:

a) No WG + both slits open --> no loss;

b) WG + only one slit open --> 6% loss;

c) WG + both slits open --> < 0.1% loss.
(Note: Anyone wishing to see a summary of the Afshar experiment, see post #11 (click here) of this thread.)

--------------------------------------

One More Important Point

One more important point needs to be made. The "tenability of CI" is quite independent of the "experimental validity the Afshar results", for those very results (even if there turns out to be some factor which invalidates the experiment) are precisely what CI predicts!

--------------------------------------
 
  • #45
Okay I appreciate your impartiality Eye_in_the_Sky and ZapperZ. I'm interesting in trying to understand what's actually going on and so I find the epistemological side interesting.

But with Eye_in_the_Sky I do believe you are confusing the quantum formalism with the Copenhagan Interpretation. All the quantum interpretations agree with the formalism. What the Copenhagen Interpretation suggests is the the outcome of the experiment is dependant on how you set the experiment up, on the detection itself. The formalism predicts Afshars results as expected, but Afshsar is measuring the 'particle' going through the slit and the interference patterns and this is why the interpretation itself is challenged - not the formalism which is common to all the interpretations.
 
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  • #46
Rebuttal to SimonA

SimonA said:
... But with Eye_in_the_Sky I do believe you are confusing the quantum formalism with the Copenhagan Interpretation.
In an earlier post, I responded to the following question:

Do you have any idea how Afshar concludes this separates one QM interpretation from another?
The essential content of my response was (from post #13 of this thread):

I think it's fair to say that, in the literal sense, by definition, an "interpretation of a formalism" is something necessarily consistent with that formalism. Of course, in the process of formulating such an interpretation, one could err in some way, and consequently, end up with something which does, in fact, contradict the formalism.

... what Afshar and Cramer have claimed[*] regarding "Copenhagen" and "Many Worlds" amounts to the following:

These interpretations fail on account of certain unwitting implications which contradict the quantum formalism.

That is to say, Afshar and Cramer claim that the authors of these interpretations have unintentionally "stepped out of line" with the quantum formalism, making assertions which, when given the proper consideration, turn out to have implications which contradict the formalism itself.[**]
_____________________


[*] This is only one of two parts of their claim. The other part is that these interpretations fail in relation to what the experimental facts happen to be (whence the significance of the Afshar results).

[**] Does the content of this post serve to dispel the strangeness about which ZapperZ wrote (in the second post of this thread)?
... SimonA, does this information cause you to change your belief concerning the above cited potential point of confusion on my part?

--------------------------
--------------------------

SimonA said:
... Afshsar is measuring the 'particle' going through the slit ...
No, Afshar is not measuring the 'particle' going through one (or the other) of the slits. Afshar is measuring the 'particle' position at the screen σ2 (see diagram).

An "inference" is then made by which the "σ2-measurement" is deemed to be physically equivalent to the "slit-measurement".

I could now go on and cite for you various principles of CI and how they "forbid" such an "inference". But that may well do nothing to change your opinion, because in your view CI - as a "formal body of principles" - is inconsistent. That means: if your position is true, then one can use CI to prove anything(!). Therefore, in order to satisfy you, I must "step out" of CI and produce a generalized-consistency-proof for CI (... which, if not impossible, is probably next to impossible).

So, then, what we really need in order to settle this matter (once and for all) is a clear argument - which you yourself (or by an authority you trust) find to be acceptable - by which CI (allegedly) implies that the "σ2-measurement" and the "slit-measurement" are physically equivalent ... and I will then plainly demonstrate how that argument involves the erroneous application of some principle.

[... Perhaps, you can quote a source, or provide a link. In the absence of that, perhaps you would accept the manner in which I am able to "fill in the gaps" in Cramer's PowerPoint Presentation. In fact, I have already attempted to do just that in post #15 of this thread, entitled Cramer, in the name of "Copenhagen".

Moreover, in post #19 of this thread, in the second half of that post, I have provided two distinct points of view from CI which (with the appropriate consideration) may (... although, I doubt it) convince you of the invalidity of Cramer's claim.]

---------------------
 
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  • #47
I offer my criticism to this Afshar/Cramer's point not based on an inherent philosophy, but rather on the experiment itself. That is why I want to reserve my comments till I see the DETAILS of the measurement - usually it is in the details where it can make or break an experiment.

From what I have read so far, there is one major problem that I have detected <no pun intended> - the detection mechanism itself. I have pointed out already one problem with assuming a 100% efficiency of a photo detector. The 2nd problem is that in a photon detector, when you try to detect it, you DESTROY it. ALL photon detectors that I know of require that the photon be absorbed, and either current or photoelectrons are then emitted. This current/photoelectrons are the tell-tale signs that a photon was there.

Therefore, I am VERY suspicious of a claim that (i) a photon passed through a particular slit and THEN (ii) that photon is later on detected at a screen/detector. You can only make claim (i) only if you have a 2-slit setup for example, and you BLOCK the other slit, or put a photodiode at the other slit (and thus destroying the photons that hit that slit). This isn't what was done in this experiment from what I have understood.

This is why I want to wait till the damn thing comes out, examine the details, and THEN figure out how valid the experimental results are. ONLY after that can we address if the results mean one thing or another, which isn't necessarily as clear as one thinks. It isn't unusual that a set of results can be interpreted in widely different ways (the magnon and phonon coupling scenario for the "kink" in ARPES spectra for the cuprate superconductors is a prime example), especially when it is still an active, research front field.

Zz.
 
  • #48
ZapperZ said:
I offer my criticism to this Afshar/Cramer's point not based on an inherent philosophy, but rather on the experiment itself.
I have two questions:

(i) Are you speaking of the same Afshar experiment alluded to in Cramer's PowerPoint Presentation (i.e. the one in post #1 of this thread)?

(ii) Are you the same ZapperZ who wrote (in post #2 of this thread):

ZapperZ said:
... So how he [Cramer] came up with the conclusion that they [CI and MW] offer a result that differ from the QM formalism itself is puzzling. This is because if that is true, then one can LOGICALLY falsify both interpretations without having to do any experiment.
Please answer: "yes, yes" / "yes, no" / "no, yes" / or "no, no".
 
  • #49
Eye_in_the_Sky said:
I have two questions:

(i) Are you speaking of the same Afshar experiment alluded to in Cramer's PowerPoint Presentation (i.e. the one in post #1 of this thread)?

(ii) Are you the same ZapperZ who wrote (in post #2 of this thread):

Please answer: "yes, yes" / "yes, no" / "no, yes" / or "no, no".

(i) yes + the Cramer's Analog comments + http://users.rowan.edu/~afshar/ + conversation with someone who has actually seen the first version of the preprint that was retracted from arXiv.

(ii) yes (unless my evil twin Skippy has been up to no good again).

Zz.
 
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  • #50
(i) Are you speaking of the same Afshar experiment alluded to in Cramer's PowerPoint Presentation (i.e. the one in post #1 of this thread)?
ZapperZ said:
(i) yes + the Cramer's Analog comments + http://users.rowan.edu/~afshar/ + conversation with someone who has actually seen the first version of the preprint that was retracted from arXiv.
Then, hold it one itty-bitty second! Where in the galaxy! did you get the impression that in the Afshar experiment a measurement of any kind is performed at the site of the slits?

(... or was it Skippy who answered question (i)?)
 
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