On Tuesday, June 12, 2018 at 11:36:07 PM UTC, Bruce wrote: > > From: <[email protected] <javascript:>> > > > On Tuesday, June 12, 2018 at 11:03:28 PM UTC, Bruce wrote: >> >> From: <[email protected]> >> >> >> *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 * > 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 * > > 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 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.
