On Tuesday, July 10, 2018 at 4:42:44 PM UTC-6, Brent wrote:
> On 7/10/2018 3:01 PM, agrays...@gmail.com <javascript:> wrote:
> *IIRC, the above quote is also in the Wiki article. It's not a coherent 
> argument; not even an argument but an ASSERTION. Let's raise the level of 
> discourse. It says we always get a or b, no intermediate result when the 
> system is in a superposition of states A and B.. Nothing new here. Key 
> question: why does this imply the system is in states A and B 
> SIMULTANEOUSLY before the measurement? AG  *
> Because, in theory and in some cases in practice, there is a direct 
> measurement of the superposition state, call it C, such that you can 
> directly measure C and always get c, but when you have measured and 
> confirmed the system is in state c and then you measure A/B you get a or b 
> at random.   The easiest example is SG measurements of sliver atom spin 
> orientation where spin UP can be measured left/right and get a LEFT or a 
> RIGHT at random, but it can be measured up/down and you always get UP.  Any 
> particular  orientation can be *written* as a superposition of two 
> orthogonal states.  

*When you're trying to explain esoteric issues to a moron in physics, you 
need to be more explicit. These are the issues that cause confusion and 
caused me to fail to "get it". After some subsequent posts, you seem to be 
saying that in an SG spin experiment where the measurement base is UP/DN, 
the system being measured is ALSO in a superposed LEFT/RIGHT state which is 
also measured (by an SG device designed to measured spin?), and that the 
LEFT/RIGHT superposed state persists with some persistent eigenvalue after 
UP/DN is measured. It's murky for us morons.  How does one get the system 
to be measured in a superposition of RIGHT/LEFT; what is the operator for 
which that superposition is an eigenstate, and what is the value of the 
persistent eigenvalue?*

*Furthermore, you finally assert that since the RIGHT/LEFT state persists 
-- meaning that particle is in some DEFINITE state after the spin is 
measured -- and since (as you finally, finally assert) that that state can 
be written as a superposition of UP/DN, all is well -- in the sense that we 
can now be certain that the system is physically and simultaneously in the 
UP and DN states (which I am claiming is a fallacy). *

*HOWEVER, assuming that I understand your argument after filing the gaps in 
your presentation (and pointing to some unanswered issues), I now must 
"rant" again that the UP/DN superposed representation is NOT unique. Thus, 
since there are finitely many or uncountable many such representations, and 
since (as per LC) QM has no preferred basis, your argument for the physical 
simultaneity of UP and DN states fails. I mean, I could write the 
superposed states in the basis (UP + DN) and (UP - DN), or in many other 
bases. Absent uniqueness of bases, one cannot assert that the system is 
physically and simultaneously in any particular pair of basis vectors.*


> This is true in general.  Any state can be written as a superposition of 
> states in some other basis.  But it is not generally true that we can 
> prepare or directly measure a system in any given state.  So those states 
> we can't directly access, we tend to think of them as existing only as 
> superpositions of states we can prepare.
> Brent

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