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areas. But we do things that are quite rare, and almost no one in the world has
the particular tool set that we have. Well, that's great - we're the leaders! But
there's no one else.
So I think we have the problem of needing to help enable some other groups
to do what we do so that hopefully they compete with us and move the field
forward ... but don't beat us too badly. It's a funny problem - there are not
enough people able to do what we do - but maybe there will be after some of
these new results get disseminated. Maybe it will convince a few more people
that this is worth trying.
To me, QCA as an ambition is a little bit like quantum computing as an
ambition. We may not achieve the desired ends exactly, but I'm quite sure that
the road there is going to be worthwhile. There are just so many beautiful
phenomena and capabilities emerging that will be good for something - many
things - maybe even including QCA and quantum computing. And I think it's a
worthwhile road now because we have these multiple building blocks emerging -
this fabric that can provide passive components, active components, and sensors.
I didn't show it in my talk, but we can make a little strip of silicon between two
contacts that can exquisitely sense arriving molecules electrically. So, yes, it is
tempting to think, in this tiny little patch of silicon, we could have a chemical
nose, providing some activation so we could make a decision based on that and
release the drug or whatever. Some kind of ambition like that. Maybe that is the
kind of niche we should be seeking.
Lent
(Craig): I guess I take a pretty long view. The initial motivation for QCA
was to make something as small as possible. And at the time we did start as small
as possible. People had just learned to make quantum dots out of a patterned,
two-dimensional electron gasses, and that seemed like the smallest thing that we
could pattern and make. We did not have CMOS in mind, but we were asking:
What is the limit of small?
I start with the question: Can humans pattern matter at the smallest scale
possible and do useful things? It's hard to see how you could pattern matter
- engineer matter to do useful things - at a scale smaller than that of atoms,
molecules, or artificial molecules. You have individual molecular orbitals and
you're configuring them, you're laying them out in a particular way to do useful
things. I don't know that there can be anything smaller than that. Just having
that thought forces you to also think that it had better be really low power,
because it will otherwise melt immediately. As we heard from Ismo [Hanninen],
we're on the road to there with CMOS now, so it's a lesson we've already learned
practically. So: what are the small size limits structures, and, intimately related
to that, what are the low power limits for doing useful things?
The idea of using a field to couple two things that have binary states, trans-
lated into the magnetic domain, is a big bonus. As we've seen several times, and
Wolfgang described beautifully, these are much easier to fabricate now and they
work at room temperature. An awful lot of the thinking about the architectural
implications in QCA maps one to one, and everything starts with the ques-
tions of how we can represent the information and how the information here be
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