When asked what he likes best about working for Google, physicist John Martinis does not mention the famous massage chairs in the hallways, or the free snacks available just about anywhere at the company's campus in Mountain View, California. Instead, he marvels at Google's tolerance of failure in pursuit of a visionary goal. “If every project they try works,” he says, “they think they aren't trying hard enough.”

Martinis reckons that he is going to need that kind of patience. In September, Google recruited him and his 20-member research team from the University of California, Santa Barbara, and set them to work on the notoriously difficult task of building quantum computers: devices that exploit the quirks of the quantum world to carry out calculations that ordinary computers could not finish in the lifetime of the Universe.

It is a vision that has frustrated Martinis and many other physicists ever since it was proposed in the early 1980s. In practice, the quantum effects essential in such a computer are incredibly fragile and hard to control: if one stray photon or vibration from the outside hits the device in the wrong way, the calculation will collapse. Even today, after three decades of effort, the best quantum computers in the world are barely able to do school-level problems such as finding the prime factors of the number 21. (Answer: 3 and 7.)

The result has been a rate of progress so slow that sceptics often compare quantum computing to fusion energy: it is a revolutionary technology that always seems to be decades away.

But maybe not. Many physicists in the field think that their 30-year slog may finally be on the verge of paying dividends. Not only can they now generate quantum bits, or 'qubits', that last for minutes instead of nanoseconds, they are also much better at correcting the system when errors arise from outside perturbations and other causes. At the same time, quantum-software engineers are coming up with applications that could justify the expense of developing these machines, such as finding new catalysts for industrial processes.

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