Re: causing trouble

[John M <***>]

Tim,
I think you missed one line from your "reply":
"I agree".
Thanks for the additional teaching ideas.
John

----- Original Message -----
From: "Tim Gwinn" <***>
To: <***>
Sent: Saturday, April 17, 2004 8:35 PM
Subject: Re: causing trouble


> JohnM said:
> > Question about Q-measurement (I really know very little about
Q-science):
> > Isn't it changing the system only because what we call
> > 'measuring" is indeed
> > the destruction (extraction?) of a substantial component in the
> > model-system
> > we visualize? In which case the word is used wrongly.
>
> John,
>
> I would say that it is because all "measurement" is, at root, the physical
> interaction of (at least) two systems: the system under study and the
meter
> (i.e., measuring device). In the case of quantum measurements of
> non-commuting variables, like position and momentum, we do not (currently)
> have a way of physically interacting with the quantum system in a way
which
> ascertains the value of one of these variables without the physical
> interaction causing some change in the other variable that is greater than
> some particular degree of precision.
>
> Another way to say it is that a meter works by having a dynamic induced on
> it by the object system in the physical interaction of the two systems. In
> most macroscopic measurements, the meter is designed to NOT induce a
> detectable dynamic on at least some variable(s) of the object system. In
the
> case of quantum measurements, we cannot design a meter which does not
induce
> a detectable dynamic on some variable(s) of the object system. To me, it
> remains debatable whether this is truly a fundamental physical limitation
or
> whether future knowledge will allow us to design meters that avoid this
> problem.
>
> Regards,
> Tim