Dalo

The idea that observation changes the object or phenomenon observed is a central tenet of the Copenhagen interpretation of quantum mechanics. I will not attempt to discuss the meaning of this principle for the whole domain of the theory, but will limit myself to the case I have presented in this thread.
Double slit experiments show interference patterns when one or two slits are open, but those same patterns seem to disappear when the experimenter tries to determine through which slit the particle has passed.
I have claimed that this disappearance is a mere theoretical phenomenon, based on the belief that it is the only sensible explanation when one takes into account the dual nature, or at least the wave, theory of light.
I would like to make it clear that my claim is not incompatible with this theory. The interference patterns may well be the result of constructive and destructive interference of particles moving together through the slits. They may even be the result of single particle interference.
What is essential is the reason why they seem to disappear when "observed".

I have found no indication, neither in the literature, nor in the reactions received in this forum, of an empirical proof that interference patterns effectively disappear when observation is involved. 
Rather, I am evermore convinced that the disappearance is a theoretical assumption, or conclusion if one prefers, rather than an observation.
No empirical proof of the disappearance of the interference patterns has ever been given, this, as far as I know.

If that is the case we are confronted with philosophical consequences that need to be explicitly stated. One of them is:
The idea that observation changes the result of an experiment, whatever the further merits of the idea, remains unproven in the case of double slit experiments.

Just now, Mordred said:

What do you define as empirical. Hold your hand out so you can touch it? We have provided numerous experimental evidence for you to examine.

Secondly it is your obligation to provide the evidence to support your argument under the rules of the Speculation forum

Empirical by scientific criteria.

I have nothing to prove, since the facts are recognized by everybody, including you. What I am asking is that you prove what you claim, that the theory, any theory you may choose, leads to the practical results I have mentioned.

3 minutes ago, Mordred said:

We have provided numerous experimental evidence for you to examine.

This is the whole point, isn't it? You claim that you have provided empirical proofs, but I cannot see how what you have presented relates to the questions posed. Since you are the one claiming that you have proofs, the least you can do is show them unambiguously. Maybe I have not understood them, so why don't you tell me exactly what your empirical proofs consist of?

1 minute ago, Mordred said:

Sure under QFT, when waves constructive interfere the amplitude of the wave increases. This is described by the creation and annihilation operators. In other words new photons get created by these increases. Old ones not in phase with each other via the sum over Histories under Bohm and QFT annihilate. That simple enough?

So far we have shot down your arguments due to lack of understanding them on your part. Care to go over the material I provided and make an informed decision?

Nope, all you have done is explain or refer to theories I am not attacking. What I am looking for is much more modest:

show me an empirical proof of both points:

- that a particle can go through both slits; or at least,

- that observation destroys interference patterns in a double slit experiment.

As you see, nothing complicated, and you can use any theory you want as long as you do not stop at the theory, but show the empirical results.

Just now, Mordred said:

 Well thus far I have shown you don't understand the theories your supporting. I provided you what you need to learn to fix this lack. What you believe or don't believe isn't what I spend my time on forums dealing with. You keep thinking of particles as bullet like objects by that last descriptive. A wave can do precisely that Travel through two slits at one time.

 

I know the theory, now show me the results in the particular case I have described.

Just now, Mordred said:

That's been done as empirically as possible. Your refusal to accept all the references provided isn't my problem.

You did not show at any time that

- a particle can go through both slits at the same time,

- that the interference pattern is destroyed by observation.

Your experiments, however impressive, are irrelevant to this thread.

17 minutes ago, Mordred said:

How can you make claims without even understanding the theories your quoting in your defenses?

Isn't your argument itself theoretical?

 

My claim is empirical as can be. It can be easily infirmed, all you need to do is show one single experiment in which observation destroys the interference patterns. Empirically, not theoretically.

By the way, I am not quoting any theory to my defense. I am using examples from different books to show cases of double slit experiments. My claim does not need Bohm, Bohr or Einstein to make it empirical.

Just now, Mordred said:

  I am asking you to truly understand what is involved and supplying this material to assist you in such an enterprise. Remember one of the rules on any wave-function.  Probabilistic or not, measuring causes interference due to needing to interact via other waveforms (wave functions). A probabilistic wave-function is not a physical wave-function ( there is a Add to distinct difference, example correlation functions). With the Heisenberg we involve both, but not only of the particle locality region but also any field coordinates.

  The problem with Copenhagen an QM is more specifically the position operator itself. In QFT this is downgraded to a propagator and the field is upgraded to Operator.  Significant difference I mentioned this numerous times, most metaphysics papers rarely examine the math fully.

I'll have to remember this line from 5.2 with regards to QM its nicely put in a very succinct manner.

"One of the main arguments of the Copenhagen Interpretation of quantum mechanics is that it is meaningless to ask about the position of a particle when it is not being detected. This means that if the trajectory of the particle is not being continually tracked, no information other than the start and end points of the trajectory can be known."

section 5.2

 Definitely applies to QFT methodology

 Anyways its a good reference to help understand properly the physics and not the metaphysics arguments.

.

 

Those are theoretical arguments, now show me how they apply to the problem at hand. If you argue that observation in itself destroys the interference pattern, it would only mean that the theory is unprovable and must therefore be considered as a metaphysical position.

18 minutes ago, Mordred said:

Yes but isn't it reassuring to see certain Bowmian lessons already being applied under QFT ? though with more rigor under treatment

 

I am not sure what you are expecting from me. I have no opinion on QFT. I do not feel the need to attack it, nor to defend it.

What I do not understand is how all you have been saying relates to the following:

- in a double slit experiment, when one slit is open nobody doubts that all particles go through that slit, even if single particle interference may create interference patterns.

- when two slits are open, there is a clear interference pattern, and the question is how that happens. The theory is constructive and destructive interference. Okay.

- when the experimenter tries to find out through which slit the "particle" has gone through, it is said that the interference pattern disappears.

- I say, that is not true, that it has never be shown in a real experiment. All we have are theoretical justifications.

If you think that you can prove my claim wrong, empirically prove my claim wrong, and not just by appealing to theoretical considerations however respectable they may be, then I welcome your contribution and will change my mind accordingly.

1 minute ago, Mordred said:

So what does that do to your reassurance now?

It leaves me slightly indifferent. The debate between Copenhagen and Bohm is interesting, but certainly not life changing.

4 minutes ago, Mordred said:

Of course they relate. These devices repeat the older experiments. Your arguments have been based on older and out of date understandings.

Time to get modern, time to actually understand what Bohmian theory is really about under the math because it actually involved a spin zero field. Thats the third component.

Let me get you a proper paper on Bohmian pilot wave.

I can understand the wrong impression my references may have conveyed. But I am not beholden to the Bohmian theory, even though I find the fact that there is an alternative to the Copenhagen interpretation very reassuring.

My claim does not depend on the validity of the Bohmian approach, even though it is incompatible with Bohr's convictions.

48 minutes ago, Mordred said:

1) start with particle entanglement diodes with a RC circuit to regulate the rate of production.

2) use Logic gates to seperate the entangled pairs

3) pass each single photon through slits

4) count the hits at specific locations on the quantum detection silicon wafers (quantum detectors

We weren't interested in preserving the entangled states themselves hence the seperation methodology.

First reaction to the first article.
The article is obviously way above my pay grade, and I would certainly not presume reviewing it.
To be honest, I do not see how it relates to the subject of this thread. It concerns definitely not a double slit experiment, and, even if I disregard the use of a Mach-Zehnder interferometer (see my previous posts), there are, if I understood correctly, two sources of light involved, instead of one.
It certainly shows the degree of expertise of all involved in the experiment, but, once again, I fail to see the relevance to this thread

16 minutes ago, Mordred said:

The experiment has been done by others as well. These experiments were far more accurately done than my own. (that and it included a student body, where I assist at on occassions as my work time allows)

However here is an example setup.

https://www.google.ca/url?sa=t&source=web&rct=j&url=https://arxiv.org/pdf/1507.02962&ved=0ahUKEwirtOK-sojYAhVM2WMKHXLdB5kQFggiMAE&usg=AOvVaw0YryFuM4IZJkBZ3maQC8Wv

this link directly uses the Toshiba devices

https://www.google.ca/url?sa=t&source=web&rct=j&url=https://arxiv.org/pdf/1201.3475&ved=0ahUKEwirtOK-sojYAhVM2WMKHXLdB5kQFggdMAA&usg=AOvVaw0g9rlEJ0bJ4hs-jlUQfSyg

Trying to get the datasheets specifically on the detector and emitters but Toshiba changed its website.

Thank you. I will study them very carefully.

1 minute ago, Mordred said:

Yes via Toshiba quantum single dot emitters and detectors. I did this experiment with those devices.

I have no reason to doubt you. This is after all your domain. I would be very curious about the setup of the experiment though. Maybe you could post a link or a reference?

13 minutes ago, Mordred said:

Like I stated I only deal with observed evidence, and the mathematics and physics. Metaphysics bores me. Far too often it is used as a wall that prevents even understanding the topic being discussed.

Good example is the mathematical definition of Observer itself under Pilot wave theory. Do you know the mathematical definition?

Have you bothered to even study the mathematics of De-Broglie Pilot wave which is Bohmian to even understand the theory itself?

No. I leave that to mathematicians, which I am not. I consider myself a philosopher (didn't finish my Phd  through circumstances not relevant to the subject, and now I am too old to care.).

13 minutes ago, Mordred said:

Like I stated I only deal with observed evidence

did you ever observe a particle passing through two slits at the same time?

17 hours ago, Mordred said:

Ok lets describe my view point, I don't follow the metaphysics debates. I focus on what is going on under the math. Under what the models truly state under the math. I rarely see any metaphysics paper truly address what the math shows.

Here is a key detail QM  and QFT operators  are not the same. In QFT the fields are the operators. Changes a lot of the arguments or should.

 

 

Maybe you will like this quote, written by a Bohmian author:

"our most basic physical theory 
contains no account of the constitution and structure of matter,  
corresponding to the interacting particles and fields of classical physics. It is a means to 
compute the statistical results of macroobservations carried out on systems 
that are unspecified and, indeed, unspecifiable. The word 'electron' does not 
actually mean anything at all - it is simply shorthand for a mathematical 
function. Quantum mechanics is the subject where we never know what we 
are talking about. " Peter R. Holland, The Quantum Theory of Motion : An Account of the de Broglie-Bohm Causal Interpretation of Quantum Mechanics, 1993.

6 minutes ago, Strange said:

How about: all of them, until you find one that satisfies your bizarre criteria.

Why bizarre? They are really simple:

- it must concern double slit experiments; You can start a thread on interferometers and I will gladly contribute by explaining why I think they cannot be considered as the equivalent of a double slit experiment. You won't agree with me and we will have to come back to this thread.

- the disappearance of the interference pattern must be shown "live" and not as a theoretical assumption or conclusion.

34 minutes ago, Strange said:

LMGTFY

https://scholar.google.co.uk/scholar?q=single+photon+double+slit+experiment

https://link.springer.com/article/10.1007%2Fs00016-011-0079-0

http://aapt.scitation.org/doi/10.1119/1.10184

http://aapt.scitation.org/doi/10.1119/1.1987321

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.87.160401

http://aapt.scitation.org/doi/10.1119/1.1531580

https://link.springer.com/article/10.1007%2FBF00734319

 

link 1 is  a google listing. Which article am I supposed to read?

link 2 concerns interferometers. See above.

link 3 shows interference patterns. They are not the issue.

This is as far as I got.

Could you please choose one link which you think proves me wrong?

edit: link 4 is behind a pay wall

same for link 5

same for link 6

same for link 7 that also concerns interferometers.

Just now, Strange said:

ncidentally, "theoretical assumption" doesn't really makes sense. Assumptions are based on little or no evidence, theories are based on large amounts of evidence. You may have meant, "a theoretical conclusion that hasn't been observed." Except that isn't the case. It was a theoretical prediction that has been shown to be correct.

Show it to me.

2 minutes ago, swansont said:

 

here's college lab report where they did it

http://www2.optics.rochester.edu/workgroups/lukishova/QuantumOpticsLab/2008_student_assignments/opt253/getliffe_lab_2_final.pdf

I stopped as soon I came across "Mach-Zehnder interferometer". I am willing to speak about this kind of experiments in another thread. Specifically, whether they can be considered as equivalent to a double slit experiment. I am not so sure about that. I wrote about interferometers long ago in another forum and I would have to consult my notes.

To make a long story short, I do not think it is an acceptable alternative for a two slit experiment. Moreover, I do not think that (Mach-Zehnder) interferometers actually show what the theory tells us they show. Just like with double slit experiments, interpretation of the data is crucial. But then interpretation is always crucial, with all scientific experiments.

But I promise you that I would be willing to discuss them in their own thread.

6 hours ago, swansont said:

This ties back to the questions I asked, and which you still have not answered. Physics, instead of hand-waving.

It is not a matter of Physics, or Mathematics, since everybody, me included, agrees on what we can "see" happening at each double slit experiment. The question is how to interpret it.

My argument, and as far as I know, it has never been presented by anyone else, is that the so-called disappearance of the interference pattern does not actually happen, but is a theoretical assumption.

I am willing to change my mind and go with the flow on one simple condition: show me this disappearance of interference pattern in (the video of) a real life experiment. Not an animation, and not a diagram.

The two examples given above, that of the screen with the pin, and the photographic plate, both show that the "particle" goes either through one or the other slit. That is what matters. That and the fact that there is only an interference pattern when there is no observation.

The problem then becomes: does the "particle" go through one or the other slit only when it is observed? Bohr says yes, because it in fact goes through both slits. But then, according to Bohr again, only observables "exist". Which observables? The fact that the particle goes through a single slit can also be called an observable. In fact, it is the fact that the particle goes through both slits that is never observed! 

***

8 minutes ago, Mordred said:

( Don't trust pop media descriptives) 

Do the references I have given fall under this category?

21 minutes ago, Dalo said:

Bohm later changed his position

I think I confused him with de Broglie who indeed changed twice of position concerning his pilot wave theory.

1 minute ago, Mordred said:

That is specifically superposition itself.

A probability function under superposition is a probablistic state. Once measured it is a detetmined state.

Once you intefere with a wavefunction regardless of being probablistic or not, via Observation which causes interference the original wavefunction changes. You cannot measure without interfering.

All measurements cause interference

This is an assumption central to the Copenhagen interpretation of Quantum theory. It is not an empirical fact but an attempt to explain empirical observations. I understand if you consider it valid, but this is not a matter of expertise, only of "philosophical" conviction.

Bohm later changed his position, and not everybody agrees with Bohr anymore. 

In my first post, I argue that observation does not need to change the outcome of the experiment, but rather that the explanations given are themselves problematic. That is the whole point of the matter:

Does observation/measurement change the outcome? Bohr, von Neumann, Heisenberg and others are convinced that this is the case. My impression is that it is more a petitio principii.

I am very glad that you have joined the discussion because you have finally brought it to the main point.

I only do not think that the issue can be solved with technical arguments. It is a deeply philosophical/metaphysical issue.

Bohm also said on the same page:

"an electron is neither a particle nor a wave, but is instead a third kind of object which has
some, but not all, of the properties of both particles and waves."

20 minutes ago, Mordred said:

Throw away the bullet(ball) image of particles.

No problem. But It wouldn't resolve the issue of the disappearance of the interference pattern in case of observation.

7 hours ago, Strange said:

Can you provide a reference to it being used with a double slit experiment?

David Bohm: Quantum Theory (1951; edition of 1985)

"To show that this conclusion does not depend on the particular method used to
find through which slit the electron goes, let us consider, for example, the possibility
of setting up a cloud chamber at the detecting screen." p.119

I am afraid that it concerns a thought experiment, not a real one. Besides, it was used by Bohm to emphasize his point that it is impossible to know through which slit the electron went, due to the Uncertainty Principle.

"We must remember, however, that the behavior of the electron in the cloud
chamber is also limited by the uncertainty principle."

This is a limitation that the other authors quoted previously did not recognize.

I had used the vapor chamber example from memory, and my example certainly does not stroke with Bohm's interpretation. Still, I think that my argumentation still stands, even if we accept that the vapor chamber is not really a good example.