Wednesday, August 29, 2018

That chicken or egg question is unanswerable?

Hey, has anyone else noticed how often physicists from Brisbane seem to get mentioned in despatches, so to speak, about quantum experiments?   It makes me feel like I'm living in a smarter city than southerners like to give it credit for. 

This time its the University of Queensland being mentioned in a somewhat complicated explanation about a quantum experiment that seems to indicate that causation becomes very confusing in quantum systems:
Over many trials, the physicists implement different combinations of shape changes in the two paths, like choosing among a handful of setting for two different knobs. If each photon definitely takes one path or the other first, the correlations between the knob setting and the photon’s final polarization must obey certain limits. However, if both take both paths first, the correlations will exceed those limits, which is exactly what the physicists observe in a paper in press at Physical Review Letters.

As it stands, the experimenters chose the operations in the two paths independently. However, in principle the experiment shows that quantum mechanics allows for the possibility that the two processes could trigger each other, says Cyril Branciard, a physicist at the NÉEL Institute in Grenoble, France, who worked on the experiment. “One may have situations where some event A causes another event B, while at the same time B causes A.”
I suppose it's appropriate that I mention another recent report, this one about how a quantum entanglement experiment  used light from distant quasars to help rule out "freedom of choice" loopholes.

Don't worry, I'll explain later.  Or not.

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