# Re: Quantum Computing

From: Tommy McCabe (rocketjet314@yahoo.com)
Date: Sun Jul 25 2004 - 16:58:29 MDT

--- Joel Peter William Pitt <extropy@paradise.net.nz>
wrote:
> Tommy McCabe wrote:
>
> >
> >There is no reason to stop with 100 transistors.
> >However, in order to get a capacitance of "all the
> >hard disks (~1*10^11 bytes each) * made this year
> >(~1.5^10^8) * the number of years this universe has
> >been around (~1.3*10^10)", with 100 transistors,
> each
> >transistor would have to have a capcity of
> 1.95*10^27
> >(feel free to check my math) bits. That strikes me
> as
> >unlikely, considering that is larger than the
> number
> >of atoms in an entire chip with millions of
> >transistors. Going by my math, if there is only 1
> >electron that changes spin per transistor, and
> there
> >are only two states for each electron, there are
> 2^100
> >(which is around 10^32) states for the chip to be
> in,
> >but only 100 bits of storage capacity, which is
> puny
> >even by 1960's standards.
> >
> >
> From a discussion with a friend who is
> researching error correction in quantum controllers
> I remember him mentioning that
> these electrons can have an infinite number
> of states (ranging from on and off at the same
> time and other fuzzy arrangements), the only
> problem will be developing the technology to
> read and maniuplate these states with
> sufficient precision.

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 don't claim to be a physicist, but that is the
> discussion as I remember it, other more
> educated people can feel free to correct me ;-)
>
> Cheers,
> Joel
>

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