Talk:Afshar experiment/Archive 10

Page contents not supported in other languages.
From Wikipedia, the free encyclopedia


Entangled Detections

An entangled detection is a concept I had to manufacture in a recent simulation of retrocausal effects.

To keep CI and TI emperically consistent with each other (to preserve the rule that both are emperically equivalent) was a difficult problem. The source of the TI advanced wave (an emperical detection) isn't safe. The CI wave is safe because any retrocausal intervention would be the same result as any other intervention. But TI depends on specifying both ends of the time interval - so the advanced end becomes the volatile end - in the context of retrocausal interventions.

As it turns out, by allowing the advanced end of the TI wave to be entangled, any retrocausal intervention of the retarded end becomes indistinguishable from ANY intervention of the retarded end. Which also means the retarded wave (AND the composite standing wave) of TI becomes interpretationally indistinguishable from the probability wave of CI.

But it means the advanced wave is no longer capable of producing a path-like result which sort of defeats one of it's classical features - but since such is emperically invisible it doesn't affect the CI/TI emperical equivalence.

What it does do is affect the interpretational difference. It's as if there isn't any difference (once you introduce entangled detections).

An entangled detection is just what happens when you simulate a future state that has yet to occur. In simulation the state is either a detection, no detection, or an entanglement of both. Or in other words the probability wave of CI.

Once the detection occurs it is difficult to see how it can remain in an entangled state but I found that this is required (if retrocausal interventions are involved). One can use the many-worlds model as a way of imagining an entangled observable.

But the other way is to refollow the EPR experiment. Our entangled observable, in this case, is just the correlation we see between Alice and Bob's data. We are looking at an entangled observable. It is entangled across the two data sets.

At the end of the day (or should I say lunchtime) retrocausal intervention is observationally the same as any other intervention.

Carl

Back on Topic

My apologys for the last two diversions. I know I'm not supposed to do that but I can't help but feel such is necessary. Anyway ...

Back to the Afshar Experiment in particular.

I've argued this before but it needs to be clarified. The Afshar experiment is a good one. What otherwise "orthodox" opponents of the experiment fail to realise is that it's an interpretational experiment based on what Neils Bohr is "understood" to have said or meant.

What Bohr "really" meant is, in an important way, irrelvant.

We need only understand what Afshar and like minded company have thought he meant.

If I thought Bohr meant what Afshar thought he meant I'd have problems with Bohr as well.

And I'd find Afshar's experiment a perfectly valid response to such a reading of Bohr.

And I'm only one person. What about the mutitude of people out there who might have read Bohr in the same way?

What better solution to such a reading than Afshar's experiment?

Carl Looper

I should add that when I first began studying quantum theory (some twenty years ago now) I read the same quotes from Bohr as everyone else and assumed the same thing that Afshar and others had assumed. It was only because I read up on the philosophy behind the Copenhagen Interpretation that I was able to read between the lines and realise what specifically Bohr must have meant. The other route is by means of the mathematics but I find such a route prone to all sorts of interpretational tangents which, without a philosophy, can meander indefintely. The third route is to bury oneself in the orthodoxy and rabbit out the same old answers that everyone else reads in the text books. But for goodness sake - who is left to write the textbooks?


oh - and the fourth route - perhaps the most important route - is doing actual experiments. And that is what Afshar has done. So good on him I say.


Dear Carl Looper,

you completely misinterprete the issue, and I don't see why you are "back on topic"?

Yes it is true that I am interpreting the issue. But who isn't - Carl?

By the way I am satisfied by the recent changes in the main article. As I have said before - the problem is misunderstanding of the "measurement postulate", NOT complementarity. I have clearly argued that the photon's density matrix at the detectors is that of a PURE state, so it is in superposition at both detectors at once.

Yes - that's right - Carl

The "measurement" at basis D1 or D2 introduces the "sudden change" of the photon's state into D1 or D2. If one understand this - there is NO problem.

I understand that. You understand that. But a lot of people have trouble with that. - Carl

Basicly at the time of discontinuity the wavefunction of the photon has two different limits - left and right, and the function is NOT integrable at that point. So basicly the misunderstanding is to take the right limit, not the left one. So basicly this discontinuity is consequence of the "measurement postulate".

Yes again - Carl

All this stuff is just hinted in the main article, in saying that "measurement" constitues a part of the Afshar's error. Good remark! Well, I don't have anything to add. All my posts are available in the archive of Wikipedia.

And good stuff too - Carl

I just don't understand WHY everybody has stuck on a given position, and tries to convince the others.

Perhaps somebody should look in a mirror and ask themselves the same question. - Carl

If he tries to "move around" and explore the issue from different viewpoints - density matrix formalism, integrability of the wavefunction, ... a little mathematics :-), he will see that Afshar's error is purely mathematical misunderstanding, and not at all linked to what Bohr said or not! Danko Georgiev MD 03:26, 17 October 2006 (UTC)

Math is just philosophy in abbreviated form. Where the philosophy differs so too will the math. And besides which it is about how you read Bohr. The experiment constitutes a reading of Bohr. What does the "same time" mean. What does the "same experiment" mean. They can appear to refer to each other. Is "time" being used to mean an interval (the duration of the experiment) or an instant (in time). How you read this will determine the questions you ask, the experiments you build, and the math you use to represent your particular point of view. - Carl
I agree with Danko Georgiev MD -- this is way off topic. Please note the admonition at the top of the talk page and only discuss stuff relevant to the structure of the article. General speculations about QM should conducted elsewhere (sci.physics?) --Michael C. Price talk 08:43, 17 October 2006 (UTC)
I agree with Danko as well! But I don't see how I'm off topic. I'm talking about the Afshar experiment. And Micheal - you had no trouble participating in the off topic discussion of time travel so I don't think you are in a position to go all righteous just now.
Yes, and I suggested at the time that that discussion be moved elsewhere. --Michael C. Price talk 14:35, 17 October 2006 (UTC)
Ok, fair enough - Carl
I consider Danko a friend of mine. And I respect what he has to say (except when he gets all hot under the collar about Afshar). And you'll notice that Danko agreed not to post any comments at all to this discussion (so perhaps you would like to send him off to the headmaster for being a naughty boy) - but I'm happy he is contributing. He has a lot to say. Before you make any assumptions about where I'm coming from, I should say I'm an empericist, not because that was the way I was brainwashed, or that's the way it should it be, but because that is a decision I made. That all said I am quite willing to respect neo-classical alternatives. I think the Afshar experiment is a good example of where neo-classicism can go - to the extent that it can. It picks up where the rationalism of Plato, Descartes and Einstein hit a rock in the early twentieth century. And to that extent Afshar's experiment represents an important contribution to that particular history. And think about it for a moment. Why would you go to the trouble of doing such an experiment if you hadn't interpreted Bohr the way Afshar had? And you can speculate ulterior motives - but then how emperical is that ???? - Carl
Whilst I would also say I'm an empiricist we shall have to disagree about the importance of Afshar's experiment and analysis. It seems to be motivated by a misunderstanding of what complementarity (physics) means and as such of very little importance, except as a teaching aid. PS I do not question Afshar's motives but I do question his abilities / objectivity. Sorry, but that's the truth. --Michael C. Price talk 14:35, 17 October 2006 (UTC)
Thank you for airing your opinion on my "abilities / objectivity", which is just that, a personal opinion; not the "truth" as you wish to portray it. Fortunately, every knowledgeable individual can gauge the value of my work by reflecting upon it independently.--Afshar 04:28, 18 October 2006 (UTC)
Every knowledgeable individual can also see that your claim that you criticised only Deutsch's presentation of MWI, but not MWI itself, is contradicted by the historical record. If you were objective you would see that also. --Michael C. Price talk 06:43, 18 October 2006 (UTC)
Yes. It is motivated by an 'understanding' of what Bohr meant by his principle of complementarity. What does "same time" mean? What does "same experiment" mean? What does "visibility" mean? For a radical empericist the "visible" means only the observables. For a radical rationalist the visible means only what is logically/rationally understood (seen) as otherwise represented by the observables as in: "I see", said the blind man. And for those who don't know (or are on the fence) it can be a difficult interpretational problem. And so one should experiment (in the full sense of the word). As for being a "teaching aid" - what isn't? The Copenhagen Interpretation is a teaching aid. Bohr's principle of Complementarity is a teaching aid. The mathematical formalism of quantum theory itself is a teaching aid. - Carl
I might add that in relation to the history of empericism, the experiment doesn't say anything at all. So there is not much point in trying to pick it apart along such lines. At the end of the day you'll just find the math is "wrong" - not because it is wrong (math is never wrong) but because you'll be entangling how the terms are defined in the first place. You have to climb out of the small picture and see the big picture - how empericism and rationalism can collide (from a rationalist pov) yet be equivalent (from an empericist pov). There is both a gulf between the two, and none at all. It is why Cramer (a neo-classicist) can say TI and CI are emperically the same but otherwise not. Rationalism is about, given data, what is the "reality" represented by such data. Empericism is about representing or otherwise predicting the data itself - not what the data represents but how to represent the data. The probability function represents/predicts the detections you get (but only before you get them). In empericism, the data itself is the reality. The wave function is just a highly effective construct for representing (with astonishing accuracy) the data you get (before you get it). For Cramer, the detections are just a component of the picture he wants to create of a "reality" behind the data - an invisible standing wave that we can't see, but which is so utterly logical (rational) as to be totally convincing. But we can't ever see it. It's so fustrating. So we might imagine we could travel back in time and sort of sneak a peak from within our invisible time machine. That's rationalism - the ability to imagine doing this because actually doing so would probably kill the very thing we're trying to imagine. Remember, math is used to animate the characters of Toy Story - but we don't, therefore, take Toy Story to be anything other than a movie. That's why we continue to give leeway to rationalism otherwise we might have to say Buzz Lightyear is real - Carl

Dear Carl, I agree that experimental data and theory are two different things. The theory is "understanding", the data is just "something to be understood". Remember the "Patterns of discovery" by Norwood Russell Hanson (1958). Tycho Brahe and Johannes Kepler were observing the sunset from a hill - do they "see" the same object? Surely the visual image is the same in the retina of both scientists, but do they "see" the same object? NO! "Seeing" is "understanding"! "Understanding" is the "theory", not the data. Tycho Brahe sees a moving sun, with motionless Earth, while Johannes Kepler sees motionless sun with Earth orbiting!

Well, both are quite valid ways of interpreting the image. But the math involved in computing a geocentric model is horrendous. Those ancient astronomers just had a whole lot more work to do to make their models work.

Or they look at a "lead tube" on the table. Do they see the same object? NO! Tycho Brahe sees just a "bizzare tube" without purpose, but Johannes Kepler sees "the new instrument for observing the planets, as written in the letter by Galileo Galilei received before a couple of days ...".

Yes, that's right.

Now to the address the main issue - Does Afshar disprove complementarity? Does Afshar disprove Bohr's complementarity? NO!

I agree. And by exactly the same reasoning we need to know what Afshar means (not what Bohr means) to understand Afshar's experiment. - Carl

To disprove Bohr's complementarity he must have the same understanding as Bohr about complementarity (or at least correctly understant the Bohr's thesis, not invent Afshar's version of complementarity and attribute it to Bohr!), in order to disprove it.

I don't know that anyone "must" do anything. I personally would find it helpful if everyone read all the books I have read but I'm not going to send them to the gallows if they haven't. That said it's a good argument Danko. I'm having trouble knocking it down :). How about this: Afshar's reading of Bohr does not belong to Afshar. It belongs to a way of thinking that anyone is free to adopt. We can criticise this way of thinking using either Afshar's experiment (which is designed to do just such a thing) or use an alternative reading of Bohr (eg. the so called "correct" way). Which you use depends on your philosophical position. After all, Bohr could be wrong. But consider this: how do you criticise a way of reading Bohr if your reading of Bohr is what leads you to see a problem in the first place? You do what Afshar did - an experiment. That's the only way out of an interpretational implosion.

Afshar however doesn't have not only common understanding with Bohr, he has a seere shortcoming of knowledge in quantum mechanics.

I'm not interested in whether Afshar knows anything at all. Afshar could be a lunatic for all I know and it wouldn't matter one single bit. You could be lunatic for all I know and it wouldn't change anything. I'd still be listening to what you are saying and taking it in. I'm talking about the experiment and it's position in the history of thought. And that experiment has Afshar's name on it. - Carl

Afshar's work cannot be called serious unless he has basic understanding what a density matrix means, or realize the fact that QM is NON-LINEAR! Schrodinger's equation is linear, BUT measurement postulate is NON-linear, and I think that all serious scientists must know that simple fact. Decoherence DOESN'T solve the measurement postulate, because theoretically you can reverse all the diffused out information in the environment and then recover the interference. In the collapse postulate you CANNOT do that, never! Regards, Danko Georgiev MD 02:43, 18 October 2006 (UTC)

Addendum:

This is "new" argument that is basicly in the same line with previous posts. Afshar's setup discusses the photon in the interval t0 - t1 (interference), but then takes wrongly the value of the function for time > t1, and erroneously extrapolates it for times < t1 arriving at contradiction. Indeed the Afshar's logic can be applied to every kind of quantum experiment, so what is the "great" and "original" in the setup?? Also I think that the sentence in the main article saying "it is not sure whether the duality relation is satisfied in more complex setups like Afshars .." BE IMMEDIATELY DELETED! Look at the math formulation of V and D and then you see that V^2 + D^2 = 1 is trivial math fact, AND MATHEMATICS CANNOT BE DISPROVED BY ANY SETUP - NEVER!

In my universe, math is used to do theoretical physics as much as animate movies (amongst other things.) One can't necessarily know, by just looking at the math, the context in which a particular peice of math is being used. It can look "wrong" but turn out "right". It's context sensitive.

Are somebody serious to imply that if 2+2 = 4, this is true, it is not sure whether in some more complicated experimental setup one can find 2+2=5?

If the symbol "5" is reassigned the meaning "4", then, yes: 2+2=5

I hope someone will correct the main article :-) Danko Georgiev MD 03:08, 18 October 2006 (UTC)

And some math logic: classical physics vs. quantum physics, in math logical terms:

  • Classical physics - due to lack of concrete knowledge you can have states , with the clause ARE NOT PHYSICAL STATES!

So performing measurement at t1 giving output plus knowing , makes you infer retrocausatively that the state in the past was also !

  • Quantum physics - alas in QM states as are PHYSICAL, and you can make retrocausal inferences ONLY after determining whether what the physical state is:
    • - NO WHICH WAY (pure state density matrix!!!)
    • - WHICH WAY (mixed density matrix!!!)
      • Comment: note in Afshar's post that he has no proper understanding of the density matrix formalism, and makes statements that should not be done by person with PhD in physics.

Now if you have NO WHICH WAY [proved interference] you have NO RIGHT to infer retrocausally! If you have WHICH WAY - you ARE ALLOWED to infer retrocausally! What makes Afshar? He argues he can both infer retrocausally and prove interference, but this is mathematical mess, misundertstanding, parody, inconsistency, etc. I don't know why one seriously does not reconstruct the whole article, which originally was intended as advertisement of Afshar by Afshar. Danko Georgiev MD 03:26, 18 October 2006 (UTC)

Danko, again you intend to use lies to harm my reputation. You say the article "originally was intended as advertisement of Afshar by Afshar." I did not start the “Afshar experiment” page, someone else did, and you know that. Your complete lack of expertise (announced by Prof. Unruh and others) and personal ill-wish towards me have been documented by a number of Wiki admins including Gareth Hughes. Here's a reminder from your previous malintents:
"Its conclusion is clear: that your claims that Afshar falsified results (and all other claims that cannot be substantiated by verifiable sources) should cease. In my conversations with Afshar, he has been willing to do all that's possible to stay within Wikipedia policies and guidelines. Are you willing to cease from unsubstantiated claims? Thank you. — Gareth Hughes 11:41, 6 March 2006 (UTC)"
to which you replied:
"...I will restrain myself for posting comments on the Talk page of Afshar's article...therefore I do not consider anymore Wikipedia as a suitable place this debate to be continued... Danko Georgiev MD 03:43, 7 March 2006 (UTC) "
Please stick to your promise, and take your unsubstabtiated "arguments" and claims to a blog or some other site other than Wikipedia, or face the consequences of your repeated personal attacks.-- Prof. Afshar 04:07, 18 October 2006 (UTC)
Cool it both of you (Afshar and Danko). Danko's first language is not English so he should be given some leeway of expression. Afshar, please don't call Danko a liar or you might get into trouble as well. --Michael C. Price talk 06:37, 18 October 2006 (UTC)
Michael, Danko has lied above (of course, this is not his first time), and I will not give him or anyone else for that matter the right to mislead others regarding my conduct. You have not been very objective yourself, either, and have personally attacked a number of times. So, you do not qualify as an arbiter in this issue. As seen above, an admin was involved in his previous unsubstantiated claims, and if need be, I will inform him of Danko's new round of disinformation. Interesting how you allow my critics the "leeway of expression" regardless of their past misconduct, yet feel justified to criticize me when I defend myself and demand a modicum of civility. What stupendous objectivity on your part! Well done sir!--Afshar 07:03, 18 October 2006 (UTC)
I see Afshar cannot distinguish between a lie (which assumes bad faith) and a mistake. It is a common characteristic of paranoids to assume that anyone who disagrees with them is a liar and plotting against them etc etc, rather than just rebut their points objectively. PS assuming bad faith is a violation of Wikipedia:Assume_good_faith. --Michael C. Price talk 08:13, 18 October 2006 (UTC)
Thank you Dr. Price for that remote diagnosis of paranoia! If you cared to look at the history of my interactions with Dnako, you would have realized that for months I assumed good faith until I reached the conclusion that other have also reached (including an admin or two), as mentioned below. Now, what were the symptoms of Simultanagnosia? Surely you should know.--Afshar 08:29, 18 October 2006 (UTC)
I like you Afshar, as least you have a sense of humour! In the midst of answering Danko's questions don't overlook his point that is a mathematical identity for each single photon. --Michael C. Price talk 09:17, 18 October 2006 (UTC)
You might like to look at the debate between Danko and I over V, in the archive. It's in the third (last) archive. It boils down to whether V is used to represent just visible finges (ie. observable ones) and/or the implicit ones (due to the evidence of a wave provided by the wires). Danko agrees with Afshar that V can represent both explicitly observed fringes and those that are implicitly there (by virtue of the wires). Danko says it is called "negative measurement". Now I disagree with defining V this way as it is now representing both the signified (observable interference patterns) and the signifier (the interfering wave function). This makes V conceptually ambiguous. Be that as it may, one can define it anyway one likes. In Afshar's experiment there are no observable interfenece patterns since the wavelet from a particular aperture is not emperically observed during interference (apart from the minimal loss to the wires). Once the wavelet has emerged from the interfering field it carrys no information of any encounter there (other than the minimal loss to the wires). That's how waves work. They can pass through one another and emerge unscathed. So when it arrives in a detector it only carrys with it information about which hole it passed through. Now the experiment is still clever because we get to "see" (in the rational sense) interference without (f)actually observing such (in the emperical sense) so therefore we also get to see (in the emprical sense) which aperture the 'particle' passed through. This is the clever aspect of the experiment. It is what makes it important. There other ways of doing this but this one is very simple and is specifically designed to do so. And while it appears to contradict Bohr (even if it doesn't really) that's not entirely the point. It provides a way of seeing the magic of nature in both senses of the word "seeing". Bohr only provides the emperical meaning of "seeing". Afshar provides both. How you represent this mathematically is an exercise. -Carl (Addendum: Interestingly the retrocausally constructed observation of "which way" the particle went is defined in terms of the actual detection - the emperical 'particle'. Until this detection occurs it is not yet emperically defined. There is only it's signifier (or 'placeholder') - ie. the wave function, which we we often call a 'particle' as well (for want of a better word). Concession to rational analysis can occur after a detection but why? Why not argue that "which way" information is not just a concession to rationalism but exclusively the province of rationalism? Well that's right, emperically we can't establish which way the 'particle' went. Our 'particle' is the wave function which has passed through both apertures. When the detection occurs the role of the signifier passes to the detection, and the wave function is now the signified. And to signify the wave function (a pure signifier) we need a number of detections, from both detectors - if we want a good picture of it, rather than just a picture of that portion which went through one aperture. But then that is the purpose of the wires - to signify the full wave function - leaving the detections, or just one detection to signify, not really which aperture the detection passed through, (it passed through both) but itself - an emperical particle - Carl)
Danko and good faith?? I can't stop laughing. That's so funny. Danko making an innocent mistake ... Carl
Opportunity for an experiment here. Dear Danko. Did you make a mistake or did you just make that story up about Afshar? Come on you can tell us. I mean, I don't know. Michael thinks you might have made an innocent mistake. - Carl
Dear Afshar, as I have seen many times you NEVER reply on the mathematics, or physics, you keep complaining and calling others "liars", "crack-pots", etc. and always appeal to admins as if the problem has to be solved in court, not by physics?! I have posted on your talk page as well that this is my last touch on the talk page of your pet experiment, and I will discuss the issue on the registered user talk pages in the future. I hope this will satisfy you. Just a friendly advice: you will get more support by other physicists if you discuss the errors in the math posted by me, not classifying me as "liar". Regards, Danko Georgiev MD 07:41, 18 October 2006 (UTC)
Danko, I (and Prof. Unruh, Motl, Drezet, and others) have wasted many hours explaining your errors both mathematical and physical, and have all confirmed that you have no grasp of the subject matter. If you insist I can publicly disclose their e-mails regarding you. I do not wish to spend any more time on correcting your errors; I am simply ensuring your other vices don't mislead others. As for me, I do not need anyone's support, as my work speaks for itself. At any rate, the real debate is carried out in papers outside Wikipedia, and you are welcome to act accordingly.-- Afshar 07:57, 18 October 2006 (UTC)
If you are serious about revealing the contents of private emails here then I think you need the permissions of Unruh, Motl, Drezet, and others -- not of Danko. --Michael C. Price talk 09:20, 18 October 2006 (UTC)
It's been previously discussed by them, and otherremarks are posted in public domain. It's matter of putting the links here.--Afshar 13:47, 18 October 2006 (UTC)

I have wasted many hours in private conversations trying to explain introductory quantum mechanics to Danko. While his eagerness and enthusiasm are commendable (eagerness and enthusiasm are the cornerstones of good research and strong careers), I found that he has a very very very long way to go in his study of mathematics, as he demonstrated a lack of mastery of complex numbers, not to mention great difficulty with basic concepts such as differential equations, functions, and the like. I don't know if there is a technical way to do this, but I propose banning Danko from contributing to these talk pages, as his presence is clearly disruptive.

Danko, should you read this: there is no insult intended, and I strongly do encourage you to continue your studies. Its a marvelously deep and wide topic. However, for the benefit of all parties, I do urge you to refrain from further postings on this talk page. linas 16:12, 16 November 2006 (UTC)

Danko, Sorry I said the above. The whole talk page seems to be one big debating ground. I suppose if everyone wants to debate, they should, and I should not attempt to censor. Sigh. My bad. linas 04:34, 17 November 2006 (UTC)


reback on earth

I have not so much time to visit this page since few months. However I observe that things are going curiously : some discussions and comments are obviously useless and some users seem not to respect their promesses concerning the nature of their interventions. In particular I wonder why the introduction of the main page is so agressive (it seems that Afshar is presented in front of a public tribunal for his convictions ). An other example concerns the sentence: The modern understanding of quantum decoherence and its destruction of quantum interference provides a mechanism for understanding the appearance of wavefunction collapse and the transition from quantum to classical. As such there is no need, in the decoherence view, for an a priori introduction of a classical-quantum divide as enshrined by complementarity.[7] Any experiment that claims to violate complementarity needs to address this issue. What for to complicate the topic? The subject is not the interpretation of complementarity (this should be presented in a page concerning decoherence and complementarity) but the experiment realized by Afshar. Finally why this long bibliography. This is not historical page describing the life of Bohr or Einstein. I dont think that it clarifies something to discuss about the life of Afshar (this is not really useful for the understanding of the experiment).

I think (but this only a suggestion) that many users should spend their time in a more constructive way (for example by contributing to clarify many pages which need help if they like it ). Here the topic does not progress so let the page in peace and limit ourselves to minor changes.

Aurelien Drezet, Graz Drezet 18:55, 24 October 2006 (UTC)

PS : Linas is courageous to spend so much time here

The page has been at peace for quite a while now... --Michael C. Price talk 19:06, 24 October 2006 (UTC)
Are you joking? just read again (be strong.. ) the list of comments writren in the last 10 days. This is not a discussion forum to discuss about the philosophy of quantum mechanics. I am sure that there is a lot of space for that somewhere else (but not here).
Drezet 18:55, 24 October 2006 (UTC)
By "page" I meant the article, not this clogged up talk page which, I agree, has much irrelevant gunk. --Michael C. Price talk 23:47, 24 October 2006 (UTC)