On Sun, Oct 20, 2019 at 8:32 AM John Clark <[email protected]> wrote:
> On Fri, Oct 18, 2019 at 6:31 PM Bruce Kellett <[email protected]> > wrote: > > >> *> if you erase or not the welcher weg information 'before' the signal >>>> photon hits the screen, then presumably some, presently unknown physics, >>>> could send this information to the screen and influence the result there.* >>>> >>> >>> So you admit it. If you continue to insist Many Worlds do not exist then >>> to explain an experiment that has been performed many times you must >>> postulate new physics and mess with Schrodinger's Equation. >>> >> >> > Not at all. The results of the experiment are easily explained within >> the structures of conventional quantum mechanics, whatever interpretation >> one wishes to adopt. There is nothing mysterious here. >> > > There is a lot of mystery here! In 2007 entangled photons were sent 89 > miles between La Palma and Tenerife, the decision to erase or not to > erase was made in less time than it took for light to travel those 89 miles > and hit the detector: > > Quantum Spookiness Spans the Canary Islands > <https://www.scientificamerican.com/article/entangled-photons-quantum-spookiness/> > > The last potential loophole, the freedom of choice loophole, was pretty > much closed in April 2018. That loophole says that maybe your measurement > settings that chose between erase and don't erase are not really random > after all, there might be a deterministic process that makes the choice and > misleads us: > > Quantum entanglement loophole quashed by quasar light > <http://www.astronomy.com/news/2018/08/distant-quasars-confirm-quantum-entanglement> > > They state that: > > *"Arguably the most interesting assumption is that the choice of > measurement settings is “free and random,” and independent of any physical > process that could affect the measurement outcomes. As Bell himself noted, > his inequality was derived under the assumption “that the settings of > instruments are in some sense free variables, say at the whim of > experimenters, or in any case not determined in the overlap of the backward > light cones.”* > > So to close this loophole they didn't use a standard random number > generator to make the choice to erase or not erase the information in the > short amount of time it takes light to travel those 89 miles before (yes > BEFORE) the photon hit their detector; instead they used the light from a > distant quasar to make the decision, so if its a conspiracy to mislead us > (as Superdeterminism says) it's a grand conspiracy indeed. They conclude: > > *"This experiment pushes back to at least 7.8 billion years the most > recent time by which any local-realist influences could have exploited the > “freedom-of-choice” loophole to engineer the observed Bell violation"* > It seems that the fundamental problem here is that you are confusing tests of Bell's inequality on entangled particles with delayed choice experiments. These are different things. > >> If you decide to erase or not to erase after the photon passes the >>> slits but before it hits the photographic plate then to explain the results >>> you've either got to embrace Superdeterminism, backward causality or Many >>> Worlds. >>> >> >> *> No, you have got it wrong here. No need for any of this. * > > > That's it? That's all you've got to say? If you have a explanation for all > the odd stuff coming from the 2 slit experiment that has been bedeviling > scientists for a century, a explanation not involving Superdeterminism, > backward causality or Many Worlds then please enlighten a poor mortal such > as myself. > If you are confused by this, then read the explanations that we have offered, by Carroll or Wikipedia. [...] 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? [....] > *> 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. I pass the photon through the slits and entangle it with some spin state that will be spin-up for the left slit, and spin-down for the right slit. I store these particles for a billion or so years until long after the original photons have hit the screen and have been recorded photographically. I then decide to measure my stored "which-way particles". If I measure them in the up-down basis, I can tell which slit the photon went through, so I do not see any interference. However, if I measure my stored particles in an orthogonal basis, such as the left-right basis, I have quantum erased the which-way information, so I do see interference by selecting either the left- or right- polarized particles. The decision of which to measure was clearly made *after* the original photons hit the screen, so it is not erasing the which-way information *before* they hit the screen. You say you are not an expert on this.....I think that has become very clear..... 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/CAFxXSLTUKp35teNohH3KNL_8tbXXtqdgx92SQ1Metey-fovh7A%40mail.gmail.com.
