Sick of silicon? Semiconductors too Web 1.0 for you? You could make a turing machine out of old socks if you tried hard enough.
These are the computing technologies that came before our time—and those that are yet to come into their own. These weird sisters might factor polynomials or solve Sudoku, but they sure as hell won't run Doom.
Nanocomputers
Who'll be the first to make a computer from carbon nanostuff?
Though the two technologies go hand in hand, nanocomputing isn't quite the same as its quantum counterpart. The latter is a mindbending journey into probablistic effects at the subatomic level. The former is merely very small indeed.
In fact, the fabrication of traditional computing components is already headed close to the nanoscale barrier: Intel just commercially released its Penryn series of processors, fabricated on a 45-nanometer process. Two years ago, 90nm was the norm. Onwards and minutewards.
There are many problems associated with such scale, however — semiconductor transistors' performance diminishes the smaller they get. The path forward, then, may require a switch to new nanotechnological wonders such as carbon nanotubes — or to one of the other strange technologies listed here.
Nanotube-based transistors have already been made, sensitive to a single electron: as long as computers are electrical, that's as efficient as it gets. Caltech hopes to see the commercialization of nanowire computers in a matter of years.
Mechanical Computers
Pure machines, just as the Victorians, Greeks and steampunk fantasists would have 'em.
Machines have always been modeled on real-world physical systems, but modeling them to solve computational problems is an application with historical echoes going back long before the days of Charles Babbage.
The earliest known example is an analog astronomical calculator known as the Antikythera computer, discovered in 1901 as a corroded myriad of components strewn around an ancient shipwreck. It took scientists over a century to conclusively map out its workings.
Probably constructed in around 100BC by Rhodian engineers famous for making automata, the device may have been a serious navigational tool—or an expensive curiosity. Either way, they were common enough for Cicero to write of such machines in his philosophical dialogues.
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Chemical Computers__
Chemical reaction-diffusion computers crunch numbers by doing what chemicals do best with one another: interconversion. A semisolid goo represents data as differential concentrations of elements, which react with one another in such a way as to compute stuff.
If may sound messy, but the physics are simple and production, in principle, lacks the sensitivity and monumental difficulty of semiconductor fabrication. Gooware is computing on tap—literally!
Pictured is one early application: a storage controller.
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Optical Computers__
Out with electrons, in with photons. Put like that, it doesn't seem that big a change, does it? The two particles' differences, however, make for a world of novelty.
Fancy a computer that runs at the speed of light? Alas, that assumption is just a delicious misconception: in truth, optical computers run hotter and less efficient than their traditional counterparts. Research is ongoing, however, and the technology holds enormous promise for the future. Instead of inefficient electricity roasting around on the surface of metal pathways, guided by physical logic gates, light might one day beam cooly about, with different intensities representing different binary states. All that would be needed to create a logic gate is a refractive material that shunts light a different way depending on how bright it is.
Talk about a bright idea.
Neural Computers
The sci-fi-sounding notion of building computers from living neurons finds root in the real-world science of wetware. After all, this is exactly how the brain works: why not take a leaf from the Renaissance's book and accept no mistress but nature herself?
Bill "Robot Brain" Ditto, of the Georgia Institute of Technology, featured in a BBC story a few years ago, in which he said he was amazed that today's computers "are still so dumb." The creator of a computer made from bits of leech, his result is self-correcting, deliberately nonlinear, and able to form its own neural connections.
Not only is it the most lifelike of the weird computers listed here, it's the one that holds the most promise of going crazy and destroying mankind in a fit of pique, led astray by its imperfect organic nature. The H in HAL stands for Heuristic, lest we forget.
Biochemical Computers
DNA codes for life. But it could also code for computers. The chemical structure of DNA inherently offers a parallel computing platform made from the stuff of life itself.
The problem is figuring out how to make it work.
Programmable molecular computers built from enzymes and DNA molecules are already operating in the lab, with its organic nature leading to wild speculation on possible applications. For now, however, it just plays tic-tac-toe.
In the future, we could create tiny programmable cells that run around fighting cancer or disease, for example, without flooding the human body with metals and silicates. Or we could create the chilling opposite: real-life computer "viruses," in the sinister form of custom-designed pathogens.
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The Domino Computer
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As if to prove a point — that a Turing-complete computer can be embodied in the strangest of things — kinetic artist Tim Fort has built logic gates and memory elements out of popsicle sticks.
Usually conceptualized as a domino computer, such machines are limited only by the availability of dominoes and gravity. Here's a few notes on how they can be constructed. They would, of course, be enormous, slow and utterly useless, but so what? We're building a $130bn space station, so why not one of these?
Furthermore, the whole idea begs for a 2001: A Space Odyssey monolith joke.
Quantum Computers
Sudoku. That's all D-Wave's quantum computer is good for right now, and even then they wouldn't let us hacks see it in the flesh.
By lining up subatomic particles to encode information in a manner similar to the binary data found in conventional computers, such computers create "quantum bits," subject to the strange workings of quantum physics. The payoff is that calculations get done without any old-school relativistic inefficiencies getting the way: less heat production, less power consumption, more grunt.
Crafting these strange beasts into general computing machines, however, is another matter entirely. When the gilded rays of tomorrow's sunrise peek over the horizon, perhaps quantum computers might go as far as to play Tetris, or even check mail.
