Re: Download a new book on quantum mechanics and relativity.
From: Bilge (dubious_at_radioactivex.lebesque-al.net)
Date: 09/24/04
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Date: Fri, 24 Sep 2004 05:30:08 -0000
Eugene Stefanovich:
>Bilge wrote:
>> OK, then let me apply that to a test of quantum mechanics.
>> I prepare electrons with their spins along the x-direction.
>> I measure the z projection. Using your notion of quantum
>> mechanics, I can't know ahead of time what the probability
>> of finding the spin along +/-z,
>
>Why not? If you know for sure that electrons' spins were aligned
>along the x-axis, then you can calculate that the probabilities of
>finding their spins along +/-z are 0.5/0.5. If you do not know
>how exactly electrons were prepared, you should measure.
That isn't how you do an experiment. In an experiment you compare
a theoretical prediction to a measurement. If the two are inconsistent,
the experiment wins and the theory goes.
>> so I say that the probability
>> of +z is P_up and -z is P_down. I now count 25 particles with
>> +z and 75 paricles with -z.
>
>That's fine so far, except that your ensemble is very small
>(just 100 copies) and the measured probability will have a substantial
>error.
No, there won't. The error in the measurement is zero. I didn't
say there were any background counts. In any case, make the counts
75 zillion and 25 zillion. Stop digressing on irrelevant tangents.
>> According to you, I've just
>> measured the wavefunction, so the wavefunction must be:
>>
>> |x> = 0.5 |+z> +/- 0.866 |-z>
>
>Here we go: your ensemble was too small and measured frequencies
I'm not going to follow along with a stupid digression. If you
didn't understand the point, then you certainly won't understand
anything else, but you did confirm what I said about you not
making a very good connection from theory to experiment.
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- In reply to: Eugene Stefanovich: "Re: Download a new book on quantum mechanics and relativity."
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