[RC5] Chloroform Used To Build Quantum Computer
gindrup at okway.okstate.edu
gindrup at okway.okstate.edu
Thu May 7 21:07:08 EDT 1998
You don't state your e-Mail address, so I can't respond to you
directly.
"Quantum computer" is currently ill-defined. The term has been used
to describe:
1) "chemically combinatorial" problem solvers. These are special
purpose computers, expressed as chemical processes, in which
parallelism is achieved through having a mole or so attempted
solutions generated at a time. Compared to the problem domains in
which this method has been tried, a mole is a pretty big number.
This is a purely nondeterministic parallel computation. The
success/failure and mechanism of the computation are tightly coupled
to the quantum mechanical properties of the molecules involved. The
University of Southern California has a nontrivial collection of
people who do this sort of thing:
http://www-hto.usc.edu/
2) "nonlocal effect" optimization finders. This relies on the sort
of global information effects that appear to affect, for instance,
the exact selection of condensation sites in crystals. This
definition is not too widely used because it is very difficult to
implement the solutions in this hardware. For example, how do
energy minimizing aperiodic crystals form out of a tremendous
sequence of condensation events?
3) "quantum multi-valued" parallelization is sometimes used to
search multiple branches in a search tree simulatneously. If you
are doing this chemically, then you are doint (1) above. If you are
doing this with single atoms and binding sites, then you are doing
(2) above. If you are using intermediate molecules and relying on
superpositions of multiple states to allow simultaneous searching
through problem domain hunks that are represented by the multiple
states, then you are doing this third kind of computing.
(3) is, theoretically, the most promising. (1) requires more and
more reactant and the *probability* of finding the optimal solution
is dependent on the number of active moleclues, the search space
size, and the reaction predelictions. (2) is too hard to use to set
up problems. Essentially the only problems that can be solved by a
type (2) computer are the problems that the computing machinery
itself presents. This is not particularly helpful.
Type (3) computers have the advantage that, in principle,
parallelization like that in type (1) can be increased a few orders
of magnitude by using smaller data-representation machinery. In
fact, if supersposition is used, the single data items are
represented in fractional elementary particles.
One English group has used these thoughts to encode about 8 bits
in the electron of a Hydrogen atom. they estimate that ~100 bits
could be usefully stored and retrieved in an H atom, so imagine two
RC5-56 keys being encoded on a single atom. Then apply the "RC5
decoding" transformation to the combined system of a microgram of H
in about a microsecond. Well, that's one challenge problem down.
The superposition method is even more interesting than that...
Encode two different trial keys on one H atom by putting the atom in
a superposition of the two representational states. Apply the
transforming physical process (which in this case is much less
delicate than in the previous paragraph). Now (I tread lightly on
the "hard part"...) extract the answer.
In principle, type (3) quantum computers can compute about 4 orders
of magnitude more parallel-ly than type (1) computers.
Related to this is a recent result concerning the "square-root of
NOT". A quantum-mechanical process that takes atoms encoding bits
and puts them in a superposed state. It takes the atoms in the
superposed state and finishes the migration to their negation. So,
when applied twice, the operator is a NOT. It turns out that this
one operator is a complete set of Boolean operators.
All the elements exist but for the ones that are interrupting
silicon computing right now... It's too hard to get the data into
and out of the computing cores. The supercomputer that was going to
be used to do DES-II all at once had the same problem. It's running
time tripled due to I/O by the processors...
-- Eric Gindrup ! gindrup at okway.okstate.edu
______________________________ Reply Separator _________________________________
Subject: Re: [RC5] Chloroform Used To Build Quantum Computer
Author: <rc5 at llamas.net> at SMTP
Date: 5/7/98 10:42 AM
Karl G - NOC Admin wrote:
Hello
Could anybody tell me, what a quantum computer is? Or give me an URL?
> Chloroform Used To Build Quantum Computer
>
> In a traditional binary computer each bit has a definite state--either 1
> or 0. But in the quantum world, a bit is both 1 and 0.
Quantum world?
Yes quantum world, is a completely other thing, than the normal world.
But it's absolutely nonsense, to assume a thing to be in two states at
the same time. The trick is, that even from the exact calculation we can
only say something about the propability of the thing to be in a special
state. What the correct state is, we can only say, after we measured the
system. Only by opening the box, we can say, if Schr\"odingers cat is
dead or not. The interpretaion of the whole thing is still open. A lot
of things about the measuring process are not yet understood.
Hope I didn't tell too much nonsense.
Hilmar
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