I Determinism, realism, hidden variables

[Derek Potter]

Is it what you "believe"? how would you write this reality mathematically? equality, inequality, with another relation?

Sure I believe that it is possible. That's why I said it.

I have no idea why you would want to write it mathematically. An entity is postulated without mentioning observers. Observers are defined, not postulated. Observer-dependent phenomena are derived. This is done without invoking the fact that observers are not postulated.

But let's assume we write something like
reality(observer_1) = reality(observer_2)
Bearing in mind that the theory does not invoke this statement, where does that get you?

 

[naima]

I see that in the Bell's paper about beables, he uses the words light cones.
He also uses the Bell's relation about local hidden variables where the speed of light is absent.
Is there in his proof something about ftl signal? The Ockham razor principle tells us that it is not necessary to invoke light speed.

 

[Derek Potter]

Is there in his proof something about ftl signal? The Ockham razor principle tells us that it is not necessary to invoke light speed.

Yeah, you can put one of the systems in a perfect box after Schroedinger has finished tormenting his cat in it.
(Every experiment needs a cat.)

 

[Derek Potter]

Does the act of "measurement" not produce an entanglement relationship between aspects of the system, and the measurement apparatus ? Shouldn't this count as an "interaction" ?

Steven was talking about the "standard" way QM is presented. The standard approach just asserts observation of eigenvalues. What you describe is measurement theory and may account for eigenvalues. Certainly this is why Steven mentioned MWI which definitely claims to account for them as well as everything else that people find strange. Or not.

 

[stevendaryl]

I see that in the Bell's paper about beables, he uses the words light cones.
He also uses the Bell's relation about local hidden variables where the speed of light is absent. Is there in his proof something about ftl signal? The Ockham razor principle tells us that it is not necessary to invoke light speed.

In EPR, there are the following relevant events:

1. e_1: A pair of particles is created at one location.
2. e_2: Alice chooses her detector settings.
3. e_3: Alice measures the spin of one of the particles.
4. e_4: Bob chooses his detector settings.
5. e_5: Bob measures the spin of the other particle.

Bell's assumption is that a measurement result can depend only on facts about the causal past of that measurement. So he assumes that Bob's result at e_5 cannot depend on anything that happens at e_2 or e_3, and that Alice's result at e_3 cannot depend on anything that happens at e_4 or e_5. In terms of light cones, Bell is assuming that

• e_2 and e_3 are not in the backward lightcone of e_5
• e_4 and e_5 are not in the backward lightcone of e_3

If those assumptions do not hold, then Bell's proof is invalid. It's easy to come up with a classical (non-quantum) model that can explain the EPR correlations in that case.

Ockham's razor is not relevant here, because Bell is not trying to explain anything. He's trying to prove that no explanation (of a certain type) is possible.

 

[naima]

I see that in the Bell's paper about beables, he uses the words light cones.
He also uses the Bell's relation about local hidden variables where the speed of light is absent.
Is there in his proof something about ftl signal? The Ockham razor principle tells us that it is not necessary to invoke light speed.

And it is what is done in the Bertlmann's socks paper (written later)
You say that
"Bell's assumption is that a measurement result can depend only on facts about the causal past of that measurement."
Where it is needed in the derivation of the inequality (1984 paper)?

 

[stevendaryl]

You say that
"Bell's assumption is that a measurement result can depend only on facts about the causal past of that measurement."
Where it is needed in the derivation of the inequality (1984 paper)?

It's clear that Bell's theorem is false without the assumption about lightcones.

Let P(A, B | \alpha, \beta, \lambda) = the probability that Alice gets result A and Bob gets result B, given that Alice chooses detector setting \alpha, Bob chooses detector setting \beta, and that \lambda is some unknown parameter shared by both particles. We can write, in perfect generality:

P(A, B | \alpha, \beta, \lambda) = P_A(A | \alpha, \beta, \lambda) P_B(B| A, \alpha, \beta, \lambda)

where P_A(A | \alpha, \beta, \lambda) = the probability that Alice gets result A, given \alpha, \beta, and \lambda, and P_B(B | A, \alpha, \beta, \lambda) = the probability that Bob gets result B, given A, \alpha, \beta, and \lambda.

Now, Bell assumes the following:

1. P_A(A | \alpha, \beta, \lambda) = P_A(A | \alpha, \lambda) (Alice's result cannot depend on Bob's setting)
2. P_B(B | A, \alpha, \beta, \lambda) = P_B(B | \beta, \lambda) (Bob's result cannot depend on Alice's setting, or Alice's result)

These two assumptions imply the following form for P(A,B|\alpha, \beta):

P(A,B|\alpha, \beta) = \sum_\lambda P_{hv} (\lambda) P_A(A |\alpha, \lambda) P_B(B|\beta, \lambda)

The result predicted by quantum mechanics for the twin-pair, spin-1/2, anti-correlated EPR experiment is:

• There are 2 possible results for each measurement: A = spin-up or spin-down, B = spin-up or spin-down.
  
• P(A,B|\alpha, \beta) = \frac{1}{2} sin^2(\frac{\beta - \alpha}{2}) (if A = B)
  
• P(A,B|\alpha, \beta) = \frac{1}{2} cos^2(\frac{\beta - \alpha}{2}) (if A \neq B)

Bell proved that it is impossible to find functions P_{hv}, P_A, P_B that give those results. If you allow Bob's result to depend on Alice's setting and result, so that his probability has the form P_B(B | A, \alpha, \beta, \lambda), then it is possible to find functions P_{hv}, P_A, P_B that give those results. So Bell's proof depends on the fact that Bob's result is not influenced by Alice's setting or result.

 

[naima]

I liked your answer because it enables us to see what is really used.
$\beta$ does not appear in Alice's probability. It is true. But $\lambda$ has not to be a number. It may be a couple of numbers.
the first could be a property of something near Bob and the other the property of something near Alice.
The problem becomes the locality of $\lambda$

 

[Paul Colby]

What I don't like about Bell's argument as presented is the phrase "Bob's result" is set next to $P(B\vert \beta, \lambda)$ which is not really what I think Bob's result actually means. Alice could have perfect pre-knowledge of Bob's individual measurements (particle by particle) and Bob could still believe things are random.

 

[stevendaryl]

I liked your answer because it enables us to see what is really used.
$\beta$ does not appear in Alice's probability. It is true. But $\lambda$ has not to be a number. It may be a couple of numbers.
the first could be a property of something near Bob and the other the property of something near Alice.
The problem becomes the locality of $\lambda$

\lambda is by definition something localized to the pair creation event. \alpha represents properties that are local to Alice, and \beta represents properties that are local to Bob.

 

[stevendaryl]

What I don't like about Bell's argument as presented is the phrase "Bob's result" is set next to $P(B\vert \beta, \lambda)$ which is not really what I think Bob's result actually means. Alice could have perfect pre-knowledge of Bob's individual measurements (particle by particle) and Bob could still believe things are random.

I don't understand what you mean. In what I wrote, B is a variable that takes on two possible values: spin-up in whatever direction Bob chose, or spin-down in whatever direction Bob chose. P(B | \beta, \lambda) is the assumed probability that Bob will get result B given that he chose setting \beta (the orientation of his detector) and the hidden variable has value \lambda.

I don't understand what the relevance of Alice's pre-knowledge is. If Alice has perfect knowledge about what Bob's result will be, that means, in terms of the model I gave, that:

P_B(B | A, \alpha, \beta, \lambda) = 0 or 1.

Since Bob doesn't know the value of A or \lambda, the relevant probabilities for him are:

P_B(B | \alpha, \beta) = \sum_\lambda \sum_A P_{hv}(\lambda) P_A(A | \alpha, \beta, \lambda) P_B(B | A, \alpha, \beta, \lambda)

Yes, it's possible for P_B(B | \alpha, \beta) = \frac{1}{2} even though P_B(B | A, \alpha, \beta, \lambda) = 0 or 1.

 

[Paul Colby]

I don't understand what you mean.

Sadly, this may hold for me as well. It appears possible for Alice and Bob to have multiple wave functions describing different states of knowledge about the two particles and have no contradictions (at least in my mind) between the two of them. I don't see that as being reflected in Bell's probability starting point though it may well be. It's also clear that Bell's stating point is not tenable from what's known about physics otherwise a $P_{hv}(\lambda)$ would exist. Well, I have to attend a wedding so duty calls.

 

[stevendaryl]

It's also clear that Bell's stating point is not tenable from what's known about physics otherwise a $P_{hv}(\lambda)$ would exist. Well, I have to attend a wedding so duty calls.

That's what Bell proved, that QM is not consistent with the sort of local theory that Einstein wanted. So you're agreeing with Bell, not disagreeing with him.

 

[stevendaryl]

Well, I have to attend a wedding so duty calls.

Have a good time, and best wishes to the happy couple.

 

[naima]

There are different kinds of locality, and people should distinguish them. The two most important kinds are signal locality and Bell locality.

Could you explain why Bell locality is not a signal locality? thanks

 

[Derek Potter]

Could you explain why Bell locality is not a signal locality? thanks

Let's see if anyone disagrees with this.

Bell locality means that A cannot affect B at spacelike separation.
Signal locality means that signals cannot be sent from A to B at spacelike separation.
Signalling has a precise meaning which is explained nicely in No-communication theorem

Obviously, Bell locality implies signal locality.
However signal locality does not imply Bell locality.

Signal locality is not invoked in the derivation of Bell's theorem. Neither does the theorem imply that signal locality is broken. The only reason for worrying about it is that if it were broken, both QM and special relativity would be broken too. So it is useful to make sure that when anyone talks about entanglement and non-locality, it means Bell non-locality.

 

[Demystifier]

Could you explain why Bell locality is not a signal locality? thanks

As Derek Potter said, it is possible to have signal locality without Bell locality.

 

[martinbn]

Bell locality means that A cannot affect B at spacelike separation.

This is not clear to me. What does it mean "to affect", given that there is no signaling? To me "to affect" means that A is the cause (or part of the cause) of B. If we exclude magic how does that work without signaling?

 

[DrAupo1]

Regardless of the experiments trying to prove subjective reality,versus objective reality,one thing seems to be overlooked:The internal mechanism by which we observe the results of any experiment.The human brain.There are processes within our brain that are not entirely understood,and some would argue are happening on a quantum level.I think we will never truly understand our own brain..if it were that simple,we would be too simple to comprehend it.We cannot be truly objective in our observations because we are imprisoned within our own subjective reality,thus all results,are perceived subjectively,even those that appear to be objective.The only way to observe total objective reality is to not exist in this dimension of space time.It is an intractable problem from our position.You cannot start by assuming that you do not exist.

 

[Derek Potter]

I'm guessing you didn't read the link I provided.
Signalling involves passing data from an external source to B via A. A making up random or uncontrollable data and sending it to B is therefore not signalling.

 

[martinbn]

I'm guessing you didn't read the link I provided.
Signalling involves passing data from an external source to B via A. A making up random or uncontrollable data and sending it to B is therefore not signalling.

I assume that was addressed to me. I did read and I am familiar with the theorem. But my questions is: what does it mean to affect if there is no signaling? The question is just about the terminology, to affect means what exactly?

 

[Derek Potter]

Regardless of the experiments trying to prove subjective reality,versus objective reality,one thing seems to be overlooked:The internal mechanism by which we observe the results of any experiment.The human brain.There are processes within our brain that are not entirely understood,and some would argue are happening on a quantum level.I think we will never truly understand our own brain..if it were that simple,we would be too simple to comprehend it.We cannot be truly subjective in our observations because we are imprisoned within our own subjective reality,thus all results,are
perceived subjectively,even those that appear to be objective.The only way to observe total objective reality is to not exist in this dimension of space time.It is an intractable problem from our position.You cannot start by assuming that you do not exist.

That is just metaphysical sophistry. The discussion here is about what actually happens - as verifiable in the laboratory. I could spend/waste days discussing thje objective/subjective boundary but a) it is quite unnecessary b) it is irrelevant to this topic and c) it would be against forum policy and would get the thread closed immediately by the mods.

 

[Demystifier]

This is not clear to me. What does it mean "to affect", given that there is no signaling? To me "to affect" means that A is the cause (or part of the cause) of B. If we exclude magic how does that work without signaling?

Signal is an affect controlled by a human. It is possible to have an affect which cannot be controlled by a human, in which case we have affect without signaling. See also
https://www.physicsforums.com/threa...ctual-definiteness.847628/page-2#post-5319182

 

[martinbn]

Signal is an affect controlled by a human. It is possible to have an affect which cannot be controlled by a human, in which case we have affect without signaling. See also
https://www.physicsforums.com/threa...ctual-definiteness.847628/page-2#post-5319182

A star emits light, which melts a comet. No humans involved, still there is signaling.

 

[Demystifier]

A star emits light, which melts a comet. No humans involved, still there is signaling.

No, it would not be called signaling.

 

[Derek Potter]

I assume that was addressed to me. I did read and I am familiar with the theorem. But my questions is: what does it mean to affect if there is no signaling? The question is just about the terminology, to affect means what exactly?

My apologies, I overlooked that you are a science advisor.

"Exactly"? I hope you are using that term colloquially. It is no use asking me for a formal definition of anything.

Informally, it means that events at A can cause events at B even though it is impossible for external data to control A so that B receives the message. So A and B can, for instance, agree about a random variable. That's not signalling as C cannot control it and so cannot control the result on B.

 

[martinbn]

No, it would not be called signaling.

I see. But isn't this a non-standard use of terminology?

My apologies, I overlooked that you are a science advisor.

Sorry, I didn't mean to be patronizing.

"Exactly"? I hope you are using that term colloquially. It is no use asking me for a formal definition of anything.

Informally, it means that events at A can cause events at B even though it is impossible for external data to control A so that B receives the message. So A and B can, for instance, agree about a random variable. That's not signalling as C cannot control it and so cannot control the result on B.

That's how I understood the meaning of "affect". But then if A and B are spacelike, how can A cause anything at B?

 

[Demystifier]

I see. But isn't this a non-standard use of terminology?

Maybe, maybe not. For instance, wikipedia at
https://en.wikipedia.org/wiki/Signal_(electrical_engineering)
says:
"Definitions specific to sub-fields are common. For example, in information theory, a signal is a codified message, that is, the sequence of states in a communication channel that encodes a message."

It does not define "communication" and "message", but those words sound quite anthropomorphic to me.

 

[Derek Potter]

A star emits light, which melts a comet. No humans involved, still there is signaling.

Humans don't have to be involved. The question is whether we could in principle send a message using A's effect on B. Humans are in effect a placeholder for a system which is the source of a message. so unless you postulate some way of controlling the radiation externally, there is no signalling. An alien race hurling planets into the star to create solar flares thereby communicating with a bug living on the comet would qualify as signalling.

This stuff is not very difficult (proof: I can understand it. QED) The only point in discussing it at all is to allay any concerns that entanglement might break relativity.

 

[LaserMind]

Think of entangled particles like two alternating flashing pixels on a screen.

Neither pixel has any information about its position yet when one is red the other is green and vica-versa.

They do not signal each other at all and have no knowledge of each other's state (color) yet their color-flashing behavior is perfectly correlated and instantaneous.

 

[Demystifier]

But then if A and B are spacelike, how can A cause anything at B?

E.g. by not being described by a hyperbolic partial differential equation. Then what equation is relevant? Nobody knows for sure, but one well known possibility is the equations of Bohmian mechanics. They are non-local, in a sense similar to equations of non-relativistic Newtonian gravity.

 

[martinbn]

E.g. by not being described by a hyperbolic partial differential equation. Then what equation is relevant? Nobody knows for sure, but one well known possibility is the equations of Bohmian mechanics. They are non-local, in a sense similar to equations of non-relativistic Newtonian gravity.

Yes, that's a possibility. But that would be signaling with infinite speed (or at least with no bounded speed). So why would that be called [insert adjective]-locality?

That's is still my confusion. The distinction between signal locality and Bell locality. It seems that better words would be simply locality and non-locality. Yet, it seems that there is some kind of Freudian distinction between non-locality and Bell-locality. Where the second one has some kind of causal relation ( things at A affect those at B) but it is done without any local interaction (which is what I thought signaling means).

 

[Derek Potter]

Think of entangled particles like two alternating flashing pixels on a screen.
Neither pixel has any information about its position yet when one is red the other is green and vica-versa.
They do not signal each other at all and have no knowledge of each other's state (color) yet their color-flashing behavior is perfectly correlated and instantaneous.

And Bell proved that if you simulate spacelike separation, what you describe cannot be achieved.

 

[martinbn]

Think of entangled particles like two alternating flashing pixels on a screen.

Neither pixel has any information about its position yet when one is red the other is green and vica-versa.

They do not signal each other at all and have no knowledge of each other's state (color) yet their color-flashing behavior is perfectly correlated and instantaneous.

Sure, but neither affects the other i.e. neither causes the other to flash a certain colour.

 

[Derek Potter]

Sure, but neither affects the other i.e. neither causes the other to flash a certain colour.

And there can be no common cause if spacelike separation is present or simulated.

 

[Ilja]

Well, you say, Bell non-local experiments are evidence for non-local cause. Bell non-locality is not an interaction in the same sense as passing a signal. It's not a non-local interaction in this sense. It's more like precognition.

The point is a different one.

In Bell's theorem, we have a 100% correlation and exclude, via the violation of Bell's inequality, that it may be explained by a common cause in the past. $C\to A$ and $C\to B$. This leaves two explanations: $A\to B$ and $B\to A$. Above would violate Einstein causality.

But any correlation which has two such explanations cannot be used to send information, nor from A to B, nor from B to A, because this would be in contradiction with one of the two remaining explanations.

So, it is our situation, our imperfect knowledge, which makes the difference. We don't know which explanation is the correct one. One may be the correct one. And there may be, on the unknown, fundamental level, as well a usual signal, with some finite speed, simply a larger one than c, nothing more "nonlocal" than our existing theories.

 

[martinbn]

And there can be no common cause if spacelike separation is present or simulated.

Yes, but you state that they can affect each other in some other way without sending signals.

 

[stevendaryl]

I assume that was addressed to me. I did read and I am familiar with the theorem. But my questions is: what does it mean to affect if there is no signaling? The question is just about the terminology, to affect means what exactly?

The difference has to do with what variables governing a situation are visible, and what variables are controllable. For Alice to signal Bob, it must be the case that variables that are controllable by Alice can affect variables that are visible to Bob. You can have effects without signals if the variables controllable by Alice only affect variables that are not visible to Bob.

Let me illustrate this with an EPR-inspired example:

We have a pair of devices, one belonging to Alice and one belonging to Bob, each with the following features:

• It has a dial that can be set to any value between 0 and 2 \pi.
• It has an internal memory that can store a real number between 0 and 1. Initially, the value is 1/2.
  
• It has a light bulb that can either be on or off.
• It has a button that can be pressed.

Let P_A be the internal value for Alice's device, and let P_B be the internal value for Bob's device, and let \alpha be the dial setting for Alice's device, and let \beta be the dial setting for Bob's device. When Alice pushes the button on her device,

• With probability P_A, her light comes on, and Bob's device's internal variable is set to f(\alpha, \beta).
• With probability 1 - P_A, her light goes off, and Bob's device's internal variable is set to 1 - f(\alpha, \beta)

When Bob pushes his button,

• With probability P_B, his light comes on, and Alice's device's internal variable is set to f(\alpha, \beta).
• With probability 1 - P_B, his light goes off, and Alice's device's internal variable is set to 1 - f(\alpha, \beta)

So in this set-up, Alice pushing the button affects Bob's device: it causes the internal variable to change values. But she cannot control what value it changes to. The only thing that Alice controls is her setting \alpha, and the only things that are visible to Bob are his own setting and the light bulb state. Based just on what's visible, Bob cannot deduce anything about Alice's setting, so it's not possible for Alice to signal to Bob.

The distinction between "affecting" and "signaling" depends on some variables being "hidden"---not visible or directly controllable.

 

[Derek Potter]

Yes, but you state that they can affect each other in some other way without sending signals.

I didn't say quite that. I said that even if they affect each other (Bell non-locality) - perhaps by sending something that we can't control - it doesn't automatically mean we can send signals (signal non-locality).

 

[Derek Potter]

the two remaining explanations

Do you mean non-causality and non-definiteness etc?

 

[Paul Colby]

In Bell's theorem, we have a 100% correlation and exclude, via the violation of Bell's inequality, that it may be explained by a common cause in the past. C→AC→AC\to A and C→BC→BC\to B. This leaves two explanations: A→BA→B A\to B and B→AB→AB\to A. Above would violate Einstein causality.

Thanks for the clarity. I really haven't invested enough time becoming familiar with these concepts. So, one may construct purely classical examples for which $A\rightarrow B$ and $\rightarrow A$ isn't a violation and isn't a mystery. From my perspective the issues aren't in some apparent non-local "cause" since the quantum and classical examples are no different in regard to correlations of space-like separated measurements. The conceptual problems arrises because one or more components of QT are taken as what Bell referred to as beables which they clear are not. These problems are cooked into QM from the get go and are very likely have no classical resolution.

 

[Simon Phoenix]

In a probably misguided attempt to cut through all the philosophical and technical jargon I tend to try to look at these issues in rather simple terms.

In essence I think it would be a very strange theory of physics in which the results (statistics) of an experiment 'here' were affected by the settings of measurement devices 'there' - irrespective of whether here and there were spacelike separated. I do not really care whether this is technically known as 'Bell locality' or 'Einstein locality' or the locality dreamt up by my Aunt Doris.

Given that entanglement is a pretty ubiquitous phenomenon in QM (pretty much every interaction of 2 quantum systems leads to entanglement) then we can imagine hundreds, if not thousands, of different measurements, experiments and measurement devices that we could employ to demonstrate entanglement via a violation of some suitable 'Bell' inequality.

Are we to require a theory of physics in which every single possible variant of measurement and measurement device had this property that settings 'there' affect results 'here'? How do our devices and systems here even 'know' about what's happening 'there'? Is there some mystical field or potential that (in effect) transmits this information in the same kind of way for every conceivable experimental test or measurement device? Whether this (in effect) information transfer is happening slower or faster than light speed, I think that's stretching credulity a little too far for my tastes.

So, in a nutshell, we can have a theory in which we have so-called hidden variables that possesses this 'realistic' character we're used to from the variables of classical physics - but in order to make it work we have to have something that, in effect, transfers information about device settings from 'there' to 'here'. My own personal view is that the violation of 'locality' in the sense I've outlined above is a much weirder thing than the violation of 'realism'.

The dBB theory is such a theory - personally I find it weirder than QM with its complex guiding potential and non-local character. But as I guess after dicking about with a ton of unwieldy equations it gives the same answers as plain old vanilla QM then dispensing with 'realism' or 'locality' in one's metaphysical view of nature is largely a matter of personal preference.

 

[LaserMind]

I ask a question: could I write a program that simulates two pixels as entangled?

The pixels themselves have no influence on each other. All the influence is done behind the scenes by simple code.

Does that contradict Bells somehow?

 

[DrChinese]

I ask a question: could I write a program that simulates two pixels as entangled?

The pixels themselves have no influence on each other. All the influence is done behind the scenes by simple code.

You can write a program that simulates Bell for the so-called "perfect" correlations. But not for correlations at all angles. The cos^2(theta) rule can't be simulated for all pairings for randomized settings of measurements by Alice and Bob. Specifically, for Alice and Bob randomly (and independently) selecting as their measurement angles 0, 120 and 240 degrees: you will end up with wrong percentages as N gets larger. With a computer simulation, that is.

 

[Paul Colby]

I ask a question: could I write a program that simulates two pixels as entangled?

If your pixel observables commute you can.

 

[Derek Potter]

I ask a question: could I write a program that simulates two pixels as entangled?
The pixels themselves have no influence on each other. All the influence is done behind the scenes by simple code.
Does that contradict Bells somehow?

Obviously you could simulate entanglement. Just use the formulae that Dr Chinese has posted.

However it would not and cannot contradict Bell if you properly simulate the spacelike separation and fulfil the conditions stipulated in Bell's theorem.

Note that "behind the scenes" pretty well gives the game away. You would be using non-local variables. If you avoided that and kept everything else correct you would not be able to create the required correlations. A theorem is a theorem.

For a suggested protocol that avoids information leaking from one data set to another, try the Quantum Randi Challenge. https://arxiv.org/abs/1207.5294

 

[LaserMind]

Obviously you could simulate entanglement. Just use the formulae that Dr Chinese has posted.

However it would not and cannot contradict Bell if you properly simulate the spacelike separation and fulfil the conditions stipulated in Bell's theorem.

Note that "behind the scenes" pretty well gives the game away. You would be using non-local variables. If you avoided that and kept everything else correct you would not be able to create the required correlations. A theorem is a theorem.

For a suggested protocol that avoids information leaking from one data set to another, try the Quantum Randi Challenge. https://arxiv.org/abs/1207.5294

I am thinking about using spots on a computer screen to simulate entanglement of particles in space. Could I do it or would it contradict Bells?
It would have a button that when clicked then pairs of spots would reveal their correlated states (I would
random number generator to set the color of one particle (spot) exactly when its clicked and its partner's
from one color's code to give the other color).

If I can do that without disobeying some law then isn't it a pretty good simulation of what we have in real life?

 

[DrChinese]

I am thinking about using spots on a computer screen to simulate entanglement of particles in space. Could I do it or would it contradict Bells?
It would have a button that when clicked then pairs of spots would reveal their correlated states (I would
random number generator to set the color of one particle (spot) exactly when its clicked and its partner's
from one color's code to give the other color).

If I can do that without disobeying some law then isn't it a pretty good simulation of what we have in real life?

First, you should really start a new thread to discuss simulating entanglement via code.

Second, there are a number of past threads on this subject too.

Third, you should thoroughly understand the issues involved BEFORE you further take up anyone's time. There is no problem with measurements at the same angle (assuming you use spin or polarization as an observable). It is other angles that have a problem, and you are apparently unaware of the QM rules there.

Actually, I guess I have the order of the above exactly reversed.

 

[Derek Potter]

I am thinking about using spots on a computer screen to simulate entanglement of particles in space. Could I do it or would it contradict Bells?
It would have a button that when clicked then pairs of spots would reveal their correlated states (I would
random number generator to set the color of one particle (spot) exactly when its clicked and its partner's
from one color's code to give the other color).
If I can do that without disobeying some law then isn't it a pretty good simulation of what we have in real life?

But that is not what entanglement means. It's a lot more complicated than just a correlation. See Dr Chinese's earlier post. And even the Alice and Bob scenario where there is perfect anti-correlation only occurs if they chose their detector orientations to be the same. You don't even have anything corresponding to their detector angles. And even that perfect correlation doesn't illustrate entanglement because it doesn't violate Bell's inequality - you can explain it with a contrived classical explanation. Only when you have the whole lot can you claim to be simulating entanglement. And you won't be able to do that without having some behind the scenes non-locality. In other words you'll be able to simulate quantum results only by cheating on the conditions.

 

[Ilja]

Do you mean non-causality and non-definiteness etc?

No, as described after the : sign, a direct causal influence $A\to B$, or, alternatively, $B\to A$.

Counterfactual definiteness is not an assumption, but derived from the EPR argument. And to reject causality is not an explanation, it means to reject the very idea to search for explanations. Without causality we are back to astrology. (Not exactly, even astrologers have searched for explanations).