Quantum computers inch closer?

[Ed Gerck]

Jaap-Henk Hoepman wrote:

> On Mon, 02 Sep 2002 17:59:12 -0400 "John S. Denker" <jsd at monmouth.com> writes:
> > The same applies even more strongly to quantum computing:
> > It would be nice if you could take a classical circuit,
> > automatically convert it to "the" corresponding quantum
> > circuit, with the property that when presented with a
> > superposition of questions it would produce "the"
> > corresponding superposition of answers.  But that cannot
> > be.  For starters, there will be some phase relationships
> > between the various components of the superposition of
> > answers, and the classical circuit provides no guidance
> > as to what the phase relationships should be.
>
> In fact you can! For any efficient classical circuit f there exists an
> efficient quantum circuit Uf that does exactly what you describe:
> when given an equal superposition of inputs it will produce the equal
> superposition of corresponding outputs.

Jaap-Henk,

a proof of existence does not allow one to automatically convert a classical
circuit to "the" corresponding quantum circuit, which was the original comment
by John. Devising QC algorithms from classical algorithms should not be
the best way to do it, either.

Cheers,
Ed Gerck



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