Re: the two slits versus schrodinger's cat

From: Greg Gerardin (g.gerardin_at_danka-studio.com)
Date: 08/17/04 

Date: Tue, 17 Aug 2004 19:56:07 +0200

"Bjoern Feuerbacher" <feuerbac@thphys.uni-heidelberg.de> a écrit dans le
message de news:cftao6$jor$1@news.urz.uni-heidelberg.de...

[snip]

> > Right, i'm a french canadian (and living in France) Am I that bad in
english
> > ? ;)
>
> Most of your post was o.k., but the first sentence above... ouch.

I know I have problems with some specific kind of sentences...
argh

*shy*

[snip]

> > But this
> > superposition is expressed by a probability wave, am i wrong?
>
> The states are (or better, can be represented by) probability waves.
> A superposition of states is itself again a state and therefore can
> also be represented by such a wave.
>
> "superposition of states" means roughly that the object is in
> two states at once. More mathematically: it has probability amplitudes
> for being in both states, and the total state is a linear combination
> of these two states (the coefficients being the probability amplitudes).

ok i get it!

[snip]

> > And what's an Hilbert space? Is it more like a mathematical object, or a
> > quantum object? (ok I should check this out by myself)
>
> A mathematical object. Are you familiar with vector spaces?

I'm familiar with nothing.

Basicaly, i'm just a graphic designer and a programmer (got few scientific
*basis* tho.. i have studied vectors (newtonian/euclidiean) back in the
college days -> arrows representing forces...hmmm... kinda like geometry
applied to physics... but i don't think it's related to "vector spaces", is
it?

[snip]

> > But... but if i see a trace on the left, I know that the photon went
through
> > the left slit,
>
> No. Why do you think so?
>
> The photon could also have gone through the right slit and turned around
> there to travel onwards in a different direction. Photons don't have
> to travel straight. According to the path integral interpretation of
> QM, they instead go on *all paths at once*!

oh well, ok! I see your point, even tho I don't see why the photon would
turn just like that without any reason (since the experiment is in a
controlled environnement)

> > same thing if I see a trace on the right... and if i see an
> > interference pattern, I know that the photo went through both slits... ?
>
> You don't get an interference pattern from one single photon.

Ok i understand this now. That's really what I had wrong in the first
place. I though that the pattern was directly caused by the wave and its
interference.....!! (that was stupid when I think about it now) Now I got it
allright. The wave describes the probability of the photon to manifest
itself (as a particule) somewhere in space...

>
>
> > So yes, it tells me through which slit the photon went!
>
> No, it does't.
>
>
>
> >>>Following that the
> >>>photosensitive screen really shows and maintains the wave nature of the
> >>>photon,
> >>
> >>It does not do that. The photosensitive screens works by using the
> >>*particle* nature of the photon, not its wave nature!
> >
> >
> > But then how come the interference?
>
> Due to the wave being there. The wave does the interference and, in a
> sense, "guides" the photons. (note that I don't want to embrace
> deBroglie's idea of "pilot waves" here)

You know what, there's a beautiful statue of de Broglie right in front of my
window... I think the de Broglie statue "guided" me to this newsgroup :)

Thanks for everything, you really helped my clarified those concepts of wave
functions, states, etc..

Ciao
Grge

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