I would call it "physicalism", but that would imply that they are willing to incorporate any finding that contradicts their worldview into their belief system if experiments in physics were to support it, and we know that's not going to happen. I don't like the "new atheist" term either, because it implies a predominance of religious belief over philosophy. So... Yeah. Everybody knows the boundaries of materialism and you may try to dodge them all you want, like Sam did, but it remains the best way to identify the recalcitrant crowd. Sorry.
Against Realism
- Thread starter Neil
- Start date
Arouet
Member
This is another question I'm asking myself: is this experiment purporting to refute realism generally, or just local realism? (I don't know much about the philosophy of realism.not sure if there are different types, including local and non local variants. I'll have to look into that as well.)
Arouet
Member
The authors of the loophole paper put out a couple videos to help explain what's going on: http://hansonlab.tudelft.nl/loophole-free-bell-test/
The paper is not arguing "if" it happens, but "how" it happens. Do the particles have a pre-existing tendency that only becomes apparent once measured (as stated by local realism) or not? If not, how can they communicate FTL?
Local realism is heavily tied to classical physics, quantum mechanics can shrug experiments like this off by citing quantum non-locality, ect. Superluminal communication is usually regarded as a big "no-no" in traditional interpretations of relativity, although some people have proposed some alternatives (there are some outlier hypotheses as well, such as wormholes, LOL, but let's focus on these) to still fit these experiments within it, which are the so-called "loopholes". In other words, the concept of this experiment is not really new, but the methodology is exquisitely designed to mess around with those that still hold on by eliminating any possible loopholes.
Edit: The fact that you accept entanglement non-chalantly means that you likely don't support local realism.
Local realism is heavily tied to classical physics, quantum mechanics can shrug experiments like this off by citing quantum non-locality, ect. Superluminal communication is usually regarded as a big "no-no" in traditional interpretations of relativity, although some people have proposed some alternatives (there are some outlier hypotheses as well, such as wormholes, LOL, but let's focus on these) to still fit these experiments within it, which are the so-called "loopholes". In other words, the concept of this experiment is not really new, but the methodology is exquisitely designed to mess around with those that still hold on by eliminating any possible loopholes.
Edit: The fact that you accept entanglement non-chalantly means that you likely don't support local realism.
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Arouet
Member
Bell's inequality is part of what I'm trying to understand but before I get there I'm just trying to understand what exactly is meant when we say two particles are entangled.
If the two particles, due to entanglement are in synch with one up and the other down and continue to spin at the same rate then knowing something about one automatically tells us something about the other, without anything being communicated at all. That is what my impression was in any event - but I'm not sure that my impression was correct. I haven't been able to find a good simple site answering this question though.
Yeah, I removed that opening sentence, it seemed pretentious... But, nevermind.
Yeah, that is close to the traditional interpretation given by QM. But that is not accepted by anyone that truly believes in local realism... And they usually poke holes into the methodology of our Bell test experiments and create local hidden variable theories to fit the entanglement into the classical paradigm.
This one is different, by eliminating the loopholes you are also eliminating the possibility of any LHVT, validating QM.
Edit: More below.
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Basically, you have a group that believes there are hidden variables in our understanding of the quantum world and that it is incomplete, making it vulnerable to assimilation into the classical model. These guys are taking the postures of Einstein-Podolsky-Rosen and making them their own.
Then there's the group that supports quantum theory at face value. They adopt Bell's theorem (Bell's inequality is established by it), which states that the predictions of any LHVT would contradict the predictions of QM.
Both groups interpret the phenomena in their own way.
Then there's the group that supports quantum theory at face value. They adopt Bell's theorem (Bell's inequality is established by it), which states that the predictions of any LHVT would contradict the predictions of QM.
Both groups interpret the phenomena in their own way.
Arouet
Member
Thanks...but then what I am now missing is what the connection is between that and what is being suggested is being tested here.
In my reading I got the gist of what they were getting at with closing loopholes - let's just assume for the sake of the argument that they're correct there. This isn't where I'm getting hung up. What I'm trying to figure out is why FTL communication or something along those lines is being invoked here?
My conception of what it means for them to be synced must be off.
For example, if we have two trains going in opposite direction going the same speed, assume no friction or equal friction, and the trains stop at a time we're blinded to. If we measure the distance from 0 that train A has travelled we automatically know the distance train B has travelled - without any communication between them.
That's obviously in the classic example - my question is: is something similar presumed to go on on the quantum level when they say two particles are entangled, and if that's not what they are saying, then what exactly is meant by entanglement?
Arouet
Member
To clarify: I'm trying to get at why they assume hidden variables are needed other as opposed to assuming that the two particles are locked into the same pattern? It occurs to me that if being locked into the same waveform through entanglement means they supposedly act "randomly" in the same way - does this entail that what is random isn't so random? Is that what is meant by hidden variables? I think I'm going backwards in my understanding now! Should go to bed! :(
Thanks for your input here though, do you have a background in physics?
Neil
New
The most parsimonious explanation, in my opinion, is that mathematically, the entangled particles form a single quantum system. Once observed through measurement, the wavefunction of this single system collapses into two particles that are of course correlated. In a sense, there is no faster than light transfer of information that occurred since both particles existed as a single quantum state outside of spacetime, and only manifested as two particles once observed. In other words, there were not two particles flying apart from each other in spacetime, so there was no faster than light transfer of information needed between the two. The processing occurs non-locally, and observations creates the manifestation of the particles from this informational field.
Arouet
Member
Found this simple explanation at livescience which I found helpful: http://www.livescience.com/28550-how-quantum-entanglement-works-infographic.html
So this is what I understand:
So I see now where the suggestion of FTL communication is queried. The article refers to measuring one affecting the other. I'm trying to nail down why they think it is one affecting the other (requiring some sort of information transfer at the time of measurement) vs. some variation of the classical train example I gave above, in that at the time of entanglement the particles' spins were aligned in opposite directions and remained that way up until the time each was measured.
Wiki on spin states that "Although the direction of its spin can be changed, an elementary particle cannot be made to spin faster or slower." Could this indicate that it's actually more similar than I thought to the train example where I assumed no friction?
(note: I'm not proposing these in the expectation that I've uncovered anything novel or am disagreeing with any particular interpretation - this is just my process of thinking through these concepts. I'm sure the issues that I'm raising have been well addressed by the brilliant minds who have studied QM.)
So this is what I understand:
- QM holds that an unobserved photon exits in all possible states simulateously (superposition)
- when observed/measured exhibits just one state
- when entangled, upon observing/measuring photon A, photon B shows the opposite state
- implication being that something occurs when measuring photon A that affects photon B to show the opposite
So I see now where the suggestion of FTL communication is queried. The article refers to measuring one affecting the other. I'm trying to nail down why they think it is one affecting the other (requiring some sort of information transfer at the time of measurement) vs. some variation of the classical train example I gave above, in that at the time of entanglement the particles' spins were aligned in opposite directions and remained that way up until the time each was measured.
Wiki on spin states that "Although the direction of its spin can be changed, an elementary particle cannot be made to spin faster or slower." Could this indicate that it's actually more similar than I thought to the train example where I assumed no friction?
(note: I'm not proposing these in the expectation that I've uncovered anything novel or am disagreeing with any particular interpretation - this is just my process of thinking through these concepts. I'm sure the issues that I'm raising have been well addressed by the brilliant minds who have studied QM.)
Arouet
Member
Neil, remind me, do you have a physics background? Are you able to interpret the math?
I have no way of evaluating what you've said. I've read several times now the description of the two particles acting as a single quantum system. I just don't know what that really means.
Does anyone know of a good lay friendly site that breaks down the math? The sites I've looked at either deal with the math technically or refer to the math in broad strokes. I'd like to see a site that shows the calculations and then provides a lay description of what they each indicate, and why there are different interpretations. (I recognise that it may not exist because it strikes me that it would be pretty tough to do which is why most sites seem to be all technical or only describing the math in broad strokes.
This has been a good discussion so far (though it has distracted me from the freewill thread which I still want to get back to Neil!)
Arouet
Member
Googled "quantum math explained" came up with this compendium on the lesswrong site which looks promising: http://lesswrong.com/lw/r6/an_intuitive_explanation_of_quantum_mechanics/
Neil
New
Nope, no physics background. I have very little education. I have had guidance over the years from popular physics books along with help interpreting them from my brother, who was a math/physics major. I am limited in my ability to "see" what the math is saying, but some examples to me are clear such as the single system in entanglement, or the uncertainty principle (which is easy to see it's not like the colloquial explanation of bouncing photons to measure changes things).
I have found Henry Stapp to be helpful in explaining the meaning behind some of the mathematics. For example, he explains the nature of operators and how this differs conceptually from classical theory.
He is also very good at explaining something seemingly complex like decoherence theory into simple explanations of density matrices, and explaining why it doesn't solve the measurement problem.
Here is a link to almost all of his papers and presentations:
http://www-physics.lbl.gov/~stapp/stappfiles.html
You can browse the subjects and hopefully find some of interest. I also highly recommend his book, The Mindful Universe.
Neil
New
By the way, I think Zeilinger holds a view similar to mine in the sense of emergent manifestations of physical objects from a non-local information background (field). Zeilinger is big on the quantum teleportation of quantum information, and it is difficult to interpret this along with all other experimental data in any realistic objective way.
People that attempt to maintain realism end up unable to fit all experiments, and end up trying to come up with all sorts of contortions like backwards causation, faster than light signaling, etc. but even with these contortions, realistic models fail at some point. Common is the inability to account for quantum teleportation, delayed choice, and virtual particles from quantum electrodynamics. I find it incredible that many theorists are MWI supporters yet MWI fails on many of these accounts. Objective collapse models such as GRW and Penrose objective reduction seem untenable due to the size of entangled and superposed molecules now experimentally demonstrated.
Essentially, physicists have tried and failed for the last 80 years to come up with an objective realist interpretation that works. It is still the subjective Copenhagen and von Neumann interpretations that work.
Many current physicists act like Heisenberg, Pauli, Schrödinger, etc were naive and just didn't know what they were talking about, but with the failure of objective interpretations, it seems to me that they may have had a pretty good idea of what was going on.
People that attempt to maintain realism end up unable to fit all experiments, and end up trying to come up with all sorts of contortions like backwards causation, faster than light signaling, etc. but even with these contortions, realistic models fail at some point. Common is the inability to account for quantum teleportation, delayed choice, and virtual particles from quantum electrodynamics. I find it incredible that many theorists are MWI supporters yet MWI fails on many of these accounts. Objective collapse models such as GRW and Penrose objective reduction seem untenable due to the size of entangled and superposed molecules now experimentally demonstrated.
Essentially, physicists have tried and failed for the last 80 years to come up with an objective realist interpretation that works. It is still the subjective Copenhagen and von Neumann interpretations that work.
Many current physicists act like Heisenberg, Pauli, Schrödinger, etc were naive and just didn't know what they were talking about, but with the failure of objective interpretations, it seems to me that they may have had a pretty good idea of what was going on.
Arouet
Member
Yep, having a math brother would be helpful! (damn, my brother is just a special in internal medicine, helpful in limited cases but not for most stuff we discuss here! :))
I meant to make a post on this in the freewill thread. I read the Stapp paper you posted there and dug up a couple others by him. I agree that I found him very helpful and lay friendly (though I wasn't satisfied with how he dealt with the freewill issue but i'll bring that back up in the thread.)
Thanks for the link to the complete collection!