Talk:Einstein–Podolsky–Rosen paradox/Archive 1

message: Some questions conserning the EPR paradox 
1.Considering a particle with zero spin decaying in to two particles A and B with non zero spin. Is the behavior of the two new particles A and B and their " choice " of spin direction, due to conservation of spin in an interaction, caused by the collapsing of one two particle wavefunction AB at the time of measurement?
2.By this I mean that each of the two wavefunction states{Aup, Bdown},{Adown,Bup) are states of ONE wave(AB), not two seperate wavefunctions A and B and is therefore no more a paradox then the instantanious collapse of the wavefunction in general( the wavefunction occupies space). 
3.Does Reactions with larger arrangements of states also chooses all the states at the same time, only the information we get out of measuring one particle does'nt tell us as much about the other particles, cause there are many wavefunction states that contains the measurement?
4.Can the measurement of one of the paricles be considered as cutting the tie between the two paticles and splitting the one twoparticle statefunction AB in to two singleparticle statefunctions A and B?
Any help in clarifying these things would be great!JanBanan 23:13, 29 January 2006 (UTC)
thread_title:  EPR paradox? 

message: IF the electrons were opposite each other when they were together, of course they'd still be opposite once they were apart. The article doesn't demonstrate that there's any paradox.user:hackwrench
:Have you actually read the article? -- CYD
Yes, and it doesn't actually establish the contradiction when "locality", "realism", and "completeness" is added that this experiment is designed to cure.
Also, entangledness just becomes another hidden variable.
:I don't understand what you mean. "Entangledness just becomes another hidden variable" means nothing. -- CYD
They can't detect whether or not two atoms are entangled, thus hidden.
Yeah, I don't get it either. "We have seen that a quantum state cannot possess a definite value for both x-spin and z-spin. " No, I do not see how that is explained. So if you measure x, you won't know z...so what? Why is that weird? What happens if you measure x and z? You'll know x and z for the other electron, right? Again, big deal. I fail to understand the significance.--Theropod-X 20:04, 24 June 2006 (UTC)
thread_title:  Doesn't clearly explain the paradox 

message: It would be a good thing to put that thing on hold, until you consider what I have to say about  the lead paragaph:
The EPR paradox is a thought experiment named after Einstein, Podolsky, and Rosen who devised it in 1935 to attack the theory of quantum mechanics by demonstrating a seemingly paradoxical consequence. It was the subtlest and most successful of the several objections Einstein raised against quantum mechanics, which he disliked for its use of probability.
Properly, it is an illustration of one philosophical objection to the Copagenhagn Consensus.  Bohr, Einstein  and their elite collegues struggled to deal with the implications of scientific discoveries after 1922.  This community process, carried out in person, corrospondance, and journals, resulted in a  meeting to developed a framework for further scientific research. Together they reached a concensus named after the city where they met.
Very crudely, Bohr  won Einstein lost. 
Bohr, who had his ideas refined through hundreds of hours of conversation and warm letters exchanged with Einstein, increased his stature in the scientific communmity. Einstein while respected, became increasingly irrelevant as time went by. The 1935 ERP paper was probably the high point of his later career.Relationship between the two men was strained and became more distant with time. Quantum Mechanics went on to become the most successful theory of all time.
Nils, is one of the best philosophers of the 20th centuary. The reason that
ERP is subtle was because Bohr's position had to become subtle in response to several years of dialogues with elite minds, especially Einstein.
For what its worth  Two16 and what moral  you can find.
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Is is appropriate to use a link to "Probability" in the second paragraph when "probabilistic" is really referring to the antonym of "deterministic"?  The Probability link does not describe this model of the universe but rather basic probability in math.  (Perhaps it is being used correctly, here and elsewhere, but it doesn't appear so in context of Einstein's objection). - Texture 22:01, 21 Nov 2003 (UTC)
thread_title:  Two16 on lead para 

message: I agree that the whole page got a bit too long.
I  suggest to leave the top of the page
which gives conceptual overview, and which mentions
as a link to other pages - more technical and/or mathematical topics
such as
 
# EPR setup
# Bell Inequality (derivation, assumptions)
# entanglement 
# Do some still try to 'escape Bell'  ..
# any other technical issue
So, we move the technical stuff of the  current EPR page 
(the bottom half) to those linked pages-
leaving just the conceptual overview here ..
But I notice that  Bell already moved once, to  a separate page,
and came back.. so I would liketo ask if there are  any objections?
I also do thank all those who  corrected my clumsy markup
- and spelling and grammar too.
I am stil learning how do this - how the markup works
This was actually is my first contribution - so I am quite a newbie Petr 07:01, 2004 Jan 15 (UTC)
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A minor point - is "potentia" singular, plural or invariant?  It looks like a Latin plural (of a would-be "potentium", perhaps) but is used as both a plural and a singular in the text.  This needs to be corrected if it is incorrect; maybe a brief note could be added (along the lines of "singular: 'potentium'" [or whatever]) if it is already correct. -- Paul G 14:35, 9 Feb 2004 (UTC)
thread_title:  spliting the page 

message: (William M. Connolley 09:06, 22 Jun 2004 (UTC)
replies: text: Of the several objections to the then current interpretation of the quantum mechanics spearheaded by Einstein, the EPR paradox was the subtlest and most successful. The EPR paradox has not been resolved or explained, in a way which agrees with classical intuition, to this day. It brought a new clarity and permanent shift in thinking about 'what is reality' and what is a 'state of a physical system'. First, a review of the history:
This seems misleading to me, because although "successful" in the sense of stimulating debate it was a total failure in its primary goal - to shake QM. To say "The EPR paradox has not been resolved or explained, in a way which agrees with classical intuition" is similarly odd. Vast swathes of QM share this same feature of not being explicable in a classical sense. Better would be: resolution of the EPR "paradox" within the framework of QM has strengthened the mainstream "copenhagen interpreation" view of QM.
(William M. Connolley 09:22, 29 Jun 2004 (UTC)
thread_title:  Para from the intro... 

message: Despite my disagreement with CYD about the spin singlet state (which I think can be resolved by adding text or deleting text or marginally changing text), Lethe and CYD ---I think, myself and possibly others, seem to agree that  the more serious problem with the article is dealing with or accomodating a minority viewpoint which is hostile to the commonly accepted view of entanglement.  As I said, I don't consider myself qualified to act as a "reviewer" for her work. This puts the article into a state in which it is misleading to a reader unwilling to tackle the debate implicit in that article.  Also why was the experimental setup for EPR moved somewhere else?CSTAR 16:30, 22 Sep 2004 (UTC)
thread_title:  POV? 

message: Feynman was perfectly happy to consider probability amplitudes.  Probability amplitudes aren't probabilities. Whta's the problem? Why is Caroline Thompson so determined to use one formalism -- classical mechanics and probabilities to explain QM? This is surely not an instance of Occam's razor. This is more like Occam's fingernail which perpetuates an itch.CSTAR 01:22, 3 Nov 2004 (UTC)
thread_title:  Probability amplitudes 

message: I'm surprised C. T. didn't pick up on an obvious "incompleteness" of the statistical interpretation of EPR-Bohm given in the previous section. Namely, that it would seem that a minor modification of this scheme (involving three individuals: A-Alice, B-Bob and E-Eve the eavesdropper)  could also prove that there is no protocol which would with high probability indicate whether an eavesdropper was present.  This would directly contradict the schemes now being proposed (even comercially developed) for quantum key exchange.  Unfortunately, I haven't thought about this enough to give an adequate answer, although I do (now at least) believe in quantum key exchange or at least "key size amplification". CSTAR 18:37, 9 Nov 2004 (UTC)
thread_title:  Quantum key exchange 

message: The section with that name sounds really fishy.  The book is not closed? On what exactly is the book not closed? Of course the book in science is never closed. The scientific method should always allow criticism and reexamination, but who are we kidding? If somebody wants to do this research as a hobby that's fine.  But certainly we shouldn't pretend that finding these loopholes is mainstream physics and even more irresponsibly suggest to some kid reading this article and wanting to do science that this is a great area for future research.CSTAR 03:50, 11 Nov 2004 (UTC)
replies: text: Today, most physicists believe ... that the principle of locality does not hold. Therefore, the EPR paradox would only be a paradox because our physical intuition does not correspond to physical reality. However, the book is not closed yet on this issue.
Oh Really? The purpose of the argument I gave abive in this page (in the section quantum operations and locality) was to show that in fact, locality is preserved at least statistically.  Moreover,  I would argue that for quantum states, the statistical interpretation (formalized by density matrices) is the only operationally meaningful one.CSTAR 04:29, 11 Nov 2004 (UTC)
thread_title:  Modern perspectives? 

message: The result stated and shown above concerning no information transfer between Bob and Alice (formulated using quantum operations) is essentially the No-communication Theorem as formulated in the Peres and Terno paper referenced below. I don't know whose result  this is originally, although the authors Peres and Terno credit Florig and Summers (I haven't seen their 1997 paper).  
BTW I think the proof presented above is a little more detailed mathematically than the one in Peres Terno.
Maybe we should start an article on the no-communication theorem as a relevant support for information theoretic aspects of causality.  CSTAR 21:31, 18 Nov 2004 (UTC)
thread_title:  The no-communication theorem 

message: * D. Bruss, Characterizng Entanglement, arXiv:quant-ph0110078 v1 12 Oct 2001 (The relevance of protocols)
* D. Deutsch, The Structure of the Multiverse, April 2001 (I don't remember where I got this from).
* M. Florig and S. J. Summers, J. Math Phys 38, 1997.
* A. Peres and D. R. Terno, Quantum Information and relativity Theory, arXiv:quant-ph/0212023, v1 4 Dec 2002
CSTAR 16:22, 6 Nov 2004 (UTC)
thread_title:  Some references 

message: In the section on resolving the paradox I'd like to see some comments on how realist theories based on loopholes relate to EPI and Fisher information. Anyone? Kuratowski's Ghost 16:04, 6 Apr 2005 (UTC)
thread_title:  EPI 

message: Though some appear to be minor wordsmithing changes, some of these seem to be very strange and highly idiosyncratic. In particular, the use of the expression quantum mechanic theory is very unusual. These should be reverted to CYD's last version. --CSTAR 20:23, 21 Apr 2005 (UTC)
thread_title:  Recent changes 

message: I thought that one of EPR was not a physicist, but a logician, who helped Einstein with the reasoning, but didn't know much about physics. Am I mistaken? --MarSch 14:21, 13 Jun 2005 (UTC)
thread_title:  physicist?