On Mon, Jul 30, 2018 at 8:33 PM Bruce Kellett <[email protected]> wrote:
> From: Jason Resch <[email protected]> > > On Mon, Jul 30, 2018 at 7:36 PM Bruce Kellett <[email protected]> > wrote: > >> From: Jason Resch <[email protected]> >> >> >> On Mon, Jul 30, 2018 at 6:12 PM Bruce Kellett <[email protected]> >> wrote: >> >>> From: Jason Resch <[email protected]> >>> >>> >>> On Mon, Jul 30, 2018 at 12:29 AM, Bruce Kellett < >>> [email protected]> wrote: >>> >>>> From: Jason Resch <[email protected]> >>>> >>>> >>>> On Mon, Jul 30, 2018 at 12:13 AM, Brent Meeker <[email protected]> >>>> wrote: >>>> >>>>> ?? Quantum computers cannot calculate anything more than classical >>>>> computers. There are some algorithms that allow a QC to calculate >>>>> something faster; but the domain and range is the same. >>>>> >>>>> So absent that reason does it follow that the wave function is merely >>>>> a convenient (and very accurate) tool? >>>>> >>>>> >>>> Tool for what? Predicting probabilities of finally measured values? >>>> >>>> What then can we say about the intermediate values and the computation >>>> itself? Does it exist and happen, or does the final result merely >>>> materialize magically like the live or dead cat? >>>> >>>> >>>> Does the spot on the screen behind two slits materialize magically? Or >>>> arise as a consequence of the interference in the one world? >>>> >>>> In many-worlds, all possible screen spots occur in different worlds. >>>> But the separation into distinct worlds happens only on decoherence at the >>>> screen -- the interference all happens in the original single world. >>>> >>> >>> What is the photon in each world interfering with? >>> >>> >>> It's a wave, so it's interfering with itself. Just like water or sound >>> waves. >>> >> >> You are saying "a photon is a wave" as if that is an explanation and to >> avoid the main point. If a photon is a wave, and it is interfering with >> other waves, then in other words, it's interfering with other photons. >> >> >> No, it is interfering with itself. Don't be mislead by the water/sound >> wave analogy. >> >> > You can use "itself" only if this "it" can be in multiple locations and > heading in different directions. > > > That is a property of waves. But you will only ever observe a single > photon from this wave..... > Waves/Photons, doesn't matter what you call them. Within the quantum computer this wave/photon is simultaneously in many different locations/doing many different things, performing computations and doing useful work using all of its separate superposed instances of itself. Once it's done doing all this work it settles down on a final value which we can read. And it will be correct, and may have finished an enormous computation in a short period of time, if and only if, it did in fact split up and do all these independent things simultaneously. > > On that we agree. But where did those other photons come from? How did >> they get to be in different positions going in different directions? >> >> >> They aren't. >> > > How do do you explain the experiment with beam splitters and recombining > light at a half silvered mirror to interfere and only be reflected one way? > > > Photons have both wave-like and particle-like properties. That is quantum > physics. > So do you accept or reject that this "wave" can be in different places simultaneously? > > > Why do these "waves" (photons) behave in all the same ways as photons, > they reflect off mirrors, pass through strained glass (only if the glass is > the same color as the photon), are blocked by opaque objects, travel at c, > etc? > > > Ah, the mysteries of quantum physics. Photons do not have a purely > classical description. Get used to it. > >> >> It's many shadow partners in other worlds. World is a confusing term >> unless we define it. >> >> >> I agree. Frequently, many-worlders follow Deutsch and have a >> schizophrenic attitude to "worlds" -- they are either any component of any >> possible superposition, or the semi-classical endpoint of the process of >> decoherence. In the first case, "worlds", as components of a superposition, >> can interfere. In the second case, worlds are effectively orthogonal and >> cannot interfere. Equivocating between these meanings causes endless >> confusion -- and idiot physics. >> >> I always use the term "world" in the second sense, so worlds are >> orthogonal and cannot interfere. >> >> We might also say the system of the photon is in many states, while the >> rest of the system (us, the screen) remain in one state, until we interact >> with the many-state photon system. So in that sense, you could argue the >> screen and us are in one world until the decoherence. But the system of >> the photons can't properly be described as any singe photon system. >> >> >> Because the photon is a wave. The attempt to eliminate waves or fields >> from physics in favour of a purely particle ontology failed. Feynman was >> most disappointed by this, but if you think you can do better than >> Feynman......... >> >> "Newton thought that light was made up of particles--he called them >> "corpuscles"--and he was right. We know that light is made of particles >> because we can take a very sensitive instrument that makes clicks when >> light shines on it, and if the light gets dimmer, the clicks remain just as >> loud--there are just fewer of them. [...] I want to emphasize that light >> comes in this form--particles. It is very important to know that light >> behaves like particles, especially for those of you who have to gone to >> school, where you were probably told something about light behaving like >> waves. I'm telling you the way it *does* behave--like particles. You >> might say that it's just the photomultiplier that detects light as >> particles, but no, every instrument that has been designed to be sensitive >> enough to detect weak light has always ended up discovering the same thing: >> light is made of particles." -- Richard Feynman >> >> >> Feynman was wrong when he wrote this. Even he eventually saw that this >> was wrong -- it couldn't be made to work. >> >> > Do you have a source I could read on this? > > > The failure of the Wheeler-Feynman absorber theory was always a > disappointment to Feynman. I can't recall an exact source, but I think more > recent books on the history and interpretation of QT probably cover the > development of Feynman's thought. > > The main argument against Feynman's "all is particles" idea is the > existence of Hawking and Unruh radiation. These are effects of quantum > fields in curved space-time, and there is no particle explanation. See > Wald: "Quantum Field Theory in Curved Spacetime", or his "General > Relativity". Or the book by Birrell and Davies. > Thank you, I will check these out! Jason -- 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 post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
