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.
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 percent of the time, Google has another 40 percent and the research association has 20 percent.
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.
"We're still in the early stages," said Biswas, but added that testing is going well. "We are trying to see what it can do. It's not a turnkey situation. It's a very exotic field. It's like in the early days of computing when we had computers with vacuum tubes and card readers."
D-Wave's system at NASA may be the first commercially available quantum computer, but it's not the first quantum machine. Basic quantum computers have been built before. In 2000, scientists at the Los Alamos National Laboratory demonstrated a working 7-qubit system.
In 2011, Brownell said, D-Wave, to prove it was on the right track, built a quantum computer running 8 qubits. However, the company hasn't proved that its 512-qubit machine works as a quantum computer, and that's because, he said, it simply can't be proven.
"These are such complex systems they can't be modeled by all the computers in the world put together," Brownell said. "That will never be completely provable."