Action at a distance is realized. Quantum computer.
‘Quantum Internet’ Inches Closer With Advance in Data Teleportation
Their research, unveiled this week with a paper published in the science journal Nature, demonstrates the power of a phenomenon that Albert Einstein once deemed impossible. Quantum teleportation — what he called “spooky action at a distance” — can transfer information between locations without actually moving the physical matter that holds it.
https://www.nytimes.com/2022/05/25/technology/quantum-internet-teleportation.html
Their research, unveiled this week with a paper published in the science journal Nature, demonstrates the power of a phenomenon that Albert Einstein once deemed impossible. Quantum teleportation — what he called “spooky action at a distance” — can transfer information between locations without actually moving the physical matter that holds it.
https://www.nytimes.com/2022/05/25/technology/quantum-internet-teleportation.html
Comments (111)
“After entanglement, you can no longer describe these states individually,” Dr. Northup said. “Fundamentally, it is now one system.”
Einstein did not like the quantum model. He still understood physics under the old deterministic model.
What does that have to do with fishing?
I am not a good audience for your stand up routine.
Quoting Jackson
Einstein clung to the realist view. He absolutely believed that the Universe was just so, independently of anything the observer did. So he could never accept the uncertainty principle was anything other than a lack of knowledge about the object. 'The dependence of what is observed upon the choice of experimental arrangement made Einstein unhappy', wrote John Wheeler. 'It conflicts with the view that the universe exists "out there" independent of all acts of observation'. But Einstein's views on this question have been refuted by subsequent experimental evidence.
Quantum mechanics is more in line with how I think. The deterministic model never made sense to me.
Entanglement doesn't mean that you do something to one end and it can be measured at the other. Information could be sent faster than light with such a mechanism, and this is what they seem to be claiming here.
Entangled particle behavior isn't action at a distance, but only correlation of measurement at a distance.
Quoting WayfarerHe would not have liked what Bell contributed to it all. Einstein was very much a realist (the universe in a state independent of measurement) which sort of suggests a Bohmian attitude, but Einstein also clung to locality (that effect cannot precede cause) and Bell proved that you have to choose between the two principles. I prefer the locality principle, but my preference doesn't invalidate the strict realist (counterfactual) view. Poor Einstein couldn't have his cake and eat it too, but I don't think lived long enough to know that.
Teleportation has been demonstrated at least a decade ago, but it wasn't done faster than light. When asked if it was the same physical matter at the source and destination, they replied "does it matter?". The original object was destroyed in the process, similar to Star Trek transporter. It wasn't a cloning booth which is necessarily limited by Heisenberg.
If you are a physicist you may prefer reading the journal article:
Qubit teleportation between non-neighbouring nodes in a quantum network
https://www.nature.com/articles/s41586-022-04697-y
[quote=John Stewart Bell, quoted in Quantum Profiles, by Jeremy Bernstein] The discomfort that I feel is associated with the fact that the observed perfect quantum correlations seem to demand something like the "genetic" hypothesis. For me, it is so reasonable to assume that the photons in those experiments carry with them programs, which have been correlated in advance, telling them how to behave. This is so rational that I think that when Einstein saw that, and the others refused to see it, he was the rational man. The other people, although history has justified them, were burying their heads in the sand. I feel that Einstein's intellectual superiority over Bohr, in this instance, was enormous; a vast gulf between the man who saw clearly what was needed, and the obscurantist. So for me, it is a pity that Einstein's idea doesn't work. The reasonable thing just doesn't work.[/quote]
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Quoting noAxioms
The article I referred to was not about teleportation but about using the principles of entanglement for secure communications.
All that said, I'm the first to admit that I'll never understand quantum computing.
Same here! Einstein's worldview didn't allow for spooky action at a distance - it just didn't gel/jibe with his other ideas, whatever they were. The likely culprit was his light speed limit postulate + causality as understood in physics (cause must precede effect); it boils down to the same thing I suppose.
Last I checked, quantum entanglement was, for some reason, not communication-apt i.e. we can't use to transmit info. I was wrong then and so was Einstein. Too bad!
Realism and non-locality are compatible. If the wave function is real, it constitutes a causal, non-local fork, causing both
Realism and non-locality are compatible. A wave function is a non-local real causal fork, correlating distant measurements.
Yes, that's the Einstein I've grown to know. When it came to putting together special relativity, several others were working on similar theories, but he was able to see what was needed and not let old biases get in the way of drawing a very unintuitive conclusion.
The first thing you do is the simple train thought experiment which trivially (without equations even) demonstrates the Relativity of Simultaneity (RoS), which even today many people cannot accept. Lorentz was one of the others and had a significant head start on the work, but 'buried his head in the sand', attempting to get a workable theory that didn't embrace RoS.
That comment was an admittedly poorly placed reply to the OP which suggests that entanglement is a form of teleportation, which it isn't. The teleportation of which I speak is real, but it doesn't work faster than light.
As for the secure communications, yes, entangled particles are used for that, although I could not describe how it works exactly without looking it up. It has nothing to do with fast messages, but it can be used to tell if the message had been seen/copied between source and destination. It sort of works like the self-destructing messages in Mission Impossible except the message isn't destroyed, but a detector says that the recipient isn't the first recipient.
So their polarization states would be opposite when both were measured. Not sure what you're quoting, but it implies the unmeasured one has a determined state, which is demonstrably false. But the quote says how they manage to deliver an entangled pair to very different locations without having to 'mail' one of them.
Better than random. That's all? I would have hoped for better reliability than that.
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Quoting Agent SmithAnd said spooky action has never been demonstrated, so his 'other ideas' (principle of locality, or cause before effect as you put it) is quite safe. Only a non-local interpretation like Bohmian mechanics posits said spooky action, and also the effect-before-cause that comes with it. They've demonstrated effects caused by decisions that were made years into the future. A local interpretation would deny that description of the same experiment.
Did Einstein ever suggest otherwise, that entanglement could be used for communication? If so, then there really would have been falsification of locality, a principle which has never been falsified. Einstein was not wrong about that one, but he hasn't been proven right either, and never will. These things are simply interpretation dependent and not provably right or wrong. If they were, they'd be actual theories, not just interpretations.
It is definitely true that a measurement on one part of system with spatially separated components doesn't influence a measurement on the other part but the outcome of the other part is fixed still. Of course you can't know what is fixed because the observer on the other side had to send that information FTL. Which is exactly which is not possible! The only thing the other observer measures is what you measure. He would know what you measured. Which is based on chance. So no useful information can be sent. Any popular shoutings that information has been teleported (and there are myriads!) is empty shouting.
:up:
https://www.science.org/content/article/china-s-quantum-satellite-achieves-spooky-action-record-distance
‘Better than random’ I took to mean a re-confirmation of the Bell inequality i.e. if there had been no entanglement demonstrated then results would have been random.
Quoting noAxioms
Wait - wasn’t the Bell inequality, and its subsequent validation by Aspect and Zellinger, precisely a demonstration of that?
Quoting noAxioms
Quanta Magazine has an explainer called How Bell's Theorem Proved Spooky Action at a Distance is Real, in case there is any question about that.
By 'spooky action', I'm referring to cause and effect events being separated by a space-like manner, in other words, faster than light. If such a thing (or reverse causality) could actually be demonstrated without begging additional postulates, that would be a falsification of all local interpretations.
It seems to be pop-science nonsense. All of relativity would crumble if locality was falsifiable.
Some clues: "Bell demoted locality from a cherished principle to a testable hypothesis".
Bell did no such thing. The article also seems to presume that Bell's theorem demonstrates this violation of the principle of locality, when it fact it demonstrates that (with the exception of one loophole) one of two principles must be false, the other being the principle of counterfactual definiteness.
"correlated, even when the particles are far apart and measured nearly simultaneously". This wording suggests absolute simultaneity, evidence of a naive writer, or one simply pandering to a naive reader. I mean, when they take the two widely separated measurements, which measurement is the cause of the result (effect) of the other? Which way does the action 'go'?
"Hidden variable theories can explain why same-axis measurements always yield opposite results without any violation of locality"
This is opposite of what I know, that the hidden variable interpretations (Bohm in particular) are the ones that deny locality, while the local interpretations (MWI or RQM or even Copenhagen) do not require hidden variables. Once again, either the author seems uninformed, or Bohm has been spinning his view in a new way.
The article seems very much to assume something like Bohm's interpretation since the assume the electron already has a spin along a certain axis before it is measured. But that assumption doesn't invalidate the local interpretations.
"Let’s now assume the world is described by a local hidden variable theory, rather than quantum mechanics."
HVT (as they're calling it) is an interpretation of QM, not a theory separate from it. QM theory doesn't describle what's going on, but rather specifies what will be measured. It is an empirical theory, while HVT is metaphysical conjecture with zero empirical predictions.
"both labs will obtain the same result 75% of the time. This exceeds Bell’s upper bound of 67%.
That’s the essence of Bell’s theorem: If locality holds and a measurement of one particle cannot instantly affect the outcome of another measurement far away, then the results in a certain experimental setup can be no more than 67% correlated."
What bell actually demonstrated is that entanglement cannot be explained by classic means.
A classic entanglement is to split a coin edge-wise. If you look at one half here and see heads, you know the other guy has the tails, but it doesn't mean any faster-than-light action took place. Quantum correlations are stronger than that and cannot be a function of classical physics. This article totally misrepresents that conclusion and begs a principle that local interpretations do not.
I'm not claiming to be an expert on all this, but this article seems to be asserting things that Bell did not.
A note: Maybe entanglement isn't a causal phenomenon, you know. True one particle's state is affected by the other particle's, but this isn't a case of one causing the other but...something else.
Sorry but I believe Quanta’s article has it right, I think you’re the one misunderstanding the issue. (My physics is rudimentary but my English comprehension is ok.)
Quoting noAxioms
It's a challenge to realism. That's what is 'spooky' about it.
Quoting noAxioms
"Ben Brubaker is a freelance science journalist whose writing has appeared in Quanta Magazine, Scientific American and The Conversation.... He has a PhD in physics from Yale University and conducted postdoctoral research at the University of Colorado, Boulder."
How?
SUBTOPIC: The challenge? and Entanglement
?? Agent Smith, noAxioms, et al,
PREFACE: Establishing an attitude that accepts or denies a theory and be prepared to work with it is NOT so great a challenge.
Quoting Wayfarer
(COMMENT)
But in both cases (1) the study of the very fast [Relativity], and (2) the study of the very small [QM], represent progress on a scale we have never seen before. And while the two do NOT currently interlock or mutually support the other (in all the critical ways), it is NOT likely that we will discard them any time soon.
We will still teach classical mechanics - and use it in all the same critical ways that Newtonian technology has dragged us over the last 300+ years, it may very well serve us over the next 300 years. The legacy of the giants ([I]Isaac Newton, James Maxwell, and Albert Einstein, each once members of the Royal Society[/i]) will be remembered forever. We stand on their shoulders.
Most Respectfully,
R
That quote was attributed to me, but they were not my words, it was a quote from John Bell.
Quoting Rocco Rosano
That is not too far from the advice to 'shutup and calculate' - don't worry about the fact that it's weird, just use it.
Quoting Agent Smith
The very short version is, non-locality means that when you measure the properties of a particle in one position, the properties of the entangled particle are also fixed by that measurement at that instant of measurement, regardless of the distance between the two. 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. See this entry.
//PS// - I had questioned NoAxiom's claim that 'all relativity would crumble' if non-locality was falsifiable. As the video below explains, this is because it suggests that causal relationships seem to propogate at faster than the speed of light, so in that sense, this claim is correct.//
Muchas gracias for the illimuinating explanation. I think I already said this before and it was probably to you that I said it to you. There's an alternative to giving up on Einstein's theory with its cosmic speed limit for physicists and that is to admit nonphysicalism of information (nothing physical can travel faster than light).
Have a look at the interview pinned to my profile page of Christian Fuchs who has originated an interpretation called Quantum Baynsianism (QBism for short, article name A Private View of Quantum Reality.) Some relevant passages:
I find that highly persuasive, because it lines up so well with phenomenology, as distinct from objectivism. Objectivism is 'what you see looking out the window'. Phenomenology is 'you looking out the window'. So it includes the observing subject.
So what is being called into question is not reality, but a mind independent reality - the purported reality that exists 'out there now', always already there that we either perceive, or not. That is what is called into question by quantum mechanics. But, he goes on to say:
So again, what is being called into question is scientific realism, but in a very specific sense, one which I think is peculiar to what you could call the early modern or modern period.
This is the question I've been wanting to ask - Did the action at a distance take place at a rate faster than the speed of light? If not what's the big deal. It is my understanding that data transfer at a speed greater than light is believed not to be possible, even given quantum entanglement. Does the experiment described contradict that?
'Instantaneous' means 'no time'. That's why Einstein couldn't accept it.
Quoting 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.
Quoting T Clark
That's why it's a big deal. Hence Niels Bohr's oft-quoted statement, 'Those who are not shocked when they first come across quantum mechanics cannot possibly have understood it.'
(For the attribution of that quote, it's in Werner Heisenberg's book Physics and Beyond: Encounters and Conversations, in the chapter on Positivism, Metaphysics and Religion. It relates to a lecture Bohr gave to representatives of the Vienna Circle when they came to Copenhagen. Bohr felt by their polite applause and lack of questions that they didn't understand what he was telling them, 'otherwise they would have been shocked by it'. I think this still holds true.)
It is my understanding that is not the same as information being transmitted at a rate greater than the speed of light. I admit I don't understand why not. Wikipedia says:
Superluminal communication is a hypothetical process in which information is sent at faster-than-light (FTL) speeds. The current scientific consensus is that faster-than-light communication is not possible, and to date it has not been achieved in any experiment.
Yes, I know Wikipedia is not an unimpeachable source.
I've struggled with the whole idea. I keep holding on to the the no-superluminal-communication floatation device hoping someone will rescue me.
Not competent to speak on the subject - but it's still fun.
It seems the particles must be either, in some sense, the same particle or, in some sense, in the same location.
Madness.
And you wouldn't be alone in that, but I've long since reconciled myself to it.
I don't know if this is related or not, but I recall reading that electrons/particles are only a fuzzy probability distribution (pure potential) and acquire a fixed locus i.e. pop into existence at the moment of observation (actualization of potential); in a sense, the mind via measurement/observation causes particles to be (mind-dependent reality).
Not that this solves anything.
Of course! All of what we are talking about ‘fell out of the equations’ so to speak. Superposition, for instance, about which it’s difficult to form any kind of real concept.
Quoting Wayfarer
This wording suggests that there is a concept of 'instantaneous', or absolute simultaneity, which is an entirely naive wording.
What they have is two measurement events of these entangled particles and those two events are separated in a space-like manner. That means that there exists some frames where those two events are simultaneous, and many frames where one occurs first, and many where the other occurs first.
But the wording in the above statements suggests that there is but one measurement that somehow 'instantaneously' changes the state of the other particle, even in the absence of it being measured, which is exactly begging not only absolute simultaneity, but also that there is an objective state of reality independent of measurement. Begging the latter assumption voids any falsification of locality. Local interpretations cannot presume an objective reality (again, with that one loophole exception), per Bell.
Quoting T ClarkFaster 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.
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.
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.
Quoting noAxioms
The instantaneous nature of the correlation is precisely the point at issue. Whether the measurement of one changes the state of the other is another point at issue.
Quoting 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 intepretation with some sources (other than technical physics papers), please do.
Perhaps for a start you could explain why Einstein objected to the suggestion of entanglement with the word 'spooky'.
Thanks. It's hard to grasp.
[quote= Wikipedia entry on Quantum Entanglement; https://en.wikipedia.org/wiki/Quantum_entanglement#Meaning_of_entanglement]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.
[/quote]
I watched the video and, as I understand it, it confirms the statement from Wikipedia I quoted before:
The current scientific consensus is that faster-than-light communication is not possible, and to date it has not been achieved in any experiment.
I'm just as confused as I was, but the guy in the video doesn't seem to be.
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.'
I'm by no means suggesting a solution, but I think it's important to at least acknowledge what the paradox is. (Richard Feynman said 'Do not keep saying to yourself, if you can possibly avoid it, 'But how can it be like that?' because you will get 'down the drain,' into a blind alley from which nobody has yet escaped. Nobody knows how it can be like that.') That's why I think quantum physics is kind of like sorcery. ;-)
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.
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.
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.
So Copenhagen was perhaps a poor example because there is now much writing about it, and many contradictory metaphysical assertions all bearing the same name. Metaphysically, I don't think there is one accepted version and no one accepted author of the interpretation. I don't think there is an accepted scientific paper that IS the Copenhagen interpretation. As for articles written in understandable language, you can find ones that support just about any assertion you like just like the Bible can be used to justify whatever evil you have in mind today. So I'll not link to one that supports my locality assertion since you can equally find one that asserts otherwise.
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.
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.
Quoting Clarky
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.
My best friend, a fellow math prof, departed a physics major after he enrolled in QM.
Yes. The statements seem to be contradicting each other, but I'm confident they aren't because a lot of really smart people have said so. That doesn't mean I understand it. I am comfortable believing that something is true even though I don't understand how. It gives me something to think about.
It seems to me that what you call faster than light action-reaction is equivalent to communication. It seems I'm wrong about that.
To do with reference frames and the relativity of time of measurement, I guess.
I can only get information from popular science, like Quanta Magazine and PBS Space Time, but the writers in those media are qualified in physics, in fact both have PhD's in the subject. Nowhere have you referred to any sources, so I'm inclined to believe them over you.
And I can understand what they are saying, whereas I can't understand your objections. For instance:
Quoting noAxioms
Choose between what principles?
Quoting noAxioms
Of course not. The 'copenhagen interpretation' is not a scientific theory. Quantum theory is a scientific theory. The Copenhagen interpretation are philosophical speculations about what it means. The expression was coined by Werner Heisenberg, one of its advocates, in one of his popular science and philosophy books written in the 1950's
Here is one example quoted by Matt O'Dowd in the PBS video:
[quote=Neils Bohr]It is meaningless to assign reality to the Universe in the absence of observation.[/quote]
Here, it is explained, "object permanence" is being questioned. It is typical of the 'copenhagen interpretation'.
Quoting noAxioms
:roll:
Quoting noAxioms
That is the subject of the first article I quoted in this thread, about the Chinese communications satellite.
So, you're disputing that this is evidence of 'spooky action at a distance'? That is what the article is about. There seems to be some major disconnect here. I know it's a tough topic and I'm not wanting to be discourteous. But I am going to say that I think to all intents, (a) simultaneous and instantaneous mean the same in this context, and (b) how this can happen is a mystery, but it can't be disputed that it does happen. Over and out.
It is my understanding that the Copenhagen Interpretation is not a "philosophical speculation." It represents a refusal to speculate. Metaphysics pared down to a minimum.
Quoting 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. Or is it the other way around. Please don't ask me to explain,
:smile: A particle feels more real than a wave function. It's got that tangible quality that (say) an apple/rock has. That should, in my humble opinion, count for something.
Good pick up. Speculate is the wrong word. But it does concern meanings. You can find Heisenbergs Physics and Beyond on archive.org, it has many conversations with Bohr and Pauli.
I appreciate the reference, but I'm not sure that anything I read is going to clarify things for me. I will take a look.
Quoting Jarjar
That's how I've always understood the quantum experiments. Like there is a misunderstanding about what exactly is being shown.
Walking in front of a mirror could constitute "spooky action at a distance". But I've never really had success teleporting myself with a mirror; even thought it appears that I have jumped across the room instantly.
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".
--
[*] "What can we learn from Bell’s inequality? For physicists, the most important lesson is that their deeply held commonsense intuitions about how the world works are wrong. The world is not locally realistic. Most physicists take the point of view that it is the assumption of realism which needs to be dropped from our worldview in quantum mechanics, although others have argued that the assumption of locality should be dropped instead." - Quantum Computation and Quantum Information - Nielsen and Chuang
Both of those links are really helpful. Thanks.
I agree.
It does, but you seem to be on thin ground to be agreeing with a pop site written for the lay public instead of say grad students. Argument from authority doesn’t help. These PhDs write differently for different audiences.
Per RoS, there is no unambiguous meaning to ‘instantly’ at a distance. Relative to a local measurement event, there are different times at the distant location, each simultaneous with the measurement event, but relative to different frames. That’s RoS in a nutshell.
If one asserts objective time and space (there’s only one time on say Mars that is actually simultaneous with a given moment on Earth), it is a rejection of Einstein’s theory which posits only that all frames are equally valid and speed of light is c in any inertial frame. Neither of those is true if one posits an absolute frame, which necessarily implies light speed being something other than c in any other frame.
That’s all besides the point of this entanglement topic. The point I’m really trying to get at is the implied assumption of Bohmian mechanics in the article. Only in Bohmian mechanics are the asserted statements true, and indeed, in that interpretation, locality is (and must be) violated. For the PhD to never explicitly call this out is bad form. There are other interpretations, including many well known that hold to the principle of locality.
Such articles are not accepted as evidence at a site like physicsforums.com. A college level textbook is, but most college courses teach quantum mechanics theory and barely touch on the interpretations, which is not theory.
Principle of locality and principle of counterfactual definiteness, the latter being summarized in wiki thus:
In quantum mechanics, counterfactual definiteness (CFD) is the ability to speak "meaningfully" of the definiteness of the results of measurements that have not been performed (i.e., the ability to assume the existence of objects, and properties of objects, even when they have not been measured).
The articles you quote all speak meaningfully of unmeasured things, and rightfully drive that to demonstration of contradiction of locality.
Agree, but the other interpretations are specific speculations about what it means. I’m saying there’s not one speculation that is the official Copenhagen speculation. With the other interpretations, one can point to one paper that defines the initial (and sometimes revised) view.
Quoting ClarkyThis sounds close to the mark.
[quote=Clarky]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. Or is it the other way around. Please don't ask me to explain,[/quote]I didn’t watch any videos, but that sounds right: CFD vs locality. Yes, if locality isn’t violated, there isn’t superluminal causality. That’s what locality means.
With CFD, there’s not only superluminal causation, there’s reverse causation, with effect demonstrated years before the cause.
This is a rejection of CFD, but if CFD is accepted (as your articles do), then that’s a different speculation. CFD can’t be proved, but neither can it be falsified.
[quote=Wayfarer]Here, it is explained, "object permanence" is being questioned. It is typical of the 'copenhagen interpretation'.[/quote]Copenhagen indeed does not typically list CFD as a premise (on wiki say), but I went hunting for an article you might like, and they all say different things, and the vast majority of the articles I found made meaningful statements about unmeasured things.
They put a beam splitter in space. Is that so remarkable? There is no maximum distance to entanglement, so ‘smashing’ some kind of distance record seems news worthy only to the lay public. I’ve seem similar claims of smashing the speed record, which, per RoS, is utterly meaningless.
Yes, for the reasons I posted, not one of which has been refuted by somebody who understands the basics.
I don’t deny the correlation at a distance. I deny that this is necessarily any kind of ‘action’, which would constitute a falsification of, among other things, all of relativity theory. There are several interpretations that ‘speculate’ local physics that account for the correlation. None of them presume CFD (yet again, with a single loophole exception, which is superdeterminsim)
Quoting Landoma1It can be. Nobody has proven locality. It just hasn’t been falsified.
That's because physics forum gives short shrift to anything the classify as philosophy. I've posted there a bit.
Quoting noAxioms
Thanks for clearing that up. That's what I had thought you were doing. But I still don't think you've come to terms with Einstein's objection, and the subsequent experiments that falsify it.
//ps// and there's no correlation until a measurement is made. That is another important point. It's not as if the correlation pre-exists the measurement - that is precisely what the Bell inequality disproves.//
Here's the wiki article on counterfactual definiteness https://en.wikipedia.org/wiki/Counterfactual_definiteness
They have a whole subforum for quantum interpretations, and yes, it's all philosophy in there. But they have standards for what constitutes an authoritative source, so say Everett's paper on Relative State Formulation is an authoritative source, but the wiki page on MWI is not. The latter is much easier to understand, and actually gets it reasonably correct.
In mysticism, the principle is that every object must be recreated at each moment of passing time. This is the moment of the present. The principles employed by modern physics make the moment of the present observer dependent. This renders the moment of recreation of the object as vague.
Quoting Wayfarer
Simultaneous means at the same time, and as noAxioms explained, in relativity theory whether or not two events are simultaneous may be dependent on the frame of reference. This implies that whether one event is prior to another, or posterior to the other, is also frame dependent.
Instantaneous is more of a mathematical concept derived from calculus I believe. I think it represents an infinitesimal period of time. So for instance, if one event causes another, the one is prior to the other, and there must be an infinitesimal amount of time which separates the two. The concept is useful for applying mathematics to acceleration. Acceleration has never been adequately understood by human beings.
From past posts I assume you refer to instantaneous acceleration.
Indeed they do. The current top thread is on interpretations of non-locality. Hey, I could spot the error in the first sentence of the second paragraph straight away, so I must understand something.
I've participated in a few discussions on Physics Forum and even started a thread, but one of the later discussions I posted - I can't remember exactly the substance, but I think it was about the reality of number - was locked immediately on the grounds of being too philosophical (the mod said nobody there had expertise on questions of that kind).
Quoting Metaphysician Undercover
But logically, as the superposition refers to all of the elements in an entangled system, then to measure the one is to measure the other.
Acceleration in general, is not well understood. If an object is at rest, and later it is in motion, then there must be a time when acceleration is infinite, when it goes from zero motion to having some motion. This
problem, of accurately representing acceleration, is tied together with the problem of representing how a force acts on an object, such as when one object hits another. I believe the acceptable way of representing this (application of force), is through the means of fields, so that the kinetic energy of the one object is represented as potential energy in relation to the other object. There is always a discrepancy between the two which is written off as entropy.
Quoting Wayfarer
The issue is with those who "dispute that there is any 'effect' at all". Of course measurement has an affect, because that is how measurement in quantum systems is done, by eliciting an effect. If there is an effect in the measuring device then by Newton's third law there is also an effect on the thing measured. That thing being measure is the system. I believe the mode of measurement is to measure a part of the system, then through logic and extrapolation, extend this to the entirety of the system.
The problem of entanglement is an extension of the simple measurement problem; physicists have no accurate way to measure any part of a quantum system. A "particle" does not have independent existence, it is always a part of something. Be wary of the use of "system" as well. A system is always artificial, or else it is how something natural is represented as "a system". If it is artificial, there is losses of energy to the system, accounted for with entropy. And representing something natural as "a system", is to neglect aspects of the reality of the thing, accidentals in Aristotelian terms.
:up:
Here's some more from Peres that argues for the locality point-of-view.
Quoting Quantum Information and Relativity Theory - Asher Peres, Daniel R. Terno, 2003
Thanks again. I downloaded the paper, although it may be a bit over my head.
What does 'locally realistic' mean? It doesn't make a lot of sense as plain English.
Incidentally, I've been reading an article on QBism. As far as I understand it, it makes sense to me.
[quote=Chris Fuchs]Schrödinger thought that the Greeks had a kind of hold over us — they saw that the only way to make progress in thinking about the world was to talk about it without the “knowing subject” in it. QBism goes against that strain by saying that quantum mechanics is not about how the world is without us; instead it’s precisely about us in the world. The subject matter of the theory is not the world or us but us-within-the-world, the interface between the two.[/quote]
That really nails it for me, because, if you think about it, it actually lines up with Kant.
:up:
Quoting Wayfarer
Below is the broader quote that that phrase was taken from, describing Bell's Theorem. Both locality and realism are technical terms. Don't equate the latter with philosophical or scientific realism. In the sense used here, realism is the assumption that a superposition has a well-defined value independent of measurement (also termed counterfactual definiteness). So, for example, that a particle described by a superposition as being "here + there" really is just here or there independent of measurement, we just don't know which it is.
:up: As Fuchs implies with "us-within-the-world", there's no view from nowhere.
Quoting Wayfarer
Just to be precise here, measurement involves an interaction between a measurer and what is being measured. That Alice measures her entangled particle doesn't imply that a measurement has been made or ever will be made on Bob's entangled particle. Instead, if both Alice and Bob do measure their particles and later meet up to compare notes, then they will find that their measurements are correlated per the predictions of quantum theory. That is, Alice needs to not just perform her local experiment, she also needs to locally interact with Bob and his measurement.
Then again, physicists and the rest of us can count on both realism and locality in the world where we live our lives. I'm not saying the results of quantum mechanics aren't important, but they are scale-dependent. Here at human scale, we can live our lives as we always have.
Yes, for macroscopic systems at low velocities in weak gravitational fields, QM and relativity approximate classical Newtonian mechanics (as an emergent classical limit).
I was referring to this thread on physics forum. I felt I had spotted an error that the first response set straight but this is obviously not the place to discuss Physics Forum threads. I only went there because @noAxioms mentioned there was a sub-forum on interpretations, and that was the first thread I looked at.
Add 'and naturalists' :wink:
Quoting Clarky
People do say that often when encountering the paradoxical quality of quantum mechanics. But don't forget that the subject concerns what has always been thought of as the 'fundamental constituents of reality'.
I may be demonstrating my limited physics knowledge here but does the theory that 'dark energy,' (which I take to infer an energy type that is undetectable using any current known scientific technology) is the cause of the accelerating expansion rate, not contradict the evidence that the total energy of the spatial vacuum is zero?
:up: Yeah I've read some of it as well and I felt the familiar whoosh as the explanations went above my head. I was hoping you or @noAxioms could improve my grasp of it a little.
Yes but surely the 'force' of dark energy must overcome the 'negative' pull of gravitation to create an accelerating expansion. So does the dark energy effectively add to the positive 'push' of the 5% matter content of the universe? So that the totality of energy from the vacuum > 0.
There is also the issue of dark matter? Does that proposed 95% of all 'matter' not also not add to the positive push and gravitational pull of the vacuum? One clump of dark matter will be gravitationally attracted to another clump, yes? I think I will take @Wayfarer's advice and post this as a question on quora. I will direct it at some of the physicists there.
DE isn't worn by particles. Its a property of space that pushes matter away from each other. There are no force exchange particles involved. There is a question on quora: "Is it possible to use DE to do work?" A similar one (the same, I guess) on PSE.
Look here
Maybe physics is philosophy. Or at least a part of it. Like metaphysics is a part too.
Me neither, to my shagrin! I am interested in all the implications of science and of philosophy to a lesser degree due, to its dalliances with the esoteric and the metaphysical/supernatural but I am still interested in those aspects as I have to know and be able to explain and provide evidence for why I disagree with their significance/existence.
Doesn't help me, as QFT suggests there are no particles, just field excitations which can be labeled such for the purposes of scientific calculations. Is energy a 'property of space?' Why do some forms of it 'push' and others 'pull.' I don't expect you to have answers as science does not know what energy is. I don't think the term 'space' is currently understood much beyond the terms 'expansion' or '3D volume.' I am merely airing some of my confusions.
Well, in a sense graviton field oscillations do the trick. Gravitons can travel in higher dimension. Which could be the reason it's so weak. But for a philosophy forum this is too much, I guess. You could ask on a physics forum.
Science doesn't know?
What if the total energy in the universe is not zero? This is the case for gravity. The amount of matter energy indeed equals the amount of gravitational potential energy. But there is expansion.
Are you indicating surprise at the fact that science does not yet have all the answers?
Quoting Landoma1
What point are you making?
That the total energy is not zero.
Energy is motion. Half mass times velocity squared. Or mass times SoL squared.
As Landoma1 says, dark energy doesn't dilute with expansion, but matter does, so as we expand, the density of matter drops, as does its total percentage.
About 6 billion years ago the dark energy and total matter balanced and expansion was linear. It has been accelerating from that 'stop' ever since.
And no, I'd not be able to explain vacuum energy better than the sites you visit.
I hesitate to use quora since they've no mechanism to propagate better answers to the top. There is a lot of very wrong info on quora. I look things up on say physics stack exchange, but don't have an account there.
Quoting WayfarerThat's pretty much my purpose in delving into the phyiscs. I want to know it well enough to glean the implications, but not so well that it's critical that I learn tex.
Quoting universenessScience is in the business of predicting what something does, and not so much declaring what something is.
Quoting Landoma1No so sure that is meaningful. For one, most kinds of energy are not conserved in a cosmological frame. In the absence of a net force, a moving rock will slow over time. Light energy drops as expansion stretches out its wavelength. But negative energy also tends towards zero, so you can't know if total energy is on the rise or not, or maybe is always zero.
I don't get those numbers, if 68% is undetectable dark energy then where is the detectable energy like electromagnetism? Not part of the 32% matter I assume?
Quoting noAxioms
Yep, I get that but not the individual density within galaxies as they are gravitationally bound.
New 'matter' is also created is it not? new stars, new galaxy formations, does this not also add to the density per unit area of space or is it balanced by star deaths etc? or is this factor insignificant to the 'big picture.?'
Is there an equivalence, such as dark e = dark m dark c squared?
Quoting noAxioms
I appreciate the advice but I tend to pay most attention to those on quora who declare their qualifications but I still look for confirmation and dissension on places like the physics stack exchange and on youtube offerings from the established cosmology/physics community. I like to read the 'crank' stuff on quora as well as it's good to see the ways in which skewed thinking can operate. It helps me better recognise it in myself.
Quoting noAxioms
I know what you mean but I think science makes a great effort to explain what IS, and rightly so. This will always be demanded of science imo. I want to predict what a system does, absolutely, but I don't want to see the universe as a black box I can never peer inside of. I want to know its inner workings and so does science imo. I think science does seek to know what something IS.
Surely this is not true in a frictionless vacuum, like space. If you push a rock in space it will go on forever unless it meets something along its path.
Sean Caroll makes this very point, when he describes motion that does not need a sustaining cause.
PhD?
Part of the 5% baryonic matter, the only energy that participates in EM.
Birth and death of stars doesn't create or destroy matter. Stars are made of pre-existing matter. Trivial amounts of matter are formed by processes like pair production, but such matter isn't long lived.
Matter is definitely destroyed (converted to radiation) via nuclear combustion.
Agree. That's why I'm here, and not just on the science sites. I'm a moderator on one science site, but I mostly have to deal with cranks and spammers.
Quoting universenessI had to put back the context you took out. Newton's laws (the rock moves at the same speed forever, what Carroll is talking about) works in an inertial metric, but not an expanding one. It's why no galaxy has a peculiar velocity (speed relative to the cosmic frame) much greater than a couple percent of c, despite the fact that they usually have something pulling (accelerating) them in some preferred direction. Virgo cluster is our most significant influence, and our peculiar motion (the motion of our local group relative to that cosmic frame) is indeed in that direction, but that motion is slowing as Virgo grows further away. Our local group will never reach even that, let alone the bigger masses like the Great Attractor or the much more massive Shapley Attractor, all in more or less the same direction, or the Dipole Repeller in the opposite direction giving us a push. All that force in the same direction and yet we're slowing (relative to that cosmic frame).
So its affects are detectable, ok I see the distinction.
Quoting noAxioms
I assume that massless photonic energy is part of the 32% matter you mentioned. I think I just got sidestepped by the label 'matter' placed next to the 32% as I assumed matter to mean 'has mass.'
Quoting noAxioms
Ok, I just didn't understand the significance of 'cosmological frame.' I thought all reference frames are 'cosmological' as they exist within the Cosmos. But I see now you are referring to the largest frame there is, the cosmic or universal frame. How galaxy clusters influence the motion of each other etc.
I don't know what you mean by 'massless photonic energy'. Perhaps you mean the radiation (the blue line in the pic. It arguably has mass since it has momentum. If it goes into a black hole, it stays there and adds its energy to the black hole's mass.
I'm speaking of a different coordinate system. Inertial frames can be used, but technically the laws of inertial frames only apply to Minkowskian (flat) spacetime, and on the whole, the universe isn't Minkowskian.
Cosmological coordinates, as I'm using them, typically refers to comoving coordinates with proper distances, as opposed to comoving coordinates with comoving distances, which is yet another way of assigning values to distant events.
I can get into more detail, but let's just pick an example of the most distant known galaxy *: In inertial coordinates, (in Earth's inertial frame) that galaxy cannot move faster than c (per special relativity) and is moving away from us at about 0.98c. The light we see was emitted from about 6 billion light years (GLY) away, and it is currently about 13.5 GLY away.
In comoving coordinates (an expanding metric), that same galaxy is currently about 31 GLY away, is receding at about 2.3c (technically a rapidity, not a velocity), and the light that we see now was emitted only about 2.5 GLY proper distance from here.
You see all kinds of distances to super-distant objects posted on the web, but in the absence of a coordinate system or some other statement of in what way the quoted figure was computed, the statement is meaningless. Clue: Distances to things is often not expressed in either of these methods called light-travel time, which is not a valid method at all. There's been articles written why that's the worst possible choice.
* I suspect J-Webb telescope is going to break the record for spotting an even more distant object. CMB doesn't count, it not being an object.
I think we are talking past each other a little but it's just nomenclature issues I think.
My physics level is 1st-year uni plus some online courses I completed but its not even graduate standard.
Photons(photonic), massless, energy (packets), radiation, yes. Energy has a mass equivalence but it does not have mass.
Quoting noAxioms
All info in a black hole will eventually come back out via Hawking radiation so it doesn't stay there forever.
Quoting noAxioms
I have heard of GLY as a billion light years. Its not a unit I have ever used. Parsecs and its kilo or mega multiples is more familiar. I do have some a little knowledge of 'comoving coordinates,' 'an expanding metric,' which takes the rate of expansion into account when considering the motion of an object such as a galaxy through space. Is this 2.3c motion for this 'furthest away galaxy,' not part of the 'eternal inflation' idea? I am probably not using the correct terminology here but I am more interested in getting the basic proposals correct without worrying too much about terminology/nomenclature.
Yeah. GO J-Webb and the re-start of the LHC! Exciting times!
The trick of modern physics, energy has inertia, without mass. But we need to be careful not to confuse the inertia pf energy with the inertia of mass.
But does energy actually move? A human 'Mexican wave' looks like movement in the horizontal but its actually each individual human moving up and down in the vertical,
Same with water waves, it's just undulating water until it meets land and the breaker wave 'falls over' or crashes into the land. If QFT is correct and particles are field excitations then particle movement would be similar undulations, would they not? So energy inertia would be a change in velocity due to some underlying quantum effects/fluctuations happening within field structures.
My thinking is probably inaccurate and too simplistic here. No doubt, I would greatly benefit from a much deeper delve into areas like classical mechanics and comparing it with quantum mechanics. Another entry on my wish list.
I got the ridiculous message, i]"You’ve reached your limit of free articles. Already a subscriber? Log in."[/i]. What is my limit??? I guess, zero. Because it's the first time I opened this page and even visited nytimes.com!! Why don't they say simply "You must be a subscriber to read articles" or even more silmply, just ask me to log in! Yes, even reknown places like New York Times can be ridiculous.
OK, this may be off topic, but one should not refer to articles which, in order to be read, one must subscribe to a website!!
I have no problem reading it and I am not a subscriber.
Good that you can. I can't.
This is what I get:
https://pasteboard.co/xQcRnLsIb06Y.jpg
I could be wrong, but the way these things usually work is that the website stores the # times you visited - but this is stored on your browser cache. Try clearing your browser cache and see if that works.
Thanks for the tip. My browser's cache is cleared everytime it closes. It's impossible that NY Times remembers me.
Bah, simply, there are perverse minds. Some more than others. These ones have no parallel! :smile:
This topic apparently referenced GN-z11, which held the most-distant record for a long time, with a redshift of 11.09.
It was broken last April where data collected from other telescopes found one at z=13.6 or so.
JWST now is going to break that record on a regular basis. It has found one at z=16.7, and even more distant objects are likely to be found. It is detecting light beyond the redshift ability of say Hubble.
My comment here was about the z=11 one.
It highlights the differences between coordinate systems.
[quote=noAxioms]
In inertial coordinates, (in Earth's inertial frame) that galaxy cannot move faster than c (per special relativity) and is moving away from us at about 0.98c. The light we see was emitted from about 6.5 billion light years (GLY) away, and it is currently about 13.5 GLY away.
In comoving coordinates (an expanding metric), that same galaxy is currently about 31 GLY away, is receding at about 2.3c (technically a rapidity, not a velocity), and the light that we see now was emitted only about 2.5 GLY proper distance from here[/quote]
Quoting universenessFine.
In inertial coordinates, the z=11 light was emitted from ~2000 mpc away and the galaxy is currently around 4100 mpc away.
In comoving coordinates, the light was emitted around 750 mpc away and the galaxy is currently around 9500 mpc away.
The new record holder isn't much further away, and the light from it was emitted from even closer than 750 mpc away (proper distance at the time).
No, it isn't something specific to eternal inflation. With regular inflation (just a bang, with no inflation still going on anywhere), you still get this same metric. The metric does include dark energy, without which there would be no acceleration of expansion, and the scalefactor would be everywhere negatively curved.
Yea, I seem to be reading articles regularly about new records being broken. Glad it survived the mishap with the 'rock'.