On Sun, Jul 11, 2021 at 10:21 AM smitra <[email protected]> wrote: > On 11-07-2021 00:59, Bruce Kellett wrote: > > On Sun, Jul 11, 2021 at 8:27 AM smitra <[email protected]> wrote: > > > >> On 10-07-2021 21:41, 'Brent Meeker' via Everything List wrote: > >>> On 7/10/2021 1:19 AM, Bruno Marchal wrote: > >>>> So, in general we can conclude by generalizing this to any large > >>>> number of particles that even with what we consider to be > >> permanent > >>>> records, you don't get rid of the theoretical possibility of > >>>> interference between the sectors where those records are > >> different. > >>> > >>> We can if the universe is expanding faster than light beyond the Hubble > >>> radius. > >>> > >> > >> The expansion of the universe is irrelevant. The information needed > >> to see the interference pattern continues to exist outside the horizon > >> when it isn't accessible to us anymore. And this is irrelevant for the > >> discussions about observations in quantum mechanics. If an observer > >> performs a measurement and the claim is that this is a unitary > >> process with the observer evolving into a superposition, while the > objection > >> > >> against this claim is that infrared photons are escaping and will > >> eventually move beyond the Hubble volume, then these photons will > >> still not have escaped beyond the Hubble horizon by the time the > observer > >> is aware of the results of the experiment. So, whether or not the > >> photons will eventually no longer be accessible, cannot be relevant. > > > > Once the photons escape from the immediate environs of the experiment, > > they are not recoverable. Try shining a torch at night to illuminate a > > tree. Now try to stop the illumination already present. You can stop > > future illumination by covering the torch, or switching it off. But > > once the tree is illuminated it is not reversible. The expansion of > > the universe, and the existence of the Hubble horizon, just makes the > > irreversibility more obvious. > > > This is only true in practice, not in principle because the escaping > photons be captured and detected in principle.
Not true. You can;t ever catch up with the escaping photons to capture them. It's also irrelevant, > because the photons that escape continue to exist, the information > contained in the photons continues to exist, even if it were true that > they could not be recovered. Then if we were to conduct an interference > experiment with the balls then we wouldn't see an interference pattern. > But if we write down where each balls lands on the screen then this > information together with information that could be obtained by > performing certain measurements on the escaping photons emitted by each > ball would still yield an interference pattern. > This is where you go seriously wrong. Simply recording where the photons land does not quantum erase the information they carried. Once the photons carry off the which way information, the interference pattern is restored only if the information carried by the photons is quantum erased. Simply running the photons into a screen (or the wall), even if you record where they land, is not quantum erasure. See, for example, the paper arXiv:1206.6578 on quantum erasure. In this paper they say "the presence of path information anywhere in the universe is sufficient to prohibit any possibility of interference. In other words, the atoms' path states alone are not in a coherent superposition due to the atom-photon entanglement." This transfers directly to the buckyball experiment under discussion. Running the photons into a screen, or the wall, does not destroy the ball-photon entanglement. 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]. To view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/CAFxXSLQDOr5CVQXgFwRnCKMA69JNCG7f5McdkC6HbW_OG-RqTA%40mail.gmail.com.
