In DepthComputer Science

Quantum or not, controversial computer yields no speedup

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Science  20 Jun 2014:
Vol. 344, Issue 6190, pp. 1330-1331
DOI: 10.1126/science.344.6190.1330

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The D-Wave computer, marketed as a groundbreaking quantum machine that runs circles around conventional computers, solves problems no faster than an ordinary rival, a new test shows. For random test problems, the time it took the D-Wave machine to solve a problem increased exponentially with the problem's size, just as with a conventional computer, report Matthias Troyer, a physicist at the Swiss Federal Institute of Technology in Zurich, and colleagues online this week in Science ( So as the size of a problem grows, the D-Wave computer produces no quantum speedup. Some researchers call the test of the controversial device the fairest comparison yet. But D-Wave argues that the computations used in the study were too easy to show what its novel chips can do.