Jacob Aron in New Scientist:
D-Wave, a company based in Burnaby, Canada, has been selling quantum computers since 2011, although critics expressed doubt that their chips were actually harnessing the spooky action of quantum mechanics. That's because they use a non-mainstream method called adiabatic quantum computing.
Unlike classical bits, quantum bits, or qubits, can take the values 0 and 1 at the same time, theoretically offering much faster computing speed. To be truly quantum, the qubits must be linked via the quantum property of entanglement. That's impossible to measure while the device is operating. But in March, two separate tests of the D-Wave device showed indirect evidence for entanglement.
Now Catherine McGeoch of Amherst College, Massachusetts, a consultant to D-Wave, has put their computer through its paces and shown that it can beat regular machines. The D-Wave hardware is designed to solve a particular kind of optimisation problem: minimising the solution of a complicated equation by choosing the values of certain variables. It sounds esoteric, but the problem crops up in many practical applications, such as image recognition and machine learning.
McGeoch and her colleague Cong Wang of Simon Fraser University, in Burnaby, ran the problem on a D-Wave Two computer, which has 439 qubits formed from superconducting niobium loops. They also tried to solve the problem using three leading algorithms running on a high-end desktop computer. The D-Wave machine turned out to be around 3600 times faster than the best conventional algorithm.
More here.