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Spintronics

Quantum computing is closer than you may think. In fact, a type of computer memory just released takes advantage of quantum effects.

Tangible evidence of the quantum revolution hit the market in July, when Freescale Semiconductor, a Motorola spinoff, began commercial shipments of magnetic random-access memory (MRAM) chips. You'll probably notice MRAM first when you buy a digital camera that doesn't take any time to store a picture. Within a matter of years, your new laptop will switch on like a light.

This is a form of rewritable memory that is stable without power.

This memory breakthrough was in large part the doing of DARPA, the Defense Advanced Research Projects Agency - the same Pentagon gang that gave us the Internet. In particular, it's due to a 62-year-old physicist named Stuart Wolf, who recently left DARPA for the University of Virginia. Since 1993 the agency has invested more than $200 million in Wolf-created quantum research programs.

While MRAM is just about memory, the ability to control spin in a computational device - "spintronics" is the word Wolf has coined to describe this work - has huge implications.

Ultimately we'll be able to use quantum effects to calculate. Silicon is due to hit a heat barrier by 2015. At that point it will be impossible to increase the speed of calculation on that substrate. Is Moore's law doomed?

Well, to be technical, yes. Moore's law was specific to silicon technology. But exponential improvement in calculation technology predates the silicon chip and will outlive it as well. Silicon chips will go the way of vacuum tubes - useful perhaps for certain tasks - but largely replaced by the next paradigm.

The next step: putting spin to work in actual computation. A team at the University of California at Santa Barbara, led by David Awschalom, has made big progress in this direction by controlling electron spins in semiconductors and other materials a few nanometers in size. This could mean not just an end to overheating worries but the possibility of moving computer technology into the molecular realm. With molecular-level chips, a laptop could have more computing power than trillions of today's supercomputers.

And the paradigm after that is sub-molecular computation.

In 2004, Dan Rugar of IBM performed what the American Institute of Physics dubbed the most important experiment of the year by using a magnet to control the spin of a single electron. In theory, that means we could have subatomic-scale circuitry. At that level the behavior of particles is more complicated and can - again, in theory - do even more powerful things.

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