Instant Correlation vs. Instant Communication: Exploring the Difference

[IllyaKuryakin]

I’ve seen much confusion here concerning the difference between instant correlation at a distance and instant “communication”, or transfer of information at a distance, and a simple thought experiment can clarify the difference.

In Experiment A, we stick two coins together, one heads up and one heads down, with a bit of tape. Then we put a blindfold on and flip the coins. Being very careful not to let either coin change positions, we separate them and place one in Box 1 and one in Box 2 and seal the boxes and remove the blindfold. Box 1 stays here on Earth and Box 2 is placed on a spaceship and sent to the other side of our Galaxy, which takes our ¼ light speed spaceship 400,000 years.

Now, we open Box 1 here on Earth and find its coin is heads. Instantly we know that the coin in Box 2 is tails. So, there has been an instant correlation at a distance, but there has been no instant communication, or transfer of information, at a distance.

In Experiment B, we simply replace the 2 coins with 2 entangled electrons, so if Box A contains an electron that is spin up, Box B will contain an electron that is spin down, or visa versa. Once again, after our ¼ light speed spaceship is sent with Box B to the other side of the Galaxy, and if we open Box A here on Earth and measure its electron spin to be spin up, we know the spin of the electron in Box B on the other side of the Galaxy must be spin down.

The only difference between the two thought experiments is the spin correlation between the two entangled electrons is maintained at any distance by the math of QM. In my own humble opinion, either you accept that the math of QM is correct, as all experimental data shows it to be, or there can be no further rational examination of the issue given our current understanding and experimental data.

Those thought experiments should clear up any confusion as to how one can have instant correlations at any distance, without having any possibility of instant transfer of information or “communication” at speeds faster than light.

If I've made any mistakes in the above, please feel free to correct me, as my intention was to dispell confusion rather than create more.

Your humble servant,

Illya

 

[DrChinese]

I’ve seen much confusion here concerning the difference between instant correlation at a distance and instant “communication”, or transfer of information at a distance, and a simple thought experiment can clarify the difference.

In Experiment A, we stick two coins together, one heads up and one heads down, with a bit of tape. Then we put a blindfold on and flip the coins. Being very careful not to let either coin change positions, we separate them and place one in Box 1 and one in Box 2 and seal the boxes and remove the blindfold. Box 1 stays here on Earth and Box 2 is placed on a spaceship and sent to the other side of our Galaxy, which takes our ¼ light speed spaceship 400,000 years.

Now, we open Box 1 here on Earth and find its coin is heads. Instantly we know that the coin in Box 2 is tails. So, there has been an instant correlation at a distance, but there has been no instant communication, or transfer of information, at a distance.

In Experiment B, we simply replace the 2 coins with 2 entangled electrons, so if Box A contains an electron that is spin up, Box B will contain an electron that is spin down, or visa versa. Once again, after our ¼ light speed spaceship is sent with Box B to the other side of the Galaxy, and if we open Box A here on Earth and measure its electron spin to be spin up, we know the spin of the electron in Box B on the other side of the Galaxy must be spin down.

The only difference between the two thought experiments is the spin correlation between the two entangled electrons is maintained at any distance by the math of QM. In my own humble opinion, either you accept that the math of QM is correct, as all experimental data shows it to be, or there can be no further rational examination of the issue given our current understanding and experimental data.

Those thought experiments should clear up any confusion as to how one can have instant correlations at any distance, without having any possibility of instant transfer of information or “communication” at speeds faster than light.

Nice try, but this is not an accurate analogy at all. Have you reviewed Bell's Theorem? It addresses this explanation and demonstrates conclusively that it is incorrect. It turns out that this explanation, while initially appearing to work, does NOT follow the math of QM.

 

[IllyaKuryakin]

Nice try, but this is not an accurate analogy at all. Have you reviewed Bell's Theorem? It addresses this explanation and demonstrates conclusively that it is incorrect. It turns out that this explanation, while initially appearing to work, does NOT follow the math of QM.

Thanks for the reply. Yes, I have reviewed Bell's Theorem, but I must have difficulty explaining in clear terms, why instant correlation at a distance does not imply instant information transfer, or communication. Can you rephrase the thought experiment in correct terms? I'm sure it would be a benifit to all.

 

[DrChinese]

Thanks for the reply. Yes, I have reviewed Bell's Theorem, but I must have difficulty explaining in clear terms, why instant correlation at a distance does not imply instant information transfer, or communication. Can you rephrase the thought experiment in correct terms? I'm sure it would be a benifit to all.

The issue is that the correlations are related to the settings of distant observers. These settings can be made well after the entangled particles are created, and so late as to make them outside of each others' light cones. So no convention/classical communication is possible. You cannot see what is happening until the results are brought together. Bell's Theorem shows why the obvious solution - that the results were predetermined - cannot be correct. Follow the link below for a discussion of how that works.

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

 

[IllyaKuryakin]

The issue is that the correlations are related to the settings of distant observers. These settings can be made well after the entangled particles are created, and so late as to make them outside of each others' light cones. So no convention/classical communication is possible. You cannot see what is happening until the results are brought together. Bell's Theorem shows why the obvious solution - that the results were predetermined - cannot be correct. Follow the link below for a discussion of how that works.

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

I read your explanation of Bell's Theorm. It's much more clear than explanations I've read in the past. Thanks!

A couple important points are made. No LOCAL Hidden Variables can explain the experimental results obtained by statistical QM. As you correctly pointed out, Bell never said that Non-Local Hidden varibles could not produce the same results, and in fact Bohmian Mechanics does just that, to the best of my understanding, essentially using the exact position of particles as a Non-local Hidden Variable. Of course, due to HUP it's a Hidden Variable we can never exactly observe. In fact, I believe that John Bell said that Bohmian Mechanics did just that.

(Bell 1987, p. 160):

"But in 1952 I saw the impossible done. It was in papers by David Bohm. Bohm showed explicitly how parameters could indeed be introduced, into nonrelativistic wave mechanics, with the help of which the indeterministic description could be transformed into a deterministic one. More importantly, in my opinion, the subjectivity of the orthodox version, the necessary reference to the ‘observer,’ could be eliminated. ..."

So I suppose there is still something left to be sorted out there.

As for my little thought experiment, of course you are correct. No classical illustration can fully explain the correlation of particles at any arbitrary distance, even outside each others light cone. But that was not the point of my example. I was certianly not trying to explain how non-local effects could occur in a classical fashion. I agree that just simply cannot be done. I do however believe that Bell believed that the same results as statistical QM could be obtained in a deterministic fashion using Non-Local Hidden Variables, as referenced above, but that is a whole other discussion.

The point of my little thought experiment was to attempt to explain, even in a classical sense, how a correlation can occur without communication or information transfer. I suppose I failed in that attempt, since information really is transferred in the form of the coin being transferred by the spaceship. Perhaps the non-locality of QM is the only example of a correlation without information transfer. If that's the case, I did just what I wanted to not do, add to the confusion. My appoligies.

 

[DrChinese]

I read your explanation of Bell's Theorm. It's much more clear than explanations I've read in the past. Thanks!

...

The point of my little thought experiment was to attempt to explain, even in a classical sense, how a correlation can occur without communication or information transfer. I suppose I failed in that attempt, since information really is transferred in the form of the coin being transferred by the spaceship. Perhaps the non-locality of QM is the only example of a correlation without information transfer. If that's the case, I did just what I wanted to not do, add to the confusion. My appoligies.

You are very welcome! But you don't need to apologize around here. The point is to be able to ask questions and get some dialogue going to help learn. But don't stop here! There is a lot to be learned about this subject, and it is fascinating to no end!

For example: is this quantum non-locality instantaneous? Or is it simply faster than light? The answer is that experiments have determined it must be AT LEAST 10,000 times faster than c!

Testing spooky action at a distance

"In science, one observes correlations and invents theoretical models that describe them. In all sciences, besides quantum physics, all correlations are described by either of two mechanisms. Either a first event influences a second one by sending some information encoded in bosons or molecules or other physical carriers, depending on the particular science. Or the correlated events have some common causes in their common past. Interestingly, quantum physics predicts an entirely different kind of cause for some correlations, named entanglement. This new kind of cause reveals itself, e.g., in correlations that violate Bell inequalities (hence cannot be described by common causes) between space-like separated events (hence cannot be described by classical communication). Einstein branded it as spooky action at a distance. A real spooky action at a distance would require a faster than light influence defined in some hypothetical universally privileged reference frame. Here we put stringent experimental bounds on the speed of all such hypothetical influences. We performed a Bell test during more than 24 hours between two villages separated by 18 km and approximately east-west oriented, with the source located precisely in the middle. We continuously observed 2-photon interferences well above the Bell inequality threshold. Taking advantage of the Earth's rotation, the configuration of our experiment allowed us to determine, for any hypothetically privileged frame, a lower bound for the speed of this spooky influence. For instance, if such a privileged reference frame exists and is such that the Earth's speed in this frame is less than 10^-3 that of the speed of light, then the speed of this spooky influence would have to exceed that of light by at least 4 orders of magnitude. "