On Mon, Dec 25, 2017 at 12:41:35PM -0800, [email protected] wrote: > > > > *Spin measurements are irreversible in principle, not simply FAPP. Bruce > showed that on Avoid2 IIRC. I think this means the measurement process,at > least in this case, must be non-linear. If that's true, then how can a > linearprocess such as decoherence, model measurements? AG*
Maybe Bruce can comment, but in general, for a reversible process, the evolution operator needs to be unitary (ie probability preserving). A non unitary (but linear) process will be irreversible. > > > > > von Neumann's proposal was to use projection operators, which are > > linear, but non-unitary. Being non-unitary is a problem, given unitary > > evolution is one of the foundational axioms of QM. > > > > > > *Unitary evolution does not extend to the measurement process; > onlyevolution of the wf prior to measurement. AG * Yes - that is exactly the measurement problem. -- ---------------------------------------------------------------------------- Dr Russell Standish Phone 0425 253119 (mobile) Principal, High Performance Coders Visiting Senior Research Fellow [email protected] Economics, Kingston University http://www.hpcoders.com.au ---------------------------------------------------------------------------- -- 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 https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
