On Wednesday, June 13, 2018 at 12:05:34 AM UTC, Bruce wrote: > > From: <agrays...@gmail.com <javascript:>> > > > On Tuesday, June 12, 2018 at 11:36:07 PM UTC, Bruce wrote: >> >> From: <agrays...@gmail.com> >> >> >> On Tuesday, June 12, 2018 at 11:03:28 PM UTC, Bruce wrote: >>> >>> From: <agrays...@gmail.com> >>> >>> >>> *Doesn't the superposition of states used in the cat problem. or indeed >>>> any quantum superposition, requires the system being measured to be >>>> isolated? AG * >>>> >>> >>> *As I see it, the total system represented by the wf ( (Alive, >>> Undecayed) + (Dead, Decayed) ), leaving out Dirac symbols, must be isolated >>> if it's regarded as a superposition. If so, this implies the cat is also >>> isolated. AG* >>> >>> >>> That is the root of your problem in understanding superpositions. There >>> is absolutely no requirement for the system to be isolated in order for >>> there to be a superposition. In fact, the opposite is the case -- each >>> branch of the superposition decoheres by interacting with, and becoming >>> entangled with, the environment. That is how quantum measurement theory >>> proceeds. Isolation from the environment is a condition you made up, and it >>> is not required. >>> >>> Bruce >>> >> >> For reasons not worth explaining, I have had doubts whether a >> superposition requires isolation. But what it does require, at least in the >> cat paradox, is interference among the components. Otherwise, Schroedinger >> couldn't have concluded that the superposed wf implies the cat is >> simultaneously alive and dead. So the issue becomes whether a macro object >> like a cat has a well defined wave length, which IIUC, is the necessary >> condition for interference. AG >> >> >> That is another misunderstanding on your part. Interference between >> components is not necessary for a superposition. >> > > > *I didn't make that claim. I claimed that interference is necessary for a > system in a superposition to be simultaneously in all components of the > superposition. AG * > > > I don't know what that means! >
*You're being modest. Go back to the seminal QM experiment, the double slit. The pattern on the screen reflects the reality of interference, from which we get the interpretation that the system is somehow in both component states simultaneously, each slit causing a component in the superposition. Or the interpretation for the hoi polloi that quantum particles can be in two different positions simultaneously. AG * > > As Brent explained, being "regarded as a superposition" is just choosing a >> coordinate system. For the cat, we can have the 'alive/dead' coordinate >> system, or an '(alive+dead)/(alive-dead)' coordinate system. In the first, >> the cat is either alive or dead; in the second the cat is in a >> superposition of the two states whichever basis vector you choose. There >> is nothing magical about this, it is just a matter of how you look at it. >> Superpositions of classical macro objects are always possible, just by >> rotating the basis vectors. >> > > > * So if one chooses a basis where the cat is simultaneously alive and > dead, is this a problem for QM? AG * > > > No problem for QM -- one does it all the time. It might not be the most > useful basis, but that doesn't mean it isn't possible. > *Since you earlier acknowledged that Schroedinger showed the "absurdity" of alive/dead simultaneously, are you now saying the absurd is not only possible in QM, but even when it's never observed? AG* > In general, however, one has a 'preferred basis'; a basis which is stable > against environmental decoherence -- the one corresponding to what one > actually sees in the laboratory. > *You and Brent refuse to explain how decoherence solves the case of alive/dead simultaneously if it implies that that result in fact persists if only for a very, very short time. AG* > > 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 everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
