## Classical&QM Probability and Prob/WaveFunction Collapse

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• ... Let me first briefly introduce myself. I was trained as a theoretician, and did QED and particle physics, albeit quite a few years ago. But, for most of my
Message 1 of 3 , Mar 31, 2003
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Let me first briefly introduce myself. I was trained as a
theoretician, and did QED and particle physics, albeit quite a few
years ago. But, for most of my adult life I've worked in business,
doing statistics, modeling, and consulting.

My question is: why is quantum probability, different from "classical
probability?" After years of working with probability I'm more
convinced than ever that the two are basically not different --
probability is probability. (Certainly the computational approaches
are quite different)

When I do a coin toss, I do not know what will happen, other than the
chances will be equal for either possible outcome. But when the coin
lands I know whether we are talking heads or tails, and the state of
my mind goes from the uncertainty of 50-50 chances, to full certainty
of the outcome. For practical purposes, the wave packet, the
probability function, collapses to the outcome, which ends up in
a "pure" state. In applications of probability to marketing,
medicine, sports, finance, and so on, we typically finesse the actual
collapse, knowing as we do the brain/mental processes that govern our
change of knowledge are a bit beyond our ken, at least for the
present.

When you do an electron scattering experiment, for example, once the
counters start registering events, you know what happened -- at time
t, counter A went blip, so we know with certainty that an electron
hit counter A. For that matter, when we make a classical computation
of the radiation patterns from an antenna with a new configuration,
we certainly will do measurements to determine the efficacy of our
computations. Once we do the measurements, we reduce an initial
uncertainty to certainty -- does this not reduce the wave packet?

So, my question is, once again, why is quantum probability different
from the probability that many, many nonphysicists use -- with great
success, and without ever worrying about any wave packet reduction?
Regards,
Reilly Atkinson

(Again I agree that the Schrodinger equation for the wave function,
and a stochastic dynamics equation for probabilities of consumer
purchasing behavior are very different -- conceptually and
mathematically. The issue is what the computational results mean.)
• ... IMHO, there is no real difference, using the MWI interpretation. And your examples are quite nice. Any truly random events always represent branches of
Message 2 of 3 , Apr 1, 2003
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ormand2000 wrote:
>
> My question is: why is quantum probability, different from "classical
> probability?" After years of working with probability I'm more
> convinced than ever that the two are basically not different --
> probability is probability. (Certainly the computational approaches
> are quite different)

IMHO, there is no real difference, using the MWI interpretation. And

Any truly random events always represent branches of the multiverse,
whether the events are macroscopic or microscopic.

And of course in the MWI there is no collapse; by looking at the result
of the experiment we just find out which branch we are in, and we know
that the other branches are just as real.

-- Gary Oberbrunner
• ... But then you follow Heisenberg (at least with respect to some of his writing) taking the wave as a description of our (psychological ignorance). ...
Message 3 of 3 , Apr 1, 2003
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At 01:23 01/04/03 +0000, ormand2000 wrote:
>[snip] Once we do the measurements, we reduce an initial
>uncertainty to certainty -- does this not reduce the wave packet?

But then you follow Heisenberg (at least with respect to some of
his writing) taking the wave as a description of our (psychological
ignorance).

>So, my question is, once again, why is quantum probability different
>from the probability that many, many nonphysicists use -- with great
>success, and without ever worrying about any wave packet reduction?

Because quantum probability is given by the square of a "probability
amplitude", and we have evidence that that amplitude behaves
like a wave so that it interferes independently of
the observers. How could our "ignorance" interferes with reality?
Many World, or many minds helps to figure out what happens ...

Bruno
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