Implications of Quantum Physics

[KrazyHorse]

what actual schrodinger thing?

[TCO]

the cat. Or more broadly speaking the radioactive atom.

[KrazyHorse]

here. take a single electron (S = 1/2) and polarise it in z direction (Sz = 1/2)

Now send it through a beam splitter which sends Sx = 1/2 states to the right and Sx = -1/2 states to the left

Recombine the "beams" of electron (each of which only has a half of the electron in it!) and voila! interference between the two available pathways for a single electron...

edited slightly...

[KrazyHorse]

Originally posted by TCO
the cat. Or more broadly speaking the radioactive atom.

Schrodinger's cat is all messed up as a demonstration of quantum principles. It's only really useful as shock treatment to get you used to the fact that things can have indefinite states. It would be almost impossible to decay an atom without performing a measurement on its state.

[Kuciwalker]

Originally posted by KrazyHorse
< GP |TCO > = 1

[Seeker]

"Because other choices (for instance what the spin of some other particle in Beijing is) have no effect on the thing being measured...


None whatsoever?


Not if your experiment is done right..."

But how can any experiment, "done right" or not, isolate itself from the tiny but unpredictable influence of mass-bearing objects moving around in the universe? I mean, the gravity of distant stars and other objects must have some very small but measurable and non-isolate-able effect on any particle you are trying to measure.

[KrazyHorse]

They will have some effect on the state of the particle in question, but they will not completely destroy the admixture of states. State superposition is not an all-or nothing thing; it is possible to have the state

(1/2)| 1 > + ((3/4)^(1/2))| 2 >

just as easily as you can have ((1/2)^(1/2)) (| 1 > + | 2 >)

what I'm saying is that if you run the experiment right you will be left very close to an even admixture of | 1 > and | 2 > despite interaction with the outside world (it will jiggle you a bit to one side or the other, but not totally into one state)

[TCO]

what goes down in stat mech world?

[KrazyHorse]

?

[TCO]

Do you have an admixture of states?

[KrazyHorse]

You have a number of possible states that a given particle can be in with given probability

Not the same thing. In stat mech it's in one or the other...

[TCO]

I like that better.

[TCO]

Do your solved a stat mech problem dance!!!

[Ted Striker]

[TCO]

good