Undergrad CFD - Counterfactual Definiteness

[DrChinese]

Also, if you read post 2 carefully - I'm pretty sure Dr Chinese does not imply that Alice's results (alone) are dependent on Bob's setting. I think he's talking about the joint results of both Alice and Bob which are, of course, dependent on the relative angle of the settings.

You are right, of course. I said: "Both settings (A and B) are inputs to something (I don't know what or where or when). Therefore the outcomes at A and B reflect in some manner the mutual relationship of both settings. Therefore they are not independent."

We must consider the entire context. So I don't see how we can separate Alice and Bob's measurement choices from the rest of the experiment.

 

[Eye_in_the_Sky]

Does anyone have a comment on this part?

separable & mutually non-influencing → IRRELEVANCE

So, in expanded form, the shorthand expression will read as:

IF

the joint-state of their instruments, in spacetime, is separable

AND

their instruments are mutually non-influencing

THEN

each one's setting is IRRELEVANT to the outcome of the other .

Now, go back to the original expression:

separable & mutually non-influencing → IRRELEVANCE .

This is a property of spacetime.

True or false?

 

[DrChinese]

...the joint-state of their instruments, in spacetime, is separable...

It's all a part of the full context. So they would not be separable as you described.

The Bohmian has the easier time discussing this particular point as nothing is isolated by space - everything is affected by everything else. In other interpretations, there are somewhat more complex explanations, as both space and time (spacetime) are factors.

 

[morrobay]

Does anyone have a comment on this part?

separable & mutually non-influencing → IRRELEVANCE

True or false?

What about separable + mutually non-influencing = locality.
And from Bells Bertlmanns Socks , p. 4'
Einstein had no difficulty accepting that affairs in different places could be correlated.
What he could not accept was that an intervention at one place could influence, immediately affairs at the other "
And to address your OP : A joint measurement on entangled ( non separable) particles at A and B
"The state of affairs relevant to outcome at A is not independent of setting at B.

 

[Eye_in_the_Sky]

What about separable + mutually non-influencing = locality.
And from Bells Bertlmanns Socks , p. 4'
Einstein had no difficulty accepting that affairs in different places could be correlated.
What he could not accept was that an intervention at one place could influence, immediately affairs at the other "
And to address your OP : A joint measurement on entangled ( non separable) particles at A and B
"The state of affairs relevant to outcome at A is not independent of setting at B.

Both of us consider the statement below to be false:

The 'state of affairs' relevant to the outcome at A is independent of the setting at B.

(And so by symmetry, the statement with A and B transposed is also false.)

It seems to me that by "independent" we both 'mean' the same thing.

Now, let's bring in what you quote from Bertlmann's Socks:

Einstein had no difficulty accepting that affairs in different places could be correlated. What he could not accept was that an intervention at one place could influence, immediately, affairs at the other.

It is Bell himself who underlines the word "influence" in that second sentence. Yet, I disagree with the use of that word there. As I see it, 'locality' (in our context) has two aspects to it:

1) state 'separability' (of Alice and Bob's instruments) ;

2) influences 'cannot be superluminal' .

Thus, the correct diction for expressing the (alleged) 'nonlocal' nature of the intervention must have in it a notion of both influence and state.

I will rewrite 1) and 2) as:

1) separability ;

2) local causality .

Now, the quote from Bertlmann's Socks was brought by you in connection with a suggestion you made at the opening of your post:

What about separable + mutually non-influencing = locality.

I'd rather write it like this:

separability & local causality = locality .

Of course, in our case (due to 'spacelike separation') it is true that 'local causality' would imply 'mutually non-influencing'. So,

spacelike separation & locality → separable & mutually non-influencing ,

and

separable & mutually non-influencing → IRRELEVANCE .

Here again are the meanings of the terms I am using:

separable: the joint-state of Alice's (measuring) instrument and Bob's (measuring) instrument, in spacetime, is separable

mutually non-influencing: each one's instrument is uninfluenced by that of the other

IRRELEVANCE: each one's setting is IRRELEVANT to the other's outcome

_________

The next part in the argument I would like to make is this:

There is another aspect of how IRRELEVANCE is to be understood/applied.

This aspect is in connection with any consistent theory (purported to be about the phenomenon under consideration), as follows:

If Bob's setting is IRRELEVANT to Alice's outcome, and if the theory in question is CORRECT in this regard, then:

No contradiction can arise in the theory by supposing that Alice's outcome for (the hypothetical setting) b₂ would have been the same as that for (the actual setting) b₁.

This is a property that any consistent theory of the phenomenon is expected to have.

... Morrobay, can you see where I am going with this? ... Does ANYONE (reading this) see where I am going?

Well (if I am not wrong), the above considerations lead to the conclusion that ONE of the following statements is TRUE:

B) Quantum Theory is inconsistent.

C) Bob's setting is IRRELEVANT to Alice's outcome, but Quantum Theory is INCORRECT in this regard.

A) Bob's setting is NOT IRRELEVANT to Alice's outcome.

I [am forced to] choose A), and I am thinking about this:

separable & mutually non-influencing → IRRELEVANCE .

 

[Simon Phoenix]

Both of us consider the statement below to be false:

The 'state of affairs' relevant to the outcome at A is independent of the setting at B.

OK - without getting too bogged down with the precise meaning of 'state of affairs' let us assume that this statement is false.

In other words, it is assumed there is some 'state of affairs' that is 'relevant' to the outcome at A that can be changed by a change of setting at B.

But what does 'relevant' mean? It can only mean that there is some measurable consequence - if there were no such consequence (no measureable change in the actual pings or dings) then in what sense would one actually describe it as 'relevant' to an outcome?

So let's assume there is some source S which emits these entangled particles and one goes off to A and one goes off to B. In the rest frame of S we will assume that changes of settings and subsequent measurements of A and B are simultaneous (which can easily be arranged with appropriate synchronisation). We will also consider A and B to be spacelike separated.

Let's suppose that 2 observers Clive and Doris are moving with respect to S such that Clive judges the changes of settings and measurements at A to occur before those at B. In Doris' frame she judges that the changes of settings and measurements at B occur before those at A.

The results, or the outcomes, the actual pings and dings on the detectors, are clearly independent of inertial frame.

Clive's perspective, based on our assumption that there IS some change relevant to the outcome, is that A has influenced the outcome at B. Doris would say the opposite. Given that the choices of measurement setting are made independently how does the frame-independence of the results make any kind of sense under the assumption that changes of settings influence 'states of affairs' relevant to an outcome?

Is it changes at A that are influencing the outcome at B, or changes at B that are influencing the outcome at A?

How can we then ascribe some influence on the frame-independent results to changes of either setting?

 

[morrobay]

Both of us consider the statement below to be false:

The 'state of affairs' relevant to the outcome at A is independent of the setting at B.

Not so sure this statement is false now : At spacelike separation the only thing that is happening instantaneously in EPR - Bell experiments when the setting at A or B is changed is the relative angle: 1/2 (sin θ/2)² and outcome correlations.

 

[Eye_in_the_Sky]

In my opinion, there is no way to make sense of the notion of one thing influencing another without indulging in counter-factual reasoning. You want to say that flipping a light switch caused the light to come on, but how can you distinguish that from mere correlation?

As Scotty never said to Kirk "It's correlation, Jim, but not as we know it"

_________

The meaning of "cause" here (in my way of thinking) necessarily involves the counter-factual consideration: "If I (counter to fact) had not flipped the switch, the light would not have come on".

In an unaired and never filmed Star Trek episode, for which a script was never written, Spock said:

In other words, the 'principle of causality' is rendered inapplicable if the joint-state of the "light switch" and the "light bulb" is 'nonseparable'.

Raising an open Hand, "Five by five," uttered the Vulcan.

 

[Eye_in_the_Sky]

Explanation in RBW is adynamical, so dynamical talk about "influences" wouldn't enter the explanans.

So, 'causality' as a principle has no place in RBW. Correct?

 

[RUTA]

So, 'causality' as a principle has no place in RBW. Correct?

Well, concerning quantum phenomena, that's what we would say, yes. Retrocausal advocates argue otherwise. They have a so-called “interventionist” account of causality. See the Insight https://www.physicsforums.com/insights/retrocausality/

 

[Zafa Pi]

Within QM theory if each of Alice and Bob are measuring one of a pair of entangled photons (from say √½(|00⟩ + |11⟩)) then each are observing a ±1 valued random variable with prob 1 = prob-1 = ½, irrespective of their observables (settings). These two r.v.s can range from independent to completely correlated depending on A and B's settings. That is all I understand.
If you think it is reasonable to ask whether Bob's setting has an affect on what Alice observes please propose a coherent method of how one could tell. For example, if A and B both choose the same setting then they will both observe the same value (1 or -1). Does that mean B's setting affects what Alice sees (and vise versa)?
A definition of "affect" here would be helpful. Does Alice like what she sees depending on Bob's setting?

Locality and CFD together are (is?) sufficient to prove a Bell inequality, which in turn can be contradicted by experiment. I'm not sure what more you're after. ("you" refers to anybody on this thread)

 

[morrobay]

1. Predictions for spin 1/2 pairs with Aa and Bb settings in xy plane for P++ = P-- is 1/2 (sin θ/2)²
With given settings above in setup change Aa to Aa' orientation and calculate prediction with a' - b = θ'
2. Now do experiment with Aa' setting and given Bb setting above
3. If experimental results for P++ and P-- match prediction for settings Aa' and Bb . θ', then there was no influence at Bb when setting change was made at Aa to Aa'

 

[Eye_in_the_Sky]

Well, concerning quantum phenomena, that's what we would say, yes. Retrocausal advocates argue otherwise. They have a so-called “interventionist” account of causality. See the Insight https://www.physicsforums.com/insights/retrocausality/

Thank you, for that, RUTA. I think I will have some more questions to ask you about RBW and the adynamical approach. ... But, in the mean time, I have a different sort of question on my mind and I am wondering what your opinion is.

Do you consider the statement below to be axiomatically true (where "the theory in question" can be any consistent theory 'about' the phenomenon)?

If Bob's setting is IRRELEVANT to Alice's outcome, and if the theory in question is CORRECT in this regard, then:

No contradiction can arise in the theory by supposing that Alice's outcome for (the hypothetical setting) b₂ would have been the same as that for (the actual setting) b₁.

 

[RUTA]

Thank you, for that, RUTA. I think I will have some more questions to ask you about RBW and the adynamical approach. ... But, in the mean time, I have a different sort of question on my mind and I am wondering what your opinion is.

Do you consider the statement below to be axiomatically true (where "the theory in question" can be any consistent theory 'about' the phenomenon)?

If Bob's setting is IRRELEVANT to Alice's outcome, and if the theory in question is CORRECT in this regard, then:

No contradiction can arise in the theory by supposing that Alice's outcome for (the hypothetical setting) b₂ would have been the same as that for (the actual setting) b₁.

I agree with Dr. Chinese (who is an expert in this area) -- Bob's setting is relevant to Alice's outcome in the sense that the Bell-inequality violating correlations obtain.

 

[Eye_in_the_Sky]

I agree with Dr. Chinese (who is an expert in this area) -- Bob's setting is relevant to Alice's outcome in the sense that the Bell-inequality violating correlations obtain.

Okay. Nobody knows what I'm talking about with that. So, I'll just explain what I'm trying to accomplish with it.

I am trying to resolve the dispute below.
_________

All Bell shows is if you want to have properties when not observed you need non local influences.

I agree with it (except for the usage of "All" and "is" in the sentence).

Do you agree that the following statement is also true?

[All] Bell shows [is] if you want the joint-state of Alice's ((macroscopic) measuring) instrument and Bob's ((macroscopic) measuring) instrument, in spacetime, to be separable then you need non-local influences.

No.

Its just a creelation. Thats it, that's all.

_________

SUMMARY:

Bhobba contends that the quantum correlations are compatible with both of these conditions taken together:

1) The joint state of Alice's measuring instrument and Bob's measuring instrument, in spacetime, is separable.

2) Their measuring instruments are mutually non-influencing.

I am saying that (at least) one of these conditions needs to be relinquished.
________________

Can anyone resolve this dispute? If not, can you make some helpful remarks about it?

 

[Eye_in_the_Sky]

The 'state of affairs' relevant to the outcome at A is independent of the setting at B.

OK - without getting too bogged down with the precise meaning of 'state of affairs' let us assume that this statement is false.

In other words, it is assumed there is some 'state of affairs' that is 'relevant' to the outcome at A that can be changed by a change of setting at B.

But what does 'relevant' mean? It can only mean that there is some measurable consequence - if there were no such consequence (no measureable change in the actual pings or dings) then in what sense would one actually describe it as 'relevant' to an outcome?

Consider spin-½ singlet.

Suppose Bob measures S_x and obtains the result q, where q is one of "UP" or "DOWN". Then the 'state of affairs' relevant to Alice's outcome is such that

if Alice measures S_x she cannot obtain q.

On the other hand, if Bob had measured S_y instead, then (no matter what the outcome of Bob) the 'state of affairs' relevant to Alice's outcome would have been such that

if Alice measures S_x she can obtain q.
_______

Simon – and anyone else who would like to comment – in your eyes, does the above example demonstrate 'relevance'?

 

[N88]

Okay. Nobody knows what I'm talking about with that. So, I'll just explain what I'm trying to accomplish with it.

I am trying to resolve the dispute below.
__________________

SUMMARY:

Bhobba contends that the quantum correlations are compatible with both of these conditions taken together:

1) The joint state of Alice's measuring instrument and Bob's measuring instrument, in spacetime, is separable.

2) Their measuring instruments are mutually non-influencing.

I am saying that (at least) one of these conditions needs to be relinquished.
________________

Can anyone resolve this dispute? If not, can you make some helpful remarks about it?

HTH; it's all about correlations:

Under EPRB (Bell 1964), let a and b be the orientations of the principal axes of Alice's device and Bob's device in 3-space, respectively. Then the orientation of their respective output channels is ±a and ±b, and the corresponding results are A^± and B^±.

1. Under Einstein-locality, their devices are mutually non-influencing: the state of Alice's device D(a) is independent of Bob's device D(b).

2. BUT their devices are correlated by the function: C[D(a), D(b)] = cos(a,b). When (a,b) = 0, C = 1 and the devices are parallel; when (a,b) = π/2, C= 0 and the devices are orthogonal; when (a,b) = π, C = -1 and the devices are antiparallel; etc. So their output channels are also correlated.

3. Now, let each particle pair be anti-correlated via the pairwise conservation of total angular momentum; ie, the λ heading toward Alice is the opposite of the λ heading toward Bob.

4. No surprise then that the correlation-based expectation <AB> should equal - a.b.

 

[N88]

The 'state of affairs' relevant to the outcome at A is independent of the setting at B.Consider spin-½ singlet.

Suppose Bob measures S_x and obtains the result q, where q is one of "UP" or "DOWN". Then the 'state of affairs' relevant to Alice's outcome is such that

if Alice measures S_x she cannot obtain q.

On the other hand, if Bob had measured S_y instead, then (no matter what the outcome of Bob) the 'state of affairs' relevant to Alice's outcome would have been such that

if Alice measures S_x she can obtain q.
_______

Simon – and anyone else who would like to comment – in your eyes, does the above example demonstrate 'relevance'?

Caution required: Alice cannot ever obtain S_x = q from the particle that paired with the particle from which Bob obtained S_x = q. The probability that she obtains q in the second example (Alice measures S_x; Bob measures S_y on a new particle-pair and gets ±q) is well-known.

 

[RUTA]

Okay. Nobody knows what I'm talking about with that. So, I'll just explain what I'm trying to accomplish with it.

I am trying to resolve the dispute below.

SUMMARY:

Bhobba contends that the quantum correlations are compatible with both of these conditions taken together:

1) The joint state of Alice's measuring instrument and Bob's measuring instrument, in spacetime, is separable.

2) Their measuring instruments are mutually non-influencing.

I am saying that (at least) one of these conditions needs to be relinquished.
________________

Can anyone resolve this dispute? If not, can you make some helpful remarks about it?

Both 1 and 2 are correct because the measuring devices obey classical (non-quantum) physics. To understand what's happening in that classical context with the outcomes of the quantum experiment, you need an interpretation of QM.

 

[Eye_in_the_Sky]

Both 1 and 2 are correct because the measuring devices obey classical (non-quantum) physics. To understand what's happening in that classical context with the outcomes of the quantum experiment, you need an interpretation of QM.

If you say that both 1 and 2 together are compatible with the quantum correlations, then you must also be saying that the following implication is NOT a property of spacetime:

separable & mutually non-influencing → IRRELEVANCE .

Am I right about that, RUTA? By your reckoning this is NOT a property of spacetime.
________

Here are the meanings of the terms I am using:

separable: the joint-state of Alice's measuring instrument and Bob's measuring instrument, in spacetime, is separable

mutually non-influencing: each one's instrument is uninfluenced by that of the other

IRRELEVANCE: each one's setting is IRRELEVANT to the other's outcome

 

[RUTA]

If you say that both 1 and 2 together are compatible with the quantum correlations, then you must also be saying that the following implication is NOT a property of spacetime:

separable & mutually non-influencing → IRRELEVANCE .

Am I right about that, RUTA? By your reckoning this is NOT a property of spacetime.
________

Here are the meanings of the terms I am using:

separable: the joint-state of Alice's measuring instrument and Bob's measuring instrument, in spacetime, is separable

mutually non-influencing: each one's instrument is uninfluenced by that of the other

IRRELEVANCE: each one's setting is IRRELEVANT to the other's outcome

You're trying to conflate outcomes in the measuring devices with whatever quantum system is responsible for those outcomes. Essentially at that point you're trying to make the measuring devices quantum in nature.

 

[Eye_in_the_Sky]

You're trying to conflate outcomes in the measuring devices with whatever quantum system is responsible for those outcomes. Essentially at that point you're trying to make the measuring devices quantum in nature.

You didn't answer my question.

The IMPLEMENTATION of a setting and the REGISTRATION of an outcome:
- each is an EVENT in spacetime
- each is part of the STATE-description of the instrument

So please, answer my question.

"YES" or "NO"? Is the implication below a property of spacetime?

separable & mutually non-influencing → IRRELEVANCE
________

Here, again, are the meanings of the terms I am using:

separable: the joint-state of Alice's measuring instrument and Bob's measuring instrument, in spacetime, is separable

mutually non-influencing: each one's instrument is uninfluenced by that of the other

IRRELEVANCE: each one's setting is IRRELEVANT to the other's outcome

 

[RUTA]

You didn't answer my question.

The IMPLEMENTATION of a setting and the REGISTRATION of an outcome:
- each is an EVENT in spacetime
- each is part of the STATE-description of the instrument

So please, answer my question.

"YES" or "NO"? Is the implication below a property of spacetime?

separable & mutually non-influencing → IRRELEVANCE
________

Here, again, are the meanings of the terms I am using:

separable: the joint-state of Alice's measuring instrument and Bob's measuring instrument, in spacetime, is separable

mutually non-influencing: each one's instrument is uninfluenced by that of the other

IRRELEVANCE: each one's setting is IRRELEVANT to the other's outcome

You keep talking about the measuring devices as if they're in a quantum (unobserved) state. In that case, you need an interpretation of QM to answer questions about their status in spacetime.

 

[Eye_in_the_Sky]

You keep talking about the measuring devices as if they're in a quantum (unobserved) state. In that case, you need an interpretation of QM to answer questions about their status in spacetime.

Hi, RUTA. I was digging through my old notes on my computer and came upon something which might prove helpful. It's a post of yours from some six years ago, and here's the part I'm quoting:

In today’s terminology we would say that the spacetime picture of relativity adheres to the following principles (Howard, 1997, pp 124-125):

Separability principle: any two systems A and B, regardless of the history of their interactions, separated by a non-null spatiotemporal interval have their own independent real states such that the joint state is completely determined by the independent states.

Locality principle: any two space-like separated systems A and B are such that the separate real state of A let us say, cannot be influenced by events in the neighborhood of B.

It is now generally believed that Einstein-Podolsky-Rosen (EPR) correlations, i.e., correlated space-like separated experimental outcomes which violate Bell’s inequality, force us to abandon either the separability or locality principle.

Here is the link:
https://www.physicsforums.com/threa...t-and.369328/page-28#post-2753865#post2753865
_______

From what you are saying here and now in this thread, it sounds like the belief you mentioned back then is no longer accepted. Even stronger than that, it sounds like you are saying the belief is demonstrably false. If so, what is the demonstration?

 

[Simon Phoenix]

Simon – and anyone else who would like to comment – in your eyes, does the above example demonstrate 'relevance'?

Well in this reasoning you're assuming a definite temporal order for the measurement events of Alice and Bob. But it's kind of the point of Bell experiments that the measurement events are spacelike separated (if they were not we would not able to rule out local hidden variable theories).

If the measurement events are spacelike separated then there exist frames of reference for which the events occur in the reverse order.

So is it Bob influencing Alice's 'state of affairs', or vice versa?

 

[entropy1]

I'm probably dead wrong, but this is my take on it for now:

Suppose Bob has setting b1, and Alice gets a series of outcomes S. Now suppose that if Bob had had setting b2, Alice would have got the same series of outcomes S. Then, since the correlation has changed (due to the changed settings of Bob), and Alice's outcomes are the same, Bob's outcomes must have changed. And this goes vice versa for Alice. So, this would mean that Alice's outcomes would only depend on her settings, and similarly for Bob. But then there would be no correlation dependent on the relative (!) parameters (it would be local). So, I suppose then that Bob's setting does influence the outcomes of Alice (and vice-versa). It just happens in a way that it is not noticed (locally)!

*hiding under a stone*

 

[zonde]

If the measurement events are spacelike separated then there exist frames of reference for which the events occur in the reverse order.

So is it Bob influencing Alice's 'state of affairs', or vice versa?

In Relativity simultaneity is only convention. There are no physical consequences for simultaneity because there are no FTL phenomena. If you speculate about FTL phenomena there are physical consequences for simultaneity and it can't be just convention. So it's outside of domain of applicability for Relativity.

 

[RUTA]

Hi, RUTA. I was digging through my old notes on my computer and came upon something which might prove helpful. It's a post of yours from some six years ago, and here's the part I'm quoting:

Here is the link:
https://www.physicsforums.com/threa...t-and.369328/page-28#post-2753865#post2753865
_______

From what you are saying here and now in this thread, it sounds like the belief you mentioned back then is no longer accepted. Even stronger than that, it sounds like you are saying the belief is demonstrably false. If so, what is the demonstration?

The measuring devices satisfy both principles, but the quantum systems responsible for the Bell-inequality violations do not.

 

[Eye_in_the_Sky]

You're trying to conflate outcomes in the measuring devices with whatever quantum system is responsible for those outcomes. Essentially at that point you're trying to make the measuring devices quantum in nature.

Can we, at least, agree on this much?

If one says there is no violation of 'causal locality', then one is forced to say that the PAIR of spacetime events – i.e. the IMPLEMENTATION of Bob's setting and the REGISTRATION of Alice's outcome – is 'nonseparably connected'.

 

[Eye_in_the_Sky]

Within QM theory if each of Alice and Bob are measuring one of a pair of entangled photons (from say √½(|00⟩ + |11⟩)) then each are observing a ±1 valued random variable with prob 1 = prob-1 = ½, irrespective of their observables (settings). These two r.v.s can range from independent to completely correlated depending on A and B's settings. That is all I understand.

Excellent! Me too.

All of the rest of the matter for me is mired by the poor diction and the fuzzy and entangled concepts with which we-all have fallen into using in our discussions of this topic.

A definition of "affect" here would be helpful.

If you think it is reasonable to ask whether Bob's setting has an affect ...

I have paused the statement at the word "affect"; it is a verb. The correct word is "effect"; it is a noun. I will define them both as follows:

effect: a 'state of affairs' that is brought about by a 'cause'

affect: to act, in a manner of 'causation', so as to produce an 'effect'

I will also define three more words:

influence: the agency through which an 'effect' is established

causation: the relationship between 'cause' and 'effect'

causality: the notion of 'causation'