Employing the same semiconductor-fabrication techniques used to create common computer chips, the Michigan team was able to trap a single atom within an integrated chip and control it using electrical signals.

Two Places at Once

As of yet, the technology is not applicable to typical desktop PCs or servers, but quantum computers are said to be promising because they can solve complicated problems using massively parallel computing.

That is accomplished by the quirky nature of quantum mechanics, said Christopher Monroe, a physics professor and the principal investigator and co-author of the paper "Ion Trap in a Semiconductor Chip." He explained that that chips can process multiple inputs at the same time in the same device.

"With quantum mechanics, an object can be in two places at the same time, as long as you don't look at it," he said. The quantum computer architecture can store quantum bits (qubits) of information, where each qubit can hold the numbers one or zero, or even both digits simultaneously.

When a qubit is added to a quantum system, the computing power doubles. Thus, the quantum machine can crunch numbers at a rate that is exponentially faster than conventional processors, said Monroe.

New Spin on Semiconductors

Electrically charged atoms (ions) for such quantum computers are stored in traps in order to isolate the qubits, a process that is essential for the system to work.

The challenge is that current ion traps can hold only a few atoms, or qubits, and are not easily scaled, making it difficult to create a quantum chip that can store thousands or more atomic ions. A string of such atoms, in theory, could store thousands of bits of information.

In the chip created at Michigan, which is the size of a postage stamp, the ion is confined in a trap while electric fields are applied. Laser light puts a spin on the ion's free electron, enabling it to flip it between the one or zero quantum states.

The spin of the electron dictates the value of the qubit. For example, an up-spin can represent a one, or a down-spin can represent a zero -- or the qubit can occupy both states simultaneously.

Applications for Cryptography

The quantum processor is made of gallium arsenide in a layered structure and etched with electrodes using the same type of lithography process as those used to create today's computer chips. Each electrode is connected to a separate voltage supply, and these various electrical voltages control the ion by moving as it hovers in a space carved out of the chip.

The next step is to build a bigger chip with many more electrodes, so that it can store more ions. There still is a lot of work to be done to learn how to control lots of ions in one of these chips. It won't be nearly as easy as it was with conventional computer chips, but at least we know what to do in principle, Monroe said.

"This type of integrated chip structure is significant because it demonstrates a way to scale the quantum computer to bigger systems," Monroe said. "It has applications for processing very large [data sets] such as in cryptography, for example, and there is a lot of interest in this by the government."