On 10/17/2019 2:35 PM, Bruce Kellett wrote:
I think you have misunderstood the experiments. The interference pattern is present if the welcher weg information is erased, whether the erasure takes place before or after the photons hit the screen. If the information is not erased, no interference pattern is seen, even if the idler photons drift off to infinity./> Deutsch was simply wrong when he thought that his experiment would "prove" the existence of many worlds./ Actually Deutsch didn't say that, he said his experiment would test Many Worlds not prove it correct.OK. But the alternative that Deutsch seems to have been testing was that only a conscious observer could collapse the wave function. As I have said, this has never been a serious scientific position.When the exparament is actually performed for all I or Deutsch knows it could prove that the Many Worlds idea is dead wrong. I've already told you what my best guess on the outcome so what is your prediction? When that photographic plate is developed will there be interference bands on it or not?If the welcher weg information is quantum erased, then there will be an interference pattern, whether or not it is a conscious observer who is erased.
In Carroll's version of the experiment, which has been performed arXiv:quant-ph/9903047 v1 13 Mar 1999, the experimenter who arranged that each electron has its welcher weg recorded by a spin UP (left slit) or spin DOWN (right slit) particle does, at the end of the experiment, knows there's a record of which slit each electron went thru, and he can sign an affadavit that says that information is known. But he doesn't know it /consciously/; it's recorded by all the spin particles, but not in his memory that he can bring to consciousness. We know what happens if he signs such an affadavit or if he doesn't, it's the same: if the recording spin particles are measured in a left/right basis the information is erased and the interference pattern can be discerned by considering only particles that measured left or only those measuring right.
So Deutsch was proposing to test whether the/conscious /AI which could have the recording particles as part of it's memory and presumably be conscious of the up/down spins before they were erased would produce a different result.
But I wonder what happens in Carroll's experiment if, after measuring in the left/right basis and noting that two different interference patterns can then be discerned by considering either those due to left spin recording particles or considering right spin particles, one measures the recording particles again in the up/down basis. The overall pattern is the same, it's just that you've relabeled spots on the screen according to whether the second measurement of recording particles assigned them to UP or to DOWN. Now you can consider the subset labeled UP (or DOWN). This should be a superposition of ensembles randomly selected from the left and right ensembles and in that case would not show an interference pattern...but the information has certainly been erased (twice)?
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