Japan team reports quantum computing breakthrough

IDG News Service - 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, which is a fundamental building block for quantum computing in the same way that a NAND gate is for traditional 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 computers hold the potential to revolutionize some aspects of computing because of their ability to calculate in a few seconds what might take a traditional supercomputer millions of years to accomplish.
The team reporting the breakthrough is headed by Tsai Jaw-Shen and jointly funded by NEC Corp. and Japan's Institute of Physical and Chemical Research (RIKEN). Tsai said his team has successfully demonstrated a CNOT gate in a two-qubit (quantum bit) solid-state device.
The CNOT gate is one of two gates used with qubits, which are the basic building blocks required for a quantum computer. The other, a one-qubit rotation gate, was demonstrated by Tsai's team in 1999. Now that both have been demonstrated, Tsai says one of his goals is to combine them to create something called a universal gate, which is a basic unit of a quantum computer.
"Another goal is to do some quantum algorithms based on this," he said.
One of the biggest tasks Tsai says he faces is extending the time for which the two qubits are coupled together in a state known as quantum entanglement. In this state, which is one of several exotic properties associated with qubits and crucial to quantum computing, the two qubits act together even though they are not physically connected.
Tsai announced in February that his team had succeeded in entangling a pair of qubits.
Among the startling properties of qubits is that they don't just hold either binary 1 or binary 0, but can hold a superposition of the two states simultaneously. As the number of qubits grows, so does the number of distinct states that can be represented by entangled qubits. Two qubits can hold four distinct states which can be processed simultaneously, three qubits can hold eight states, and so on in an exponential progression.
So a system with just 10 qubits could carry out 1,024 operations simultaneously as though it were a massively