On Fri, Oct 18, 2019 at 8:16 PM Philip Thrift <[email protected]> wrote:
> On Friday, October 18, 2019 at 1:36:33 AM UTC-5, Philip Thrift wrote: >> >> On Thursday, October 17, 2019 at 6:05:00 PM UTC-5, Brent wrote: >>> >>> 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)? >>> >>> Brent >>> >> >> >> >> So, in the end, it seems that reading Carroll's book is a huge waste of >> time after all, if his "explanation" leads to confusion. >> >> @philipthrift >> > > > e.g. What Sean proposes is a middle decoherence [from his blog]: > > The trickiness relies on the fact that by becoming entangled with a single > recording spin rather than with the environment and its zillions of > particles, > > *the traveling electrons only became kind-of decohered*. > > With just a single particle to worry about observing, we are allowed to > contemplate measuring it in different ways. If, as in the conventional > double- slit setup, we measured the slit through which the traveling > electron went via a macroscopic pointing device, we would have had no > choice about what was being observed. True decoherence takes a tiny quantum > entanglement and amplifies it, effectively irreversibly, into the > environment. In that sense the delayed-choice quantum eraser is a useful > thought experiment to contemplate the role of decoherence and the > environment in measurement. > > > In terms of Many Worlds, it sounds like a Middle World. > Even in Sean's analysis it is clear that delayed choice has nothing to do with many worlds: you get the same analysis in single world or collapse theories, such as GRW. Bruce -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. 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