It’s official: Google has attained quantum supremacy. According to today’s post on the AI Blog (and Nature article, “Quantum Supremacy Using a Programmable Superconducting Processor”), the search giant’s 54-qubit processor (“Sycamore”) managed to solve a computation that would have taken the world’s fastest supercomputer 10,000 years in just 200 seconds.
Quantum-computing rival IBM has refuted Google’s breakthrough, however, claiming that its Summit machine can do the same calculation in a still-practical 2.5 days. (“Quantum supremacy” is defined by many experts as “the moment a quantum computer performs a calculation that, for all practical purposes, a classical computer can’t match.”)
Google stands by their 10,000 year estimate, though several computer experts interviewed for this article said IBM is probably right on that point. “IBM’s claim looks plausible to me,” emailed Scott Aaronson of the University of Texas, Austin. So assuming they’re right, is 2.5 days a practical amount of time? Maybe it is for some tasks, but certainly not for others.