On 6/12/2018 4:21 PM, [email protected] wrote:
On Tuesday, June 12, 2018 at 11:03:28 PM UTC, Bruce wrote: From: <[email protected] <javascript:>>*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. BruceFor 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
Another invented condition. The cat never has a "well defined wave length". It's different parts, all the way down to the atomic level have different masses and momenta. Together the classical cat is defined by a bundle of macroscopically similar vectors in a very high dimensional Hilbert space. Interactions, as with poison gas molecules, can cause those vectors to evolve differently. But they are "interfering" in any basis you could define all the time.
You have been misled by reading about experiments in which one */observes/* and */measures/* interference. It's like saying you need to isolate atoms of a gas in order for them to collide.
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