The Quantum Quest for a Revolutionary Computer

Quantum computing uses strange subatomic behavior to exponentially speed up processing. It could be a revolution, or it could be wishful thinking

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Photograph by Gregg Segal for TIME

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D-Wave's co-founder and chief technology officer is a 42-year-old Canadian named Geordie Rose with big bushy eyebrows, a solid build and a genial but slightly pugnacious air--he was a competitive wrestler in college. In 1998 Rose was finishing up a Ph.D. in physics at the University of British Columbia, but he couldn't see a future for himself in academia. After taking a class on entrepreneurship, Rose identified quantum computing as a promising business opportunity. Not that he had any more of a clue than anybody else about how to build a quantum computer, but he did have a hell of a lot of self-confidence. "When you're young you feel invincible, like you can do anything," Rose says. "Like, if only those bozos would do it the way that you think, then the world would be fine. There was a little bit of that." Rose started D-Wave in 1999 with a $4,000 check from his entrepreneurship professor.

For its first five years, the company existed as a think tank focused on research. Draper Fisher Jurvetson got onboard in 2003, viewing the business as a very sexy but very long shot. "I would put it in the same bucket as SpaceX and Tesla Motors," Jurvetson says, "where even the CEO Elon Musk will tell you that failure was the most likely outcome." By then Rose was ready to go from thinking about quantum computers to trying to build them--"we switched from a patent, IP, science aggregator to an engineering company," he says. Rose wasn't interested in expensive, fragile laboratory experiments; he wanted to build machines big enough to handle significant computing tasks and cheap and robust enough to be manufactured commercially. With that in mind, he and his colleagues made an important and still controversial decision.

Up until then, most quantum computers followed something called the gate-model approach, which is roughly analogous to the way conventional computers work, if you substitute qubits for transistors. But one of the things Rose had figured out in those early years was that building a gate-model quantum computer of any useful size just wasn't going to be feasible anytime soon. The technical problems were just too gnarly; even today the largest number a gate-model quantum computer has succeeded in factorizing is 21. (That isn't very hard: the factors are 1, 3, 7 and 21.) So Rose switched to a different approach called adiabatic quantum computing, which is if anything even weirder and harder to explain.

An adiabatic quantum computer works by means of a process called quantum annealing. Its heart is a network of qubits linked together by couplings. You "program" the couplings with an algorithm that specifies certain interactions between the qubits--if this one is a 1, then that one has to be a 0, and so on. You put the qubits into a state of quantum superposition, in which they're free to explore all those 2-to-the-whatever computational possibilities simultaneously, then you allow them to settle back into a classical state and become regular 1's and 0's again. The qubits naturally seek out the lowest possible energy state consistent with the requirements you specified in your algorithm back at the very beginning. If you set it up properly, you can read your answer in the qubits' final configuration.

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