by Cyrus Farivar
05.07.07 | 2:00 AMWhile large-scale quantum computers remain in the domain of science fiction, a joint team from Japan announced Thursday that it has been able to take a small but crucial step in pursuit of this advanced goal.
NEC, the Institute of Physical and Chemical Research, or RIKEN, and the Japan Science and Technology Agency, published a paper in the May 4 issue of the journal Science, outlining the ability to “controllably couple qubits.”
In classical computer science, bits — or binary digits — hold data encoded as ones and zeros. In quantum computing, data is measured in qubits, or quantum bits. As such, a qubit can have three possible states — one, zero or a “superposition” of one and zero.
This unique property theoretically makes quantum computing able to solve large-scale calculations that would dwarf today’s supercomputers. But qubits in isolation are not very useful. It’s only when they can be connected to one another that large-scale processing becomes possible.
Controllable qubit coupling is analogous to the wiring of transistors on a circuit board. When qubits are coupled, they can affect one another — thus acting as something like classical logic gates.
“This is an absolutely crucial set of tools for quantum computing to have — the ability to controllably couple qubits,” said Dmitri Averin, a physics professor at Stony Brook University, and an expert on quantum computing.
The NEC group is the second team in the world known to have controllably coupled qubits. John Clarke and his team at the University of California, Berkeley, published their results, albeit using a different technique, in December 2006, also in Science.
This latest study confirms the results of the Clarke group.
