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Author Topic:   the underlying assumptions rig the debate
PaulK
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Posts: 17822
Joined: 01-10-2003
Member Rating: 2.2


Message 196 of 246 (323718)
06-20-2006 3:04 AM
Reply to: Message 195 by randman
06-20-2006 2:52 AM


Re: Zeilinger's view
quote:
Please substantiate that. Where does he say "information is already fixed"? The quantum eraser shows the exact opposite, that information can be erased.
I stated that according to Zeilinger information that we already know is fixed - and it is quite clearly stated int eh quotes that I already provided.
The quantum state is exactly that representation of our knowledge of the complete situation which enables the maximal set of (probabilistic) predictions for any possible future observation...
According to Zeilinger's idea of the relationship between QM and Information Theory the Quantum State IS a representation of the information we have. The uncertainty is in the information we don't have.
Zeilinger explains "collapse" in terms of gaining more information, and updatign the representation to reflect that (and thus reducing uncertainty - and in information theory, information IS reduction in uncertainty).
quote:
Nope, not at all. You exhibit a major misunderstanding of what the quantum eraser experiment shows. It shows that indeed you can see a change in the photon's path back again; that once collapsed, the photon's path can become uncollapsed.
You're going to have to substantiate that - say, by referring to experiments where the path information is measured and only then "erased" as opposed to experiments where it is erased without being measured.
e

This message is a reply to:
 Message 195 by randman, posted 06-20-2006 2:52 AM randman has replied

Replies to this message:
 Message 200 by randman, posted 06-20-2006 3:25 AM PaulK has replied
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Percy
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Posts: 22392
From: New Hampshire
Joined: 12-23-2000
Member Rating: 5.2


Message 197 of 246 (323719)
06-20-2006 3:17 AM
Reply to: Message 191 by randman
06-20-2006 2:04 AM


Re: Read Iblis' last post
randman writes:
These could be good discussions, if you treated them with respect and intellectual honesty.
I believe I made a suggestion earlier regarding references to people's honesty. Third time's a charm!
You've somehow acquired the false belief that I've been claiming I know what Wheeler's actual views on causality violations are. What I've said is that whatever Wheeler's actual views are, it is definitely not a view of mainstream science that causality violations have been demonstrated and are consistent with quantum theory.
A quick Google didn't reveal any helpful websites regarding what you've claimed about Wheeler. If you want to suggest one or two, I'll take a look. But to remind you once again, I'm just giving my interpretation of the views of modern science. If Wheeler had different views about causality violations then it looks to me like modern science has rejected them.
One thing I did find via Google was an essay called Quantum Philosophy by John Horgan, a science writer at Stevens Institute. It looks like many of the things you have been saying have come from there, like the claim that you can uncollapse a wave function. My own reading is that Horgan is confused about quantum theory in a manner similar to your own confusion, but I'll defer to Cavediver as to whether Horgan has actually got things wrong. I found I couldn't be quite sure because it seemed to be a combination of correct and incorrect information.
One thing the Google did tell me, though, is that there seems to be a wide variety of opinion among scientists about interpretations of quantum theory, and even greater variety about what might be discovered in the future.
--Percy

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Percy
Member
Posts: 22392
From: New Hampshire
Joined: 12-23-2000
Member Rating: 5.2


Message 198 of 246 (323720)
06-20-2006 3:20 AM
Reply to: Message 191 by randman
06-20-2006 2:04 AM


Re: Read Iblis' last post
I see your post has more than doubled in length since I began composing my reply. I'll have to look it over later.
--Percy

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randman 
Suspended Member (Idle past 4899 days)
Posts: 6367
Joined: 05-26-2005


Message 199 of 246 (323722)
06-20-2006 3:23 AM
Reply to: Message 197 by Percy
06-20-2006 3:17 AM


Re: Read Iblis' last post
Percy, there is a wide variety of interpretations, which is why I tried to stress first what is observed in these experiments. If we can agree on that, and it's not so challenging to do that, then we could agree and disagree on the interpretations, but you guys seemed to refuse to agree on the process as seen from a human perspective, and that's frustrating. I didn't see enough grappling with the actual experiments here, but a lot of bashing me when I was presenting repeatedly what occured in the experiments, regardless of how you wish to interpret it.
As far as uncollapsing a wave-function, it's not my claim. It's the claim of Mandel and others that did these experiments, and imo, it is demonstrated fact.

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randman 
Suspended Member (Idle past 4899 days)
Posts: 6367
Joined: 05-26-2005


Message 200 of 246 (323723)
06-20-2006 3:25 AM
Reply to: Message 196 by PaulK
06-20-2006 3:04 AM


Re: Zeilinger's view
So in your view, if we send a photon towards 2-slits that has been measured before, it will not exhibit wave-like qualities?

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 Message 196 by PaulK, posted 06-20-2006 3:04 AM PaulK has replied

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randman 
Suspended Member (Idle past 4899 days)
Posts: 6367
Joined: 05-26-2005


Message 201 of 246 (323724)
06-20-2006 3:27 AM
Reply to: Message 198 by Percy
06-20-2006 3:20 AM


Re: Read Iblis' last post
It's a bad habit. Right after posting, I have more thoughts and try to do a quick edit before any responses and add more to it. Probably need to cut that out.

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PaulK
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Posts: 17822
Joined: 01-10-2003
Member Rating: 2.2


Message 202 of 246 (323725)
06-20-2006 3:33 AM
Reply to: Message 200 by randman
06-20-2006 3:25 AM


Re: Zeilinger's view
As I understand it, Zeilinger is saying that if the path information is measured then we will not get an interference pattern. Even with a "quantum eraser" later hiding that information from later observations of the photon (if such an arrangement is physically possible - I don't know that it is).t

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randman 
Suspended Member (Idle past 4899 days)
Posts: 6367
Joined: 05-26-2005


Message 203 of 246 (323726)
06-20-2006 3:36 AM
Reply to: Message 196 by PaulK
06-20-2006 3:04 AM


Re: Zeilinger's view
You're going to have to substantiate that - say, by referring to experiments where the path information is measured and only then "erased" as opposed to experiments where it is erased without being measured.
Well, let's consider the quantum eraser experiment or one of them. The photon passes through a polarizer and is measured and so takes on one path, but if we put a scrambler, a third polarizer in front of it, it will then revert back and take on the wave pattern.
Now, I hear what you are saying. The 2nd run is with different photons and so you are saying if the photons were measured and then moved down and sent through some process so we couldn't determine what path they took from that point on, that they would stay in the single path mode and not show a wave pattern.
Personally I disagree, but first let me point out that no experiment I know of has validated your idea here. It shouldn't be too hard to do, but it hasn't been done that I know of (maybe someone else knows of something?).
But I want to ask you something. Do you really think the same photon arriving theoritically down the road to a different group of people is not going to show a wave-like pattern unless they too somehow devise a way to determine what path the photon took?
Edited by randman, : No reason given.

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 Message 196 by PaulK, posted 06-20-2006 3:04 AM PaulK has replied

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PaulK
Member
Posts: 17822
Joined: 01-10-2003
Member Rating: 2.2


Message 204 of 246 (323727)
06-20-2006 3:49 AM
Reply to: Message 195 by randman
06-20-2006 2:52 AM


Re: Zeilinger's view
quote:
However, he does indeed think the past is formed by the present questions; the photon's path is determined by the observer's question, and so implies an actual connection between conscious observation and reality.
I don't remember anything speciically dealign with this point. So far as I can tell mechanical observatisn are entirely good enough in Zeilinger's view.
quote:
For example, what if the information is lost. Say the initial observers are all dead. Does the photon revert back to wave-like status in it's path?
Zeiinger doesn't address that question in the material I've seen, so I don't know what his view is on the matter.
quote:
In the quantum eraser experiment, it is clear that if one were to measure the photon at one point, it would have travelled along one path. I think in the context of what I am talking about, you are not seeing the significance of that. Imo, the causal effect of the photon at that point in time, whether observed or not, is likely to be the effect of the photon in a collapsed state, and history at that point in time would reflect that. Now, you can say it is indeterminate, like Wheeler, but if you do, you are also stating that perhaps a great deal of the past is indeterminate.
We're discussing Zeilinger's views, not mine. I am not sure to what extent Zeilinger carries his ideas of indeterminacy to the macroscopic level or to ordinary history.
The rest of the paragraph seems confused. It doesn't make sense to me at all.e

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 Message 195 by randman, posted 06-20-2006 2:52 AM randman has replied

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PaulK
Member
Posts: 17822
Joined: 01-10-2003
Member Rating: 2.2


Message 205 of 246 (323731)
06-20-2006 3:56 AM
Reply to: Message 203 by randman
06-20-2006 3:36 AM


Re: Zeilinger's view
quote:
Personally I disagree, but first let me point out that no experiment I know of has validated your idea here. It shouldn't be too hard to do, but it hasn't been done that I know of (maybe someone else knows of something?).
In other words you know of no experimental evidence to substantiate your view, but nevertheless you hold that "my" view - by which you mean Zeilinger's - is wrong.
Given that you don't know the actual facts of the matter don't you think that you should refrain from referring to Zeilinger's view as a "major misunderstanding" ?e
Edited by PaulK, : Provide reason for edit here.W

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randman 
Suspended Member (Idle past 4899 days)
Posts: 6367
Joined: 05-26-2005


Message 206 of 246 (323732)
06-20-2006 4:06 AM
Reply to: Message 204 by PaulK
06-20-2006 3:49 AM


Re: Zeilinger's view
I don't remember anything speciically dealign with this point.
The photon's path is a past event.
So far as I can tell mechanical observatisn are entirely good enough in Zeilinger's view.
You should reread your quotes of him you provided in context. He referred to the whole apparatus and experimenter, I believe, when he made the comments you referred to.
Also, you need to go back and edit in the links. I have given a lot of links and people won't know what you are referring to.
Zeiinger doesn't address that question in the material I've seen, so I don't know what his view is on the matter.
My quote of Zeilinger was where he believed as others such as Mandel that the determining factor in whether we observe a wave or particle path is whether we can know what the particle-path was. I think you have been reading him by some of your comments, and glad to see that, but at the same time, I am not necessarily agreeing with all of his ideas. The basic idea of what the criterion is based on experiments that others agreed with as well is my point.
Imo, if that criterion is present, the photon's path will appear to take only one path and in our universe, we shall see no interference pattern, and at that point the photon will have an impact as having taken one path. But if that criterion is not present, then the photon will not have taken one path and the interference pattern will be there as a real effect in our universe.
Now the question is if down the road someone observes a photon without being able to know even in principle the path, then the photon imo will have taken all possible paths even if someone in the past could and did measure the photon's path. Why do I think this?
Because the simple criterion is whatever at any point in time can be known of the path, that will be the way the photon behaves. If at any point in time, it becomes not possible to know the path a photon took even in principle, then the photon will have taken all possible paths even if in the past it took only one path. The criterion changes and so does the path (at least in the universe of our experience).

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 Message 204 by PaulK, posted 06-20-2006 3:49 AM PaulK has replied

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randman 
Suspended Member (Idle past 4899 days)
Posts: 6367
Joined: 05-26-2005


Message 207 of 246 (323734)
06-20-2006 4:15 AM
Reply to: Message 205 by PaulK
06-20-2006 3:56 AM


Re: Zeilinger's view
In other words you know of no experimental evidence to substantiate your view, but nevertheless you hold that "my" view - by which you mean Zeilinger's - is wrong.
Wrong. First, Zeilinger, Wheeler and Mandel and others all agree that the criterion for whether the photon behaves as a wave or particle is whether can know the path; what we can know about it. That was my point in quoting Mandel and Zeilinger on this point.
Now, do all these men agree on everything? No, they do not, but they agree on that point and it appeared you did as well.
The experimental data supports that point, namely that at any point in time that whether the photon behaves as a wave or particle depends on whether in principle we can know it travels in a single path like a particle. If that is not determinable at that point in time, then it travels like a wave taking all paths.
So if the same photon, based on this principle, at any point in time can be determined to travel along a single path, it will travel along that path. But if at a later point in time, it cannot be determined what path that same photon took even in principle, then it will have taken all possible paths even if in the past situation it took only one path.
That's what these experiments show. Now, if you want to say there is some limiting factor, go ahead, but they are not seen in experiments relating to quantum mechanics. You have to apply classical mechanics, and frankly, you just don't have any evidence or experiments to support your view on the quantum level.
Edited by randman, : No reason given.

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 Message 205 by PaulK, posted 06-20-2006 3:56 AM PaulK has replied

Replies to this message:
 Message 210 by PaulK, posted 06-20-2006 1:38 PM randman has replied

  
Larni
Member (Idle past 164 days)
Posts: 4000
From: Liverpool
Joined: 09-16-2005


Message 208 of 246 (323752)
06-20-2006 7:03 AM
Reply to: Message 188 by Iblis
06-19-2006 8:43 PM


Re: more on delayed-choice experiments
Iblis writes:
Without the detector, it happens at the back wall.
Aha! The fog clears.....
Thanks mate, I knew the bare bones of the split light experiment and had been seduced by 'teleporting' and such like.
Thanks for putting me straight, I will take 'New Scientist' with a pinch of salt .

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PaulK
Member
Posts: 17822
Joined: 01-10-2003
Member Rating: 2.2


Message 209 of 246 (323895)
06-20-2006 1:29 PM
Reply to: Message 206 by randman
06-20-2006 4:06 AM


Re: Zeilinger's view
quote:
You should reread your quotes of him you provided in context. He referred to the whole apparatus and experimenter, I believe, when he made the comments you referred to.
I just did. There's no reference to consciosuness in the immediate context of any of the quotes, nor is there any claim that the experimenter should be considered part of the experimental apparatus.
I'll deal with the rest in my reply to your next post..
Edited by PaulK, : No reason given.

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PaulK
Member
Posts: 17822
Joined: 01-10-2003
Member Rating: 2.2


Message 210 of 246 (323905)
06-20-2006 1:38 PM
Reply to: Message 207 by randman
06-20-2006 4:15 AM


Re: Zeilinger's view
quote:
So if the same photon, based on this principle, at any point in time can be determined to travel along a single path, it will travel along that path. But if at a later point in time, it cannot be determined what path that same photon took even in principle, then it will have taken all possible paths even if in the past situation it took only one path.
This is not Zeilinger's view. First I will deal with the logical problem. If we measure the photon's path before it meets the quantum eraser then it's path is knowable and so your argument fails.
To go to Zeilinger's view I will repeat the quote:
As long as no observation whatsoever is made on the complete quantum system comprised of both photons our description of the situation has to encompass all possible experimental results. The quantum state is exactly that representation of our knowledge of the complete situation which enables the maximal set of (probabilistic) predictions for any possible future observation...
If we do not make the observation we do not have the information on th path and thus we must still represent the photon as "smeared" accross all paths. If we do make the observation then we do have the information and any future observations must be consistent with that information
Thus I conclude that in Zeilinger's view the photon is only collapsed prior to meeting the eraser if we measure it's path. If we do not then - according to the statement above - it remains in the "smeared" state.
Unless you have experimental evidence to the contrary it's just your opinion versus Zeilinger's.(

This message is a reply to:
 Message 207 by randman, posted 06-20-2006 4:15 AM randman has replied

Replies to this message:
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