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D-Wave has announced this month its largest ever quantum chip containing 2,000 qubits

Quantum computing firm D-Wave has announced this month its largest ever quantum chip containing 2,000 qubits — double the capacity of its previous biggest system. The chip is scheduled to ship next year, and if it lives up to its promise, it would solidify D-Wave’s position at the forefront of quantum computing, a potentially revolutionary field that would change computing as we know it. But despite D-Wave’s confidence, scientists and academics say the company has never proved its advantages over normal computers. 

The Canadian firm’s quantum computing chips are based around a process known as quantum annealing. This renders a set problem (like, for example, trying to find the quickest route home passing through certain points) as a topographical map of peaks and troughs, with the optimum answer to the question defined as the lowest point on that map. While regular computers using static 1s and 0s would have to traverse the entire map to find that point, quantum computers — which use quantum bits, or qubits, that represent 1s, 0s, and both at the same time — can effectively tunnel through the landscape, find the lowest point much faster.

But researchers say the benefits of D-Wave’s method have never been proved. A study published in Science in 2014 found that tasks performed on the company’s machines were no faster than conventional computers. The scientists were looking for evidence of "quantum speedup" — the signature advantage of quantum computers which holds that the more calculations you throw at them, the greater a difference in speed they show when compared with classical machines. The paper in Science did not rule out the possibility of D-Wave creating quantum speedup, but certainly found no evidence for it.

The pair note that papers published by D-Wave and partners supposedly showing its quantum advantage are generally pitting its $15 million chips against the class of processor you’d found in your laptop. What’s more, they say, testers tend to pick computational challenges that D-Wave's chips have been optimized for, giving the company’s tech a home-field advantage. This, they say, leads to impressive but misleading claims that D-Wave's technology has been proved to be "100,00,000 times faster" than classical computers.

Kuperberg adds that D-Wave’s qubits are also of low quality compared to those produced by other researchers. "Just because [their chips] are quantum, that doesn’t make them a quantum computer," says Kuperberg. "That's like saying that any invention that is influenced by air must be an airplane. Of course, it's not true; it might instead be bagpipes."

Williams noted that while it's true you can't measure the quality of a chip in the number of qubits alone, D-Wave's new software functionalities would also deliver extra power. "We are at least a decade ahead in my opinion and if we can sustain our current pace of innovation we’ll remain a decade ahead, forever," he said.

Aaronson and Kuperberg would disagree, but say they’re still optimistic about the wider future of quantum computing. Troyer, too, mentions many other promising projects, including those at Microsoft, IBM, and the University of Oxford. Indeed, there have been rumors this year that a team at Google working under one John Martinis (separate to the group testing D-Wave’s chips) are getting near to a breakthrough, with results expected in the coming years.

source: Googleblog, Newscientist

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