# Re: Quantum Computing

From: Aaron McBride (themcbrides@mindspring.com)
Date: Sun Jul 25 2004 - 23:46:44 MDT

Tommy McCabe wrote:

> <clip>
>
>Spin, in quantum particles, refers to, basically, how
>many revolutions a particle goes through before it
>looks identical to when it started. Particles can have
>whole-numbered spins, like 1, or decimal spins, like
>1/2. Thus, we can classify particles based on their
>native spin. And though there are an infinite number
>of different spins, such a statement about the
>capacity of these electrons would require there to be
>a total of ~2*2^(10^27) different spins used. This
>strikes me as being huge enough to be highly unlikely.
>Mind you, I am not a physicist either, so if anyone
>has a more accurate explanation of what spin is or how
>it can be used to store information, please don't
>hesitate to correct me.
>
>
>
I'm no physicist either, but I don't think you're quite right when you
say there are an infinite number of spins. All electrons are spin 1/2.
All photons are spin 1. Etc...

I believe (and this is where I don't really understand what I'm talking
about) anytime you measure the spin of an electron it either comes out
as "up" or "down", never part way in between. So, there are really two
states for the spin of an electron. (Yaaay, binary rules!)

Because they are fuzzy little things, and you don't know if they're up
or down until you measure them, they're really distributed between the
two states. One hundred electrons like this would then, in a way be in
2^100 different states at once. Somehow with quantum computers, this is
useful. I think when they're talking about lots of hard drives, they're
trying to compare that 2^100 with how many hard drives it would take to
list all of the numbers between 0 and 2^100-1 simultaneously.

Ok, that's enough conjecture from me. Are there any real physicists or
quantum computer scientists in the house that can clear this up?

-Aaron

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