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Quick answer

What is quantum advantage?

By Muhammad Atif2 min readReviewed 12 October 2026
The short answer

Quantum advantage means a quantum computer has done a specific task faster, or better, than the best known method on ordinary computers. The older term "quantum supremacy" means much the same. The word that matters is specific: so far, demonstrations of advantage have mostly used tasks designed to suit quantum hardware, rather than problems anyone needs solved.

What it does and doesn't mean

  • It means a quantum machine beat the best classical method known at the time, on one particular task.
  • It doesn't mean quantum computers are faster in general, useful for business yet, or close to breaking encryption.
  • It can change. Every claim invites classical experts to find a better method, and sometimes they do.

A real example

2019: THE CLAIMSycamore, 53 qubits: about 200 secondsvs an estimated 10,000 years classically DAYS LATER: THE RESPONSEIBM: a better classical method coulddo it in about two and a half days THE FOLLOWING YEARSclassical methods narrowedthe gap much further
A real scientific milestone, and a typical life cycle for an advantage claim: the quantum result stands, but the classical comparison keeps improving. The task, sampling from random circuits, was chosen because it's hard to simulate, not because anyone needed the answer.

Useful advantage is the next milestone

The milestone researchers are working towards is useful advantage: a quantum computer solving a problem people actually care about, such as simulating a molecule, better than any classical method. Most experts expect it first in simulating chemistry and materials, the areas described in what quantum computers are good at. Breaking encryption needs far larger, error-corrected machines; see what a cryptographically relevant quantum computer is.

How to judge a claim

Ask whether the task was useful, whether the classical comparison was the best available, whether the machine used error-corrected qubits, and whether independent experts have checked it. How to read a "quantum breakthrough" headline walks through those questions with examples.

Common confusions

  • "Quantum advantage means encryption is about to break." No. Advantage on a sampling task says nothing about running Shor's algorithm at scale.
  • "Supremacy means better at everything." No. It means better at one task, under one comparison.
  • "Once claimed, it's settled." No. Claims are tested for years, and some have been overturned by better classical methods.

Sources and further reading

Tags show what kind of source each one is (how sources are used). Checked against these sources on 12 October 2026. Spotted an error? Email hello@plainquantum.com and it will be corrected, with a note.

  1. ExperimentQuantum supremacy using a programmable superconducting processorArute et al. (Google), Nature, 2019
  2. Company announcementOn "quantum supremacy"IBM Quantum blog, 2019
  3. Peer-reviewed paperQuantum Computing in the NISQ era and beyondJohn Preskill, Quantum, 2018
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