Did the action at a distance take place at a rate faster than the speed of light? — T Clark
Does the experiment described contradict that? — T Clark
If not what's the big deal. — T Clark
The 'Bell inequalities' experiments confirm that the correlation between the two particles that occurs at the measurement of one of the pairs is instantanous. — Wayfarer
The article is correct - information cannot be transmitted faster than light. Yet in the Bell experiments, the correlation between separated particles is instaneous. So, information is not being transmitted between the two particles, and yet the correlation is happening. By what means does it happen? You see the question? — Wayfarer
So making a measurement here creates an outcome there without any apparent means for that information to be transmitted - because it's instantaneous, then it is faster than the speed of light which is the upper limit for any actual transmission. — Wayfarer
This wording suggests that there is a concept of 'instantaneous', or absolute simultaneity, which is an entirely naive wording.The 'Bell inequalities' experiments confirm that the correlation between the two particles that occurs at the measurement of one of the pairs is instantanous. — Wayfarer
Faster than light yes. Into the past even in the case of delayed choice experiments, which have been performed with cause occuring years after the effect.Did the action at a distance take place at a rate faster than the speed of light? — T Clark
This wording suggests that there is a concept of 'instantaneous', or absolute simultaneity, which is an entirely naive wording. — noAxioms
the wording in the above statements suggests that there is but one measurement that somehow 'instantaneously' changes the state of the other particle, — noAxioms
Copenhagen is about as local as it gets, and it being an epistemological interpretation, all it says is that a measurement here causes knowledge here of what the other measurement will be when we learn of it. — noAxioms
The thing that locality denies is not the faster than light relationship between measurements, but the 'action' part. No local interpretation suggests that anything changes at the far particle when the near one is measured. Copenhagen is about as local as it gets, and it being an epistemological interpretation, all it says is that a measurement here causes knowledge here of what the other measurement will be when we learn of it. Other local interpretations word it differently, but none suggest any FTL action. — noAxioms
Quantum entanglement is the physical phenomenon that occurs when a group of particles are generated, interact, or share spatial proximity in a way such that the quantum state of each particle of the group cannot be described independently of the state of the others, including when the particles are separated by a large distance. The topic of quantum entanglement is at the heart of the disparity between classical and quantum physics: entanglement is a primary feature of quantum mechanics lacking in classical mechanics.
Measurements of physical properties such as position, momentum, spin, and polarization performed on entangled particles can, in some cases, be found to be perfectly correlated. For example, if a pair of entangled particles is generated such that their total spin is known to be zero, and one particle is found to have clockwise spin on a first axis, then the spin of the other particle, measured on the same axis, is found to be anticlockwise. However, this behavior gives rise to seemingly paradoxical effects: any measurement of a particle's properties results in an irreversible wave function collapse of that particle and changes the original quantum state. With entangled particles, such measurements affect the entangled system as a whole.
Such phenomena were the subject of a 1935 paper by Albert Einstein, Boris Podolsky, and Nathan Rosen, and several papers by Erwin Schrödinger shortly thereafter, describing what came to be known as the EPR paradox.Einstein and others considered such behavior impossible, as it violated the local realism view of causality (Einstein referring to it as "spooky action at a distance") and argued that the accepted formulation of quantum mechanics must therefore be incomplete.
Later, however, the counterintuitive predictions of quantum mechanics were verified in tests where polarization or spin of entangled particles was measured at separate locations, statistically violating Bell's inequality. In earlier tests, it couldn't be ruled out that the result at one point could have been subtly transmitted to the remote point, affecting the outcome at the second location. However, so-called "loophole-free" Bell tests have been performed where the locations were sufficiently separated that communications at the speed of light would have taken longer—in one case, 10,000 times longer—than the interval between the measurements.
According to some interpretations of quantum mechanics, the effect of one measurement occurs instantly. Other interpretations which don't recognize wavefunction collapse dispute that there is any "effect" at all. However, all interpretations agree that entanglement produces correlation between the measurements and that the mutual information between the entangled particles can be exploited, but that any transmission of information at faster-than-light speeds is impossible.
Quantum entanglement has been demonstrated experimentally with photons, neutrinos, electrons, molecules as large as buckyballs, and even small diamonds. The utilization of entanglement in communication, computation and quantum radar is a very active area of research and development. ...
Paradox
The paradox is that a measurement made on either of the particles apparently collapses the state of the entire entangled system—and does so instantaneously, before any information about the measurement result could have been communicated to the other particle (assuming that information cannot travel faster than light) and hence assured the "proper" outcome of the measurement of the other part of the entangled pair.
— Wikipedia entry on Quantum Entanglement
Don't be mislead, the statement you've quoted is wrong in every particular, to my knowledge. Review Matt O'Dowd's PBS Space Time video above, he gives the correct account of the issue, and also of the Copenhagen interpretation. — Wayfarer
The current scientific consensus is that faster-than-light communication is not possible, and to date it has not been achieved in any experiment. — Clarky
I'm talking about relativity of simultaneity (RoS). If you don't know what that is, then you don't have the tools to assess the validity of my criticism of the wording used in the article. If you do know what it means, then you know that the article wording implies absolute simultaneity, something often done in pop articles but not science papers. This is why you don't get your science from pop articles, despite the credentials of the author.I don't believe so. You haven't read the evidence about it. If it was as trivial a matter as you're suggesting, then there would be nothing to discuss. — Wayfarer
The correlation of the measurements is simultaneous (very different from instantaneous) in a few frames and not in most. The absence of a frame specification renders the assertion meaningless, and even if they did supply the frame specification, they've still only demonstrated simultaneity of correlated measurements, not action-reaction.The instantaneous nature of the correlation is precisely the point at issue.
That of course has not been demonstrated. If for instance the measurement of one collapsed the state of the other, the abrupt cessation of superposition of the remote particles could be measured and that would constitute FTL communication and it would be news indeed. But no such thing has ever been demonstrated.Whether the measurement of one changes the state of the other is another point at issue.
Copenhagen was originated as an epistemological view: Back in the early days, quantum physics defied classic description, so they came up with a set of rules about what could be known about a system. You could have two people standing next to each other and one would know the result of a measurement and the other not. No metaphysical interpretation would suggest that the superposition of the measured system itself was collapsed for one of the two people and not the other simply pending verbal communication.Copenhagen ...
— noAxioms
I'm not a physicist, but based on the plain English accounts that I've read of this matter, of which there are quite a few, I don't think this is so. If you would like to validate your interpretation with some sources (other than technical physics papers), please do.
Einstein was a realist and very held to the principle that there was an objective state of the universe even in the absence of measurement. But his theory of relativity strongly suggests he held to (heck, he defined) the principle of locality, that cause must precede effect. Bell showed that you must choose between the principles. No valid interpretation of QM can postulate both of them, and many postulate neither.Perhaps for a start you could explain why Einstein objected to the suggestion of entanglement with the word 'spooky'.
Ah, but the spooky-action folks are not claiming communication, they're claiming FtL action-reaction. But if there was a (remote) empirical test for this having actually happened at the reaction side, a message could be sent via this test, so it would constitute communication. So despite all the assertions, they've not falsified locality.The current scientific consensus is that faster-than-light communication is not possible, and to date it has not been achieved in any experiment. — Clarky
That is true. But as the article then says. 'the paradox is that a measurement made on either of the particles apparently collapses the state of the entire entangled system—and does so instantaneously.' — Wayfarer
Ah, but the spooky-action folks are not claiming communication, they're claiming FtL action-reaction. But if there was a (remote) empirical test for this having actually happened at the reaction side, a message could be sent via this test, so it would constitute communication. — noAxioms
I'm talking about relativity of simultaneity (RoS). If you don't know what that is, then you don't have the tools to assess the validity of my criticism of the wording used in the article. — noAxioms
(the) theory of relativity strongly suggests... the principle of locality, that cause must precede effect. Bell showed that you must choose between the principles — noAxioms
I don't think there is an accepted scientific paper that IS the Copenhagen interpretation. — noAxioms
It is meaningless to assign reality to the Universe in the absence of observation. — Neils Bohr
All the articles I've seen linked from this topic contain language that assert the objective reality, which of course must contradict locality, but to disprove locality, one must do so without begging the objective reality since none of the local interpretations list it as one of the premises. — noAxioms
But if there was a (remote) empirical test for this having actually happened at the reaction side, a message could be sent via this test, so it would constitute communication. So despite all the assertions, they've not falsified locality. — noAxioms
Quantum entanglement—physics at its strangest—has moved out of this world and into space. In a study that shows China's growing mastery of both the quantum world and space science, a team of physicists reports that it sent eerily intertwined quantum particles from a satellite to ground stations separated by 1200 kilometers, smashing the previous world record. The result is a stepping stone to ultrasecure communication networks and, eventually, a space-based quantum internet.
The Copenhagen interpretation are philosophical speculations about what it means. — Wayfarer
Choose between what principles? — Wayfarer
that’s how I understand it too. This idea of there being permanent, unchangeable objects - the original meaning of ‘atom’! - no longer holds. So the answer to the question ‘does the electron exist’ just is the wave-function. The answer it gives is again a distribution of possibilities, not a yes/no. ‘Exists’ doesn’t apply. ‘Does not exist’ doesn’t apply. (Does that ring a Bell?) — Wayfarer
Realism and non-locality are compatible. If the wave function is real, it constitutes a causal, non-local fork, causing both — Jarjar
Choose between what principles?
— Wayfarer
The video you provided talked about the violation of realism versus the violation of locality. According to the narrator, if realism is violated, but locality isn't, there is no superluminal causality or communication. — Clarky
Spot on. As it happens, most physicists choose locality over realism [*]. This rejection of realism (precisely, counterfactual definiteness) is well summed up by physicist Asher Peres, one of the original developers of quantum teleportation, as "unperformed experiments have no results". — Andrew M
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