Quantum supremacy (or quantum advantage) is the goal of demonstrating that a programmable quantum device can solve a problem that no classical computer can solve in any feasible amount of time. The problem doesn't necessarily have to be useful; it just needs to be provably hard for classical computers. This milestone marks the point where quantum computers move from theoretical constructs to devices with capabilities beyond the reach of the most powerful supercomputers.
The term 'quantum supremacy' was coined by John Preskill in 2012. The concept, however, dates back to the early ideas of quantum computing by Richard Feynman and David Deutsch in the 1980s. In October 2019, Google claimed to have achieved quantum supremacy with their 53-qubit Sycamore processor, solving a specific random circuit sampling problem in 200 seconds that they estimated would take a supercomputer 10,000 years (though this claim was contested by IBM).
Quantum supremacy is a major milestone in the development of quantum technologies. Following Google's announcement, other teams (such as researchers in China using photonic and superconducting systems) have also reported achieving supremacy. It serves as a proof of principle that quantum computers can indeed outperform classical ones, stimulating further investment and research into building error-corrected, useful quantum computers for drug discovery, materials science, and cryptography.