Graduate Interpretation of a state in quantum entanglement

[Ken G]

People are different. Some will say unknowable parameter in a model is problem some will say that alternative poses even bigger problem for them. As log as experimental predictions come out the same there are no pragmatic grounds for confrontation between those people.

True, but the same can be said about the aether. When we looked for it, we decided it was not to be found. So we dropped it, though people are still free to keep it if they like-- as Poincare and Lorentz tried to do. But science tends to like to drop its affectations when they are found irrelevant, and I argue that saying that a property is acquired at some unknowable moment when its entangled partner is measured is a similar kind of irrelevant affectation. To drop it, we should either say that properties are aspects of a thought process and therefore are acquired when our minds find it necessary to use them, such as when they are about to be measured to check our expectation, or that properties are indeed aspects of particles but are acquired only when measured, as that is the only time something happens to the particle in question. Those are the two possibilities that include no irrelevant affectations, but neither are ever the language we find connected with entanglement!

Can you construct a causal model based on this idea that is at least in some sense better that alternative?

Sure, the causal model is that properties are not intrinsic to particles, they are intrinsic to the mathematics of quantum mechanics. Or, if that seems not realist enough, you can say that properties are intrinsic to particles, but the constraints on them are not, and properties are always only acquired during actual local interactions, i.e., measurements. In the first case, the causation is local because it is a relationship among the information in the head of the scientist, and in the latter, the causation is nonlocal because it applies to the constraints on the properties, but in neither case are the properties altered nonlocally.

Any element in our models is a concept that a scientist uses to achieve understanding and make predictions.
You are simply dodging the question of correspondence between elements in our models and reality.

I could say the same thing about the aether. Was banishing it a case of dodging the question of the medium of light? When we don't need something, we drop it, even if we used to think we really needed it-- that's not a dodge.

 

[zonde]

True, but the same can be said about the aether. When we looked for it, we decided it was not to be found. So we dropped it, though people are still free to keep it if they like-- as Poincare and Lorentz tried to do. But science tends to like to drop its affectations when they are found irrelevant, and I argue that saying that a property is acquired at an unknowable moment is a similar kind of irrelevant affectation. To drop it, we should either say that properties are aspects of a thought process and therefore has no importance as to when we say they are acquired, except when they are about to be measured, or that properties are indeed acquired only when measured. Those are the two possibilities that include no irrelevant affectations, but neither are ever the language we find connected with entanglement!

Let me just say that, I don't see correspondence between model and physical reality as irrelevant affectation.

Sure, the causal model is that properties are not intrinsic to particles, they are intrinsic to the mathematics of quantum mechanics. Or, if that seems not realist enough, you can say that properties are intrinsic to particles, but the constraints on them are not, and properties are always only acquired during actual local interactions, i.e., measurements. In the first case, the causation is local because it is a relationship among the information in the head of the scientist, and in the latter, the causation is nonlocal because it applies to the constraints on the properties, but in neither case are the properties altered nonlocally.

So the first version is solipsistic, right? But I don't get the second version. Constraints and causality is nonlocal but properties are determined locally? Sorry, you lost me.

I could say the same thing about the aether. Was banishing it a case of "dogging the question" of the medium of light? When we don't need something, we drop it, that's not a dodge.

Correspondence between model and reality is certainly something we need. I don't see the analogy with "medium of light". There is no requirement that model has to answer any conceivable question about reality. But some concepts in the model have to have correspondence to physical reality.

 

[Ken G]

Let me just say that, I don't see correspondence between model and physical reality as irrelevant affectation.

The problem is, you want there to be a preferred foliation of spacetime, as you said, such that when a property is acquired by one particle, we can say the property is also acquired by the entangled particle. But you have also admitted there is no evidence of any such preferred foliation, nor could we ever do any experiment to determine when the property was acquired, because we can do the measurement at any time and get the property u in the example I gave. So what you want to be the correspondence of which you speak, and what you can actually get, are simply not the same. This has happened many times in the history of science, and the upshot is always the same-- eventually, begrudgingly, we just stop wanting what we can't get. It happened to circular orbits, it happened to the aether, it happened to local realism, and I'm saying this is where we are with the concept of a property of a particle. All we can actually get is that either the property was always in the mind of the scientist, and all that was real was the constraint on the property, or that the property of each particle was acquired when the measurement was done on that particle, and the constraint on that outcome does not have a time associated with it. I don't object to either language, because I don't see how we could distinguish them and neither asserts more than we actually get from the experiments. But neither language is what we see in actually parlance about entanglement, and that's my issue.

So the first version is solipsistic, right? But I don't get the second version. Constraints and causality is nonlocal but properties are determined locally? Sorry, you lost me.

I wouldn't call the first version solipsistic, it is more like "it from bit" in Wheeler's language. But I can see that you are closer to preferring the second perspective, so let me explain it more. If we simply say that u is an intrinsic property of the particle, then it is natural to look for the particle's proper time when that property was acquired. We have two options:
1) it was acquired at some unknowable moment that somehow relates to when the measurement was done on the other particle, but of course we cannot even say with clarity which observation happened first, so this is never going to make much sense, or
2) it was acquired by the particle when the measurement was done on that particle, which at least allows properties to change via local interactions, but of course from Bell's theorem we all know that the result is going to have to satisfy some nonlocal constraint that will compromise to a significant degree the idea that the property is intrinsic to the particle. Still, we can save intrinsic properties if we allow them to be subject to nonlocal constraints that are intrinsic to the system to which the particle belongs, but not intrinsic to the particle itself. For me, if we cannot make the constraints intrinsic to the particle, then I see little advantage in making the properties intrinsic to the particle either, especially when I see that I only use the property concept to build expectations (in my mind) about the outcomes of observations, so it seems natural to allow that properties are mental constructs that require no "time of acquisition" in the particle proper time. But I can see that the strategy of a realist will be to maintain as far as possible to the notion of intrinsic properties of individual particles-- but if they do it at the expense of requiring a preferred foliation of spacetime, that's where the prejudice has been carried too far, and begins to sound like epicycles to me.

Correspondence between model and reality is certainly something we need. I don't see the analogy with "medium of light". There is no requirement that model has to answer any conceivable question about reality. But some concepts in the model have to have correspondence to physical reality.

Correspondence can mean nothing more than that our models create correct expectations about outcomes. What more is there, in science? We can ask for more, and hope to get more, but when we don't get more (as in the case I'm discussing), I say that the history of science has been quite clear about what will eventually happen-- we will just stop asking for what we don't get. It's happened so many times before, I wonder why we tend to think the modern era is special, and that we are not subject to our own philosophical prejudices like the ancient Greeks were, or the determinists of DesCartes' day were. But I admit that if you are a Bohmian, you are going to retain realism at all costs, and you will always need a preferred foliation whether or not there is any observational evidence of it, just as a determinist will always see a determined outcome even in what looks like the random decay of an unstable particle. That doesn't make you wrong, it makes you committed to a particular mindset and future observations might eventually corroborate you. It just doesn't usually seem to work out that way, but since I have no crystal ball I'm not saying your perspective is wrong, I'm merely trying to shed light on the difference between an aspect of a model that we actually need to get correct expectations, versus an aspect we have added for essentially purely personal reasons. What I find odd is how the normal language about entanglement so often does exactly that, almost without even noticing.

 

[zonde]

The problem is, you want there to be a preferred foliation of spacetime, as you said, such that when a property is acquired by one particle, we can say the property is also acquired by the entangled particle. But you have also admitted there is no evidence of any such preferred foliation, nor could we ever do any experiment to determine when the property was acquired, because we can do the measurement at any time and get the property u in the example I gave. So what you want to be the correspondence of which you speak, and what you can actually get, are simply not the same.

It goes a bit deeper than preferred foliation of spacetime. It's about difference between "objective" and "subjective". And I take it as a basic assumption that there is a difference given realism. Our history of acquiring knowledge seems to give support for the idea that there is such a difference. So even when there is symmetry between objective and subjective I hold on to the idea that "objective" and "subjective" are different. And here we come to correspondence between reality and model. Objective elements of model do have correspondence to reality while subjective don't (at least not direct correspondence).

For me, if we cannot make the constraints intrinsic to the particle, then I see little advantage in making the properties intrinsic to the particle either, especially when I see that I only use the property concept to build expectations (in my mind) about the outcomes of observations, so it seems natural to allow that properties are mental constructs that require no "time of acquisition" in the particle proper time.

All the reasoning in our models have to produce something that we can check against observation. So what do you need in addition to expectations about observations to say that the concept is something more than mental construct?

Correspondence can mean nothing more than that our models create correct expectations about outcomes. What more is there, in science? We can ask for more, and hope to get more, but when we don't get more (as in the case I'm discussing), I say that the history of science has been quite clear about what will eventually happen-- we will just stop asking for what we don't get.

We don't stop asking for objective world view.

But I admit that if you are a Bohmian, you are going to retain realism at all costs, and you will always need a preferred foliation whether or not there is any observational evidence of it, just as a determinist will always see a determined outcome even in what looks like the random decay of an unstable particle. That doesn't make you wrong, it makes you committed to a particular mindset and future observations might eventually corroborate you.

Realism is basic assumption of scientific approach. I will retain realism as long as I will consider scientific approach meaningful. And you should too.
Btw Bohmian mechanics is a no-collapse interpretation. Didn't you know that? So if I am arguing for non-local collapse I can't be Bohmian.

 

[Ken G]

Objective elements of model do have correspondence to reality while subjective don't (at least not direct correspondence).

So motion is objective, rather than subjective? Wasn't the whole point of relativity that motion is in the eye of the beholder, whereas Newton always thought it was an objective attribute of an object? So that's what I mean about the historical inevitability that when we don't get what we want, it takes us a long time to realize that we are wanting the wrong thing.

All the reasoning in our models have to produce something that we can check against observation.

Yes, on this we agree, this is science.

So what do you need in addition to expectations about observations to say that the concept is something more than mental construct?

The realist will always wish to say that a property is more than a mental construct, even though they will never get any evidence that it is more than a mental construct. So I can accept that realists will wish to imagine that properties of particles are intrinsic to particles. But that brings up a question that we don't even encounter if we relax our demands of realism: when was the property acquired, in the proper time stream of the particle? So already the realist has a new problem that is not even necessary to have, but if they find value in their realism, then they will tolerate having this new problem. But even so, the realist must answer the question. Your answer is that there is a preferred foliation which we have no access to and can never gain access to, but is there all the same. I'm saying we must recognize this claim is being made, and is generally made when people use language like "at the same time one particle is measured, the other particle acquires the property," yet normally people using that language are not called on to admit they are assuming an unknowable and inaccessible preferred reference frame-- something that we always admonish people not to do in relativity, but apparently have no objection to in quantum mechanics!

That's why I say if we are to be consistent, and are to reject preferred reference frames when we cannot gain any experimental access to what those preferred frames are (think "aether frame"), then the only way to allow properties to be intrinsic to particles is to say they are acquired at the only non-arbitrary time in the problem, which is when the measurement occurs on each particle. And at least that also means something is actually happening to the particle, which I would have thought realists would like! But this is not standard language, for some reason, presumably because we know the observational outcome must satisfy non-local constraints, and we don't like to separate the constraints on a property from the property itself-- even though the fact that we have to do that is more or less the point of Bell's theorem.

We don't stop asking for objective world view.

Yet we always do stop asking for something after a long enough time that we aren't getting it-- that's what happened to circular orbits, to absolute motion, to deterministic outcomes, and to local realism. But we must dig a bit deeper into the term "objective", because it can have two very different meanings that are often confused. The way you mean it is in the sense of separating the object from the scientist studying it, so you regard an intrinsic property as an objective one. But the other meaning is that "objective" means "all reasonable people can agree to it," whereas subjective means that we can have widely different opinions, but that carries no connotation that the property is intrinsic to the particle, only that reasonable people agree on the property. That latter meaning is the only one essential to science, and is preserved when saying that properties are a form of information used to make predictions. But I know that realists, like Einstein famously was, will not be easily led down that road, so that's why I offer the alternative view that still avoids the need for a preferred reference frame.

Realism is basic assumption of scientific approach.

It's nowhere in the scientific method, and that's a crucial point. The historical track record of adding requirements to the scientific method, beyond the method itself, is rather dubious!

I will retain realism as long as I will consider scientific approach meaningful.

That is a choice you are free to make. But people are also free to imagine there is an aether frame, such that the basis of relativity is incorrect. There could be a preferred foliation to motion also, such that motion is actually absolute, but there just isn't any evidence this is true or reason to hold that it is true in the absence of evidence. If your priority was really to stick to the scientific method, then you would not add aspects to it that are not in the method!

Btw Bohmian mechanics is a no-collapse interpretation. Didn't you know that? So if I am arguing for non-local collapse I can't be Bohmian.

I'm not sure what you mean there, Bohmians are not free to violate Bell's theorem. All they do is choose realism over locality-- they hold that the property of a system is determined as it unfolds in its own proper time. The "pilot wave" is their nonlocal device for enforcing the necessary correlations, so in a preferred foliation of spacetime the pilot wave would appear to move instantaneously, and in some frames it would appear to move backward in time. So the collapse in the measurement on one particle is not the issue, it is how the correlation is enforced that is the issue here. Since I start the whole question after the property is acquired, whether or not there is any collapse is of no consequence to me, that's a whole other issue. No-collapse does not mean the property was always there, it only means the property was deterministically established by nonlocal pilot waves, and in some preferred foliation of spacetime, the two properties were acquired simultaneously. The Bohmian does not say properties cannot be acquired, rather, they say they are acquired deterministically and at non-arbitrary times, and that's why I view the appeal to a preferred reference frame as Bohmian realism.

 

[Lord Jestocost]

Realism is basic assumption of scientific approach.

With all due respect, this statement makes no sense without a defining what "realism" means for you!

 

[edguy99]

Actually, you left out the most important one:
...But even if you insist on that distinction, we can still agree that we have it down to two possibilities for anyone who wishes to think that u is an intrinsic property of the particle:
1) It is an intrinsic property that is acquired at an unknowable point in the proper time history of the particle. (In which case we have the problem similar to an unknowable aether frame.)
2) It is an intrinsic property that is acquired when the measurement is done on the particle itself. (In which case people need to significantly change the language they use about when entangled states undergo their changes!)

In itemizing the possibilities, aren't you missing 3) It is an intrinsic property that is acquired when the particles are entangled?

 

[Ken G]

In itemizing the possibilities, aren't you missing 3) It is an intrinsic property that is acquired when the particles are entangled?

The only way to make that work, and obey Bell's theorem, is to invoke superdeterminism, where the measurement that is made is also part of the properties of the system, where now the system also includes the measuring device and the scientist who thinks they are making a free choice about what to measure. We certainly cannot rule out that possibility, but it just isn't the way science is set up. We are never looking for the equations that tell us what we are going to measure, we are looking for the equations that tell us what we will get when we make a choice to measure something. I'm not even sure one could convey any sense of "truth" in the scientifically testable sense to the concept of superdeterminism.

Indeed, since I regard the properties as mental devices we use to build correct expectations, it is as irrelevant to me if superdeterminism is "true" as it is irrelevant if some divine being is choosing the outcomes of all measurements. It's simply not what shows up when you do science. So if I object to claims that there is some preferred yet unknowable reference frame in which the properties are set simultaneously, I will equally object to some unknowable superdeterminism that allows the outcomes to be determined in advance of deciding on what will be measured. If we stick to quantum mechanics, we have that the entangled Bell state I'm talking about looks like |uu>+|dd>, and that state simply does not attribute either of the properties to the particles in advance.

 

[edguy99]

The only way to make that work, and obey Bell's theorem, is to invoke superdeterminism ...

Assuming the particle can be described by it Jones vector and that entangled particles have matching Jones vectors, why invoke superdeterminism?

 

[Ken G]

With all due respect, this statement makes no sense without a defining what "realism" means for you!

For the purposes of our discussion, it seems our views of "realism" overlap insofar as we both associate the concept of "intrinsic properties" that are native to the individual particles with "realism." We know that the realist must allow that entangled systems cannot confer properties to individual particles, instead the whole entangled system would then have properties, but after the measurements are said and done and the entanglements are broken, that's when the realist must allow that the individual particles have their own instrinsic properties. Personally I do not take that view, but I know that many people like realism and will not part with it so easily, but even for them I must challenge the idea that the properties are conveyed at any time other than when the individual measurements are done on the individual particles. My objection is only that the latter language is never used in entanglement scenarios, even when the realist picture of intrinsic properties is taken on (as it usually is).

 

[Ken G]

Assuming the particle can be described by it Jones vector and that entangled particles have matching Jones vectors, why invoke superdeterminism?

The Jones vector does not tell you the property that will be taken on by the particle when measured, so one cannot say that eventual property is encapsulated in the Jones vector. Hence, for you, I still ask the key question: when, in their own proper time, did the particles, post-entanglement, acquire their individual properties? I don't see how the Jones vector lends any insight there.

 

[edguy99]

The Jones vector does not tell you the property that will be taken on by the particle when measured, so one cannot say that eventual property is encapsulated in the Jones vector. Hence, for you, I still ask the key question: when, in their own proper time, did the particles, post-entanglement, acquire their individual properties? I don't see how the Jones vector lends any insight there.

Maybe I am missing something here. The Jones vector gives absolute numbers for u or d if measured on a basis vector, and the correct probability of an u or d measurement (cos^2 of the angle from the basis vector) when off the basis vector. Does not assuming the entangled particles have the same Jones vector match experimental results?

 

[zonde]

Ken G, our discussion goes into too many directions. If you want to stick to particular topic please point it out.

yet normally people using that language are not called on to admit they are assuming an unknowable and inaccessible preferred reference frame-- something that we always admonish people not to do in relativity, but apparently have no objection to in quantum mechanics!

In special relativity preferred reference frame is superfluous, but SR can certainly survive if I put a label "preferred" on one of the reference frames (just a proof of principle, no particular commitment).

The way you mean it is in the sense of separating the object from the scientist studying it, so you regard an intrinsic property as an objective one. But the other meaning is that "objective" means "all reasonable people can agree to it," whereas subjective means that we can have widely different opinions, but that carries no connotation that the property is intrinsic to the particle, only that reasonable people agree on the property. That latter meaning is the only one essential to science, and is preserved when saying that properties are a form of information used to make predictions. But I know that realists, like Einstein famously was, will not be easily led down that road, so that's why I offer the alternative view that still avoids the need for a preferred reference frame.

I would rather go with something similar to the other meaning of "objective": "all reasonable people can give consistent account of phenomena".
You need to exclude the case where people agree just for the sake of being in agreement.

It's nowhere in the scientific method, and that's a crucial point. The historical track record of adding requirements to the scientific method, beyond the method itself, is rather dubious!

Besides other things realism is in the idea about communication with other observers and recording of experimental results and other boring stuff like that.

I'm not sure what you mean there, Bohmians are not free to violate Bell's theorem. All they do is choose realism over locality-- they hold that the property of a system is determined as it unfolds in its own proper time. The "pilot wave" is their nonlocal device for enforcing the necessary correlations, so in a preferred foliation of spacetime the pilot wave would appear to move instantaneously, and in some frames it would appear to move backward in time. So the collapse in the measurement on one particle is not the issue, it is how the correlation is enforced that is the issue here. Since I start the whole question after the property is acquired, whether or not there is any collapse is of no consequence to me, that's a whole other issue. No-collapse does not mean the property was always there, it only means the property was deterministically established by nonlocal pilot waves, and in some preferred foliation of spacetime, the two properties were acquired simultaneously. The Bohmian does not say properties cannot be acquired, rather, they say they are acquired deterministically and at non-arbitrary times, and that's why I view the appeal to a preferred reference frame as Bohmian realism.

In Bohmian mechanics outcome of measurement is determined by in initial position of particle and pilot wave. Pilot wave is non-local but positions of particles are local. So in a sense measurement is determined by initial positions of particles and how experimentalist sets up the experiment and determines pilot wave. Nothing is random there so there is no collapse. We can speak only about apparent collapse.

 

[zonde]

Maybe I am missing something here. The Jones vector gives absolute numbers for u or d if measured on a basis vector, and the correct probability of an u or d measurement (cos^2 of the angle from the basis vector) when off the basis vector. Does not assuming the entangled particles have the same Jones vector match experimental results?

Calling Jones vector a "hidden variable" should give you the idea that your model can't violate Bell inequalities.

 

[edguy99]

Calling Jones vector a "hidden variable" should give you the idea that your model can't violate Bell inequalities.

You cannot call a Jones vector a "hidden variable" wrt Bell inequalities since it does not match the model that Bell examined. Specifically, the Jones vector does not give "absolute" numbers (only probabilities) when measured outside the basis vector. Bell assumes a "absolute" match between entangled particles even when measured off of their basis vectors.

 

[zonde]

You cannot call a Jones vector a "hidden variable" wrt Bell inequalities since it does not match the model that Bell examined. Specifically, the Jones vector does not give "absolute" numbers (only probabilities) when measured outside the basis vector. Bell assumes a "absolute" match between entangled particles even when measured off of their basis vectors.

Hmm, then how your model reproduces prediction of perfect correlations at any angle?

 

[edguy99]

Hmm, then how your model reproduces prediction of perfect correlations at any angle?

You are correct that the Jones vector does not predict perfect correlations at any angle. Do you have a reference for an experiment that has achieved "perfect correlations at any angle" without throwing out the non-correlated particles?

 

[zonde]

You are correct that the Jones vector does not predict perfect correlations at any angle. Do you have a reference for an experiment that has achieved "perfect correlations at any angle" without throwing out the non-correlated particles?

Yes, if I remember correctly this experiment does exactly that:
Loophole-free Einstein-Podolsky-Rosen experiment via quantum steering

 

[edguy99]

Yes, if I remember correctly this experiment does exactly that:
Loophole-free Einstein-Podolsky-Rosen experiment via quantum steering

From the article: "Alice’s result (the prediction which she makes for Bob’s result) is immediately sent back to Bob via coaxial cables. If Alice detects no photon, Bob counts this as an inconclusive event from Alice (0)."

They are throwing out all the "non-matches" as inconclusive. These would include the ones the Jones vector would predict as not being the same.

 

[zonde]

From the article: "Alice’s result (the prediction which she makes for Bob’s result) is immediately sent back to Bob via coaxial cables. If Alice detects no photon, Bob counts this as an inconclusive event from Alice (0)."

They are throwing out all the "non-matches" as inconclusive. These would include the ones the Jones vector would predict as not being the same.

They are not throwing them out. They are including them in calculations.
"To close the fair sampling loophole one must also account for Alice’s inconclusive (0) results when she detects no photon and include these results when calculating the steering value."

 

[Ken G]

Maybe I am missing something here. The Jones vector gives absolute numbers for u or d if measured on a basis vector, and the correct probability of an u or d measurement (cos^2 of the angle from the basis vector) when off the basis vector. Does not assuming the entangled particles have the same Jones vector match experimental results?

The experimental results in the scenario I gave are that u occurs half the time, and always for both particles. This is a prediction of the initial Bell state, |uu>+|dd>, so there is no issue with statistical predictions of the experiment. I am not asking why do we get that experimental result, I'm asking that if it comes out u for both particles, and we interpret that outcome as an intrinsic property of the particles after the entanglement is broken (I'm not interested in the entangled state, or the Jones vector, that's not the question), then when was that intrinsic property acquired? The Jones vector (classically), and the Bell state (quantum mechanically), are both moot on that question, so don't relate here.

 

[Ken G]

Ken G, our discussion goes into too many directions. If you want to stick to particular topic please point it out.

Perhaps the key issue is, if we both stick to the realistic perspective that u is an intrinsic property of each individual particle in the situation I describe after the entanglement is broken, then I argue the only proper time we could use to say when those properties were acquired were when the observations that came out u were performed for each particle. That is the only way to avoid an arbitrary foliation of the spacetime. You take a different approach where there is a preferred foliation that is unknowable, and I'm saying the unknowable is an unsound foundation for any scientific interpretation. Yet most entanglement language does pretend there is some unknowable foliation such that the entanglement is broken "instantaneously" for both particles, which would mean prior to the observation on an unknowable one or other of the particles. I don't like that language, common though it is, because it violates the same sensibilities we use to shout down absolute simultaneity language in relativity.

In special relativity preferred reference frame is superfluous, but SR can certainly survive if I put a label "preferred" on one of the reference frames (just a proof of principle, no particular commitment).

Yes, that's what Poincare and Lorentz tried to do, but their approach is widely viewed as unresponsive to the core lesson of relativity: that no such preferred frame exists, expressly because it would be unknowable if it did.

I would rather go with something similar to the other meaning of "objective": "all reasonable people can give consistent account of phenomena".

That cannot hold, because the "account" of what happened involves interpretation, and we cannot expect all reasonable people to arrive at the same interpretation (witness quantum mechanics interpretations). Indeed, you can't get much more subjective than interpretations-- so "accounts of phenomena" are highly subjective. Instead, we must say "objective" means that all reasonable people can agree on the outcome of the experiment, or the property that the experiment measures, but not the account of the phenomena.

You need to exclude the case where people agree just for the sake of being in agreement.

Yes, they should come to the agreement via independent paths, that's fine.

Besides other things realism is in the idea about communication with other observers and recording of experimental results and other boring stuff like that.

Sure, we must allow that what is communicated is objectively real, and the properties are objectively real, but we can do that without saying the properties are anything but objectively real concepts we communicate in order to form correct expectations. Still, I don't need to go to those less realist places, I' m content to stay at the level where the properties are intrinsic but set during measurements in all cases.

In Bohmian mechanics outcome of measurement is determined by in initial position of particle and pilot wave. Pilot wave is non-local but positions of particles are local. So in a sense measurement is determined by initial positions of particles and how experimentalist sets up the experiment and determines pilot wave. Nothing is random there so there is no collapse. We can speak only about apparent collapse.

I agree with all that, it is the apparent collapse to which I refer-- the Bohmian thinks the collapse is determined, but it's still a collapse in the sense that the particle is acquiring properties it did not possesses previously. One can take a deterministic approach without saying that all the properties have always existed. But we needn't concern ourselves with the Bohmian view, it suffices to wonder whether the properties are intrinsic, and when they are acquired.

 

[Boing3000]

That is the only way to avoid an arbitrary foliation of the spacetime.

Actually, I would like to read some reference that backup this claim. This seems to me a arbitrary claim, as as been pointed out be reference in this post.
There is one state that begin it's existence at entanglement (and the not big bang, like the reference bizarrely claim).
So there is at least a non arbitrary foliation which is pointed to by GR, and on which everybody agrees, including you : proper time. Actually, with massive particle, a testable hypothetical variation on when the correlation occur is perfectly defined, and probably within experimental range.

As a side note, few of the people making claims about "arbitrary" choice of frame(s) for labs, are willing to admit that they do an arbitrary choice of frame when deciding the orientation of detectors, which as far as I know is not included into the quantum state description, but nonetheless used into the lab(s) setup(s).

So it is possible to entangled batch of electron. It is possible to drive half of then atop the Himalaya, it is possible to bury the other half in a mine in Texas.
I am not bothered more about about computing the proper time of each batches, than to compute how to orient the detectors. Both question are answered by the unique implicit indisputable geometry of space time (causality included)

 

[zonde]

[Property] was acquired by the particle when the measurement was done on that particle, which at least allows properties to change via local interactions, but of course from Bell's theorem we all know that the result is going to have to satisfy some nonlocal constraint that will compromise to a significant degree the idea that the property is intrinsic to the particle. Still, we can save intrinsic properties if we allow them to be subject to nonlocal constraints that are intrinsic to the system to which the particle belongs, but not intrinsic to the particle itself. For me, if we cannot make the constraints intrinsic to the particle, then I see little advantage in making the properties intrinsic to the particle either, especially when I see that I only use the property concept to build expectations (in my mind) about the outcomes of observations, so it seems natural to allow that properties are mental constructs that require no "time of acquisition" in the particle proper time.

It is possible that two measurements of entangled particles are separated by large time. Then this nonlocal constraint would have to act (if we agree that it requires some physical mechanism) across time i.e. this hypothetical physical mechanism would have to "remember" how it should constrain the measurement. For me it is easier to model the situation in such a way that this "memory" is intrinsic to the particle.
But of course this is personal preference and without some experimental results that tells apart two approaches there is no solid reason to chose one approach over another.

I would like to add separate comment about this phrase:

I only use the property concept to build expectations (in my mind) about the outcomes of observations

Of course you use property concept to build expectations about outcomes and this happens in your mind. But later on you check these expectations against experimental facts. And these experimental facts do not happen in your mind. They happen in physical reality. If there is good agreement between your expectations and experimental facts you can start to speculate that there is something else in your model that corresponds to reality the way your expectations correspond to experimental outcomes. And that is the point where I start to think that this "property" might have counterpart in physical reality.

 

[Ken G]

Actually, I would like to read some reference that backup this claim.

I don't understand what you're asking for here, you want a reference that simultaneity between two widely spatially separated events requires an arbitrary foliation of spacetime? That would seem to be one of the more basic results of relativity theory, I would expect the reference would be required from anyone who claimed that simultaneity was an absolute property that did not require an arbitrary foliation (i.e., an arbitrary choice of coordinates).

This seems to me a arbitrary claim, as as been pointed out be reference in this post.

Could you perhaps find the place in that website that you are talking about, more specifically? That website would seem to summarize criticisms of Bohmian mechanics, and one of those criticisms is likely the fact that Bohmian mechanics must regard the property as being acquired at some particular time in the proper time history of the particle, which would require an arbitrary foliation of spacetime. So without some specific quotation of what you are talking about, I would expect that website to be largely in agreement with my claim, and I could then use that very website as the reference you seek.

There is one state that begin it's existence at entanglement (and the not big bang, like the reference bizarrely claim).

Of course, but as I said above, that one state evolves. In Bohmian mechanics, it later is deterministically converted into a property of the particle in question. Surely you don't think Bohmian mechanics requires that no changes in state or property ever occur?

So there is at least a non arbitrary foliation which is pointed to by GR, and on which everybody agrees, including you : proper time.

Proper time is not a foliation, it is just the "trunk of the tree." But more to the point, as I pointed out above, the proper time is precisely where the issue is left ambiguous-- we cannot say or know at what point in the proper time stream the property was acquired, unless we say it was acquired at measurement of each particle. I do not object to realists who hold to that latter position, as I said so many times, my objection is to the oft-repeated claim that the properties change "simultaneously" or "instantaneously," words that require an arbitrary foliation.

Actually, with massive particle, a testable hypothetical variation on when the correlation occur is perfectly defined, and probably within experimental range.

Certainly not, to do a correlation, you must have already done the observation on both particles, making the issue moot unless you adopt the approach I just stated-- again not what you find in popular descriptions.

As a side note, few of the people making claims about "arbitrary" choice of frame(s) for labs, are willing to admit that they do an arbitrary choice of frame when deciding the orientation of detectors, which as far as I know is not included into the quantum state description, but nonetheless used into the lab(s) setup(s).

Of course the detection frames are arbitrary. The issue is that this arbitrariness is acceptable because it is not intrinsic to the particle, like properties are supposed to be after the entanglement is broken.

I am not bothered more about about computing the proper time of each batches, than to compute how to orient the detectors. Both question are answered by the unique implicit indisputable geometry of space time (causality included)

I'm afraid I don't know what you are saying there, it sounded like something requiring a reference!

 

[Boing3000]

I don't understand what you're asking for here, you want a reference that simultaneity between two widely spatially separated events requires an arbitrary foliation of spacetime?

We are not speaking of event arbitrary separated. We are speaking of a single event called entanglement, whose "state" is testable along two perfectly non-arbitrary worldlines with precise and unique proper coordinates.

Could you perhaps find the place in that website that you are talking about, more specifically?

And in General Relativity, there is no natural way, even once chosen a space-like slice of space-time (that has no reason to possibly be a flat one) as a definition of the "initial time", to determine how space-time will have to be sliced into more "simultaneous" classes of events in the future. If we try the "simplest solution", that is taking the parameter of time defined as the age (the time spent since the Big Bang), so as to define simultaneity as equality of age, this cannot work because it will run into lots of singularities (especially at the centers of planets and stars).

(underline's mine). This site seems to make the same arguments than yours, except the fact that it admit BB as a valid starting point (a thing it seems to me your are not even willing to admit).

I would expect that website to be largely in agreement with my claim, and I could then use that very website as the reference you seek.

Except this site at least admit there is a non-arbitrary frame. My question to you is why do you claim that entanglement, which is single and uniquely defined event where to start foliation (with respect to the tools uses in the laboratory (clock AND polarizer) syncrhonized/aligned)

Of course, but as I said above, that one state evolves. In Bohmian mechanics, it later is deterministically converted into a property of the particle in question. Surely you don't think Bohmian mechanics requires that no changes in state or property ever occur?

A cases with an entangle state that evolve in time would be an even more interesting feature. But the only quibbling here is to say if there is at least one experimental system of coordinate that allow to define simultaneity and then TEST for it.

Proper time is not a foliation, it is just the "trunk of the tree."

That I certainly don't understand. I think that GR predict that little invisible clock "ticks" along each particle would be exactly at the same event/place whatever the frame used where it sits on the word-line "path". I am even pretty sure that if your beam of electron/photon just slingshot around a heavily rotating black-hole, the entanglement have no known reason (as per QM) to be "broken". And then the first question became how to orient the filters...

But more to the point, as I pointed out above, the proper time is precisely where the issue is left ambiguous-- we cannot say or know at what point in the proper time stream the property was acquired, unless we say it was acquired at measurement of each particle.

We can always relate the time of the both measurement to the proper time of particles. We can thus test/eliminate certain type of "influence", notably FLT ones.

I do not object to realists who hold to that latter position, as I said so many times, my objection is to the oft-repeated claim that the properties change "simultaneously" or "instantaneously," words that require an arbitrary foliation.

That's fair, except that I have no understanding of on what physics theory your argument stand on. Isn't GR and the equivalence principle a non-arbitrary foliation ? Ins't it the only possible (the BB one of the article seems dubiously remote to me) (and testable) foliation ?

Certainly not, to do a correlation, you must have already done the observation on both particles, making the issue moot unless you adopt the approach I just stated-- again not what you find in popular descriptions.

"Certaintly" ? How so ?. Don't we detect difference in proper time already with atomic clock ? I don't say it is easy, I say it is much more concrete then to speak about measurement made on particle in another galaxy.

Of course the detection frames are arbitrary. The issue is that this arbitrariness is acceptable because it is not intrinsic to the particle, like properties are supposed to be after the entanglement is broken.

This is no logical. If you take as granted that entanglement is not a property of particles (like Bell proved), but of detectors, the issue you have are even more problematic.
In such a case, just explain how do you orient detector if you are working on a beam of photon across the Atlantic (or maybe having bounce of satellites mirror...) Your position would appears logical to me if you can do this without ever taking the actual path of particles into consideration...(I say you have to do it even implicitly)

 

[Ken G]

We are not speaking of event arbitrary separated. We are speaking of a single event called entanglement, whose "state" is testable along two perfectly non-arbitrary worldlines with precise and unique proper coordinates.

Your statement is not responsive to the scenario I described, and the question I asked. Again, the scenario is that we have two entangled particles, which are then separated quite widely, perhaps all the way to alpha Centauri. Later, a measurement is done on one particle, achieving a "u" result, such that it is known the other particle will yield "u" if measured similarly. Then I posed this question: when did the second particle acquire the property "u"? You have not answered this question, nor is it true that there is some "unique proper coordinates" that provides an answer to the question I posed.

I am even pretty sure that if your beam of electron/photon just slingshot around a heavily rotating black-hole, the entanglement have no known reason (as per QM) to be "broken".

Yes, that would not break the entanglement, we need the "u" result somewhere in my scenario.

We can always relate the time of the both measurement to the proper time of particles. We can thus test/eliminate certain type of "influence", notably FLT ones.

I'm not sure what you mean here, but it seems to be subsumed in the question I posed above, that you have not answered.

That's fair, except that I have no understanding of on what physics theory your argument stand on. Isn't GR and the equivalence principle a non-arbitrary foliation ?

No, it isn't. A foliation is a way to parse the spatial and temporal coordinates separately, it is akin to choosing coordinates. Normally, we think of the "trunk" of the tree as the proper time of some observer, and we then "branch out" spatially in some way that has the flavor of being perpendicular to the proper time stream, but that perpendicularity is only local in GR.

"Certaintly" ? How so ?. Don't we detect difference in proper time already with atomic clock ?

The issue is not if we can detect proper time, it is if we can detect when the property was acquired. That can only be done via the measurement, which then cannot tell you when it was acquired it can only tell you when the measurement was done.

This is no logical. If you take as granted that entanglement is not a property of particles (like Bell proved), but of detectors, the issue you have are even more problematic.

I don't see any problems there, nor have you pointed to any. But notice that I never said entanglement was not an intrinsic property of the system, my entire question is about when the entanglement is broken, and refers to the properties of the particles themselves, not the properties while they are still entangled.

In such a case, just explain how do you orient detector if you are working on a beam of photon across the Atlantic (or maybe having bounce of satellites mirror...)

This is why you need a connectivity across spacetime (and GR tells you how to preserve orientation along a world line), so that you can meaningfully define the "u" state consistently for the two particles. It is arbitrary for either particle by itself, but has a meaning of "same orientation" for the correlation between the results.

 

[Ken G]

It is possible that two measurements of entangled particles are separated by large time. Then this nonlocal constraint would have to act (if we agree that it requires some physical mechanism) across time i.e. this hypothetical physical mechanism would have to "remember" how it should constrain the measurement.

Yes, what we know from experiment is that the constraint is applied somehow, and the issue for the discussion is more "when" is it applied, rather than "how" it is applied, as the former would seem to be easier to establish. However, my point is that it is not easier to establish, unless we say either that the "when" is "whenever the scientist used the notion", or for those with a more realist bent, the "when" is "whenever the measurement was done on the particle acquiring the property in question."

For me it is easier to model the situation in such a way that this "memory" is intrinsic to the particle.

But that's what Bell's theorem says it cannot be, in the sense that it cannot be a hidden local variable. So even if you hold that the property is intrinsic to the individual particle once acquired, it cannot be that the constraints on that acquisition are entirely intrinsic to the individual particle.

But of course this is personal preference and without some experimental results that tells apart two approaches there is no solid reason to chose one approach over another.

The freedom to choose here is in asserting when the property is acquired. You are choosing to answer that by looking for a preferred foliation of spacetime that is unknowable, and although that is common in the language found, it suffers the same problems as all preferred reference frames in relativity: they never show up when you look for them. They are like the person on the roll call whose name is always called but never says "present and accounted for."

Of course you use property concept to build expectations about outcomes and this happens in your mind. But later on you check these expectations against experimental facts.

But why does checking against facts imply the properties are intrinsic to the particle? Properties are testable elements of experiments, so can only be said confidently to be intrinsic to the experiment. The experiment demonstrably involves particles, and an apparatus, and a scientist forming expectations and testing them. So the property can be intrinsic to any of those, or their combination, and still be a perfectly self-consistent element that is true to the scientific process.

And these experimental facts do not happen in your mind.

Not entirely in the mind, no, but the mind is involved or it is not an experiment and cannot be shown to involve properties. So perhaps your objection is my claim that the properties are intrinsic to the analysis, but note that when I say that, I include in the analysis more than just the mind, there is also everything that the mind is making sense of-- they are all part of the analysis. So the analysis involves a mind that is considering data that comes from an apparatus that acts on a particle, those are all elements of the analysis so to say the property is intrinsic to the analysis means it is intrinsic to all of that. But the key point is, the "when" the property is acquired then has a clear answer: it is when the analysis is completed.

If there is good agreement between your expectations and experimental facts you can start to speculate that there is something else in your model that corresponds to reality the way your expectations correspond to experimental outcomes.

Sure, so "reality" is also part of the analysis. But when you discover that properties cannot be said to be acquired by particles at particular times other than when you need to use the property, you can also start to speculate that your thinking process is playing a role in the meaning of a property. And that is the point where I start to think that this "property" is intrinsic to the analysis, and the analysis, which includes my mind, the apparatus, and the particles, is all I ever meant by "physical reality."

But I realize that last bit is not going to be accepted by realists, which is why my actual point here is a strong objection to the common language that when property u is measured on one particle, that property is "instantaneously" or "simultaneously" acquired by the other particle. That language is arbitrary, undefinable, and pretty close to meaningless, given what we know about relativity. So the realists should instead hold that properties are always acquired at the time of measurement on the particle in question, and nonrealists can hold that the property is acquired just when the information is available in the analysis, as properties are only a form of information and nothing more. Neither of those approaches requires giving some unknowable meaning to "simultaneity" across large distances.

 

[PeterDonis]

there is at least a non arbitrary foliation which is pointed to by GR, and on which everybody agrees, including you : proper time.

Proper time does not give a foliation of a spacetime. It doesn't even make a valid time coordinate, since an event that lies on multiple worldlines can have multiple proper times.

 

[PeterDonis]

Isn't GR and the equivalence principle a non-arbitrary foliation ?

No. The equivalence principle has nothing to do with foliations at all (it only talks about small patches of spacetime). The principle of relativity (which is what I think you actually meant) says that the laws of physics take the same form in any coordinate chart. It says nothing at all about how to construct any particular coordinate chart (which would be equivalent to constructing a foliation).