Not me but Russell wrote that. I should have made that clear better when I posted Russell's attachment (Sorry Russell!).
----- Oorspronkelijk bericht ----- Van: "Jesse Mazer" <[EMAIL PROTECTED]> Aan: <[EMAIL PROTECTED]> Verzonden: Wednesday, July 28, 2004 08:59 PM Onderwerp: Re: Quantum Rebel > Saibal Mitra wrote: > > >Now in the article, Afshar claims to have measured which slit the > >photon passed through and verified the existence of an interference > >pattern. However, this is not the case - without the wires in > >place to detect the presence of the interference pattern, photons > >arriving at detector A have passed through slit A, and vice-versa with > >detector B and slit B. However, with the wires in place, some photons > >are scattered, indeed some photons which passed through slit A will > >arrive at detector B. With both slits open, and the wire placed > >exactly at a null point of the interference pattern, the photons > >passing through slit A and arriving at detector B exactly counteracts > >the photons passing thoguh slit B that have been lost through > >scattering. The mathematics of quantum mechanics assures this, > >coincidental this may seem. > > A poster on sci.physics.research elaborates on this point a little with a > nice thought-experiment involving enlarging the wires until they are almost > touching, at which point you just have a new set of "slits": > > http://makeashorterlink.com/?W3F012BE8 > > >Now I haven't done any calculations or read the New Scientist article > >except looking at the lab setup graphics, but if I would hazard a quick > >guess, it would be that it will turn out that even if the wires are > >placed in the interference fields valleys, the finite width of the > >wires will diffract just enough photons to erase the which-way > >information that was gained by focusing the detectors at the holes in > >the wall through the lens. > > > >Consider the limiting case with wires placed with their centres in the > >interference fields valleys as before, but expand their width so much > >that they almost touch each other. What you have now is yet another > >wall with a bunch of slits in! Obviously, almost all which-way > >information is lost after the wavefronts pass these almost > >infinitesimal slits since they will diffract the photons equally no > >matter from which hole in the *first* wall they originated, so any > >detector placed after this obstacle will be like running a new > >multiple-slit interference setup (although with the lens now severely > >defocusing the too-closely placed new slits). And since the which-way > >information from the first wall is erased, interference is free to > >happen between the first and the second wall. After the secondary wall > >the detectors can pick up which-way information causing them to behave > >as if there was little subsequent interference. > > > >Conversely, the other limiting case is with no wires (or secondary > >wall) present. Then all which-way information is present and again the > >detectors behave as if there was no interference. > > > >The experiment shows a case in between these limits and the effect I > >guessed at above could (and should, according to traditional QM) turn > >out to always cancel any attempt to find both 100% interference and > >100% which-way information. This would be better showed with some > >calculations of course... > >