Last month Jensen Huang, the boss of Nvidia, landed in Beijing with a clear message: the maker of the world’s leading artificial-intelligence (AI) chips planned to “unswervingly serve the Chinese market". America would rather it didn’t. A few days earlier the Trump administration had introduced new controls that, in effect, banned the company from selling its H20 microprocessor to China. Over the past few years America has sought to hobble its main rival in the AI race by controlling access to its advanced semiconductors. The performance of an AI processor depends mostly on two factors: computing power (how fast a...