Posted: Oct 07, 2017 8:16 pm
For those less interested in fruit flies and more interested in retro causality this is interesting.
And for those seriously interested in the subject there is this.
The appeal of retrocausality
First, to clarify what retrocausality is and isn't: It does not mean that signals can be communicated from the future to the past—such signaling would be forbidden even in a retrocausal theory due to thermodynamic reasons. Instead, retrocausality means that, when an experimenter chooses the measurement setting with which to measure a particle, that decision can influence the properties of that particle (or another particle) in the past, even before the experimenter made their choice. In other words, a decision made in the present can influence something in the past.
In the original Bell tests, physicists assumed that retrocausal influences could not happen. Consequently, in order to explain their observations that distant particles seem to immediately know what measurement is being made on the other, the only viable explanation was action-at-a-distance. That is, the particles are somehow influencing each other even when separated by large distances, in ways that cannot be explained by any known mechanism. But by allowing for the possibility that the measurement setting for one particle can retrocausally influence the behavior of the other particle, there is no need for action-at-a-distance—only retrocausal influence.
Generalizing retrocausality: with or without a real quantum state
One of the main proponents of retrocausality in quantum theory is Huw Price, a philosophy professor at the University of Cambridge. In 2012, Price laid out an argument suggesting that any quantum theory that assumes that 1) the quantum state is real, and 2) the quantum world is time-symmetric (that physical processes can run forwards and backwards while being described by the same physical laws) must allow for retrocausal influences. Understandably, however, the idea of retrocausality has not caught on with physicists in general.
And for those seriously interested in the subject there is this.
We conclude that the most plausible response to our result, other than giving up Realism, is to posit that there might be retrocausality in nature. At the very least, this is a concrete and little explored possibility that holds the promise of evading almost all no-go theorems in the foundations of quantum theory, so it should be investigated further.