The most serious national-security challenge America faces in the next decade isn’t going to be North Korea, or Russia, or even China — or at least not the China conventional geopolitical strategists think about today. It’s going to be whoever wins the race to build the world’s first large-scale quantum computer — a computer that relies on the principles of quantum physics to solve complex mathematical problems that even the world’s fastest supercomputers can’t tackle.

Here’s how the fictional CIA director in David Ignatius’s new espionage thriller puts it: “The president is obsessed with quantum computing. . . . He doesn’t …