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 [email protected] 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 [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
