Wacky Chip

Mechanical Engineering, Apr 2006 by Thilmany, Jean

QUANTUM COMPUTERS CONTINUE to be the next big thing.

Now, researchers at the University of Michigan have produced what they say is the first scalable quantum computer chip, which could lead to big gains in the quest to develop a quantum computer.

Quantum computers could solve certain problems much faster than conventional computers, thanks to the bizarre features of quantum mechanics, said Christopher Monroe, a Michigan physics professor and principal investigator on the project.

One of the most-favored-candidate quantum computer architectures would store quantum bits, or qubits, on individual atoms. The electrically charged atoms for such quantum computers are stored in what are known as ion traps. Trapping isolates the qubits from the rest of the world, which is essential for the system to behave in a quantum-mechanical fashion.

Scientists know how to program a quantum computer composed of any number of trapped ions; the problem is to get the ions trapped in the first place.

That's where Monroe's research team comes in.

With the same semiconductor fabrication technology used to make everyday computer chips, University of Michigan researchers have trapped a single atom within a semiconductor chip and controlled it using electrical signals, Monroe said.

Current ion traps can hold only a few atoms or qubits. Because they're assembled laboriously by hand, they're not easily scaled. So one of the obstacles to perfecting the quantum computer is making a scalable, integrated quantum computer chip that can store thousands of atomic ions or more , Monroe said.

The chip produced at the University of Michigan, in Ann Arbor, is about as big as a postage stamp. It's etched with electrodes, each of which is connected to a separate voltage supply. Various electrical voltages control the ion by moving it in different ways as it hovers in a space carved out of the chip.

Using existing microfabrication technology, the chip could be scaled up to include hundreds of thousands of electrodes, Monroe said.

"An integrated chip structure shows a way to scale the quantum computer to bigger systems-just like the microfabrication of conventional chips have given us the impressive gains in conventional computing speed and power," Monroe said.