From: Anders Sandberg (asa@nada.kth.se)
Date: Mon Jan 20 2003 - 14:27:23 MST
On Mon, Jan 20, 2003 at 02:04:48PM -0600, Damien Broderick wrote:
> Anders Sandberg writes:
>
> > As far as I understand things, then
> > you would get the fringes change as if the probability amplitude of the
> > potentially blocked photon was decreased (how much depends on your
> > setup). So for a very unlikely blocking you would get the fringes nearly
> > as in the typical two-slit experiment, and for a more likely blocking
> > they would move towards a no-fringe pattern.
>
> That's one of the points I remain unclear about. In the Deutsch formulation,
> interference occurs because of the interplay between measurable photons
> (etc) and their `shadow' other-world counterparts (which I sometimes think
> of, provincially, as `fauxtons'). If this actually happens, I suppose a
> reduced number of worlds with the 2 slits open should cause reduced rather
> than obliterated fringes. But I was under the impression that experiments
> (either real or gedanken) by Chiao and colleagues had shown that even *in
> principle* slit closure was enough to block interference. (Serafino kindly
> sent me some references to, e.g., interaction-free measurements --
> http://arxiv.org/PS_cache/quant-ph/pdf/0102/0102049.pdf -- etc, which are
> damaging my brain even as we speak.)
Fun paper.
Hmm, one could run the EV mirror system with the lotto results. Instead
of the bomb, place a LCD display showing the result where the photon
would be blocked if the numbers fitted your guess. Then detector D2
would start to chime if you won. I guess this is what you were after?
With the quantum Zeno effect the probability of getting the right
response without actually sending a photon through the LCD can be made
arbitrarily close to 1.
I think reasoning in terms of fauxtons is risky; to really analyse what
happes one has to do a computation of probability amplitudes in terms of
strict QM. One cannot safely use the interpretations of it to find out
what would happen.
I'm not good enough with bra's and ket's to calculate what happens; it
seems that there is room for some weirdness here.
> > You still need the photons to get to the photographic film to get
> > something measurable, so they will have to take the day to pass down the
> > beam path.
>
> Yeah, I guess so, in which case there's no obvious way to *use* such an
> effect. Sigh. (Unless Elitzur/Vaidman etc, cited above, helps out...)
I don't think so, unfortunately. On the other hand, if one exploits the
uncertainty in *where* the slit is and hopes for something like the
FTL-tunneling effect to save us. But I doubt the universe is *that* fun.
-- ----------------------------------------------------------------------- Anders Sandberg Towards Ascension! asa@nada.kth.se http://www.nada.kth.se/~asa/ GCS/M/S/O d++ -p+ c++++ !l u+ e++ m++ s+/+ n--- h+/* f+ g+ w++ t+ r+ !y
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