Quantum Computing Offers Big Hopes: But Will It Be the Next Great Technological Breakthrough or is It a Virtual Impossibility?

By Scott Canon, The Kansas City Star, Mo.

Apr. 29–If quantum computing can be done, there will be much that it can do.

A new ubercomputer could radically improve a factory’s efficiency at churning out widgets. It could fill movie screens with virtual animation realistic enough to put the Screen Actors Guild in a cold sweat. And it could make today’s Google searches look as high-tech as a butter churn.

Handed to generals, a quantum computer might transform an ordinary nation into an instant superpower. Dozens of incoming missiles could be tracked at once. It could spawn nearly invincible killer germs. It might unchain powers in conventional explosives to rival those of nuclear weapons.

All this hinges on whether the quantum computer is technology’s next fantastic breakthrough or a virtual impossibility ranking somewhere between cold fusion and finding Sasquatch.

So just what is quantum computing?

Today’s so-called classical computers make calculations using bits that can take on only the value of 1 or 0.

In quantum computing, each bit, or qubit, can take on the value of both 1 and 0 at the same time.

Quantum computers would do that mind-bending feat by exploiting the weird properties of quantum mechanics, which governs the very different behavior of the super small.

At the University of Pittsburgh, Jeremy Levy directs a quantum computing center where he’s exploring the possibility of using spinning electrons. An electron spinning clockwise, for instance, might represent a 0 while an electron spinning counterclockwise stands for 1. For a quantum computer, he would use electrons spinning both directions at the same time.

“If it’s making your brain hurt,” he said, “join the club.”

Any number of obstacles stands in the way of a practical quantum computer. For starters, the qubits would have to be isolated at temperatures colder than minus 450 degrees Fahrenheit to control matter in a special way.

Also, you would have to find a way to shut out interference from the outside world — types of noise — that tilt the process like a delicate pinball machine.

“There are reasons to believe quantum computers may not deliver on their promise,” said Jeffrey Uhlmann, a computer science professor at the University of Missouri-Columbia. “Quantum computers will be doing everything in not too many years, but they will likely be based on the same model as traditional computers.”

He studied the possibilities of quantum computing at the Naval Research Laboratory for 12 years, and still writes algorithms that could help engineers work out a world-shattering new way of making computations.

For decades, the progress of computing power has been clipping along at the speed of Moore’s Law — the prophetic observation made in 1965 by Gordon Moore, co-founder of Intel Corp., that the calculating power of computer circuits would double every couple of years. There’s long been speculation that the benefits of miniaturization would reach an end and Moore’s Law would be sadly broken.

That’s where quantum computing could step in — and leap forward.

Think of a computer circuit as a single sheet of paper on which you must pencil out multiplication tables. With classical computing, the number of math problems you can solve would be limited to the size of the page. One hope for quantum computing is that it would allow you to squeeze many more problems onto the page by writing ever smaller. Or better yet, quantum computing could facilitate parallel calculations that find the solution to problems with shortcut equations.

Or consider what would become possible with quantum computing. Imagine a computer designing the perfect molecule to tackle the AIDS virus. Trying to build a model out of the various possibilities with existing computers would take millions of years of calculations. A quantum computer might be able to lick the same problem in three or four years.

“They have elegant mathematics,” Robert Leheny, then-director of the Microsystems Technology Office at the Defense Advanced Research Projects Agency, said in a 2003 speech that hinted at his office’s hopes and doubts about quantum computing. “What they do is to set up an equation, and let the quantum devices solve it over time. But that is an analog computer. … And it has all the problems of an analog computer.”

More recently, the current head of DARPA said in an interview with a Wired magazine blogger that the Pentagon would ignore quantum computing at its own peril.

“If somebody else got it before us, (that) would be a great technological surprise. And so we’re looking into that,” Tony Tether said. “The impact of the quantum computer, if it can be done, will be really, really revolutionary. … (Because) we are worried about a technology that we don’t want to teach the world how to do, as we’re learning how to do it, well, we put controls on it.”

In fact, much of DARPA’s funding for computing research has shifted in recent years away from universities and toward institutions working behind a wall of secrecy.

That has invited speculation that quantum computing might already exist, that somewhere in the bowels of the National Security Agency quantum computers are busting code. To reveal that one existed would alert potential enemies that the secrets they think are safe are not.

Yet conventional wisdom holds that quantum computing is years away.

Earlier this year, the Canadian company D-Wave Systems Inc. claimed it had created the “world’s first commercial quantum computer” even as the company conceded it wasn’t sure it had performed true quantum calculations.

The announcement was met with immediate skepticism, perhaps voiced most strongly by those who think that the field holds great promise. For one thing, the problem solved by the computer was one that could have been achieved through classical computing, and scientists were disappointed that the firm didn’t give more details to support its claims. The company did not return calls for this story.

“Their claims are not credible,” said Umesh Vazirani, a computer science professor at the University of California-Berkeley.

He still sees great hope. Recent research has produced powerful new algorithms for isolating the fragile state of a quantum computer from outside interference.

Vazirani sees promise in the ability of quantum computers to run simulations of quantum systems, holding the potential to revolutionize the design of molecular and nanoscale systems, much the way computers today can mimic designs of much larger objects.

The great application of quantum computing comes with simulations. Designers of cars or weapons could test the performance of complex systems in a computer, rather than wait for trial and error on driving courses or target ranges after they have been built.

It’s hard to get around simulating the simulator. A working quantum computer might prove so unwieldy to build — requiring more effort to insulate the circuits, to control the temperature, to write elaborate algorithms, to find a way to capture its results — that it’s not worth the bother.

Uhlmann, the MU computer scientist who has grown more skeptical about the promise, also said those same doubts haunted other technologies. Decades ago, when a computer with less brainpower than your cell phone filled up an entire building, researchers wondered if they would ever shrink it to the size of a refrigerator.

“Some things that seem impossible,” he said, “turn out to be possible.”

To reach Scott Canon, call (816) 234-4754 or send e-mail to scanon@kcstar.com.

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Copyright (c) 2007, The Kansas City Star, Mo.

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