# Quantum Supremacy The milestone where a quantum computer performs a calculation that no classical computer can match in any reasonable timeframe. Google claimed quantum supremacy in October 2019 with its 53-qubit Sycamore processor, which completed a specific random-circuit sampling task in 200 seconds that Google estimated would take the world's most powerful classical supercomputer ~10,000 years. IBM contested the claim, arguing classical simulation could be done in 2.5 days. The term is contested on two fronts. First, the tasks demonstrated have no practical application — they are specifically chosen to be hard for classical computers and easy for quantum ones, not because anyone needs the answer. Second, "supremacy" carries connotations some researchers find inappropriate; "quantum advantage" or "quantum computational advantage" are preferred alternatives. The analytically important distinction: quantum supremacy (beating classical on any task, however contrived) vs. quantum advantage (beating classical on a *useful* task). The first has been claimed; the second has not been achieved. The gap between them — and when it will close — is what the national-security competition around [[Quantum Computing]] is really about. ## See Also - [[Quantum Computing]] — the full concept - [[Quantum Error Correction]] — what's needed to close the supremacy-advantage gap - [[Technology Lexicon]] — the full vocabulary (quantum computing section)