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Quantum rewrites the rules of computing

Sharon Gaudin | March 19, 2014
NASA, Google testing D-Wave machine while debate rages over whether it's really quantum computing.

That's not the case with quantum mechanics.

Each bit in a quantum machine -- known as qubits -- can be both a one and zero. It's about possibilities. When a qubit is constructed, it's built so you don't know if it's a one or a zero. It has the possibility of being both.

The D-Wave system with the 512 qubit chip is being tested by NASA and Google. (Photo: D-Wave)

It's not known what those qubits are until they begin to interact - or entangle - with other qubits. Based on their entanglements, they become a one or a zero. However, just because a qubit acted as a zero during one calculation, doesn't mean it will act as a zero during the next calculation. It goes back to the original possibility.

That's where the quantum computer's power comes into play.

A quantum system doesn't work in an orderly, linear way. Instead, its qubits communicate with each other, through entanglement, and they calculate all the possibilities at the same time.

That means if a quantum machine has 512 qubits, it's calculating at 2 to the 512th power at the same time. That number is so immense that there are not that many atoms in the universe, according to Rupak Biswas, chief of NASA's Advanced Supercomputing Division. Some physicists theorize that all those calculations are being done in different dimensions.

"We're so far outside of our everyday experience," said Germano S. Iannacchione, head of the Physics Department at Worcester Polytechnic Institute. "Common sense doesn't guide us here. We're trying to come up with pictures in our heads of how it works. When you're at the hairy edge of the unknown in physics and you don't have experience and common sense to guide you, you have to rely on the math. That's the only thing you can hold on to."

Despite the complexities, D-Wave's Brownell said his company has built quantum computers, using their own quantum processor built with different metals, such as niobium, a soft metal that becomes superconducting when cooled to very low temperatures.

One machine, the D-Wave Two, leased by the Universities Space Research Association, is based at NASA's Ames Research Center in Mountain View, Calif. NASA has use of the machine 40% of the time, Google has another 40% and the research association has 20%.

Google declined to talk about its work with the system. However, its experiments on the computer have led to debate on whether D-Wave's computer performs any better than classic computing or whether it is a quantum computer at all.

NASA, which has had its hands on the D-Wave Two since last September, has only been testing it, Biswas said. His group has been doing high-performance modeling and simulation on problems related to Earth sciences, aeronautics and deep space exploration.

 

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