On Monday, October 29, 2018 at 5:22:02 AM UTC-5, 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. > > Buy the book by David Albert. It will help you a lot, I think. > > Bruno > > > What superposition is described to be is always based on some background assumptions.
re: David Albert https://ndpr.nd.edu/news/after-physics/ : wavefunction realism: On this view, the quantum world fundamentally consists of a complex-valued field that exists in an extremely high-dimensional space. on reductionism: Since physical explanations are obviously reducible to physics, it must be that multiple realizability is not incompatible with reduction after all. - pt -- 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.
