Imagine a 100-transistor computer chip that could store the same amount of data as all of the hard disks made in the world this year–multiplied by the number of years the universe has been around. You could store a lot of those baby-on-vacation photos. Well, such a quantum computing device is a small step closer to reality–although still at least a decade away–according to a group of UCLA researchers. In a quantum computing experiment, the team succeeded in flipping a single electron spin upside down in an ordinary commercial transistor chip and detected that the current changes when the electron flipped. "Our research demonstrates that an ordinary transistor, the kind used in a desktop PC or cell phone, can be adapted for practical quantum computing," said Hong Wen Jiang, a UCLA physics professor.
A single electron spin represents a quantum bit, the fundamental building block of a quantum computer. Today's computers have memories made up of bits, where each bit representing either a one or a zero. A quantum computer maintains a set of qubits which represent both zero and one at the same time Two qubits represent every possible two-bit number–00, 01, 10, 11. Each additional qubit increases the number of possible numbers exponentially. Twenty qubits represent every number from 0 to more than one million, 30 qubits represent every number from 0 to more than one billion, and 40 qubits represent every number from 0 to more than one trillion. The UCLA team, working with a transistor cooled to 400 degrees below zero, shined a microwave at a single electron, controlling when it was right side up and when it was upside down by changing microwave frequencies. Their report of controlling and detecting a single electron's spin is published in the July 22 issue of Nature.
