Proof That a Quantum Computer Can Outperform a Classical One
A leaked paper has given the game away
In an article published in 2012 John Preskill, a theoretical physicist, posed a question: “Is controlling large-scale quantum systems merely really, really hard, or is it ridiculously hard?” Seven years later the answer is in: it is merely really, really hard.
Last week a paper on the matter was — briefly and presumably accidentally — published online. The underlying research had already been accepted by Nature, a top-tier scientific journal, but was still under wraps. The leak revealed that Google has achieved what Dr Preskill dubbed in his article, “quantum supremacy”. Using a quantum computer, researchers at the information-technology giant had carried out in a smidgen over three minutes a calculation that would take Summit, the world’s current-best classical supercomputer, 10,000 years to execute.
A credible demonstration of quantum supremacy, which few disagree that the leaked paper represents, is indeed a milestone. It will divide the history of the field into two eras: a “before”, when quantum computers were simply hoped to outpace even the best classical kind, and an “after”, when they actually did so. There has been much talk, including in this newspaper, about the latter era. Now it has arrived.
