Wednesday, February 22, 2006


Quantum computer works best switched off

I'm still trying to wrap my head around the idea of quantum computing, and I'm not helped in the least by stories like this.
With the right set-up, the theory suggested, the computer would sometimes get an answer out of the computer even though the program did not run. And now researchers from the University of Illinois at Urbana-Champaign have improved on the original design and built a non-running quantum computer that really works. They send a photon into a system of mirrors and other optical devices, which included a set of components that run a simple database search by changing the properties of the photon.

The new design includes a quantum trick called the Zeno effect. Repeated measurements stop the photon from entering the actual program, but allow its quantum nature to flirt with the program's components - so it can become gradually altered even though it never actually passes through.

"It is very bizarre that you know your computer has not run but you also know what the answer is," says team member Onur Hosten.

Am I the only one, in reading this, who is reminded of Charles L. Harness's "The New Reality," in which scientists, in sending a single photon through an array of prisms and mirrors, accidentally end up destroying all of reality? Not that I suspect it could happen in reality, but you never know...

Hey, thanks, Chris!

For years I've remembered that story, but couldn't remember the author or even its real title.
Jvstin, I read that story in Asimov, Greenberg, and Waugh's The Last Man on Earth, which also included Poul Anderson's "Flight to Forever", William F. Nolan's "The Underdweller", Fredric Brown's "Knock", and about a dozen other stories that haunted the corners of my head for years. It was a long time later before I realized that, if you sent a photon down a rat's maze, it wouldn't hesitate like a reluctant mouse and rewrite all of existence! (And, as much as I adored the story, it was clear that Harness wasn't hip to Schrodinger's cat, which would pretty much have put paid to the central conceit of the story.)
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