In its most practical form, the “recommendation problem” relates to how services like Amazon and Netflix determine which products you might like to try. In the spring of 2017 Tang took a class on quantum information taught by Scott Aaronson, a prominent researcher in quantum computing. The recommendation problem is designed to give a recommendation for products that users will like. The fast classical algorithm Tang found was directly inspired by the fast quantum algorithm Kerenidis and Prakash had found two years earlier. Tang never would have come up with this classical algorithm but for their quantum algorithm,” Aaronson said.