The discussion centers around an experimental investigation into non-local causality in quantum mechanics, specifically examining whether the results of the experiment can rule out various non-local causal theories. Participants explore the implications of the findings on established theories, including Bohmian mechanics, and the nature of quantum correlations.
Participants exhibit disagreement regarding the implications of the experiment for non-local causal theories, particularly in relation to Bohmian mechanics. There is no consensus on whether the experiment rules out all forms of non-local causality.
Participants note that the experiment's conclusions depend on the assumption of causal parameter independence, which may not hold for all theories discussed, particularly Bohmian mechanics. The discussion reveals complexities in the interpretation of quantum correlations and the conditions under which different theories may apply.
Experimental test of nonlocal causality
Can you elaborate? I have seen that there was a very long thread on Bohmian mechanics, but maybe you can summarize!Demystifier said:
In short, Bohmian mechanics is a non-local causal theory constructed so that it makes the same measurable predictions as standard QM. Since the experiment above certainly does not violate predictions of standard QM, it follows that it also does not violate predictions of Bohmian mechanics.harrylin said:
Well, maybe I misunderstood it, but I was almost sure that Bohmian mechanics pretends to explain correlations such as the breaking of the Bell Inequality by means of causal influence from one measurement outcome to the other. However, at the level of measurements of single pairs such inequalities cannot be broken, and the experimenters here claim that their results "demonstrate that a causal influence from one measurement outcome to the other[..] cannot explain the observed correlations". And: "Our results highlight the incompatibility of quantum correlations not only with the well-known Bell-local causal models but also with nonlocal causal models, where one measurement outcome may have a direct causal influence on the other."Demystifier said:
- so I'd like to be "demystified". 
In the paper, the authors say:harrylin said:Well, maybe I misunderstood it, but I was almost sure that Bohmian mechanics pretends to explain correlations such as the breaking of the Bell Inequality by means of causal influence from one measurement outcome to the other. However, at the level of measurements of single pairs such inequalities cannot be broken, and the experimenters here claim that their results "demonstrate that a causal influence from one measurement outcome to the other[..] cannot explain the observed correlations". And: "Our results highlight the incompatibility of quantum correlations not only with the well-known Bell-local causal models but also with nonlocal causal models, where one measurement outcome may have a direct causal influence on the other."
To me that looks like a strong disagreement. Indeed, as so often in this forum, I'm mystified
Regretfully that page does not show up at my (x,y,z,t)... However the preceding page does show up. After explaining the meaning of "parameter independence", the book states that "quantum theory [..] satisfies Parameter Independence"... Also, I regret that still no way is presented how Bohmian mechanics could break Bell's Inequality. But that's ok, we are all here in our free time and Bohmian mechanics is only a subtopic of this thread, so I won't insist. Hopefully there will be more interesting comments on the "no nonlocal causality" experiment.Demystifier said:
You might find the paper linked in this opening thread useful as it sort of relates to your question:morrobay said:
Yes.morrobay said:
Yes. All non-local correlations measured so far are such that they do not involve superluminal signals. (By a "signal", one means a transmitted message freely chosen by a human.)morrobay said:
Myrvold gives a couple of nice examples - thanks!bohm2 said:
