Do we need quantum computers to fully understand complex chemical reactions? A new result, decades in the making, shows the surprising power of ordinary “classical” machines. Introduction What Garnet Chan cares most about is basic science. He entered chemistry decades ago to understand some of the most consequential biochemical processes on Earth. But since then, he’s become a central figure in a different arena: the debate over whether quantum computers will have a decisive advantage over ordinary “classical” ones. Over the past decade, many quantum computing researchers have identified the very reactions Chan studies as an area in which quantum computers should excel. Chan, however, has long doubted that powerful quantum computers — which are still years away — will be necessary. “My main interest is in solving chemical problems. If classical computers are the right tool to do it, we should,” he said.…