Quantum-computing researchers have actually managed to build one of their fabled devices (though it had only three qubits), and have worked out the mathematics that would allow a bigger machine to solve hitherto hard problems in cryptography.

ECONOMIST: Quantum computing

Dr Swade, agreed that this was the correct approach and said a virtual recreation of the machine could solve "95% of problems" and allow them to use computer to design the thousands of individual parts needed to make the behemoth.

BBC: Campaign builds to construct Babbage Analytical Engine