A research team in Japan says it has successfully demonstrated for the first time in the world in a solid-state device one of the two basic building blocks that will be needed to construct a viable quantum computer. The team has built a controlled NOT (CNOT) gate, a fundamental building block for quantum computing in the same way that a NAND gate is for classical computing. Research into quantum computers is still in its early days and experts predict it will be at least 10 years before a viable quantum computer is developed. But if they can be developed, quantum...