QM objects do not have properties until measured?

[rubi]

OK. So in your proposal, in the Bell test, you would like to say that the preparation causes the correlations. But that means that the measurement choice of either Alice ore Bob is not a cause of the result?

Yes. The correlations are there, independent of whether they are measured or not, so they can't be caused by this choice. However, the measurement causes the particle to change its state after the measurement (be it through collapse or decoherence).

 

[atyy]

Yes. The correlations are there, independent of whether they are measured or not, so they can't be caused by this choice. However, the measurement causes the particle to change its state after the measurement (be it through collapse or decoherence).

Sure that's fine. I know you won't agree, but it basically proves Maudlin right - ones needs to change the idea of what "cause" means.

 

[rubi]

Sure that's fine. I know you won't agree, but it basically proves Maudlin right - ones needs to change the idea of what "cause" means.

I don't change the meaning of what "cause" means. $A$ causes $B$ if $B$ didn't happen without $A$ happening first. That seems to be a pretty classic definition of "cause". What is your definition of "cause"?

(Also independent of whether that's true, it doesn't prove Maudlin right. Maudlin has a mathematical error in his paper. Nothing can ever fix that.)

Edit: By the way, you have the same situation with a die: The act of rolling the die causes the die to yield some number consistent with the probability distribution $p_i=\frac{1}{6}$. The act of looking doesn't cause anything. If I roll the dice carefully, I might increase my chance to throw a 6. Whether this distribution can be calculated from a simplicial state space or not is unimportant. In fact, since we live in a quantum world, it can't. Yet, everyone would agree that the act of rolling the die caused the result.

 

[atyy]

I don't change the meaning of what "cause" means. $A$ causes $B$ if $B$ didn't happen without $A$ happening first. That seems to be a pretty classic definition of "cause". What is your definition of "cause"?

Edit: By the way, you have the same situation with a die: The act of rolling the die causes the die to yield some number consistent with the probability distribution $p_i=\frac{1}{6}$. The act of looking doesn't cause anything. If I roll the dice carefully, I might increase my chance to throw a 6. Whether this distribution can be calculated from a simplicial state space or not is unimportant. In fact, since we live in a quantum world, it can't. Yet, everyone would agree that the act of rolling the die caused the result.

It's fine, just different from the notion of cause used in Bell's theorem. I don't think it has much to do with quantum mechanics, because the preparation, and the measurement outcomes are all described by classical probability.

Cavalcanti and Lal have some comments on this approach http://arxiv.org/abs/1311.6852 (p11):
"Another way of dropping FP while keeping PCC would be to point out that correlations do not need to be explained in terms of a factorisability condition, but that the quantum state of the joint system in its causal past can itself be considered as the common cause of the correlations. An objection to this point of view, however, is that the precise correlations cannot be determined without knowledge of the measurements to be performed (the inputs x and y in Fig. 1), and these may be determined by factors not in the common past of the correlated events. A similar criticism may be made of the L-S approach. However, an advantage of the latter is that it does give an analogue of the factorisation condition (rather than simply dropping it), and thus could allow for a generalisation of Reichenbach’s Principle of Common Cause in understanding the implication of causal structure for probabilistic correlations, and be of potential application in areas such as causal discovery algorithms."

 

[N88]

… EPR arrives at this partial naive realism based explanation in EPR under condition of locality ["without in any way disturbing a system"]. Obviously rejecting "locality" renders EPR reasoning inapplicable (without rejecting realism).

On the other hand realism (in it's proper philosophical sense) can't be rejected if we hold on to scientific approach, as realism (in it's proper philosophical sense) is fundamental to science. Or more specifically science aims to explain reproducible certainty. And we favor such explanations over other types of explanations. So we (should) favor non-local explanation of reproducible certainty over local non-explanation of reproducible certainty. (Emphasis added.)

1. How do you define realism in its proper philosophical sense?
2. In your terms, but seeking greater generality, how about "science aims to explain reality"?

 

[zonde]

1. How do you define realism in its proper philosophical sense?

Describe not define.
Short description is that visible world has mind-independent existence.

2. In your terms, but seeking greater generality, how about "science aims to explain reality"?

No. You explain something in terms of something else. Explanations tie together different descriptions. Reality is very general term, so with what you would tie description of reality?

P.S. Pure philosophy is forbidden topic on PF. So if you have some questions about philosophy of science related to the topic keep it short and close to the topic.

 

[N88]

… On the other hand realism (in it's proper philosophical sense) can't be rejected if we hold on to scientific approach, as realism (in it's proper philosophical sense) is fundamental to science. ...

OK. I am here to study science, not philosophy. In scientific terms, and given your support for nonlocality, what do you mean by these phrases:
1. The scientific approach.
2. On the other hand realism (in it's proper philosophical sense) can't be rejected if we hold on to scientific approach.
3. Realism (in it's proper philosophical sense) is fundamental to science.

 

[zonde]

1. The scientific approach.

We use scientific method to reject some hypotheses and favor (accept for now) other hypotheses.

2. On the other hand realism (in it's proper philosophical sense) can't be rejected if we hold on to scientific approach.

To justify scientific method we have to assume realism.

3. Realism (in it's proper philosophical sense) is fundamental to science.

Scientific method is fundamental to science and therefore assumptions that justify scientific method are fundamental too.
https://en.wikipedia.org/wiki/Philosophy_of_science#Axiomatic_assumptions

 

[morrobay]

Nobody (I hope) is considering dropping locality as there is no philosophical framework for such a way of thinking. "Non-locality" of QM just means that QM approximates some physical mechanism that violates speed of light limit.

In terms of experimental results what differentiates between the " non locality" of QM approximating some physical mechanism violating the speed of light and particles not having definite properties before measurement ?
In other words are some describing non realism as non locality ?

 

[zonde]

In terms of experimental results what differentiates between the " non locality" of QM approximating some physical mechanism violating the speed of light and particles not having definite properties before measurement ?

These two things are not strictly related. It's because particles not having definite (certain) properties does not mean that local measurements can't have definite outcomes.
Let me give an analogy. We have a glass and we ask, does that glass have a property of being full or not after we pour some amount of water into it? Obviously glass does not have such a property because whether the glass will be full or not depends on the amount of water we are pouring into it. But if we can somehow fix the amount of water then the result will become certain.
So properties can be contextual and therefore not definite in absolute sense.

 

[Neandethal00]

QM objects do not have properties until measured?

Another way of saying this is
To a quantum particle nothing exists until it interacts with another 'object'.
From the 'object' point of view: a quantum particle doesn't exist until it interacts with the 'object'.

 

[morrobay]

These two things are not strictly related. It's because particles not having definite (certain) properties does not mean that local measurements can't have definite outcomes.
Let me give an analogy. We have a glass and we ask, does that glass have a property of being full or not after we pour some amount of water into it? Obviously glass does not have such a property because whether the glass will be full or not depends on the amount of water we are pouring into it. But if we can somehow fix the amount of water then the result will become certain.
So properties can be contextual and therefore not definite in absolute sense.

http://arxiv.org/pdf/quant-ph/0209123v2.pdf
See page 50.
5.2 locality and counterfactuality.
... while for others quantum non - locality is an artifact created by the introduction into QM notions which are foreign to it,
typically the EPR elements of reality.

 

[N88]

http://arxiv.org/pdf/quant-ph/0209123v2.pdf
See page 50.
5.2 locality and counterfactuality.
... while for others quantum non - locality is an artifact created by the introduction into QM notions which are foreign to it,
typically the EPR elements of reality.

From page 32: "A general way to express the Bell theorem in logical terms is to state that the following system of three assumptions (which could be called the EPR assumptions) is self-contradictory:
1. validity of their notion of “elements of reality”
2. locality
3. the predictions of quantum mechanics are always correct.
The Bell theorem then becomes a useful tool to build a “reductio ad absurdum” reasoning: it shows that, among all three assumptions, one (at least) has to be given up."

Can there be any doubt that #1 must be given up? And ONLY #1?

NB: #1 is the classicality assumption associated with EPR, Bell, d'Espagnat (see post #44 above) and was known to be false from the early days of QM.

 

[zonde]

http://arxiv.org/pdf/quant-ph/0209123v2.pdf
See page 50.
5.2 locality and counterfactuality.
... while for others quantum non - locality is an artifact created by the introduction into QM notions which are foreign to it,
typically the EPR elements of reality.

Yes, wording of EPR definition seems to exclude contextual HV while they are certainly realistic. But important question is whether quantum non-locality does not follow any more if we fix this problem and take contextual HV into consideration. And the thing is that Bell's inequalities are the same for contextual HV (Bell's $\lambda$ does not differentiate between the two). So it changes nothing in an idealized situation.

But there is difference for interpretation of experimental results. Prior to loophole free Bell inequality tests this distinction was important because fair sampling assumption (that opens detection loophole) applies to non-contextual HV but doesn't apply to contextual HV. So earlier Weihs experiment with fast switching polarization analyzers already excluded local non-contextual HV as a possible explanation.

 

[N88]

QM objects do not have properties until measured?

Another way of saying this is
To a quantum particle nothing exists until it interacts with another 'object'.
From the 'object' point of view: a quantum particle doesn't exist until it interacts with the 'object'.

Note that the opening sentence is a question, so another way to say it would also be a question. From the discussion so far, with its emphasis on Bell's theorem, I believe we can say this:
In Bell-tests, the correlated particles in a pair may have properties like opposite charge and identical spin, but they do not have an EPR element of physical reality as a property until measured.

 

[stevendaryl]

From the discussion so far, with its emphasis on Bell's theorem, I believe we can say this:
In Bell-tests, the correlated particles in a pair may have properties like opposite charge and identical spin, but they do not have an EPR element of physical reality as a property until measured.

I don't think it makes to add the prepositional phrase "until measured". If you believe that measurement is not magic, that it's only a matter of amplifying microscopic state variables so that they become correlated with macroscopic state variables, then I don't see how anything fundamental can happen during measurement. So if objects don't have elements of reality before measurement, then they don't after measurement, either. That's the Many-Worlds way out, to allow for even macroscopic quantities to be indeterminate.

 

[N88]

I don't think it makes to add the prepositional phrase "until measured". If you believe that measurement is not magic, that it's only a matter of amplifying microscopic state variables so that they become correlated with macroscopic state variables, then I don't see how anything fundamental can happen during measurement. So if objects don't have elements of reality before measurement, then they don't after measurement, either. That's the Many-Worlds way out, to allow for even macroscopic quantities to be indeterminate.

In my terms, correcting yours: If EPRB objects don't have EPR elements of reality before measurement, they certainly do after measurement. In EPRB, the EPR elements of physical reality are spin-up or spin-down. Just two possible observables from a probable infinity of inputs. So it is not so much an amplification of microscopic variables: it is more like a modification and extrusion of them to conform to one of the two output channels of the "measuring" device.

 

[stevendaryl]

In my terms, correcting yours: If EPRB objects don't have EPR elements of reality before measurement, they certainly do after measurement.

But how can measurement accomplish this? Measurement is just a physical interaction--what makes it special is that it's an interaction that can end up changing my brain state in a definitive way.

 

[N88]

But how can measurement accomplish this? Measurement is just a physical interaction--what makes it special is that it's an interaction that can end up changing my brain state in a definitive way.

But isn't an EPRB measuring device just a preparation device followed by a detector? If I send you a beam of randomly polarised photons and you put it through a single-channel vertically-oriented polariser, you produce a beam of half the intensity but wholly vertically-polarised. Thus the preparation part of the measuring device can accomplish great change. And this is SPECIAL - a special preparation interaction - whether you add a detector (to register the change, for your brain's sake) or not.

 

[stevendaryl]

But isn't an EPRB measuring device just a preparation device followed by a detector? If I send you a beam of randomly polarised photons and you put it through a single-channel vertically-oriented polariser, you produce a beam of half the intensity but wholly vertically-polarised. Thus the preparation part of the measuring device can accomplish great change. And this is SPECIAL - a special preparation interaction - whether you add a detector (to register the change, for your brain's sake) or not.

You're talking about a specific type of measurement, but QM doesn't make such distinction. Any time you set up a situation in which two (or more) different microscopic states lead to different macroscopically distinguishable results, then you have a measurement, and the quantum (Born) probabilities apply.

 

[stevendaryl]

You're talking about a specific type of measurement, but QM doesn't make such distinction. Any time you set up a situation in which two (or more) different microscopic states lead to different macroscopically distinguishable results, then you have a measurement, and the quantum (Born) probabilities apply.

So if you have a metastable macroscopic system such that an electron with spin-up in the z-direction will perturb it into one macroscopic state (for example, a black dot on one photographic plate), and an electron with spin-down in the z-direction will perturb it into a second, distinguishable macroscopic state (for example, a black dot on a different photographic plate), then you've measured spin in the z-direction.

 

[zonde]

You're talking about a specific type of measurement, but QM doesn't make such distinction. Any time you set up a situation in which two (or more) different microscopic states lead to different macroscopically distinguishable results, then you have a measurement, and the quantum (Born) probabilities apply.

I don't get your point. When detector amplifies microscopic state quantum phase is lost and macroscopic record is produced. Before that quantum phase is there. Say, I can split coherent unpolarized photon beam with PBS then rotate polarization in one beam and perform interference measurement. And interference pattern will be there.

EDIT: It seems I made a mistake. In order to observe interference I would have to use diagonally polarized light source or alternatively I can place diagonal polarizer before detector without rotating light beam in one path.

 

[stevendaryl]

I don't get your point. When detector amplifies microscopic state quantum phase is lost and macroscopic record is produced. Before that quantum phase is there. Say, I can split coherent unpolarized photon beam with PBS then rotate polarization in one beam and perform interference measurement. And interference pattern will be there.

EDIT: It seems I made a mistake. In order to observe interference I would have to use diagonally polarized light source or alternatively I can place diagonal polarizer before detector without rotating light beam in one path.

I'm not sure I understand your point. What I'm saying is that whenever a macroscopic record is produced such that different microscopic states lead to different macroscopic records, then the producing of that record constitutes a measurement of the microscopic state. Of course, you might also consider it to be a "measurement" (although it doesn't really correspond to the usual meaning of measurement) whenever two different microscopic states become correlated with different macroscopic states, regardless of whether those macroscopic states correspond to a persistent record, or not.

But in any case, it doesn't make sense to me to say that something physically meaningful (such as "acquiring an EPR element of reality") should hinge on correlating a microscopic state to a macroscopic state.

 

[zonde]

I'm not sure I understand your point. What I'm saying is that whenever a macroscopic record is produced such that different microscopic states lead to different macroscopic records, then the producing of that record constitutes a measurement of the microscopic state.

But you don't measure polarization of photon with detector. Meaning, detector produces record "click in H channel at ..." or for another detector "click in V channel ...". But detector does not produce record "H click at ..." or "V click at ...". It's PBS that does the trick of separating "H photons" from "V photons" whatever that means.

 

[stevendaryl]

But you don't measure polarization of photon with detector. Meaning, detector produces record "click in H channel at ..." or for another detector "click in V channel ...". But detector does not produce record "H click at ..." or "V click at ...". It's PBS that does the trick of separating "H photons" from "V photons" whatever that means.

I'm not sure what point you're making. I'm saying "Doing X constitutes a measurement of microscopic observable x". You seem to be saying: "I'm not doing X, I'm doing something different." Well, then I'm not talking about that case. I'm talking about the case in which you have a setup in which a microscopic observable x is amplified to make a macroscopic record X.

 

[Jilang]

Would it be correct to say that it is not the act of the measurement that does anything special, but the application of the magnetic field just before it that causes the quantisation of the spin in a given direction in a Stern Gerlach type experiment?

 

[AlexCaledin]

But, if I got it right, according to R. Penrose and H. Stapp, the physicist's decision to apply a certain magnetic field also is an outcome of a measurement - the physicist's consciousness measures his brain's state, thus making the choice of action. So it all seems to work according to Feynman saying about the great "chess game" of Nature - the quantum potentiality is the "chessboard" and measurements are "moves" creating actual properties and forming (reducing) the superposition of potential ones.

 

[bhobba]

But, if I got it right, according to R. Penrose and H. Stapp, the physicist's decision to apply a certain magnetic field also is an outcome of a measurement

Well I won't be nice about it and say be careful with populist stuff or something along those lines - its rubbish. Added later: Rereading it I was not 100% clear about the issue. The decision the experimenter makes is irrelevant to anything and obviously so. It could be made by a computer or simply the result of some normal process like dust particles interacting with stray photons from the CBMR. All are 'measurements', 'observations' etc etc.

You have been posting here long enough to know this consciousnesses stuff is very very fringe and most definitely not mainstream.

I need to be clear though - its a valid view - just one most reject as - well - silly - like most reject solipsism.

Thanks
Bill

 

[bhobba]

Would it be correct to say that it is not the act of the measurement that does anything special, but the application of the magnetic field just before it that causes the quantisation of the spin in a given direction in a Stern Gerlach type experiment?

No.

Whats going on is interpretation dependent.

Specify an interpretation then we can discuss questions like that.

Thanks
Bill

 

[Jilang]

No.

Whats going in is interpretation dependent.

Specify an interpretation then we can discuss questions like that.

Thanks
Bill

Isn't what I posted an interpretation?

 

[secur]

this consciousnesses stuff is very very fringe and most definitely not mainstream.
I need to be clear though - its a valid view - just one most reject as - well - silly

Irrefutable logic: this is how science makes progress! But since I'm not a QM master, it's hard to understand this difficult math. Perhaps if you could help me on one step, I can figure out the rest myself in a week or so. How do I formally write down the covariant derivative of "silly"?

 

[bhobba]

Isn't what I posted an interpretation?

No. An interpretation is something like Bohmian Mechanics, Many Worlds or Ignorance Ensemble.

Specify something like that and we can discuss it.

Thanks
Bill

 

[rootone]

How do I formally write down the covariant derivative of "silly"?

ʎllᴉs

 

[Dale]

Closed pending moderation

Edit: after discussion with the mentors we will leave the thread closed.