Bells inequality be satisfied with equivalent local QM?

[Galteeth]

How do you know in this experiment that the correlations are from specific particle pairs as oppossed to a general statistical interaction (like in some hypothetical casino where a roulette wheel that turns up black will make some other whell in the casino turn up red)?

 

[DrChinese]

How do you know in this experiment that the correlations are from specific particle pairs as oppossed to a general statistical interaction (like in some hypothetical casino where a roulette wheel that turns up black will make some other whell in the casino turn up red)?

When you look at red and black (which correspond in the analogy to settings of 0 or 90 degrees) alone, you may not notice the entanglement. I.e. it may not appear very persuasive. But when you look at a variety of angles other than 0 and 90 degrees, you can see that the particles act as a system and not as independent particles.

 

[Galteeth]

When you look at red and black (which correspond in the analogy to settings of 0 or 90 degrees) alone, you may not notice the entanglement. I.e. it may not appear very persuasive. But when you look at a variety of angles other than 0 and 90 degrees, you can see that the particles act as a system and not as independent particles.

No, I understand they act as a system. What I meant was, how do you know that specific particle pairs are correlated as oppossed to a more general systemic co-ordination?

 

[DrChinese]

No, I understand they act as a system. What I meant was, how do you know that specific particle pairs are correlated as oppossed to a more general systemic co-ordination?

Not sure I follow. Experimental correlation IS evidence of entanglement. Entanglement means the pair is acting as a system. What other option do you propose as a "general systemic coordination" ? Unentangled pairs do not exhibit cos^2 correlations.

But not all correlations are equal indicators of entanglement. For example, "perfect" correlations (0 degrees) indicate entanglement and this is the easiest way to calibrate the apparatus. But this alone does not violate a Bell inequality.

 

[Galteeth]

Not sure I follow. Experimental correlation IS evidence of entanglement. Entanglement means the pair is acting as a system. What other option do you propose as a "general systemic coordination" ? Unentangled pairs do not exhibit cos^2 correlations.

But not all correlations are equal indicators of entanglement. For example, "perfect" correlations (0 degrees) indicate entanglement and this is the easiest way to calibrate the apparatus. But this alone does not violate a Bell inequality.

I wasn't saying that what I was asking was likely per ce, just wanted to see if there is a way to know for sure. What I mean is, hypothetically, photon pair 1 and 2 could give uncorrelated results, and photon pair 3 and 4 could give uncorrelated results, but taken together as a system there could be a perfect systematic correlation. I know that's unlikely, but is there a way to know that isn't the case?

 

[zonde]

What I mean is, hypothetically, photon pair 1 and 2 could give uncorrelated results, and photon pair 3 and 4 could give uncorrelated results, but taken together as a system there could be a perfect systematic correlation. I know that's unlikely, but is there a way to know that isn't the case?

I would say that the question can be reformulated to allow more easier analysis.
Say photon 1 can be detected at two different times and we will mark them as 1A and 1B. Similarly for other photons.
Now we have four pairs 1A/2A, 1B/4B, 3A/4A, 3B/2B with additional constraint that xA/xB can not be detected both.
That way reformulated I would say it's unlikely to add anything new to the problem.