🚀 go-pugleaf

In article <1992Oct5.123002.13912@sei.cmu.edu> firth@sei.cmu.edu (Robert Firth) writes:
>In article <1992Oct3.134653.20562@oracorp.com> daryl@oracorp.com (Daryl McCullough) writes:
>
>[a neat article on the quantum zeno effect - thanks, Daryl]
>
>Just one minor point: I don't think this effect can be used to slow
>down radioactive decay.  That's an exponential process, ie if the
>atom is undecayed at time 0, then the probability it is still
>undecayed at time t is
>
>	P(t) = exp(-kt)
>
>where k = log2/halflife.

Oh-oh, not this again.  The point, as I have argued earlier, is that no
physically reasonable process can give EXACTLY exponential decay; very
general arguments show that there is a short "plateau" before the curve
approximates an exponential.  If you checked out the nucleus carefully with
a sufficiently high frequency you could "nip it in the bud" and use Zeno
to keep it from decaying.  However, even for the very slowest nuclear
decays you would have to check it out every 10^{-23} seconds or so.
(Someone may still have the references I posted on this, which I think I have
discarded.)  In real Zeno experiments one doesn't use nuclear decays,
one uses electronic transitions.  

In my posts on interpretation of QM I noted the subtleties associated
with repeated measurements and suggested how I thought one should get
the right answers for this sort of problem without postulating
"collapse," but Daryl is right in emphasizing this sort of problem as a
hurdle any successful approach to QM must overcome.