Quantum Supremacy

Quantum supremacy refers to a quantum computer completing a well-defined computational task that would take a classical supercomputer an impractical amount of time, even if the task has no practical application. Google claimed the first demonstration in 2019 with its Sycamore processor, running a random circuit sampling task in about 200 seconds that Google estimated would take a classical supercomputer roughly 10,000 years; IBM and others later argued that improved classical algorithms and more supercomputing resources could shrink that gap to days, an argument that continues for each new claimed milestone. The term is often confused with the more practically relevant quantum advantage, which specifically requires the task to be useful, not just hard. Quantum supremacy demonstrations are deliberately chosen to be classically intractable and application-free, which is exactly what makes classical researchers keep finding faster classical approaches: an easier target to beat than a real-world optimization or chemistry problem. Multiple further supremacy-style claims have followed from Google, USTC, and others, each contested by subsequent classical simulation work to varying degrees.