Double Slit Experiment and Quantum Eraser

[Cthugha]

Well, I do not consider the quantum eraser to be that weird, so I cannot tell. It may be a bit surprising that it works as is supposed classically even on the single photon level. It might be a bit uncomforting if you think of a photon as being similar to a small ball flying through space, but that is one of the worst analogies one could think of anyway - but it is nevertheless an analogy one meets on a regular basis.

It gets a bit more surprising when throwing in delayed choice, but that is a different story.

 

[micky_gta]

Here you go! http://xenophilius.wordpress.com/2012/04/23/quantum-physics-mimics-spooky-action-into-the-past/

 

[Cthugha]

What do you want to tell us using that link? It is a pretty bad pop-sci summary of a scientific paper. If you had read the article instead of posting some mediocre summary, you would have found the following statement in the conclusion area:

"If one viewed the quantum state as a real physical object, one could get the paradoxical situation that future actions seem to have an influence on past and already irrevocably recorded events. However, there is never a paradox if the quantum state is viewed as no more
than a `catalogue of our knowledge'[2]. Then the state is a probability list for all possible measurement outcomes, the relative temporal order of the three observers' events is irrelevant and no physical interactions whatsoever between these events, especially into the past, are necessary to explain the delayed-choice entanglement swapping."

No indications of changing the past or similar things happening here.

This is again a very good example for why it is a good practice to use links to the peer-reviewed publications as the foundation for a debate and not some second-hand summaries.

 

[Nadav]

This is still wrong and on the level of crackpot sites like bottomlayer. For the last time: Post some peer reviewed evidence that there is some truth to your claims or stop posting wrong stuff. Hint: You will not post peer-reviewed evidence as there is none. Or maybe you can just explain where exactly the flaw in the Ionicioiu or Kim papers is when they explain why there is obviously no retrocausality.



are you serious? before saying stuff you better check them! have you even read Kim papers?
and i quote:
"
In conclusion, we have realized a quantum eraser ex-
periment of the type proposed in ref. [3]. The experimen-
tal results demonstrate the possibility of observing both
particle-like and wave-like behavior of a light quantum
via quantum mechanical entanglement. The which-path
or both-path information of a quantum can be erased or
marked by its entangled twin even after the registration
of the quantum."

-A Delayed Choice Quantum Eraser
Yoon-Ho Kim, R. Yu, S.P. Kulik∗ , and Y.H. Shih
Department of Physics, University of Maryland, Baltimore County,
Baltimore, MD 21250

 

[Nadav]

"even after the registration"

 

[Cthugha]

are you serious?

Yes, I am serious.

before saying stuff you better check them! have you even read Kim papers?

Of course I have read them. Although they were among the first papers and therefore the understanding of the issue has obviously been advanced over the course of time.

"
In conclusion, we have realized a quantum eraser ex-
periment of the type proposed in ref. [3]. The experimen-
tal results demonstrate the possibility of observing both
particle-like and wave-like behavior of a light quantum
via quantum mechanical entanglement. The which-path
or both-path information of a quantum can be erased or
marked by its entangled twin even after the registration
of the quantum."

What is your point? The claim I answwered to was "In other words the information that the detectors can pick up must be sent somewhere so a person can read/see and know the information of where the particle passed." The above passage of that paper does not even mention any possible the role of humans in that process. The above passage is also not about retrocausality. The central point here is that "erasing" or "marking" information after an registration event is something very different than retrocausality and changing the past.

 

[Nadav]

The insertion of the interferometer took only 40 nanoseconds (ns) while it would take 160 ns for the information about the configuration to travel from the interferometer to reach the photon before it entered the slits. This means in order for the photon to “know” if it was being watched, that information would have to travel at 4 times the speed of light, which is impossible.

The Results: The photons acted like particles 93% of the time that they were observed. Even if the photon “guessed” the configuration each time, statistically speaking it would never have more than 52% accuracy. In scientific experiments, a 93% success rate is as conclusive as they come.

 

[Cthugha]

What are you talking about?

The insertion of the interferometer took only 40 nanoseconds (ns) while it would take 160 ns for the information about the configuration to travel from the interferometer to reach the photon before it entered the slits. This means in order for the photon to “know” if it was being watched, that information would have to travel at 4 times the speed of light, which is impossible.

There is no interferemeter in the Kim et al. paper. Having an interferometer and a typical timescale of 160 ns is the typical setup used in the Jacques et al. version of the delayed choice quantum eraser which by the way is an experiment which allows to draw way more conclusions than the Kim et al. paper and similar eperiments do. So in the following I assume you mean the Jacques et al. paper (V. Jacques et al., Science 315, 966-968 (2007)). A short conference proceeding version can also be found in Ann. Phys. Fr., Vol. 32, N°2-3 2007, pp. 195-197. Please indicate if you are switching to different experiments and cite the paper you are talking about.

The Results: The photons acted like particles 93% of the time that they were observed. Even if the photon “guessed” the configuration each time, statistically speaking it would never have more than 52% accuracy. In scientific experiments, a 93% success rate is as conclusive as they come.

So what does this tell us? Let me directly cite the paper you are talking about instead of secondary commentary. The conclusion of the conference proceeding version of the Jacques et al. paper cited above is:

In conclusion, the experimental results can only be explained if the light-pulse is described by either (1) a wave-and-particle theory, like quantum mechanics; (2) a wave-or-particle theory where information on the setup can travel at 4 times the speed of light; (3) a wave-or-particle theory and our QRNG exhibits undetected correlationstaht could be detected with probability a higher than 93%. Needless to say, the most reasonable option seems to be the first one!

So the conclusion is that one would need retrocausality or FTL signaling to explain the results in terms of a particle-only theory, e.g. a theory where a photon is a hard ball flying through space with well defined properties and no additional wave (whether a typical Kopenhagen interpretation version or a Bohmian guiding wave) associated. You do, however, not need retrocausality or FTL-signaling to explain the results in what the authors call "wave-and-particle theory" like orthodox qm or its other interpretations like Bohmian mechanics.

So, again. What exactly is your claim? And please stop quoting stuff out of context without giving the proper citation. It is quite time-consuming to find out what you mean.

 

[Nadav]

I agree! okay its seems you know a lot and you have a lot of points.

but ill keep it simple-for my self. and i want a simple answer if you can provide me,please,

ill give it as example:

If i did the experiment 1000 times, both results and detecton data are recorded but not been looked at.

i take half of the detector data and i erase them (without looking at them).

then i look at all of the results, will the ones without the detectors data will be different?

 

[Cthugha]

I agree!

Glad to hear that we approach agreement. :)

but ill keep it simple-for my self. and i want a simple answer if you can provide me,please,

ill give it as example:

If i did the experiment 1000 times, both results and detecton data are recorded but not been looked at.

i take half of the detector data and i erase them (without looking at them).

then i look at all of the results, will the ones without the detectors data will be different?

Let me try to grasp your experimental proposal before I give an answer. So you try some delayed choice experiment, maybe the one proposed by Jacques. et al which includes a quantum random number generator and repeat the experiment for a fixed number of times. In these experiments typically a wide range of phase shifts is measured by tilting a beamsplitter and the recorded intensity at each of the two detectors varies either sinusoidally (closed configuration, no which-way information present) or not at all (open configuration=which-way info present).

I assume you now just want to tilt the beam splitter to some angle which gives you the highest possible difference in counts between the two detectors in the closed configuration and then repeatedly measure at that position, right?

If that is correct,let us sort out what you mean by data and results. The paper states "For each photon, we recorded the chosen configuration, the detection events, and the PZT position". So I assume the chosen configuration and the PZT position are your data. Do you consider the detection events now as the results? So now your point is that you throw away and destroy all information about the settings and the chosen configuration and then have a look at the results (detection events) and want to know whether that act of destroying information about settings and the configuration makes a difference in the final results. Did I get that right?

In that case the simple answer you demand is: no, there will not be any difference. If I got something about your idea wrong please post again.

 

[Nadav]

thank you so much...

so all those stories about that human observation changes the quantum behavior from wave to particle is ********?

 

[micky_gta]

OK here is something to back me up!

http://www.laitman.com/2012/05/quantum-entanglement-affects-the-past/

 

[Cthugha]

Two comments.

First, this is again a Pop-Sci summary of some research result and the guy summarizing it is "dedicated to teaching and sharing authentic Kabbalah. Professor of Ontology, PhD in Philosophy and Kabbalah". That sounds very convincing.

Second, the article he is talking about is somewhat better, but it is the same article, your last pop-sci summary in post 32 was about. My response including the quote from the original paper I gave in post 33 still applies.

 

[DrChinese]

OK here is something to back me up!

http://www.laitman.com/2012/05/quantum-entanglement-affects-the-past/

The actual article is:

http://arxiv.org/abs/1203.4834

The reference you cited has a lot of rubbish about how this could be more readily deduced by reading the Kabbalah.

Please note that their conclusions do not actually involve any modification to existing theory. In fact, the same team has published a number of papers in the past 10 years showing how the future affects the past*. This is still amazing stuff, and their insight and application of theory represents important work.

*Of course there are alternative interpretations, but that is a subject for some other thread.

 

[al onestone]

I didn't read all the responses to this thread, but the answer is obvious. Your preparation involves a double slit , where one slit allows vertical and one allows horizontal to pass. In other words the outputs of the two slits are "distinguishable" which will never produce interference.
If on the other hand you were to rotate one output from one slit to the same polarization as the other (with a quarter wave plate) then you would get interference, due to optical indistinguishability, the core requirement for all interference/coherence effects.

 

[nikman]

Brukner and Zeilinger addressed the issue employing a double-slit apparatus along with a variation on the Heisenberg Microscope (i.e., they experimented for real with photons, not gedanken electrons).

The relevant material starts right at the bottom of the first page, following the intro.

http://www.dancing-peasants.com/sciphil/QPSI(2005)2.pdf

 

[micky_gta]

I think this proves my case, all past cases and all future posts:

http://www.youtube.com/watch?v=XEZtw1yt8Kc&feature=bf_next&list=WL02735BA928E0D9EE

 

[Cthugha]

I think this proves my case, all past cases and all future posts:

[a link to an interview with the Robert Anton Wilson, author of the Illuminatus! trilogy, commenting on quantum mechanics]

Yes, the opinion of the author of "Illuminatus!" is definitely the highest authority in quantum mechanics, proving everyone else definitely wrong. I suppose the most important contribution to this thread must have been in post # 23 then. Fnord.

 

[micky_gta]

This experiment proves my argument even more:
http://dailygrail.com/Mind-Mysteries/2012/5/Consciousness-and-the-Double-Slit-Experiment

 

[StevieTNZ]

This experiment proves my argument even more:
http://dailygrail.com/Mind-Mysteries/2012/5/Consciousness-and-the-Double-Slit-Experiment

Do you have a critical mind? Or do you believe everything you find when you do selective searches?

 

[micky_gta]

Critical based on what? The bases of all science is based on assumptions so I ask you, do you have an open mind?

 

[DrChinese]

This experiment proves my argument even more:
http://dailygrail.com/Mind-Mysteries/2012/5/Consciousness-and-the-Double-Slit-Experiment

micky_gta,

This is an unsuitable reference and should be removed immediately. If you keep posting such items, you will be reported. I thought that several earlier posts by myself and Cthugha would have steered you away from this practice.

Moderators here take this very seriously. This is PhysicsForums, not PopScienceForums.

-DrC

 

[Cthugha]

This experiment proves my argument even more:
http://dailygrail.com/Mind-Mysteries/2012/5/Consciousness-and-the-Double-Slit-Experiment

It is not my intention to hijack this thread, but maybe someone knows a bit more. The article referenced above was published in Physics Essays, a journal that is known to be devoted to fringe science. It sometimes (or even often) crosses the border.

The editor is E. Panarella, a guy who did some serious science, but is more widely known for defending cold fusion even after the Fleischmann-Pons hoax and proclaiming some strange (and wrong) effective photon theories. So far, so good (or bad). People might check the journal before submitting there and may find out that the editor is a strange guy. The associate editors are also inknown guys, at least to me. But the editorial board looks different. Some better known names are there with M.O. Scully being the most prominent one one. Might that journal be better than it looks like on first sight?

However, more strange facts occur. Like most of the people presented in that editorial board, Marlan Scully is professor emeritus. It is ok to still associate these people with their universities, but Scully is associated with the university of New Mexico. He has once been associated with that university, but left it for Texas A&M university in 1992. Now one might think that an active member of the editorial board notices the need for an update of the affiliation. Obviously it was nevertheless not updated in the last 20 years. Now the question may arise what these board members actually do.

Their role in Physics Essays is described as follows: "The editorial board members will assist the editor in the formulation of editorial policies. They are scholars from several disciplines of physics, from spectroscopy to quantum mechanics, from electromagnetic theory to astrophysics, from space physics to mathematical methods in physics, from plasma physics to philosophical aspects of physics, from chemical physics to relativity. Their scientific knowledge will be called upon to advise the editor on subjects within their field of knowledge."

To me that sounds like they were asked once whether they think that the formulation of the editorial policies of that journal is fine and then never did anything again, but are listed as "editorial board" because their names sound convincing. Do they even know that they are considered the editorial board of that journal? Does anyone know whether these people are all really interested in that journal or whether some just got scammed into giving their name away for a dubious journal?

I just posted my question here because a second-hand reference to that journal occurred here as one of many links of questionable quality. If the mods think that question should go elsewhere or to a new topic, it is of course fine if my post gets moved or I open a completely new thread.


edit: regarding the link and the article referenced therein, I would like to point out the following paper: Simmons, Joseph P., Nelson, Leif D. and Simonsohn, Uri, False-Positive Psychology: Undisclosed Flexibility in Data Collection and Analysis Allows Presenting Anything as Significant (May 23, 2011). Psychological Science, 2011.

It got some media coverage as it "unambiguously" showed using legitimate statistical analysis that listening to the Beatles song “When I’m Sixty-Four” not only makes you feel younger, but indeed actually makes you younger by almost 1.5 years. This is of course nonsense and the authors want to point out that even legitimate analysis can lead to "false positives" and seemingly verify a wrong hypothesis and that one has to look for such false positives very carefully. They also point out some guidelines for reviewers and authors that should minimize the odds of such false positives occurring. I really doubt the authors of or the refereeing process for the above Physics Essays paper followed these guidelines.

 

[DrChinese]

edit: regarding the link and the article referenced therein, I would like to point out the following paper: Simmons, Joseph P., Nelson, Leif D. and Simonsohn, Uri, False-Positive Psychology: Undisclosed Flexibility in Data Collection and Analysis Allows Presenting Anything as Significant (May 23, 2011). Psychological Science, 2011.

It got some media coverage as it "unambiguously" showed using legitimate statistical analysis that listening to the Beatles song “When I’m Sixty-Four” not only makes you feel younger, but indeed actually makes you younger by almost 1.5 years. This is of course nonsense and the authors want to point out that even legitimate analysis can lead to "false positives" and seemingly verify a wrong hypothesis and that one has to look for such false positives very carefully. They also point out some guidelines for reviewers and authors that should minimize the odds of such false positives occurring. I really doubt the authors of or the refereeing process for the above Physics Essays paper followed these guidelines.

An awesome reference, Cthugha, thanks! Here is a link to the paper itself:

http://psy2.ucsd.edu/~dhuber/Simmons_Nelson_Simonsohn_2011.pdf

This paper is one of a number which have been trying to point out, often unsuccessfully, that even professional researchers do not understand these critical points. There continues to be published studies purporting to show all kinds of effects (correlations) and are usually provided with the lame caveat: "This should not be interpreted as evidence of X effect, and more research needs to be done to determine if X effect is real." As the above article would suggest, many of these will spurious and the authors will be clueless.

For example, there is a thread over in Medical Science about coffee drinking increasing longevity.

https://www.physicsforums.com/showthread.php?t=606626

There are a variety of techniques to prevent this kind of bias, and working with peer reviewed journals is one of them. Another is consistency with already established theory. Both techniques are used at PhysicsForums to one degree or another.

 

[micky_gta]

I guess my post wasn't that bad huh?

 

[DrChinese]

I guess my post wasn't that bad huh?

Ummm, yes it was. That's why Cthugha posted his excellent comment.

I would leave well enough alone at this point.