> On 28 Oct 2018, at 13:21, [email protected] wrote: > > > > On Sunday, October 28, 2018 at 9:27:56 AM UTC, Bruno Marchal wrote: > >> On 25 Oct 2018, at 17:12, [email protected] <javascript:> wrote: >> >> >> >> On Tuesday, October 23, 2018 at 10:39:11 PM UTC, [email protected] >> <http://gmail.com/> wrote: >> If a system is in a superposition of states, whatever value measured, will >> be repeated if the same system is repeatedly measured. But what happens if >> the system is in a mixed state? TIA, AG >> >> If you think about it, whatever value you get on a single trial for a mixed >> state, repeated on the same system, will result in the same value measured >> repeatedly. If this is true, how does measurement distinguish superposition >> of states, with mixed states? AG > > That is not correct. You can distinguish a mixture of particles in the up or > down states with a set of 1/sqrt(2)(up+down) by measuring them with the > {1/sqrt(2)(up+down), 1/sqrt(2)(up-down}) discriminating apparatus. With the > mixture, half the particles will be defected in one direction, with the pure > state, they will all pass in the same direction. Superposition would not have > been discovered if that was not the case. > > And someone will supply the apparatus measuring (up + down), and (up - down)? > No such apparatuses are possible since those states are inherently > contradictory. We can only measure up / down. AG
You can do the experience by yourself using a simple crystal of calcium (CaCO3, Island Spath), or with polarising glass. Or with Stern-Gerlach devices and electron spin. Just rotating (90° or 180°) an app/down apparatus, gives you an (up + down)/(up - down) apparatus. Buy the book by David Albert. It will help you a lot, I think. Bruno > > Bruno > > > > > >> >> -- >> 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] <javascript:>. >> To post to this group, send email to [email protected] >> <javascript:>. >> Visit this group at https://groups.google.com/group/everything-list >> <https://groups.google.com/group/everything-list>. >> For more options, visit https://groups.google.com/d/optout >> <https://groups.google.com/d/optout>. > > > -- > 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] > <mailto:[email protected]>. > To post to this group, send email to [email protected] > <mailto:[email protected]>. > Visit this group at https://groups.google.com/group/everything-list > <https://groups.google.com/group/everything-list>. > For more options, visit https://groups.google.com/d/optout > <https://groups.google.com/d/optout>. -- 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.
