PHYSICS:
A First Step Toward Wiring Up a Quantum Computer
James Glanz
A team at the National Institute of Standards and Technology has gone from a single cold, trapped ion functioning as a "qubit"--the active element of a quantum computer--to two linked ions. That's a bigger leap than it sounds, because a single qubit can have two values at the same time, as opposed to the single value (zero or one) of the bits in a classical computer; therefore, just 40 qubits would make a computer that is more powerful, in some respects, than the very largest machines today. By delivering precise laser pulses to the two ions, the researchers wired them together through the ephemeral quantum-mechanical connection known as entanglement.