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Author Topic: Entangled particle connection  (Read 6684 times)

Offline SpaceMonkey

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Entangled particle connection
« on: 20/12/2014 05:55:43 »
  Let me preface my question by saying that I am not a physicist. I enjoy learning about quantum mechanics via means fairly accessible to an interested layman,
but would like a somewhat more technical explanation of particle entanglement.

  I have gotten so far as learning about the Bohr/ Einstein debate regarding the behaviors of entangled particles, and see that Bohr's theory seems to be the
prevalent theory at this point. However without delving into materials far beyond my comprehension, the best explanation I have found of his ideas is summarized
by the phrase "spooky action at a distance." Articles using this phrase rarely, so far as I have found, give any further explanation of the phenomenon.
Einstein's theory that the creation of these particles in pairs predetermines their enduring connection seems more valid to me, but again, as it does not
seem to be the commonly accepted theory, could someone try to give me a better understanding of Bohr's theory?

Thanks!


 

Offline PmbPhy

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Re: Entangled particle connection
« Reply #1 on: 20/12/2014 07:06:09 »
Quote from: SpaceMonkey
I have gotten so far as learning about the Bohr/ Einstein debate regarding the behaviors of entangled particles, and see that Bohr's theory seems to be the prevalent theory at this point.
I've heard about that debate but never read it. What did you use as a source for the debate? I'd like to read the exact same thing so that we have common reference material to go by.
 

Online jeffreyH

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Re: Entangled particle connection
« Reply #2 on: 20/12/2014 21:15:42 »
Welcome to the forum spacemonkey. It is a very interesting point that you make. I too have wondered about entanglement. I have read up on the history of the development of quantum physics but not come across this point of debate in any detail. I will be interested to see where this goes.
 

Offline yor_on

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Re: Entangled particle connection
« Reply #3 on: 20/12/2014 22:00:48 »
It's like this. You have one 'photon' that you split into two, sort of :) using a beam splitter that can be likened to a half transparent mirror. Those two 'new photons are correlated in a rather weird way through their spin (polarization). It doesn't matter for this which one you measure, the other will have a opposite spin. And doing the experiment several times you will find no order to what that first spin will be, once you measure it. The only thing you can be sure of is that no matter the first ones spin ('up' or 'down') the other photon must have a opposite spin. So you can not predict the first ones spin, and it doesn't matter for this complementary principle which way you find it to be. That's sort of weird, isn't it? Like they were able to 'communicate' instantly? And yeah, that is a spooky action at a distance.
==

Ahh Bohr, is it? Well Bohr is the father of quantum physics as I understands it, at least one of the really prominent ones, and where he and Einstein debated was just around what this 'spookiness' meant. I think Einsteins thesis there was that quantum physics was incomplete, whereas Bohr's was that this actually just was the way things was, on a quantum scale.
« Last Edit: 20/12/2014 22:09:29 by yor_on »
 

Offline SpaceMonkey

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Re: Entangled particle connection
« Reply #4 on: 22/12/2014 02:29:51 »
Quote from: SpaceMonkey
I have gotten so far as learning about the Bohr/ Einstein debate regarding the behaviors of entangled particles, and see that Bohr's theory seems to be the prevalent theory at this point.
I've heard about that debate but never read it. What did you use as a source for the debate? I'd like to read the exact same thing so that we have common reference material to go by.


It took me a bit to find the source sites for these articles, I've just had them saved to my desktop for a while, but these are the original papers by Einstein and Bohr:

"Atomic Theory and the Description of Nature" -Niels Borh
newbielink:https://www3.nd.edu/~dhoward1/The%20Quantum%20Postulate%20and%20the%20Recent%20Development%20of%20Atomic%20Theory.pdf [nonactive]

Einstein's collaborative reply, "Can Quantum-Mechanical Description of Physical Reality Be Considered Complete?" - Albert Einstein, Boris Podolsky, Nathan Rosen:
newbielink:http://www.drchinese.com/David/EPR.pdf [nonactive]

Bohr's rebuttal, "Can Quantum-Mechanical Description of Physical Reality Be Considered Complete?" - Niels Bohr
dieumsnh.qfb.umich.mx/archivoshistoricosmq/.../Bohr1935.pdf

A more modern analysis of the above referenced papers, "Revisiting the Einstein-Bohr Dialogue" - Don Howard
newbielink:https://www3.nd.edu/.../Revisiting%20the%20Einstein-Bohr%20Dialogue.pdf‎ [nonactive]

Also, among the scores of YouTube videos on the subject, I have found this one among the more informative,
"Quantum Entanglement Documentary - Atomic Physics and Reality"
 

Offline SpaceMonkey

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Re: Entangled particle connection
« Reply #5 on: 22/12/2014 02:36:01 »
It's like this. You have one 'photon' that you split into two, sort of :) using a beam splitter that can be likened to a half transparent mirror. Those two 'new photons are correlated in a rather weird way through their spin (polarization). It doesn't matter for this which one you measure, the other will have a opposite spin. And doing the experiment several times you will find no order to what that first spin will be, once you measure it. The only thing you can be sure of is that no matter the first ones spin ('up' or 'down') the other photon must have a opposite spin. So you can not predict the first ones spin, and it doesn't matter for this complementary principle which way you find it to be. That's sort of weird, isn't it? Like they were able to 'communicate' instantly? And yeah, that is a spooky action at a distance.
==

Ahh Bohr, is it? Well Bohr is the father of quantum physics as I understands it, at least one of the really prominent ones, and where he and Einstein debated was just around what this 'spookiness' meant. I think Einsteins thesis there was that quantum physics was incomplete, whereas Bohr's was that this actually just was the way things was, on a quantum scale.

But the underlying question is more of whether the act of measuring one effects the other, or if they originate with opposing spins. As far as I can see this is impossible to test, so can only be a debate. However it is Bohr's assertion
that the act of measuring one particle does effect the attributes of the other. I am curious how this could've been proven.
 

Offline PmbPhy

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Re: Entangled particle connection
« Reply #6 on: 22/12/2014 04:14:01 »
Quote from: yor_on
It's like this. You have one 'photon' that you split into two, sort of ...
No "sort of". A photon cannot be split into two, period.
 

Offline SpaceMonkey

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Re: Entangled particle connection
« Reply #7 on: 22/12/2014 06:52:46 »
Quote from: yor_on
It's like this. You have one 'photon' that you split into two, sort of ...
No "sort of". A photon cannot be split into two, period.

  Is that not the outcome of spontaneous parametric down-conversion? I agree that a photon is not split into sub-particles with separate properties
from a photon, but rather into two photons with the combined energy and momentum of the original, but is in fact split via the process.

  That is however irrelevant to the original question as this process clearly creates entangled pairs that are correlated by origin. Regardless of their
separability they remain entangled in their fundamental properties delineated in their creation from a single parent photon.
 

Offline PmbPhy

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Re: Entangled particle connection
« Reply #8 on: 22/12/2014 08:39:51 »
Quote from: SpaceMonkey
I agree that a photon is not split into sub-particles with separate properties from a photon, but rather into two photons with the combined energy and momentum of the original, but is in fact split via the process.
You just made my argument for me then. :)
 

Offline evan_au

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Re: Entangled particle connection
« Reply #9 on: 22/12/2014 20:16:49 »
Quote from: PmbPhy
A photon cannot be split into two, period.
Nonlinear optical materials can do some odd things when the electric field intensity gets up around 108 V/m (eg from an intense laser). These effects were not discovered until after the invention of the laser.

One of those things is to turn a single photon into two photons, each having:
  • Half the Frequency
  • Half the Energy
  • Half the Momentum
  • Conserving all the usual properties
  • ...But it only happens rarely (eg 1 in 1012 photons)
  • ...and only some of these are entangled
Nonlinear optical materials can also do:
  • Two photons in produce 1 photon out, at twice the frequency
  • Two photons of frequency f1 and f2 produce a photon at (f1+f2) or (f1-f2)
  • ...and a number of other tricks with light and mirrors!
  • ...in fact, many of the same techniques that radio engineers have used with nonlinear electronic devices over the past century.
I also discovered that at extremely high electric fields, a vacuum is thought to become nonlinear... I'm not sure why that is...
 

Offline JohnDuffield

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Re: Entangled particle connection
« Reply #10 on: 22/12/2014 20:54:13 »
Just for the record, I'm with Einstein on this. I'm not fond of spooky action at a distance, or any kind of quantum mysticism. And I can't explain Bohr's theory.

Good stuff evan. 
 

Offline PmbPhy

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Re: Entangled particle connection
« Reply #11 on: 22/12/2014 22:08:56 »
Quote from: evan_au
Nonlinear optical materials can do some odd things when the electric field intensity gets up around 108 V/m (eg from an intense laser). These effects were not discovered until after the invention of the laser.

One of those things is to turn a single photon into ..
Yes. I understand. I studied such optics as an undergraduate. However that doesn't mean that a single photon is split into two photons like you can split a nucleus into two nuclei.

I think it all has to do with what it means to have a subatomic particle split into two particles.
 

Offline Bill S

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Re: Entangled particle connection
« Reply #12 on: 23/12/2014 01:13:20 »
http://www.drchinese.com/David/EPR_Bell_Aspect.htm

This might not be a bad place to start looking at the refutation of EPR, and the subsequent "proof" of Bell's Theorem.
 

Offline yor_on

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Re: Entangled particle connection
« Reply #13 on: 23/12/2014 08:04:48 »
Quote from: yor_on
It's like this. You have one 'photon' that you split into two, sort of ...
No "sort of". A photon cannot be split into two, period.

Did you assume that I didn't know this Pete?
I just kept it as easy for others, meeting this for the first time, to follow as possible. because one of the arguments doing this experiments is that it is about 'photons', no matter how you treat them in the conversion from 'photon' to 'wave' then split into two 'photons' through the use of a beam splitter. And I've seen this exact reasoning in a lot of other places, and experiments, too.  The point there, why I now accept this type of reasoning, is the one whether one think light has a real duality, or not? If it has? I see nothing that stops it from behaving as a wave in one part of your experiment, to then act as a 'photon' in some other part. But I also admit to have had some difficulties with accepting it at first :)
=

Or, did you mean to tell me that this experiment is impossible to do? Just letting one 'photon' off at your source? To meet that beam splitter? what happens in such a case, if so?
« Last Edit: 23/12/2014 08:14:44 by yor_on »
 

Offline yor_on

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Re: Entangled particle connection
« Reply #14 on: 23/12/2014 08:28:26 »
I really don't know Spacemonkey :)

One of the things I really wished I could understand though. It's about statistics this one, and even though you should have a 50% correlation of the spin being either up or down, in your first measurement, I don't think you can find a correlation to how it will fall out in each single case. Let's assume that you could though? as per chaos theory, finding some hidden parameter (periodicity of 'ups' coming) defining it. Then it should be different I think. But as it seems to be it's like having what's called a 'fair coin'. Defining it as each flip of such a coin is impossible to define beforehand. That's your 'photon' before a measurement, alternatively existing in a 'super position' of 'up' and 'down', forced into a outcome by your measurement.
=

you could try this one if you like? Dr. Bertlmann's socks discussed.  and then to check the idea of it being 'ftl' signals you might look at  How Quantum Entanglement Transcends Space and Time

==

I don't agree on this questioning Einsteins ideas of locality though, or 'local causality', though. To me it seems more of a question how you define it. 'Locality', in my view is what relativity is about, it's what defines any experiment you do, you using your (local) clock and ruler, and there is no other way to do a experiment that makes as much sense to me.

That's one reason why I'm questioning the ideas of 'universal common containers' also. Because, if you can find a way to define this universe differently than through Victorian means, you might be able to find how locality actually hold true for a entanglement too. It's about 'what' connects to 'what', and how it can do it to me. Weird thoughts :)
« Last Edit: 23/12/2014 09:48:17 by yor_on »
 

Offline SpaceMonkey

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Re: Entangled particle connection
« Reply #15 on: 27/12/2014 15:48:39 »
I really don't know Spacemonkey :)

One of the things I really wished I could understand though. It's about statistics this one, and even though you should have a 50% correlation of the spin being either up or down, in your first measurement, I don't think you can find a correlation to how it will fall out in each single case. Let's assume that you could though? as per chaos theory, finding some hidden parameter (periodicity of 'ups' coming) defining it. Then it should be different I think. But as it seems to be it's like having what's called a 'fair coin'. Defining it as each flip of such a coin is impossible to define beforehand. That's your 'photon' before a measurement, alternatively existing in a 'super position' of 'up' and 'down', forced into a outcome by your measurement.
=

you could try this one if you like? newbielink:https://cds.cern.ch/record/142461/files/198009299.pdf [nonactive]  and then to check the idea of it being 'ftl' signals you might look at  newbielink:http://fqxi.org/community/forum/topic/994 [nonactive]

==

I don't agree on this questioning Einsteins ideas of locality though, or 'local causality', though. To me it seems more of a question how you define it. 'Locality', in my view is what relativity is about, it's what defines any experiment you do, you using your (local) clock and ruler, and there is no other way to do a experiment that makes as much sense to me.

That's one reason why I'm questioning the ideas of 'universal common containers' also. Because, if you can find a way to define this universe differently than through Victorian means, you might be able to find how locality actually hold true for a entanglement too. It's about 'what' connects to 'what', and how it can do it to me. Weird thoughts :)

Thanks for that reply!! As simplistic as it was, the "fair coin" example did provide some insight and clarity for me on the matter.

As for Einstein's ideas on locality, I have to agree that it is all about definition and perspective. It seems to me the greatest schisms in experimental
results come from attempting to correlate events on scales too different to be related within the same measures of space-time effects. As subatomic interactions
may seem simultaneous by our measurements of time, regardless of how precise, time "measured" by interacting photons could allow such events to be linear
from a light-speed perspective. Already well understood ramblings by those who would read this I'm sure, but it is interesting to think about the philosophical
implications of the results and theories in modern QM.

newbielink:http://www.drchinese.com/David/EPR_Bell_Aspect.htm [nonactive]

This might not be a bad place to start looking at the refutation of EPR, and the subsequent "proof" of Bell's Theorem.


 I have come across Bell's Theorem referenced in many of the articles I have read on this topic, but have never looked much further
into his works and am unfamiliar with even the general premise. Now that I've realized the Bohr-Einstein debates don't really have a
clear winner as I'd thought, seems like a perfect avenue to explore next. Thanks for the link!
 

Online jeffreyH

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Re: Entangled particle connection
« Reply #16 on: 27/12/2014 17:32:36 »
http://www.drchinese.com/David/EPR_Bell_Aspect.htm

This might not be a bad place to start looking at the refutation of EPR, and the subsequent "proof" of Bell's Theorem.

If there is something that travels at superluminal speeds....

http://drchinese.com/David/Bell_Theorem_Easy_Math.htm

"Please note that there is a way out of this seemingly impossible scenario, but the loophole may be difficult to swallow: if Einstein's Relativity is wrong, and the speed of light is NOT a limit for propagation of cause and effect (which is called "signal locality"), then that would give us a way out of the situation. Theoretically, there could exist non-local hidden variables (Bohm outlined such a theory, for example). But regardless, the net effect of Bell's Theorem is profound. Reality is somehow dependent upon how we observe it."
 

Offline yor_on

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Re: Entangled particle connection
« Reply #17 on: 02/01/2015 16:07:08 »
Not for me Jeffrey. I have a really good trust in 'c'. I also define 'c' as the symmetry break we exist in. In it 'c' becomes a clock, local.  and using such a definition time travels won't happen, not 'inside'. doesn't matter for this how one then theoretically want to define probabilities for it existing. We're inside.
 

Offline Le Repteux

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Re: Entangled particle connection
« Reply #18 on: 04/01/2015 15:09:24 »
Hi guys!

To paraphrase a well known politician, I say: "Don't ask ourselves what light can do for us, but ask the atoms what it can do for them."

While observing atoms, we develop ideas that are useful to us, but atoms are observing other atoms at a much higher frequency and since a much longer time than us. What does entanglement mean for them? Do they appear as wave or corpuscles to one another depending on their observations?  Aren't we getting more and more anthropocentric with our observations? Remember the episode of the epicycles and its anthropocentrism? Could entanglement mean that we chose the wrong viewpoint again?
« Last Edit: 04/01/2015 15:29:57 by Le Repteux »
 

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Re: Entangled particle connection
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