Quantum computing, which promises to perform calculations too difficult for even the most powerful supercomputers, is a step closer to reality. Proving a solid-state quantum computer can be built, a Yale University research team has successfully tested a two-qubit processor in a rudimentary search algorithm, according to Yale and the National Science Foundation.

Qubits, short for quantum bits, are made of artificial atoms. In the Yale research, each qubit was made up of a billion or so aluminum atoms, but acted like a single atom. While the transistors in classical microchips can either be on or off, representing a 1 or 0 in binary notation, quantum mechanics allows atoms to be in multiple states at once, enabling greater data storage and processing power.

“This lets you parallelize computation,” said Leo DiCarlo, a post-graduate researcher at Yale and a project team member.

Scientists are particularly interested in quantum computers because they are expected to model solid-state systems, proteins and chemical reactions. In addition, a quantum computer could search unstructured databases or reduce very large numbers to prime factors, said DiCarlo.

“A quantum computer is not going to be a general-purpose computer, but one that’s suited to solve very specific problems,” said the researcher.

As in all computers, cooling is important. A quantum computer relies on superconductivity, which can only be achieved by cooling the computing materials to nearly absolute zero (0 degrees Kelvin).

Key to the advance was getting the qubits to maintain their state for far longer than was previously possible—a microsecond, compared with a nanosecond previously.  The group will now work to increase the number of qubits and extend the state of the qubits to run more complex algorithms.

The work was supported in part by the Yale Center for Quantum and Information Physics (CQUIP), funded by a grant from the National Science Foundation's Division of Materials Research and Division of Physics, and by the Army Research Office and National Security Agency.