A quantum bit comes to life on a chip.

Scientists jest about making so-called quantum computers from cups of coffee (SN: 1/18/97, p. 37). Their jokes allude to extraordinary experiments that use liquids to perform simple quantum calculations (SN: 9/12/98, p. 165). Experimenters have also had some success with photons, trapped ions, and other exotic components--but not with the materials and methods used to make conventional computing devices.

Japanese researchers now report that they have built a key quantum component on silicon with a method that manufacturers already use to make some specialized microcircuits. "The reason why people are so excited is that we can make it with a very standard lithographic technique," says Yasunobu Nakamura of NEC Fundamental Research Laboratories in Tsukuba.

Quantum computers don't exist yet, but, in theory, they would perform certain calculations billions of times faster than conventional computers do. They would use quantum bits, or qubits, made from tiny particles obedient to the odd rules of quantum mechanics (SN: 4/3/99, p. 220). Whereas an ordinary bit represents either 0 or 1, a qubit represents both at once.

In the April 29 NATURE, Nakamura and his colleagues describe creating a qubit in patches of aluminum on the surface of a coated piece of silicon. At 30 millikelvins, the metal allows electrons to flow without resistance. Juxtaposing two such superconducting patches allows a pair of vibrating electrons to simultaneously occupy both patches--that is, to represent states 0 and 1 at the same time. In the prototype, however, this mixed state sparked by a voltage pulse dies out too quickly for practical computing, Nakamura says.