Bell experiments and Realism

[Alan Grayson]

Suppose we assume Bell experiments establish that Bell's inequality is violated, and that this can be interpreted to mean that hidden variables do not exist. Does this statement, if true, establish that Realism is false? By Realism, I mean the belief that the measured result of some property of a measured entity pre-exists the measurement. TY, AG

[scerir]

 

Il 15/11/2024 09:23 CET Alan Grayson <agrays...@gmail.com> ha scritto:

 

 

Suppose we assume Bell experiments establish that Bell's inequality is violated, and that this can be interpreted to mean that hidden variables do not exist. Does this statement, if true, establish that Realism is false? By Realism, I mean the belief that the measured result of some property of a measured entity pre-exists the measurement. TY, AG

What then is physics if it is not the search for the Law of Nature, the quest for the absolute

Truth, nor the Keplerian attempt to read the mind of God? Since the formation of the Royal

Society, one could describe physics as the systematic discovery of what processes we can carry out and how we can predict their outcomes. As long as the universe continues to surprise us with new opportunities and dangers, physics in this sense will be an important element of our strategy to survive and prosper in it. Since there can be no final quantum experiment, there is little reason to fear that there will be a final quantum theory.

-David Filkenstein in The state of quantum physics

 

The underlying error may be the conviction that the system itself has to be represented in

order to represent our actions upon it. In quantum theory we represent actual operations and the relations among them, not a hypothetical reality on which they act. Quantum theory is a theory of actuality, not reality. I have taken this term from Whitehead’s writings.

–David Finkelstein in The state of quantum physics

 

[Alan Grayson]

On Friday, November 15, 2024 at 1:50:20 AM UTC-7 scerir wrote:

 

Il 15/11/2024 09:23 CET Alan Grayson <agrays...@gmail.com> ha scritto:

 

 

Suppose we assume Bell experiments establish that Bell's inequality is violated, and that this can be interpreted to mean that hidden variables do not exist. Does this statement, if true, establish that Realism is false? By Realism, I mean the belief that the measured result of some property of a measured entity pre-exists the measurement. TY, AG

What then is physics if it is not the search for the Law of Nature, the quest for the absolute

Truth, nor the Keplerian aThe Insufficiency of Born's Rulettempt to read the mind of God? Since the formation of the Royal

Society, one could describe physics as the systematic discovery of what processes we can carry out and how we can predict their outcomes. As long as the universe continues to surprise us with new opportunities and dangers, physics in this sense will be an important element of our strategy to survive and prosper in it. Since there can be no final quantum experiment, there is little reason to fear that there will be a final quantum theory.

-David Filkenstein in The state of quantum physics

 

The underlying error may be the conviction that the system itself has to be represented in

order to represent our actions upon it. In quantum theory we represent actual operations and the relations among them, not a hypothetical reality on which they act. Quantum theory is a theory of actuality, not reality. I have taken this term from Whitehead’s writings.

–David Finkelstein in The state of quantum physics

As an historian of physics, what's the generally held belief in the physics community regarding the question I've posed? AG 

 

[scerir]

Il 15/11/2024 09:23 CET Alan Grayson <agrays...@gmail.com> ha scritto:

Suppose we assume Bell experiments establish that Bell's inequality is violated, and that this can be interpreted to mean that hidden variables do not exist. Does this statement, if true, establish that Realism is false? By Realism, I mean the belief that the measured result of some property of a measured entity pre-exists the measurement. TY, A

 

A "realistic" picture of entangled parties?

One must be sure there is a space-time. Gisin, Zeilinger, et al., are not so sure about that.

 

Zeilinger: “It appears that an understanding is possible via the notion of information. Information seen as the possibility of obtaining knowledge. Then quantum entanglement describes a situation where information exists about possible correlations between possible future results of possible future measurements without any information existing for the individual measurements. The latter explains quantum randomness, the first quantum entanglement. And both have significant consequences for our customary notions of causality. It remains to be seen what the consequences are for our notions of space and time, or space-time for that matter. Space-time itself cannot be above or beyond such considerations. I suggest we need a new deep analysis of space-time, a conceptual analysis maybe analogous to the one done by the Viennese physicist-philosopher Ernst Mach who kicked Newton’s absolute space and absolute time form their throne. The hope is that in the end we will have new physics analogous to Einstein’s new physics in the two theories of relativity.”

 

[John Clark]

On Fri, Nov 15, 2024 at 3:23 AM Alan Grayson <agrays...@gmail.com> wrote:

> Suppose we assume Bell experiments establish that Bell's inequality is violated,

We don't need to assume that, thanks to experiment, we know for a fact that Bell's inequality is violated.

> and that this can be interpreted to mean that hidden variables do not exist.

No! It can NOT be interpreted in that way, the violation of Bell's Inequality proves that LOCAL hidden variables do not exist IF the universe is realistic and deterministic. 

 

> Does this statement, if true, establish that Realism is false?

No, the meaning is more subtle than that. It establishes that realism *might* be false, and it establishes that if realism is true then the world can't be both deterministic and local. In Many Worlds realism is false but that's why the violation of Bell's Inequality does not prove it's correct, it only proves that it might be correct.  

> By Realism, I mean the belief that the measured result of some property of a measured entity pre-exists the measurement.

The precise definition of realism is that one and only one specific set of properties pre-exists the measurement, although some people, such as Roger Penrose, don't think that caveat is necessary because the Many Worlds idea is a Reductio ad absurdum on it's very face and thus not even worth thinking about.  I respectfully disagree with Sir Roger about that.

John K Clark    See what's on my new list at  Extropolis

prs

[Brent Meeker]

On 11/15/2024 5:08 AM, John Clark wrote:

On Fri, Nov 15, 2024 at 3:23 AM Alan Grayson <agrays...@gmail.com> wrote:

> Suppose we assume Bell experiments establish that Bell's inequality is violated,

We don't need to assume that, thanks to experiment, we know for a fact that Bell's inequality is violated.

> and that this can be interpreted to mean that hidden variables do not exist.

No! It can NOT be interpreted in that way, the violation of Bell's Inequality proves that LOCAL hidden variables do not exist IF the universe is realistic and deterministic.

How did "deterministic" get in there.  Bell's inequality is violated even if there is a local shared random variable.

Brent

 

> Does this statement, if true, establish that Realism is false?

No, the meaning is more subtle than that. It establishes that realism *might* be false, and it establishes that if realism is true then the world can't be both deterministic and local. In Many Worlds realism is false but that's why the violation of Bell's Inequality does not prove it's correct, it only proves that it might be correct.  

> By Realism, I mean the belief that the measured result of some property of a measured entity pre-exists the measurement.

The precise definition of realism is that one and only one specific set of properties pre-exists the measurement, although some people, such as Roger Penrose, don't think that caveat is necessary because the Many Worlds idea is a Reductio ad absurdum on it's very face and thus not even worth thinking about.  I respectfully disagree with Sir Roger about that.

John K Clark    See what's on my new list at  Extropolis

prs

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[John Clark]

On Fri, Nov 15, 2024 at 7:17 PM Brent Meeker <meeke...@gmail.com> wrote:

>>  the violation of Bell's Inequality proves that LOCAL hidden variables do not exist IF the universe is realistic and deterministic.

 

> How did "deterministic" get in there.  Bell's inequality is violated even if there is a local shared random variable.

A theory that is non-local, non-deterministic and non-realistic would still be compatible with the violation of Bell's Inequality, although I'm not aware of anybody proposing such a theory.  The violation of Bell's Inequality does not rule out Objective Collapse Theories even though they are realistic and local because they are also non-deterministic. The violation of Bell's Inequality does not rule out Pilot Wave Theory because it is deterministic and realistic but not local. The violation of Bell's Inequality does not rule out Many Worlds because it's local and deterministic but not realistic. You can't have all three, at least one's got to go; I think it's realism but I could be wrong.  

 John K Clark    See what's on my new list at  Extropolis

ux0
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[Bruce Kellett]

No local theory can explain the violation of the Bell inequalities. Realism and determinism are essentially irrelevant in this context.

Bruce

[Brent Meeker]

On 11/15/2024 4:54 PM, John Clark wrote:

On Fri, Nov 15, 2024 at 7:17 PM Brent Meeker <meeke...@gmail.com> wrote:

>>  the violation of Bell's Inequality proves that LOCAL hidden variables do not exist IF the universe is realistic and deterministic.

 

> How did "deterministic" get in there.  Bell's inequality is violated even if there is a local shared random variable.

A theory that is non-local, non-deterministic and non-realistic would still be compatible with the violation of Bell's Inequality, although I'm not aware of anybody proposing such a theory.  The violation of Bell's Inequality does not rule out Objective Collapse Theories even though they are realistic and local because they are also non-deterministic.

Maybe we're disagreeing about what "local" or maybe "realism" means.  I think it means that at the creation of the two photons their polarizations are fixed (realism) at the same direction, which varies randomly from pair to pair (non-deterministic), and they interact at the detectors indpendently (local).  Those conditions imply Bell's inequality.  Right? 

I don't think OC theories are local. At each detector the collapse is random, but not the photons don't share the same random value.

Brent

The violation of Bell's Inequality does not rule out Pilot Wave Theory because it is deterministic and realistic but not local. The violation of Bell's Inequality does not rule out Many Worlds because it's local and deterministic but not realistic. You can't have all three, at least one's got to go; I think it's realism but I could be wrong.  

 John K Clark    See what's on my new list at  Extropolis

ux0
prs

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[John Clark]

On Fri, Nov 15, 2024 at 9:28 PM Brent Meeker <meeke...@gmail.com> wrote:

> Maybe we're disagreeing about what "local" or maybe "realism" means.  I think it means that at the creation of the two photons their polarizations are fixed (realism) at the same direction, which varies randomly from pair to pair (non-deterministic), and they interact at the detectors indpendently (local).  Those conditions imply Bell's inequality.  Right? 

In this case "realism" would mean the photon pairs will always have opposite polarizations and the axis of polarization has always pointed to one AND ONLY ONE definite direction. People like Roger Penrose would say there is only one pair of photons so the "and only one" part is unnecessary because the Many Worlds idea is just too strange to be true, or even to be worthy of thought. However I note that although sir Roger calls it absurd even he doesn't claim it's logically contradictory.

> I don't think OC theories are local. At each detector the collapse is random, but not the photons don't share the same random value.

Yeah, that's a valid point. I think I got a little over my skis when I said objective collapse was local; it's realistic but non-local and nondeterministic.   

 John K Clark    See what's on my new list at  Extropolis

pvt

[Brent Meeker]

On 11/16/2024 4:28 AM, John Clark wrote:

On Fri, Nov 15, 2024 at 9:28 PM Brent Meeker <meeke...@gmail.com> wrote:

> Maybe we're disagreeing about what "local" or maybe "realism" means.  I think it means that at the creation of the two photons their polarizations are fixed (realism) at the same direction, which varies randomly from pair to pair (non-deterministic), and they interact at the detectors indpendently (local).  Those conditions imply Bell's inequality.  Right? 

In this case "realism" would mean the photon pairs will always have opposite polarizations and the axis of polarization has always pointed to one AND ONLY ONE definite direction.

That's not what I wrote.  First, whether the polarization of the two photons is the same or opposite is irrelevant for linear polarizers at the detectors. Second, I don't why you imagine that realism requires that the plane always be pointed in the same direction.  Everybody else defines realism as I did above: each pair has some definite plane.  I specifically stated the plane varying randomly in direction is what makes the experiment non-deterministic.

People like Roger Penrose would say there is only one pair of photons so the "and only one" part

Who are quoting?

is unnecessary because the Many Worlds idea is just too strange to be true, or even to be worthy of thought. However I note that although sir Roger calls it absurd even he doesn't claim it's logically contradictory.

OK, but I don't know how Penrose is relevant to this conversation.  I've stated my specific criticisms of MWI and they are not Penrose's.

Brent

> I don't think OC theories are local. At each detector the collapse is random, but not the photons don't share the same random value.

Yeah, that's a valid point. I think I got a little over my skis when I said objective collapse was local; it's realistic but non-local and nondeterministic.   

 John K Clark    See what's on my new list at  Extropolis

pvt

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[John Clark]

On Sat, Nov 16, 2024 at 8:46 PM Brent Meeker <meeke...@gmail.com> wrote:

> I don't why you imagine that realism requires that the plane always be pointed in the same direction.

I'm not saying that's what realism is, and I believe we agree more than you think. Realism insists that before the photons in the pair are measured they were already polarized around one and only one specific axis. And before the photons in the next pair are measured they too were already polarized around one and only one specific axis, BUT ALMOST CERTAINLY A DIFFERENT AXIS than the first pair. 

> Everybody else defines realism as I did above: each pair has some definite plane.  

That's a good definition of realism but an even better one would be "each pair is polarized around ONE definite plane". Many Worlds says before an experiment is  performed  there are photons oriented at EVERY angle that the laws of quantum mechanics allows. And that's why Many Worlds is not a realistic theory, and that's why Many Worlds is a deterministic theory. 

 

> I specifically stated the plane varying randomly in direction is what makes the experiment non-deterministic.

Yes, if Many Worlds is wrong and even the quantum wave function of the entire universe would be insufficient to predict the outcome of that experiment, then it would certainly be non-deterministic, and not just from the point of view of the experimenter, it would even be nondeterministic to God; assuming there is a God. 

 John K Clark    See what's on my new list at  Extropolis

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[Brent Meeker]

OK, we're in agreement.  I was just a little misled by "each pair is polarized around ONE definite plane", since that can be read as each, and every, pair is polarized around One definite plane which does not change from pair-to-pair.

Brent

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