On Mon, Aug 12, 2019 at 3:56 PM smitra <[email protected]> wrote: > On 12-08-2019 04:06, Bruce Kellett wrote: > > On Mon, Aug 12, 2019 at 3:48 AM Bruno Marchal <[email protected]> > > wrote: > > > > In the sense you mention I am OK, but we have a slight vocabulary > > problem. Not important, if you agree that measurement are > > self-entanglement, so that the superposition of the orthogonal state > > SlitA and SlitB, say some oblique (with sqrt(2) = 1) SlitA + SlitB is > > inherited by the observer “looking” which is which. > > > > If you do not measure which slit the photon went through, then the > > superposition of slits is not broken by decoherence. But the > > interference at the screen depends only on things like the wavelength > > of the light, the separation of the slits, and the distance between > > the slits and the screen. If you refine this calculation by taking the > > finite width of the slits into account, you convolute the interference > > pattern with the diffraction pattern due to finite slit width. This is > > an elementary calculation in physical optics, not even requiring > > quantum mechanics. But the waves at the screen cannot be orthogonal, > > or else they would not interfere. > > The states at the screen are orthogonal because they were at the start > and inner product is conserved under the unitary time evolution. >
The sits are orthogonal if you measure which slit the photon went through, in which case the interference pattern disappears, as required by orthogonality. But they are not orthogonal if they are not measured, else there would be no interference. Orthogonal states cannot interfere. Bruce -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/CAFxXSLTS994wXbC_N8R2bPSRENO9fL_i4SM-yyyZEqsrhM7wtQ%40mail.gmail.com.
