> Il 16 novembre 2018 alle 10.19 [email protected] ha scritto: > > > > On Thursday, November 15, 2018 at 2:14:48 PM UTC, scerir wrote: > > > > > > > > > > > Il 15 novembre 2018 alle 14.29 [email protected] ha > > scritto: > > > > > > > > > > > > On Thursday, November 15, 2018 at 8:04:53 AM UTC, scerir > > > wrote: > > > > > > > > > > > > > > Imagine a spin-1/2 particle described by the state psi > > > > = sqrt(1/2) [(s+)_z + (s-)_z] . > > > > > > > > If the x-component of spin is measured by passing the > > > > spin-1/2 particle through a Stern-Gerlach with its field oriented along > > > > the x-axis, the particle will ALWAYS emerge 'up'. > > > > > > > > > > > > > > Why? Won't the measured value be along the x axis in both > > > directions, in effect Up or Dn? AG > > > > > > > > > > "Hence we must conclude that the system described by the |+>x state > > is not the > > same as a mixture of atoms in the |+> and !-> states. This means > > that each atom in the > > beam is in a state that itself is a combination of the |+> and |-> > > states. A superposition > > state is often called a coherent superposition since the relative > > phase of the two terms is > > important." > > > > .see pages 18-19 here https://tinyurl.com/ybm56whu > > > > > > Try answering in your own words. When the SG device is oriented along the > x axis, now effectively the z-axix IIUC, and we're dealing with > superpositions, the outcomes will be 50-50 plus and minus. Therefore, unless > I am making some error, what you stated above is incorrect. AG >
sqrt(1/2) [(s+)_z +(s-)_z] is a superposition, but since sqrt(1/2) [(s+)_z +(s-)_z] = (s+)_x the particle will always emerge 'up' > > > > > > > > > > > > > > > > > > > > > > > In fact (s+)_z = sqrt(1/2) [(s+)_x + (s-)_x] > > > > > > > > and (s-)_z = sqrt(1/2) [(s+)_x - (s-)_x] > > > > > > > > (where _z, _x, are the z-component and the x-component > > > > of spin) > > > > > > > > so that psi = sqrt(1/2)[(s+)_z +(s-)_z] = (s+)_x. > > > > (pure state, not mixture state).. > > > > > > > > AGrayson2000 asked "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?" > > > > > > > > Does Everett's "relative state interpretation" show how > > > > to interpret a real superposition (like the above, in which the > > > > particle will always emerge 'up') and how to interpret a mixture (in > > > > which the particle will emerge 50% 'up' or 50% 'down')? > > > > > > > > > > > > > > > > > > > > -- > > > 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 > > > 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. > 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.
