Being in the here and now, in regards to quantum computers, is like being an armchair general at some indefinable moment before July 16, 1945 (or August 6th, when everybody knew). Sure it's theoretically possible to convert matter directly into energy with a chain reaction, but gosh, ain't it hard to pull off?

One of the possible applications of a practical quantum computer is breaking RSA cryptography open like an egg, because they should--in theory--factor large numbers into primes effortlessly. I took a crack at explaining how that might work in an article that, alas, is only available through the Internet Archive now:

http://web.archive.org/web/20031208141840/http://www.disench...

I called it "Count all the legs, divide by four" and that was ten years ago. I remember reading an article in The Economist which speculated that quantum computers would do their work by running computations in alternate universes (!), something to be wrestled out with physicists who still haven't settled Schrodinger's argument with the Cophenhagen Interpretation: can a cat be both dead and alive simultaneously, and are we talking about superposition or the "Many Worlds" that makes Worf's birthday cake change from chocolate to vanilla?

The explanation for what's actually going on--Copenhagen's superposition versus Many Worlds and its knee-trembling implications--can be shoved aside as long as the machine actually works. And if it works, then to "determine the behavior of proteins encoded by the human genome", exemplified by the article, is a child's toy. And that's really saying something.