Re: TECH/NEWS: Complex DNA computer built

From: Eugene Leitl (
Date: Sat Jan 15 2000 - 14:53:22 MST

Robert Bradbury writes:

> I agree 100% with Eugene.
> [side bar, note this day in history -- while Eugene and I agree "generally"
> on most things, we seldom seem to agree 100% on anything. :-)]

This is a somewhat wrong impression, since I only post when I disagree
with you. Me-too posts do not contribute to signal and are hence
noise. When I don't post, I agree with you 110%.
> The 3d molecular circuits are going to be limited by the speed of sound
> in the material determining propagation delays, but these will be much
> much faster than diffusion in solution. Faster yet will be optical
> computronium due to the decreased mass of the photons and faster
> transit times. What remains unclear is exactly *how* small we can

Oh, when I think computronium I don't mean buckygears a la NASA AMES
or similiar. Electrons are much more mobile than nuclei
(Franck-Condon), and hence computation should be done with
electrons. Photons are good for long-distance signalling, and for
providing power (laser-pumped computronium). Photons are big, unless
you use SNOM type of magic, and they typically switch only at high
fluxes (NLO), which makes them truly lousy switches. Also, with image
processing tricks (thinning et al.) you can use a projected
macroscopic bitmap as I/O for computronium blocks. Look ma, no
wires. (This is useful in the early stages when you grow computronium
in the vat from autoassembling protein-circuitry complexes (protein
because you need a lot of control in regards to complementary
shapes, and it's the only easy available bootstrap technology)).

Once you have mechanosynthetic nano, you can go ballistic electronics
in buckytubes. Graphenes are hardy, have a good (albeit strongly
anisotropic) heat conductivity, and one could imagine pumping
cryofluids through orthogonal buckytube channels through the main
crystal. Reversible computation (amount of ones and zeros stays the
same) will also help a lot here.

> get the transmitters & receivers of the photons (compared with atoms
> or electrons). If we can get to the point of pumping single-atom electron
> energy states reliably using single photons (which is different from quantum
> computing), then we shall have really really dense and really really fast
> computronium indeed.

Recent results seem to indicate that charge transfer in photosynthetic
antenna complex is not so very sophisticated and fine-tuned as one
would assume. One can use tricks like these to harvest energy for
optically pumped computronium, since otherwise you need photon fluxes
high enough that you're destroying the circuitry.

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