On Monday, October 29, 2018 at 10:22:02 AM UTC, Bruno Marchal wrote: > > > On 28 Oct 2018, at 13:21, [email protected] <javascript:> wrote: > > > > On Sunday, October 28, 2018 at 9:27:56 AM UTC, Bruno Marchal wrote: >> >> >> On 25 Oct 2018, at 17:12, [email protected] wrote: >> >> >> >> On Tuesday, October 23, 2018 at 10:39:11 PM UTC, [email protected] >> 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. >
*I don't understand. With SG one can change the up/down axis by rotation, but that doesn't result in an (up + down), or (up - down) measurement. If that were the case, what is the operator for which those states are eigenstates? Which book by Albert? AG * > > 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]. >> 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. >> >> >> > -- > 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. > For more options, visit 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.
