🚀 go-pugleaf

jbaez@nevanlinna.mit.edu (John C. Baez) writes:

>It seems, by the way, that Sarfatti knows his transformation is unitary
>and couldn't care less:

I assume you meant "not unitary"...

>In article <BssCHF.JxB@well.sf.ca.us> sarfatti@well.sf.ca.us (Jack Sarfatti) writes:
>>#2 The mistake you keep making is to take a fragmentary view. You keep
>>saying that the matrix is not unitary. So what! I am using both Feynman
>>rules
>>from preparation to irreversible detections and this process is not unitary.
>>If you
>>want to describe the total behavior of my device then of course the matrix
>>from
>>start to finish is not unitary because of measurements!
>>

I think that what Mr. Sarfatti is calling the "Feynman rules" are
basically the Copenhagen interpretation.  He's trying to say that
it doesn't matter that his putative system evolves in a nonunitary
manner because a measurement happens at some point, which does
something nonunitary to the state vector.

A measurement, though, doesn't perform just any arbitrary nonunitary
transformation in this interpretation:  it performs a *projection*
of the state vector into an eigenstate of the observable being
measured.  Sarfatti's transformation isn't unitary evolution or
the projection one gets from a measurement.

The commuting of observables at spacelike separation prevents
spacelike communication via quantum entanglement precisely
*because* the measurements act like eigenstate projectors.  An
eigenstate of one such observable is always in an eigenspace of
the other, so the order in which the projections occur doesn't
matter, and there's no way one measurement can affect the result 
of the other.

Mr. Sarfatti: Does Schrodinger's 1930 result assume that measurements
act in this way, or does it allow something not present in modern
QM?

>[...] the nonunitarity of your process goes
>against what I'd call "standard quantum mechanics" and a clear symptom
>of that fact is that you claim that you can get faster-than-light
>communication!  

Your bias against collapse hypotheses is showing itself... :-)

But, seriously, this evolution doesn't even correspond to the
transformation performed by collapse.


-- 
Matt McIrvin, professional gradgrind, amateur Usenet drifter