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In the world of peer-reviewed academic quantum computing experiments, it's rare to get two coherent superconducting qubits, so 16 would be a breakthrough. "In the absence of evidence from D-Wave that its 16 qubits are coherent, scientists are understandably sceptical," says Vazirani. "If D-Wave's qubits are not coherent, as many scientists suspect, its computer would be classical, not quantum. This would still be consistent with the results of the demo, since the decohering qubits would act like classical random bits, and the adiabatic computer would act like a classical computer implementing simulated annealing, which would be

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quite fast for a small 16-bit Ising problem." D-Wave, says Vazirani, hasn't even bothered to test for coherence.

Algorithm blues

Vazirani is also scathing about the algorithm on D-Wave's Orion. "It wishes to use it to solve the Ising model, which is thought to be beyond the reach of classical computers," he says, "but there is no known efficient algorithm for solving the Ising model using this adiabatic approach."

"Quantum computing is an exciting field that has caught the imagination of the public," says Vazirani. "This is a good thing. But if the quantum computing effort starts to mingle fact with fiction, then the entire effort loses its credibility."

On one level, D-Wave's reticence is fair enough. After all, it is a commercial company, not a university, so it thrives on trade secrets and eventual sales, not citations. But at present, investors are asked to take a lot on faith.

This means that D-Wave's first quantum computer is itself something like a quantum paradox. It's sealed in a box marked 'secret'. In that box, there are two superposed states - a working quantum computer, and a disappointing phoney.

Until the box is opened, we won't know.