On Thu, Feb 26, 2015 at 09:55:26PM +1100, Bruce Kellett wrote: > > >Does a measuring apparatus always have to be eigenvalue of some > >position operator, though? > > If you are doing quantum mechanics, yes. The result of any > measurement is an eigenvalue of the corresponding operator, and the > system is left in the corresponding eigenstate. > > > >What about variants of the experiment that > >record the results of the measurement as bits in a computer > >memory. Surely that would be in a basis that is eigenvalue of the > >charge of the memory cell transistor, not a position operator at all? > > That is not a measurement unless you can specify the relevant > quantum operator. It is usually the case that most measurements, of > whatever quantity, boil down to pointer positions. That can be > recorded digitally if you like, but the basic measurement is still a > position measurement and you need a basis in the corresponding > Hilbert space in order to specify what are the > eigenvalues/eigenvectors of the possible results. > > Bruce >
I changed the title of this subthread, as I think it is an interesting point worth exploring further. I have heard this claim made vaguely before, though I don't remember whom - do you have any references where someone has advanced this argument? I still think the claim unlikely - the measurement of an interference pattern of coherent light doesn't seem to involve any position basis that I can see, for example. I realise this seems a bit like whack-a-mole, but you are defending a strong thesis, and in the absence of a well-articulated reasoning for it, to see potential counter-examples deconstructed in front of my eyes is educational. :). Cheers -- ---------------------------------------------------------------------------- Prof Russell Standish Phone 0425 253119 (mobile) Principal, High Performance Coders Visiting Professor of Mathematics hpco...@hpcoders.com.au University of New South Wales http://www.hpcoders.com.au Latest project: The Amoeba's Secret (http://www.hpcoders.com.au/AmoebasSecret.html) ---------------------------------------------------------------------------- -- 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 everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at http://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
