Testing whether entanglement is a matter of information or non-local?

[Imafungi]

First, no one actually understands the underlying mechanism by which entanglement works. That is why there are multiple interpretations. From 1935 until Bell's Theorem, your local realistic explanation was considered one possible interpretation (the EPR interpretation for lack of a better name).

However, Bell showed that interpretation to be flawed. The EPR interpretation has since been proven incorrect many times over in experiment. Until you read and understand Bell, you won't make any progress towards understanding WHY the EPR interpretation is wrong. Better yet, read the EPR paper first and then Bell.

BTW: In QM, the ordering of the measurements on Alice and Bob (particles 1 and 2) do not affect the outcome in any discernible fashion.

Bells theorem doesn't say anything about this more intuitive and rational interpretation being impossible, do you have an example of an experiment or logical argument which proves this analogy is not appropriate in regards to 'quantum entanglement experiments'?:


There is a red ball and a blue ball. You and I are in another room blindfolded. A random person walks in the room with the red ball and blue ball and puts each in a bag. You and I walk in the room and each grab a bag. I go to the moon. You stay there. We know without looking that the results will be 1 red ball and 1 blue ball. I look in my bag on the moon, and its the blue ball. I instantly know that your ball is the red ball.

If this analogy can be used to describe every entanglement experiment, the analogy would be related to the 'spooky entanglement interpretation'; I got my bag and you get your bag. I go to the moon. Before I or your look in our bags, I have a red/blue ball in my bag, and you have a red/blue ball in your bag. When the bags were in the same room before they were separated, they were entangled. When I looked in my bag the red/blue ball turned into a blue ball, which then faster than the speed of light, notified your red/blue ball to turn into a red ball.

 

[stevendaryl]

There is a red ball and a blue ball. You and I are in another room blindfolded. A random person walks in the room with the red ball and blue ball and puts each in a bag. You and I walk in the room and each grab a bag. I go to the moon. You stay there. We know without looking that the results will be 1 red ball and 1 blue ball. I look in my bag on the moon, and its the blue ball. I instantly know that your ball is the red ball.

That's exactly the sort of explanation for entanglement that Bell proved doesn't work (at least not without faster-than-light communication). In your analogy, there is only one question: "Is the ball red, or is it blue?" The answer for one ball has to be the opposite of the answer for the other ball, and you can certainly come up with a "hidden variable" explanation, namely the color of the ball is determined from the beginning, and it never changes.

In the quantum case, there are many different questions you can ask about an entangled particle. Specifically, for any direction $\vec{D}$, you can ask (of an electron): Does the electron has spin-up in direction $\vec{D}$, or spin-down?

If you produce an entangled electron/positron pair, and send the electron to one experimenter, Alice, and send the positron to the other experimenter, Bob, then the predictions of quantum mechanics are:

1. No matter what direction $D_A$ that Alice picks, she gets spin-up half the time, and spin-down half the time.
2. Similarly for and direction $D_B$ that Bob picks.
3. However, the probability that both measure the same result (up or down) is $cos^2(\theta/2)$, where $\theta$ is the angle between Alice's direction and Bob's direction.

[edit: I should have written $sin$ instead of $cos$ in that expression]

It's not immediately obvious, but there is no way to explain this correlation--that $cos^2(\theta/2)$--using a hidden-variable explanation. That's what Bell proved. So you were just not correct in saying:

Bells theorem doesn't say anything about this more intuitive and rational interpretation being impossible

 

[Imafungi]

That's exactly the sort of explanation for entanglement that Bell proved doesn't work (at least not without faster-than-light communication). In your analogy, there is only one question: "Is the ball red, or is it blue?" The answer for one ball has to be the opposite of the answer for the other ball, and you can certainly come up with a "hidden variable" explanation, namely the color of the ball is determined from the beginning, and it never changes.

In the quantum case, there are many different questions you can ask about an entangled particle. Specifically, for any direction $\vec{D}$, you can ask (of an electron): Does the electron has spin-up in direction $\vec{D}$, or spin-down?

Yes, red or blue was my analogy for spin up or spin down.

I haven't seen any evidence that has led me to believe that when 'entangled particles are created', two particles with completely distinct properties arent created, which maintain their properties until measurement.

I asked in a follow up question to my original analogy, something which would force me to consider non locality and your spooky action interpretation of entanglement, which is:


When the first particle is measured, and the second particle is not measured. When the first particle is measured, at that instant does the second particle alert a system of its state? As in, is it in a superposition in some apparatus either just vibrating in place or traveling around in a circle, and then the first particle is measured, and that second particle just instantly finds the nearest detector to exclaim to the experimenters that its entangled pair had been measured?

Or do the experimenters have to measure the second particle by themselves after the first is measured?

 

[Nugatory]

Bells theorem doesn't say anything about this more intuitive and rational interpretation being impossible, do you have an example of an experiment or logical argument which proves this analogy is not appropriate in regards to 'quantum entanglement experiments'?:

Here's the entire logical process (which may have gotten lost in the details in some of the discussion above):

1) If the more intuitive and rational interpretation is correct, then Bell's inequality must hold. That's the "theorem" part; Bell's theorem proves that if the result of an observation is determined solely by the properties of the observed object (no quantum spookiness, we find a red ball in the bag when open it because the ball was red all along) the inequality must hold. To get an interesting example we have to be looking at more than one property of the balls - we'd extend the analogy to say that not only is one ball blue and the other red, but also one ball is made of wood and the other of plastic, one ball has a white stripe painted on it and the other doesn't. The intuitive model that you're thinking about says that when we open the bag and find a red plastic ball with no stripe, it's because we put a red plastic ball with no stripe into the bag so that's what was there all along and the other bag must contain a blue wooden ball with a stripe.

2) Under certain conditions, quantum mechanics predicts results in which the inequality will be violated. . Therefore, either the inequality is never violated and quantum mechanics is wrong; or the inequality is sometimes violated and the intuitive/rational explanation is wrong. It's not possible for the intuitive/rational explanation to be correct and for the inequality to be violated.

3) In actual experiments the inequality is violated.. Therefore, the intuitive/rational explanation cannot be correct.

 

[bhobba]

Bells theorem doesn't say anything about this more intuitive and rational interpretation being impossible, do you have an example of an experiment or logical argument which proves this analogy is not appropriate in regards to 'quantum entanglement experiments'?:

Bells theorem rules out naive reality:
http://en.wikipedia.org/wiki/Naïve_realism
'Bell's theorem proved that every quantum theory must either violate local realism or counterfactual definiteness.'

Local realism and counterfactual definiteness are, by definition, the assumptions of naive realism.

You can retain one or the other - but not both.

Which do you want to get rid of? Personally I don't believe in either - but that's just me.

This is VERY well known.

Thanks
Bill

 

[Nugatory]

first particle is measured, at that instant does the second particle alert a system of its state? As in, is it in a superposition in some apparatus either just vibrating in place or traveling around in a circle, and then the first particle is measured, and that second particle just instantly finds the nearest detector to exclaim to the experimenters that its entangled pair had been measured?

Or do the experimenters have to measure the second particle by themselves after the first is measured?

We always have to measure both particles.

In fact, we cannot even detect the entanglement until after we compare the results from both sides. We set up our two detectors, you sit at yours and I sit at mine, and we record the state of the particles that come by. You'll see some spin-up and some spin-down and so will I, and it'll be as random as if we were each flipping our own coin and recording heads/tails.

Then we get together and compare notes. At exactly noon, you saw a spin-up particle and I saw a spin-down one - interesting, but we'd expect that to happen one in every four times if we were just flipping coins so it's no great surprise. Then we see that at three seconds past noon, you and I both detected particles, and one was up and one was down... And a few seconds after that we both detected particles again, and again one was up and the other down... And slowly the pattern emerges.

 

[bhobba]

Science cannot exist without philosophy when considering generally 'philosophy' is 'to think'.

Scratching my head about that. Here is its definition: 'the study of the fundamental nature of knowledge, reality, and existence, especially when considered as an academic discipline.'

Its not 'to think', its to think in a certain way about certain issues. Just like the other fundamental science concerned with logic - mathematics - is also about thinking - but thinking about certain issues in its own way.

There is a well known 'conflict' between science and philosophy that IMHO illustrates the point. The very influential philosopher Kant said Euclidean geometry was a priori. Kant was a great philosopher and his view held a strong sway. However the equally as great mathematician, and mathematical physicist, Gauss, found otherwise. But the climate at the time was such he held off publishing because it would have meant going up against Kant.

Here is a bit of fiction illustrating the view at the time:
http://www.ralphmag.org/EQ/gauss-kant.html

But truth can't be denied, and Kant was wrong. In general in 'conflicts' between philosophers and science, science is usually proven correct. Indeed philosophers generally don't agree on anything, whereas scientists agree on quite a lot.

I think Wienberg sums the view up quite well:
https://www.google.com.au/url?sa=t&...-4DgDQ&usg=AFQjCNHg_elaIirwh-1Q7Al_kVaI8Fz8YA

Thanks
Bill

 

[stevendaryl]

Yes, red or blue was my analogy for spin up or spin down.

I haven't seen any evidence that has led me to believe that when 'entangled particles are created', two particles with completely distinct properties arent created, which maintain their properties until measurement.

That's what Bell's proof shows, that such an interpretation of entanglement doesn't work (at least, not without faster-than-light influences).

When the first particle is measured, and the second particle is not measured. When the first particle is measured, at that instant does the second particle alert a system of its state? As in, is it in a superposition in some apparatus either just vibrating in place or traveling around in a circle, and then the first particle is measured, and that second particle just instantly finds the nearest detector to exclaim to the experimenters that its entangled pair had been measured?

Or do the experimenters have to measure the second particle by themselves after the first is measured?

The timing of the two measurements is pretty arbitrary. You produce an electron/positron pair, Alice at some later point measures the spin of the electron. Bob later measures the spin of the positron. The correlations don't depend on the order of the measurements, or the timing. Bob might not perform his measurement until long after Alice performs hers.

When you are asking for "evidence" for something, do you mean an experiment that doesn't require you to do any math to understand the result? The idea that entanglement can be explained by pre-existing properties of the two particles sounds plausible, and you have to actually do some math to see that it doesn't work out.

For example, let's try to explain the EPR results assuming that electrons and positrons have actual spins that point in some direction. When a correlated pair is created, the two spin directions are opposite: The electron's spin is in some random direction $\vec{S_e}$ and the positron's spin is in the opposite direction $\vec{S_p} = - \vec{S_e}$. That's simple enough.

Now, we have to account for the fact that no matter what spin direction Alice decides to measure, she finds either spin-up or spin-down. So even though the spin can point in any direction, there are only two possible measurement results. How is that possible? Well, you can assume that if the electron's spin is in direction $\vec{S_e}$, and Alice measures the spin in direction $\vec{D_A}$, then Alice will measure spin-up if the angle between those is less than 90 degrees, and will measure spin-down if the angle is more than 90 degrees.

Similarly, if Bob measures the spin in direction $\vec{D_B}$, and the positron has spin $\vec{S_p}$, then he will measure spin-up if the angle between those is less than 90 degrees, and spin-down if the angle is more than 90 degrees.

That explains the perfect anti-correlation: If Alice and Bob both choose the same direction: $\vec{D_A} = \vec{D_B}$, then they always get opposite results. Great!

But what if they choose slightly different angles? Then this model predicts that the probability that Alice and Bob get the same result (both spin-up or both spin-down) is $\theta/180$, where $\theta$ is the angle between $D_A$ and $D_B$ (in degrees). The QM prediction is $sin^2(\theta/2)$. The two predictions aren't the same. QM predicts a much STRONGER correlation than this model.

So this particular model doesn't work. How do you know a variant won't work? That's really what mathematics is good at: proving something about an infinite number of possibilities without checking each possibility individually.

 

[stevendaryl]

There is a well known 'conflict' between science and philosophy that IMHO illustrates the point. The very influential philosopher Kant said Euclidean geometry was a priori. Kant was a great philosopher and his view held a strong sway. However the equally as great mathematician, and mathematical physicist, Gauss, found otherwise. But the climate at the time was such he held off publishing because it would have meant going up against Kant.

Hmm. Whether it was a philosophical argument, or not, it seems that if Kant had an argument showing that non-Euclidean geometry is impossible, then the argument was wrong. He made a mistake in the argument, somewhere. I don't see how that is an indictment against philosophy in particular, except that they need to tighten up their standards for rigor of arguments.

 

[bhobba]

I haven't seen any evidence that has led me to believe that when 'entangled particles are created', two particles with completely distinct properties arent created, which maintain their properties until measurement

That's the assumption of reality, which in this context means properties exist prior to measurement.

Specifically Bells theorem shows you can't have local reality and counterfactual definiteness. Counterfactural definiteness is the outcome can be computed. Locality means influences can't travel faster than light.

You can reject anyone on those three things - but you can't have them all - with a caveat I will mention later.

For example Bohmian mechanics rejects locality, but has counterfactual definiteness and reality.

I hold to the statistical ensemble interpretation which rejects both realism and counterfactural definiteness but keeps locality - here locality means locality in the sense of QFT otherwise known as the cluster decomposition property - which states - as per Wienberg in his famous QFT text - 'It is one of the fundamental principles of physics (indeed, of all science) that experiments that are sufficiently separated in space have unrelated results…'. Specifically this refers to uncorrelated systems - Bell theorem refers to correlated systems.

Others have other takes.

It even possible to have all three if you believe QM is an approximation to some deeper theory eg primary state diffusion is a theory of this type.

In discussions of this type Bell came up with the Bertlmann's socks analogy:
http://thelifeofpsi.com/2013/10/28/bertlmanns-socks/

Added Later:

I forgot to add counterfactual definiteness and reality are closely related - but are subtly different. I think most would accept or reject both together. I certainly would because I simply can't get my mind around the idea you can compute the outcome of an observation and it in some sense doesn't exist before the observation. I suppose its possible, but its a pretty subtle sort of difference. Also some seem to weaken realism to not being determined by a conscious observer.

Thanks
Bill

 

[DrChinese]

Bells theorem doesn't say anything about this more intuitive and rational interpretation being impossible, do you have an example of an experiment or logical argument which proves this analogy is not appropriate in regards to 'quantum entanglement experiments'?:


There is a red ball and a blue ball. You and I are in another room blindfolded. A random person walks in the room with the red ball and blue ball and puts each in a bag. You and I walk in the room and each grab a bag. I go to the moon. You stay there. We know without looking that the results will be 1 red ball and 1 blue ball. I look in my bag on the moon, and its the blue ball. I instantly know that your ball is the red ball.

If this analogy can be used to describe every entanglement experiment, the analogy would be related to the 'spooky entanglement interpretation'; I got my bag and you get your bag. I go to the moon. Before I or your look in our bags, I have a red/blue ball in my bag, and you have a red/blue ball in your bag. When the bags were in the same room before they were separated, they were entangled. When I looked in my bag the red/blue ball turned into a blue ball, which then faster than the speed of light, notified your red/blue ball to turn into a red ball.

It is clear you haven't read Bell (1964) at all, since your analogy is precisely what it was meant to address. The EPR (1935) paper used a similar example as yours. I assume you have not read it either, since that was what Bell was responding to. And experiments such as Aspect et al (1982) confirm that local realism (your analogy) can be ruled out. See the links on this page:

http://www.drchinese.com/David/EPR_Bell_Aspect.htm

If you would like a simple explanation of how Bell's Theorem rules out hypotheses such as yours, the following is about as easy as it gets:

http://www.drchinese.com/David/Bell_Theorem_Easy_Math.htm

The short version is that your analogy works fine for red/blue balls. No one disputes that, and that is why EPR stood for 30 years. Bell realized the analogy failed with certain pairs of measurements. In your analogy: red balls and balls that are a mixture of 1/3 red and 2/3 blue. QM makes accurate predictions for these variations, while local realistic theories make inconsistent predictions. This is because local realistic theories have a requirement that QM does not: the outcome of a measurement on Alice must be completely independent of the nature of a measurement performed on Bob in another location.

 

[DrChinese]

I asked in a follow up question to my original analogy, something which would force me to consider non locality and your spooky action interpretation of entanglement, which is:

When the first particle is measured, and the second particle is not measured. When the first particle is measured, at that instant does the second particle alert a system of its state? As in, is it in a superposition in some apparatus either just vibrating in place or traveling around in a circle, and then the first particle is measured, and that second particle just instantly finds the nearest detector to exclaim to the experimenters that its entangled pair had been measured?

Or do the experimenters have to measure the second particle by themselves after the first is measured?

You are asking a question no one knows the full answer to. It is "possible" that measurement of Alice affects Bob non-locally via an instantaneous change. There are other interpretations that explain the situation too. In the Bohmian Mechanics view, there is a pilot wave which influences both particles instantaneously and that is the common cause.

 

[bhobba]

I don't see how that is an indictment against philosophy in particular, except that they need to tighten up their standards for rigor of arguments.

That is the exact problem with philosophy - their arguments are so tight just about every philosopher believes something different and the others need to tighten up their arguments :tongue::tongue::tongue::tongue:.

The issue is they can't or don't want to use that final arbiter - experiment.

Thanks
Bill

 

[QuestionMarks]

The issue is they can't or don't want to use that final arbiter - experiment.

To be fair, a philosopher might also be a scientist. Historically, that's quite what natural philosophy was. Given this, your statement might be a bit disingenuous. Philosophy is quite useful wherein experimental capabilities do not currently exist or wherein one is attempting to determine which experimental route to pursue. Now in current culture, the tendency you mention might exist, but as stevendaryl said, I wouldn't see that as an indictment against philosophy itself (maybe just the trending people who do it).

I think we should resist that line of dialogue though. The value of philosophy is a bit off-topic and could easily I imagine spurn a whole other quite heated thread. Such questions of value are a bit philosophical themselves, and thus maybe not quite kosher forum rules. I do think Imafungi's questioning is a bit more related to the OP, which albeit was answered, may help others gain more insight.

 

[Imafungi]

1) If the more intuitive and rational interpretation is correct, then Bell's inequality must hold. That's the "theorem" part; Bell's theorem proves that if the result of an observation is determined solely by the properties of the observed object (no quantum spookiness, we find a red ball in the bag when open it because the ball was red all along) the inequality must hold. To get an interesting example we have to be looking at more than one property of the balls - we'd extend the analogy to say that not only is one ball blue and the other red, but also one ball is made of wood and the other of plastic, one ball has a white stripe painted on it and the other doesn't. The intuitive model that you're thinking about says that when we open the bag and find a red plastic ball with no stripe, it's because we put a red plastic ball with no stripe into the bag so that's what was there all along and the other bag must contain a blue wooden ball with a stripe.

2) Under certain conditions, quantum mechanics predicts results in which the inequality will be violated. . Therefore, either the inequality is never violated and quantum mechanics is wrong; or the inequality is sometimes violated and the intuitive/rational explanation is wrong. It's not possible for the intuitive/rational explanation to be correct and for the inequality to be violated.

3) In actual experiments the inequality is violated.. Therefore, the intuitive/rational explanation cannot be correct.

Ok, I am with you on 1).

2). Is it not true the the quantum mechanical predictions that result in the inequality are based off of equations which include probabilities, in other words, equations infused with ignorances? And so you are saying from the vantage point of complex puzzles (equations) with missing pieces, a possible thought to have is that by bashing the puzzles together an outcome will occur which is different than the intuitive logic we are used to expecting from reality?

3). This is the step I am up to, and in the sense that I am asking; how exactly has an experiment disproven my analogy, in what exact way? Because so far I have only seen experiments which could be interpreted to be analogous with my analogy. I have not seen a reason to believe that in my analogy, what believers of spooky action at a distance are saying is, in that scenario with the bag, the real classical expression of that, in the bag would be a red/blue ball and a red/blue ball in the other, each in superposition, and when one is measured, it tells the other at faster than the speed of light to turn into the opposite color of the measured.

Which is why a follow up question I asked was; When the first particle is measured in an entangle experiment, does the second particle (without human interaction) alert the experimenters that its entangled partner has been measured?

Do you comprehend what I am trying to get at with this question? Because if the answer is no, is the answer that 'both particles no matter what order being measured, must be willfully observed by the experimenters at a time of their choice?

 

[Imafungi]

Bells theorem rules out naive reality:
http://en.wikipedia.org/wiki/Naïve_realism
'Bell's theorem proved that every quantum theory must either violate local realism or counterfactual definiteness.'

Local realism and counterfactual definiteness are, by definition, the assumptions of naive realism.

You can retain one or the other - but not both.

Which do you want to get rid of? Personally I don't believe in either - but that's just me.

This is VERY well known.

Thanks
Bill

I believe that just because we can't measure things exactly doesn't mean they don't exist exactly, moreover, they most probably/definitely do.

I believe it is impossible for reality to not be tautological. Logical, reality = reality. This is why/how math works at all. I believe at all times/time reality equals itself exactly. It is not only always locally real, but always foreignly real as well, it is always only real.

And counterfactual definiteness appears to be regarding how well a human can grasp the total truth of reality, and it appears that quite obviously it concludes a human may have trouble doing this. This is no reason to believe that because a human cannot fully describe the totality of reality at all times, that the totality of reality is not exactly the totality of reality at all times.

 

[Imafungi]

We always have to measure both particles.

In fact, we cannot even detect the entanglement until after we compare the results from both sides. We set up our two detectors, you sit at yours and I sit at mine, and we record the state of the particles that come by. You'll see some spin-up and some spin-down and so will I, and it'll be as random as if we were each flipping our own coin and recording heads/tails.

Then we get together and compare notes. At exactly noon, you saw a spin-up particle and I saw a spin-down one - interesting, but we'd expect that to happen one in every four times if we were just flipping coins so it's no great surprise. Then we see that at three seconds past noon, you and I both detected particles, and one was up and one was down... And a few seconds after that we both detected particles again, and again one was up and the other down... And slowly the pattern emerges.

If that is the case, then I do not know why it wouldn't be assumed that the particles when created were always their definite states, that when entangled particles are created 2 particles with opposite attributes are created?

The only reason I would suspect that this wouldn't be assumed, is because some people think that because equations say 'before you look at something you don't know what its qualities are', that means 'before you look at something a thing doesn't have qualities'.

 

[Imafungi]

Scratching my head about that. Here is its definition: 'the study of the fundamental nature of knowledge, reality, and existence, especially when considered as an academic discipline.'

Its not 'to think', its to think in a certain way about certain issues. Just like the other fundamental science concerned with logic - mathematics - is also about thinking - but thinking about certain issues in its own way.

There is a well known 'conflict' between science and philosophy that IMHO illustrates the point. The very influential philosopher Kant said Euclidean geometry was a priori. Kant was a great philosopher and his view held a strong sway. However the equally as great mathematician, and mathematical physicist, Gauss, found otherwise. But the climate at the time was such he held off publishing because it would have meant going up against Kant.

Here is a bit of fiction illustrating the view at the time:
http://www.ralphmag.org/EQ/gauss-kant.html

But truth can't be denied, and Kant was wrong. In general in 'conflicts' between philosophers and science, science is usually proven correct. Indeed philosophers generally don't agree on anything, whereas scientists agree on quite a lot.

I think Wienberg sums the view up quite well:
https://www.google.com.au/url?sa=t&...-4DgDQ&usg=AFQjCNHg_elaIirwh-1Q7Al_kVaI8Fz8YA

Thanks
Bill

I am truly sorry for being so general, I was originally considering saying 'to critically think', and I understand where you are coming from and why. I personally believe that philosophy is 'to think' about everything that can be thought about, and here is where you and even I must make the mark, that I understand there are an infinite combination of possible letters that can be made of the english alphabet and surely there would be no point in spending life times thinking of all those combinations, but I do view it in the sense of some type of absolute. That is to say; right now, and always, in an abstract way, the potential for all philosophic thought has existed. Surely it all cannot be achieved and realized in an instant, some has to be chipped away at for years and years, some needs to be realized before in order for others to (like the wheel needed to be made before the car) but anyway, I do believe the work of science requires thought, critical thought, philosophy. I believe science was born of philosophy, when pure idol thinking ran dry, and physical meddling began, but there needs to be valuable thought behind the meddling for the meddling to mean anything and matter, and that is why I made the statement I did.

 

[Imafungi]

That's what Bell's proof shows, that such an interpretation of entanglement doesn't work (at least, not without faster-than-light influences).

Where is the evidence of his proof though, is it not just an argument like my argument, it seems like circular logic, I can call my argument a proof and say it shows that such an interpretation of entanglement works, proving Bells proof wrong.

When you are asking for "evidence" for something, do you mean an experiment that doesn't require you to do any math to understand the result? The idea that entanglement can be explained by pre-existing properties of the two particles sounds plausible, and you have to actually do some math to see that it doesn't work out.

Since as it appears you have caught me red handed, why not work to my weaknesses and prove me wrong as plain and simply as possible? Or do you need bells and whistles and smoke and mirrors to make your beliefs right?

Ok, I tried to follow your math and I cant. So to just use two created entangled particles. When one is measured spin up, and the second is measured spin down. What is any experimental evidence that; When two entangled particles are created (before any measurement/observation) one of the entangled particles exists in a spin up state, and the second exists in a spin down state. What is the experimental evidence that says that physically is impossible? For a pair of entangled particles to be created that have exact and opposite states.

So far the only evidence I have seen of entanglement experiments are; 'The results of the experiments are that when measured the particles had opposite states'.

I am a very open minded, and skeptical, person. I want to know truth, why would I want to know anything other. I have no bias, I have no stake, I am honest to myself and others. I appreciate your effort in trying to explain to me mathematically why I am wrong, but I could not follow and so I am sorry.

Oh but I do believe I may have caught something; "The electron's spin is in some random direction and the positron's spin is in the opposite direction . That's simple enough"

According to what I am saying, they would not be in random directions, that's the whole point of my argument. I know we can only know in the hindsight is 20/20 way what the spins are after measuring. But you are trying to prove my argument wrong by using the style of ignorance I am arguing against. At least I think that's what seems to be the case.

 

[QuestionMarks]

Imafungi, I'm wondering if you should start a new thread for this? Seeing as you've posted quite a few replies in succession here and that the OP is answered, maybe this would allow restructuring of your question in a more consolidated format?

I think a sufficient answer to you though can be found from reading stevendaryl's comment, which I haven't seen you respond to directly. You analogy's predictions would be different from those of QM, and those of QM have won experimentally. If you want the name of the experiment, I'm not familiar enough historically with which one is the best to show this.

Also, chugging through the EPR and Bell's topics are something you really should do, and depending on which reading you do on Bell, you may get to see the experiments there. I don't remember seeing you respond to DrChinese on that. That will help put you a bit more on the same page with the discussion you're seeing.

 

[bhobba]

I believe that just because we can't measure things exactly doesn't mean they don't exist exactly, moreover, they most probably/definitely do.

Why do you believe that?

Science is about correspondence with experiment, not what you believe.

So exactly what QM experiments lead you to that view? There are many experiments that suggest its in deep trouble, such as the double slit experiment where no one has been able to figure out how to predict what position the particle or photon will be detected at. So, not based on a gut feeling, your belief, philosophical waffle about determinism, yada, yada, yada, exactly why do you believe that?

Thanks
Bill

 

[Nugatory]

3). This is the step I am up to, and in the sense that I am asking; how exactly has an experiment disproven my analogy, in what exact way? Because so far I have only seen experiments which could be interpreted to be analogous with my analogy. I have not seen a reason to believe that in my analogy, what believers of spooky action at a distance are saying is, in that scenario with the bag, the real classical expression of that, in the bag would be a red/blue ball and a red/blue ball in the other, each in superposition, and when one is measured, it tells the other at faster than the speed of light to turn into the opposite color of the measured.

To see the quantum mechanical effect and violation of Bell's inequality, you have to look at more than one property. All of the Bell experiments are analogous to the following (of which your red/blue ball analogy is a special case, one in which the inequality violation happens not to appear): Not only is one ball blue and the other red, but also one ball is made of wood and the other of plastic, one ball has a white stripe painted on it and the other doesn't. There are now eight possible combinations: striped or not, red or blue, plastic or wood.

As before, we put the two balls in two bags and ship them off to two separated observers. Each observer records one property of his ball (the Rules of Quantum Mechanics forbid simultaneously observing more than one property). Now when we get together and compare notes, it might happen that I observed a red ball and you observed a striped ball; then we know that your ball was blue and striped and mine was red without a stripe, and we don't know which ball was plastic and which was wood. Other times I'll observe a plastic ball and you'll observe a striped ball; then we'll know the composition and stripe of both of our balls.
(Note that your one-observable red-blue analogy is just a special case of this model, in which we always only look at the color of the balls)

Bell's inequality, applied to this situation, says that the number of red plastic balls at my side (that is, my ball was red and yours was wooden, or mine was plastic and yours was blue) must be less than or equal to the number of red balls with a stripe plus the number of unstriped plastic balls. The importance of Bell's theorem is that it shows that any system that assigns all three values to both balls when the pair is set up will have to honor this rather common-sense conclusion.

We can do something analogous with spin-entangled particles: we each measure the spin of our particle along one of three axes: 0, 120, or 240 degrees. Up or down on the 0 degree axis are analogous to red and blue; up and down on the 120 degree axis are analogous to striped or not striped; and up and down on the 240 degree axis are analogous to wood or plastic. If the result of a spin measurement depends only on properties that the particle was assigned when the entangled pair was created, then the number of up-0 down-240 particles at my side (that is, I measured up-0 and you measured up-240, or I measured down-240 and you measured up-0) must be less than or equal to the number of up-0 up-120 particles plus the number of down-120 down-240 particles.

However, the quantum mechanical prediction in this case is that Bell's inequality will be violated. And when we do the experiment... It is.

 

[Imafungi]

It is clear you haven't read Bell (1964) at all, since your analogy is precisely what it was meant to address. The EPR (1935) paper used a similar example as yours. I assume you have not read it either, since that was what Bell was responding to. And experiments such as Aspect et al (1982) confirm that local realism (your analogy) can be ruled out. See the links on this page:

http://www.drchinese.com/David/EPR_Bell_Aspect.htm

If you would like a simple explanation of how Bell's Theorem rules out hypotheses such as yours, the following is about as easy as it gets:

http://www.drchinese.com/David/Bell_Theorem_Easy_Math.htm

The short version is that your analogy works fine for red/blue balls. No one disputes that, and that is why EPR stood for 30 years. Bell realized the analogy failed with certain pairs of measurements. In your analogy: red balls and balls that are a mixture of 1/3 red and 2/3 blue. QM makes accurate predictions for these variations, while local realistic theories make inconsistent predictions. This is because local realistic theories have a requirement that QM does not: the outcome of a measurement on Alice must be completely independent of the nature of a measurement performed on Bob in another location.

Ok, so I think I may understand this whole situation now.

The situation is;

QM assumes superposition.

Which leads to exact position upon measurement.

Which leads to 'if these two particles had equal probabilities of resulting in an exact position, but when I measured each they were definite, and opposite, how come they are always opposite?'.

Which leads to, they must always be opposite because they are physically linked in some way.

Which leads to, 'when I measure one particle, and go from its superposition state, to its exact position state, it must utilize its physical link in some way to force the particle that is physically linked to it, to change into the other half of the shared probable outcome'.

Which leads to, 'my equation using probability and superposition is useful to predict events'.

Which leads to, 'you saying that my equation using probability and superposition is not true, is not useful in predicting events'.

Which leads to, 'Therefore, my equations must be true, and your statement must be false'.


Am I looking at this situation properly? You believe that because my statement that "local realism is true" or "when entangled particles are created, they are not in superpositioned states, they are in exact and opposite states. They are in the states that they are in when they are measured, that they are in when they are created" is not useful at predicting events, that it cannot be a true statement?

And just to be sure, that last quote I wrote, 'They are in the states that they are in when they are measured, that they are in when they are created'. I don't necessarily believe that this is exactly and fully true, though the consequences are all the same. What I mean by that is, it is possible that (in my opinion, so far) entangled particles are created and in that instance are created with/as exact and opposite qualities/states and that by measuring them alters or reverses their qualities and states, but by nature of them being opposite before hand, and the equipment of measurement being the same for both, its effect on them could alter them in such a way that they remain their nature of being opposites, though were not in the same states as when they were created.


But anyway, am I getting it right, that your main point is, 'why would a theory that includes probabilities and superposition be so good at predicting events of reality if events of reality didnt include probabilities and superpositions?'. Is that the gist?

 

[bhobba]

To be fair, a philosopher might also be a scientist. Historically, that's quite what natural philosophy was. Given this, your statement might be a bit disingenuous.

I don't hold philosophy in particularly high esteem for the exact reason I have mentioned a number of times - philosophers can't agree on anything.

Indeed some philosophers are also scientists and conversely. I am no expert on the history of science but I think the rise of science as a discipline separate from philosophy occurred a long long time ago - certainly these days they have well and truly gone there separate ways.

As Wienberg points out most certainly in recent times it hasn't been of much use. Indeed philosophers like Kuhn have advanced positions I think virtually anyone into science would disagree with. From the Wienberg link I gave previously: 'But in the last chapter Kuhn tentatively attacked the view that science makes progress toward objective truths: "We may, to be more precise, have to relinquish the notion, explicit or implicit, that changes of paradigm carry scientists and those who learn from them closer and closer to the truth." Kuhn's book lately seems to have become read (or at least quoted) as a manifesto for a general attack on the presumed objectivity of science.'

Kuhn has lost the plot IMHO.

But, as you mention, this isn't the thread to discuss philosophy, nor the forum.

There is a site called the Philosophy Forums more suited to that. If you want to pursue it further drop me a line and we can take it over there.

Thanks
Bill

 

[stevendaryl]

Where is the evidence of his proof though, is it not just an argument like my argument, it seems like circular logic, I can call my argument a proof and say it shows that such an interpretation of entanglement works, proving Bells proof wrong.

Calling something a "proof" doesn't make it one.

Since as it appears you have caught me red handed, why not work to my weaknesses and prove me wrong as plain and simply as possible? Or do you need bells and whistles and smoke and mirrors to make your beliefs right?

Bell's theorem shows that your belief is WRONG. It's not showing that any particular alternative belief is right. What he showed was wrong was the belief that once the particles separate, it's predetermined what the result of every possible measurement will be. That cannot possibly be the case.

To see this, you really have to look at and understand the mathematics. Only the very simplest theories can proved right or wrong without using any math, and quantum mechanics is certainly way beyond that.

Ok, I tried to follow your math and I cant. So to just use two created entangled particles. When one is measured spin up, and the second is measured spin down. What is any experimental evidence that; When two entangled particles are created (before any measurement/observation) one of the entangled particles exists in a spin up state, and the second exists in a spin down state. What is the experimental evidence that says that physically is impossible?

What you don't seem to understand about electron spin is that it's not absolutely spin-up or spin-down. It's measured to be spin-up or spin-down relative to a particular direction. For example, let's pick three different directions as follows: Let direction A be straight up. Let direction B be at a 120 degree angle from A. Let direction C be in the same plane as A and B, but 120 degrees away from each.

Alice and Bob both use the same three directions. Every time an entangled pair is produced, Alice randomly picks one of the three directions to measure the electron's spin, and Bob randomly picks one of the three directions to measure the positron's spin. What they find, through many many trials, is the following:

1. No matter which direction Alice chooses, she gets spin-up half the time and spin-down half the time.
2. Same for Bob.
3. If Alice and Bob pick the same direction, they ALWAYS get the opposite result.
4. If Alice and Bob pick different directions, then 1/8 of the time, Alice gets spin-up and Bob gets spin-down. 1/8 of the time, Alice gets spin-down and Bob gets spin-up. 3/8 of the time, they both get spin-up. 3/8 of the time, they both get spin-down.

So it's not as simple as "Alice and Bob always get the opposite result". That's what happens when they both choose the same direction, but that's not what happens when they choose different directions. So your idea that it's predetermined that Alice will always get the opposite of Bob is wrong. It's more complicated than that.

A more sophisticated model is this: Every correlated pair has an associated label. One of 8 possible labels:

1. $ABC$
2. $AB\bar{C}$
3. $A\bar{B}C$
4. $A\bar{B}\bar{C}$
5. $\bar{A}BC$
6. $\bar{A}B\bar{C}$
7. $\bar{A}\bar{B}C$
8. $\bar{A}\bar{B}\bar{C}$

$A$ in the label means that Alice will measure spin-up in that direction, and Bob will measure spin-down. $\bar{A}$ in the label means that Alice will measure spin-down in that direction, and Bob will measure spin-up. Similarly for $B, \bar{B}, C \bar{C}$.

So your idea that the outcomes are fixed ahead of time can be generalized by these labels: The outcome is fixed for every choice of measurement direction, (although different directions can have different results).

So to complete this hidden variable model, you need 8 numbers:
$P(ABC), P(AB\bar{C}), ...$ giving the probabilities of each of the 8 labels.

To match the predictions of quantum mechanics, the probabilities have to add up correctly.
There is no possible choices for those 8 numbers that reproduce the predictions of quantum mechanics. There is no way to see that, other than to do some math. We could simplify it
by assuming certain symmetries, which is that swapping A and B shouldn't change anything. Swapping A and C shouldn't change anything. Swapping spin-up for spin-down shouldn't change anything. So with those assumptions, there are only two numbers:

$P(ABC) = P(\bar{A}\bar{B}\bar{C} = x$
$P(AB\bar{C}) = P(A\bar{B}C) = P(\bar{A}BC) = P(\bar{A}B\bar{C} = P(\bar{A}\bar{B}C) = P(A \bar{B}\bar{C}) = y$

To reproduce the predictions of quantum mechanics, it must be that
$P(ABC) + P(AB \bar{C}) = x+y = 1/8$
$2x + 6y = 1$ (because the probabilities have to add up to one).

These two equations have the solution:

$y = 3/16$
$x = -1/16$

Since probabilities have to be positive, this is ruled out. So there are no possibilities left. Using deterministic hidden labels can't work.

 

[DrChinese]

... Ok, I tried to follow your math and I cant. ...
I am a very open minded, and skeptical, person. I want to know truth, why would I want to know anything other. I have no bias, I have no stake, I am honest to myself and others. ...
According to what I am saying, they would not be in random directions, that's the whole point of my argument. ...

Imafungi,

You are willfully picking and choosing what you accept, what you believe, etc. and it has little to do with science, and learning more. The mutually contradictory nature of your comments show as much. You are obviously telling us and doing very little listening.

First, read EPR (1935). If you read that, you would know - without any math at all - that there is an element of reality associated with anything that can be predicted in advance with certainty (according to a reasonable definition of reality). Entangled particles fit the bill, and no one has really ever claimed otherwise since QM came to the scene. Measure particle A at ANY angle X. You now know entangled partner particle B's attribute at X with 100% certainty - not probabilistic as you say. They too felt that

Next, make EPR's assumption that the result of A's measurement can in any way be based on the nature of the measurement made at B. Otherwise we would live in an observer-dependent reality, something EPR felt was unreasonable.

Lastly, you must conclude that the outcome of all possible measurements on each of a pair of entangled particles must in fact be predetermined. That was the one that Bell discovered could not be correct. The math of the Bell paper can be a bit convoluted, so go to my own page which arrives at the same point in a simpler fashion:

http://drchinese.com/David/Bell_Theorem_Easy_Math.htm

If you won't take the time to understand Bell, no one can much assist you here. Our goal is to present you with information for you to study and understand on your own.

And if, after you understand Bell, you still have questions: by all means, start a new thread and we can discuss. But it is really outside of forum rules for you to post your personal arguments here. You would need to present suitable citations first. You should also not be issuing veiled challenges to others.

Please take this as a kindly nudge, and please double check the forum rules if you are unsure on my points. The moderators take this quite seriously, and especially so in this subject area.

 

[bhobba]

Bell's theorem shows that your belief is WRONG.

Indeed it does.

But what I want to know is why he believes it in the first place.

I suspect he hasn't cottoned onto the idea our intuitions formed here in the commonsensical classical world may not apply in the micro world.

Its not that physicists have pulled such ideas out of the hat for some kind of perverse pleasure. They were forced to it for very good reasons.

Thanks
Bill

 

[DrChinese]

...But anyway, am I getting it right, that your main point is, 'why would a theory that includes probabilities and superposition be so good at predicting events of reality if events of reality didnt include probabilities and superpositions?'. Is that the gist?

No, it is not the gist. QM could be wrong. The question is whether local realism could be as accurate as QM. And the answer to that is NO.

Your logic makes little sense, read my post preceding this (61). To be clear: If you continue the discussion without listening to my suggestions, you will be reported immediately.

 

[Imafungi]

Why do you believe that?

Science is about correspondence with experiment, not what you believe.

So exactly what QM experiments lead you to that view? There are many experiments that suggest its in deep trouble, such as the double slit experiment where no one has been able to figure out how to predict what position the particle or photon will be detected at. So, not based on a gut feeling, your belief, philosophical waffle about determinism, yada, yada, yada, exactly why do you believe that?

Thanks
Bill

So a couple of thousands of years ago if scientists measured that the Earth was flat in experiment, would the Earth have been flat, or at least that's what you would be forced to believe? I know that's a bad example, but only because there may not be anything in which would lead you to reason in those times that the Earth is round, besides perhaps using the roundness of the sun to make a posit, but that wouldn't be science I guess.

I have been quite clear with my reasoning in my replies. I am a lover of science and truth, I am merely asking questions.

I believe determinism because I have seen or thought of no possible way it can be explained or shown to be breakable. That is if the universe is natural. The only things I can think of that might break determinism are 'a mind' and maybe a computer random number generator(?), maybe. But would that, and all things, still not be determined and limited by laws, laws which them self are determinations?

I don't know what double slit experiment has to do with believing that; 'that which exists, exists as that which that is'.

I will try to express my logic as to why I stated what I did in the reply you are replying to.

Do you believe 'something' exists? (something at all, as in, there is something besides nothing)

Do you believe that the total quantity of 'something' that exists is always finite? (as in, cannot be created or destroyed, only transformed)

Do you believe that for 'something' to transform into 'something else', it first had to 'be' 'something'?

Than you must believe that, 'that which exists (all the something) is always equal to itself', in that, 'that which exists, is always equal to that which exists'. It is a finite quantity, it transforms/changes, which is what time is.

I don't know, at least not yet, or haven't seen or considered, a realistic or logical, meaning possible, way in which a reality that exists, that is 'true something', can have non local properties.

I suppose a potentially important part of this belief in mine is that there must be a 'smallest possible quanta', theoretically and actually. Though I suppose the possibility of the smallest possible quanta being much much much smaller than the average smallest quanta of our material universe, may be able to be used as the excuse for non locality (is this where all the folded and hidden dimensions come in?). In the sense that the reason for spooky action at a distance is because this relatively large quanta massed material universe we exist in/of exists 'on top of' a much smaller quanta material universe which behaves in ways so foreign from we have been ingrained to be used to, that it is possible for its standard functions to annoy me and Einstein by its seemingly physical impossibility.

So if spooky action at a distance is true, and the universe is real, physical/material/energetic, what is the leading candidate/idea/theory as to the physical mechanism that causes it?

 

[TumblingDice]

The "klink" you're about to hear is the sound of a thread being locked...

 

[bhobba]

I believe determinism because I have seen or thought of no possible way it can be explained or shown to be breakable... I don't know what double slit experiment has to do with believing that; 'that which exists, exists as that which that is'.

Its got to do with objects having a property independent of if its observed to have that property. In the double slit experiment precisely what position does the particle have when not observed? If it has a definite position how does it interfere with itself? There is a way out of this so you can preserve your preconceived view of the world (eg BM), but its far from clear if the shenanigans required for this is a-priori required. The world may simply be like that.

Do you believe 'something' exists? (something at all, as in, there is something besides nothing)

Sure.

Do you believe that the total quantity of 'something' that exists is always finite? (as in, cannot be created or destroyed, only transformed)

No I do not believe that eg its an experimental fact beyond refute photons for example are not conserved.

That said a VERY deep discovery of physics is the connection between symmetries and conservation laws:
http://www.physics.ucla.edu/~cwp/articles/noether.asg/noether.html

Also note this was the discovery of mathematics and was so startling it is doubtful without mathematics it would have ever been discovered.

Do you believe that for 'something' to transform into 'something else', it first had to 'be' 'something'?

Well your stated premise - namely its first of all something - makes it a trivial statement.

Than you must believe that, 'that which exists (all the something) is always equal to itself', in that, 'that which exists, is always equal to that which exists'. It is a finite quantity, it transforms/changes, which is what time is.

Since there are things like photons not conserved it's obviously false.

So if spooky action at a distance is true, and the universe is real, physical/material/energetic, what is the leading candidate/idea/theory as to the physical mechanism that causes it?

Does everything have to have a cause? Any theory has some premises. Those premises may be explained by some deeper theory or not. But until such a deeper theory is discovered your guess is as good as mine what is fundamental and what isn't.

Thanks
Bill

 

[mfb]

This thread is done...