On Mon, Oct 21, 2019 at 1:19 AM John Clark <[email protected]> wrote:
> On Sat, Oct 19, 2019 at 5:57 PM Bruce Kellett <[email protected]> > wrote > > >> Because the choice to erase or not to erase is delayed until long >>> after the photon has passed the slit, it could be made a billion years >>> after it passed the slit, and the decision could be made one nanosecond >>> before the photon hit the photographic plate, but it must be *before* >>> or you will see nothing new or interesting. >>> >> >> > Exactly what do you think that you will see in that case? and why do >> you think it uninteresting? >> > > If you decide, one nanosecond *BEFORE* the photon hits the screen, to > erase the information about which slit the photon went through a billion > years ago then you will always see a interference pattern, and that > indicates a billion years ago the photon must have gone through both slits. > But if you decide, one nanosecond *BEFORE* the photon hits the screen, > NOT to erase the information about which slit the photon went through a > billion years ago then you will NOT see a interference pattern and you will > know that a billion years ago the photon must have gone through one and > only one slit. I find that result to be so interesting and surprising that > I feel no necessity to spell out why. But if the information is erased > after the photon hits the screen then the results are neither interesting > or surprising because it wouldn't tell us anything new we didn't discover > in 1801. > I may not have been sufficiently clear in what case I was asking about. You claim that nothing interesting is seen if you make the choice between observing which-way information and quantum erasing it after the signal photons have been recorded on the screen. It seems that you think you will just see Young's interference fringes whatever you do *after* the record is made at the screen. But that is false, as has been demonstrated in many experiments. It does not matter whether you make the choice between which-way and quantum erasure before or after the photons hit the screen. That is what the experiments of Zeilinger and his associates show. These are the experiments where the decision to erase or not were made 144 km away from the lab in which the interference measurement was made. See the original paper at https://arxiv.or/abs/1206.6578 *>>> Yes, of course you do: you just select the subsets of photons that >>>> were quantum-erased by passing the left polarizer (respectively, the right >>>> polarizer) to see the interference patterns emerge from the apparent >>>> no-interference blob.* >>>> >>> >>> >> Ah Bruce.....in that case you are very obviously erasing the which >>> way information BEFORE it hits the screen or photograph that you're looking >>> at! >>> >> >> *> You will have to explain that to me.* >> > > If you place a polarizing filter oriented in the left-right direction over > one slit and a polarizing filter oriented in the up-down direction over the > other slit and shine a light through both slits and onto a screen you will > not see a interference pattern on that screen because the filters have > encoded information onto the photons about which slit they went through. > However if you then place a third polarizing filter, this time oriented at > a intermediate 45 degree angle, after the slits but *BEFORE* the screen > then "the interference pattern emerges from the apparent no-interference" > because that 45 degree filter has erased the which way information that was > encoded on the photons *BEFORE* any photons hit the screen that you're > looking at. > That is not the experimental set-up of the Zeilinger et al. assessment of delayed choice. Read the sources I have quoted....... > *You say you are not an expert on this.....I think that has become very >> clear.....* >> > > It's perfectly true I'm not a expert on this, but I certainly hope you're > not claiming that you're different and are an expert because that would be > laughable. > I can at least read the original papers, and the summary and analysis given by Carroll or on Wikipedia. It seems that you have been unable to understand any of these sources. Bruce You have demonstrated a profound lack of understanding of a basic fact that > is taught in the first minute on the first day in a first course on The > Delayed Choice. If you don't even understand the basic facts of the > experimental setup how in the world can you hope to interpret the results? > -- 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/CAFxXSLTkiRdCqGYwYPA%3DNkZmzjEOTn0V-Vt6hMrLhu91vrYQfA%40mail.gmail.com.
