Saturday, December 3, 2011

A computer that thinks like the universe

The Boston Globe has a breathless essay about the future of quantum computing:
The creation of the modern computer in the 1940s was a watershed moment in that quest; today’s super-fast computers are still essentially built on that achievement. Now, however, we’re poised to take another leap forward. That leap is the quantum computer?—?a computer built on an atomic scale. Though they’re still mostly theoretical, quantum computers would use individual atoms to do their computations, instead of circuits etched in silicon. Such a computer wouldn’t just be built differently?—?it would also think differently, using the uncertainty of particle physics instead of the rigid on/off circuitry of a modern computer.

For years, excitement about quantum computing has been growing among scientists and tech visionaries. Quantum computers, if they succeed, promise to make a whole new range of problems accessible to computers, from breaking difficult codes to unlocking complicated biological processes now out of reach for even the fastest machines. The hype has, at times, verged on science fiction, and there are still many skeptics who argue that quantum computers might be physically impossible, or at least too technically complicated to work.

In recent years, however, a series of increasingly capable prototypes have brought the future a little closer. And as that future approaches, it is also starting to attract another kind of attention: Quantum computers, some researchers argue, will help us think differently about what we can and can’t know, and forge a new understanding of how the world of logic and information connects to the material one. Quantum computing, says Seth Lloyd, a researcher at MIT, might “allow us to understand the universe in its own language” — a prospect that has energized philosophers as well as scientists. ...

That’s the dream, at least. The rise of quantum computing theory has been accompanied by a vigorous debate about whether it can work at all. It may never be technically feasible to build the computers at a large scale. Some also think that the quantum approach to computing is, in some basic sense, getting physics wrong. As Scott Aaronson, a computational complexity theorist at MIT, has written, “It’s entirely conceivable that quantum computing is impossible for some fundamental reason.”
At least the essay admits that the whole thing may be impossible.

I think that quantum computing will eventually be understood to be impossible, just as perpetual motion machines are contrary to the laws of physics. So how has anyone made progress?

There are people who also claim to be making progress towards a perpetual motion machine. They increase the efficiency of some device, in the hope that they will eventually exceed 100%. They never do, of course, and their progress is an illusion.

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