Quantum computers promise to revolutionise the digital world, but how do you tell if a computer really is harnessing the power quantum mechanics? It's a question that has plagued the only computer manufacturer claiming to produce quantum-powered machines – D-Wave Systems of Burnaby in British Columbia, Canada – since they went on sale.
Today, the publication of further inconclusive tests of the machines is a reminder of just how difficult it is to get an answer. We explain why it's so hard to test a quantum computer – and whether we'll ever get an answer to the D-Wave conundrum.
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