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So a few weeks ago, I was listening to MIT Prof. Seth Lloyd on NPR explaining the experiment behind this promo text:
The paper was published in *Science* in 2003 - Aspelmeyer et al., Long-Distance Free-Space Distribution of Quantum Entanglement. You can find it on sciencemag.org, but registration is required. Prof. Lloyd was certainly under the impression that quantum entanglement is real. A free popular-press summary: http://physicsweb.org/article/news/7/6/20/1
Digging a bit further, I also found this press release
You can find this article on nature.com, but again, registration is required.
These purported demonstrations of quantum entanglement are more recent (2003) than the experiments in the 1970s and 1980s which the article Clauser and Horne's 1974 Bell test currently discredits. My preliminary sampling of professional opinion suggests to me that the peer-reviewed physics community is of the opinion that quantum entanglement has been convincingly demonstrated. I therefore dispute the claim made on Talk:Clauser and Horne's 1974 Bell test that "[t]here is as yet no convincing evidence that quantum entanglement occurs." I invite discussion of the 2003 experiments and further investigation of peer-reviewed articles and the opinions of professional scientists and engineers, to resolve the dispute. -- Beland 02:41, 17 Aug 2004 (UTC)
I'm not sure that there is not much dispute over the experimental results. It's pretty clear that there no generally experimentally accepted results that contradict QM. You can find lots of loopholes by which you can argue that local realist models are still correct. However, it is also the case that any local realist models are going to have to deal with explaining the phenonmenon that looks like quantum entanglement.
Roadrunner 04:43, 17 Aug 2004 (UTC)
Roadrunner 03:51, 21 Aug 2004 (UTC)
Roadrunner 03:51, 21 Aug 2004 (UTC)
Roadrunner 03:51, 21 Aug 2004 (UTC)
Roadrunner 03:51, 21 Aug 2004 (UTC)
I've added a couple of links re Bell test loopholes recently. Too much has been written about quantum entanglement on the assumption that the experiments have confirmed it convincingly. Re the apparent (limited) success of applications of entanglement, some readers might be interested in an article I've archived [1] that has yet to find a publisher. It seems likely that the real world is producing something useful by way of real correlations of phase and frequency but not otherwise taking much notice of accepted theory. The net result is better described by classical wave theory, adapted to allow for the behaviour of modern beamsplitters and photodetectors. Caroline Thompson 08:42, 1 Jul 2004 (UTC)
I toned down Reeh-Schlieder remark, as I see no much beef in the Reeh-Schlieder theorem for quantum entanglement. RS simply states that the non-local effects aren't exactly zero but vanish exponentially with distance. And it is a very general statement about all states and local operators. QE in QFT would need larger correlations for a smaller set of states. Pjacobi 09:33, 9 Jul 2004 (UTC)
Perhaps some kind soul could write a non-formal section explaining how particles become entangled and some of the interesting effects of entanglement. I am sorry to say that this article is incomprehensible to those of us who are not students of physics or who have had but a single year of college physics. I am also sorry to say that it seems to have gotten less comprehensible over the last year or so.
I realize that part of the reason I find this article so difficult to understand is the result of precision. Unfortunately, that precision has become excruciating.
I've looked at one of the press releases you gave, re
The experiment looks fascinating, but they seem to be using the word "entanglement" to mean just ordinary correlation. There is no mention of having done a Bell test to establish it. Instead the press release says:
But at the end of the day it will be just such ordinary correlations that will be used in what they will call "quantum computing", which will never really use the kind of entanglement that can infringe Bell inequalities since this kind simply does not happen. We're at an impasse, I'm afraid. I should love to re-write the page but my version would not be about "quantum entanglement" as quantum theorists understand it. Their version exists only on paper and in their formulae.
Incidentally, I've read: M. Riebe et al, “Deterministic quantum teleportation with atoms”, Nature 429, 734-737 (2004) which was in the news recently. Here they establish entanglement by measuring "fidelity" which, they say, cannot exceed 66.7% under local realism. What, however, is one to make of this?
So they've established entanglement but not ruled out local realism! That's nonsense. I have not been able to find out quite what "fidelity" is, but judging from the context it seems to be much the same as "visibility", and tests based this depend on the assumption that the system obeys Malus' Law. I suspect that they never check this thoroughy. Caroline Thompson 09:13, 3 Sep 2004 (UTC)
![]() | This page is an archive of past discussions. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page. |
![]() | This page is an archive of past discussions. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page. |
So a few weeks ago, I was listening to MIT Prof. Seth Lloyd on NPR explaining the experiment behind this promo text:
The paper was published in *Science* in 2003 - Aspelmeyer et al., Long-Distance Free-Space Distribution of Quantum Entanglement. You can find it on sciencemag.org, but registration is required. Prof. Lloyd was certainly under the impression that quantum entanglement is real. A free popular-press summary: http://physicsweb.org/article/news/7/6/20/1
Digging a bit further, I also found this press release
You can find this article on nature.com, but again, registration is required.
These purported demonstrations of quantum entanglement are more recent (2003) than the experiments in the 1970s and 1980s which the article Clauser and Horne's 1974 Bell test currently discredits. My preliminary sampling of professional opinion suggests to me that the peer-reviewed physics community is of the opinion that quantum entanglement has been convincingly demonstrated. I therefore dispute the claim made on Talk:Clauser and Horne's 1974 Bell test that "[t]here is as yet no convincing evidence that quantum entanglement occurs." I invite discussion of the 2003 experiments and further investigation of peer-reviewed articles and the opinions of professional scientists and engineers, to resolve the dispute. -- Beland 02:41, 17 Aug 2004 (UTC)
I'm not sure that there is not much dispute over the experimental results. It's pretty clear that there no generally experimentally accepted results that contradict QM. You can find lots of loopholes by which you can argue that local realist models are still correct. However, it is also the case that any local realist models are going to have to deal with explaining the phenonmenon that looks like quantum entanglement.
Roadrunner 04:43, 17 Aug 2004 (UTC)
Roadrunner 03:51, 21 Aug 2004 (UTC)
Roadrunner 03:51, 21 Aug 2004 (UTC)
Roadrunner 03:51, 21 Aug 2004 (UTC)
Roadrunner 03:51, 21 Aug 2004 (UTC)
I've added a couple of links re Bell test loopholes recently. Too much has been written about quantum entanglement on the assumption that the experiments have confirmed it convincingly. Re the apparent (limited) success of applications of entanglement, some readers might be interested in an article I've archived [1] that has yet to find a publisher. It seems likely that the real world is producing something useful by way of real correlations of phase and frequency but not otherwise taking much notice of accepted theory. The net result is better described by classical wave theory, adapted to allow for the behaviour of modern beamsplitters and photodetectors. Caroline Thompson 08:42, 1 Jul 2004 (UTC)
I toned down Reeh-Schlieder remark, as I see no much beef in the Reeh-Schlieder theorem for quantum entanglement. RS simply states that the non-local effects aren't exactly zero but vanish exponentially with distance. And it is a very general statement about all states and local operators. QE in QFT would need larger correlations for a smaller set of states. Pjacobi 09:33, 9 Jul 2004 (UTC)
Perhaps some kind soul could write a non-formal section explaining how particles become entangled and some of the interesting effects of entanglement. I am sorry to say that this article is incomprehensible to those of us who are not students of physics or who have had but a single year of college physics. I am also sorry to say that it seems to have gotten less comprehensible over the last year or so.
I realize that part of the reason I find this article so difficult to understand is the result of precision. Unfortunately, that precision has become excruciating.
I've looked at one of the press releases you gave, re
The experiment looks fascinating, but they seem to be using the word "entanglement" to mean just ordinary correlation. There is no mention of having done a Bell test to establish it. Instead the press release says:
But at the end of the day it will be just such ordinary correlations that will be used in what they will call "quantum computing", which will never really use the kind of entanglement that can infringe Bell inequalities since this kind simply does not happen. We're at an impasse, I'm afraid. I should love to re-write the page but my version would not be about "quantum entanglement" as quantum theorists understand it. Their version exists only on paper and in their formulae.
Incidentally, I've read: M. Riebe et al, “Deterministic quantum teleportation with atoms”, Nature 429, 734-737 (2004) which was in the news recently. Here they establish entanglement by measuring "fidelity" which, they say, cannot exceed 66.7% under local realism. What, however, is one to make of this?
So they've established entanglement but not ruled out local realism! That's nonsense. I have not been able to find out quite what "fidelity" is, but judging from the context it seems to be much the same as "visibility", and tests based this depend on the assumption that the system obeys Malus' Law. I suspect that they never check this thoroughy. Caroline Thompson 09:13, 3 Sep 2004 (UTC)
![]() | This page is an archive of past discussions. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page. |