The discussion centers on the experiment conducted by Ringbauer and colleagues, which demonstrates that causal influences between measurement outcomes cannot explain observed correlations in quantum mechanics. Their findings indicate that nonlocal causality is ruled out, particularly in the context of the CHSH experiment. The experiment's design, which involved fixing the outcome of one photon’s measurement, confirmed that no concurrent changes occurred in the other photon, thereby supporting the conclusion that quantum mechanics supersedes nonlocal causal theories, including Bohmian mechanics. However, the experiment does not eliminate all forms of nonlocal causality, particularly those that do not conflict with quantum predictions.
PREREQUISITESPhysicists, quantum mechanics researchers, and students interested in the foundations of quantum theory, particularly those examining the implications of nonlocality and causality in quantum experiments.
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:
