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In this case, D-Wave’s qubits lasted about 10 nanoseconds, and the calculation Prof. Troyer tested takes 20 microseconds — 2,000 times as long.

“That’s why we don’t know how quantum they are,” he said. “They are quantum for a short time and then at some time they become more classical, and the question is just how much it needed.”

D-Wave’s co-founder and chairman was dismissive, saying the research might already be outdated and predicting an “astronomical” improvement in performance in a few years.

“Troyer’s comments are one snip in a continuum, one little piece of information,” said Haig Farris, a venture capitalist.

“If you go back to the start of computing in the ’50s, when they first commercialized the transistor, all the transistors could do in those days was run a tiny little clock. It took 50 years and a trillion dollars worth of expenditures to get the whole computing industry where it is today. So we’re a step along that way, and we’re very early stages. Whatever [Prof. Troyer] has to say a year or two from now will be irrelevant.”

Others were less optimistic.

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The D-Wave strategy was to take a “shortcut” that has led to a dead end, or over a cliff, said Raymond Laflamme, executive director of the Institute for Quantum Computing at the University of Waterloo.

“What D-Wave’s people have claimed is they can manipulate information with the rules of quantum mechanics and have a gain at doing this. What we see from the paper … is that no such gain has been seen up to now,” he said.

“That certainly puts on the table the question of how do we characterize that device, then. It seems that from that analysis, it is consistent with a device whose quantum behaviour doesn’t help for computation.”

Even a classical computer, like a laptop or a smartphone, has quantum properties, but they are so fleeting as to be irrelevant.

“I think that is what is happening here with the device that the people at D-Wave have,” Prof. Laflamme said.

National Post

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