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Why haven't we got useful quantum computers yet?

Four years after Google first demonstrated the supremacy of quantum computers over ordinary ones, why aren't these exotic machines being used for practical problems?

By Alex Wilkins

5 September 2023

Quantum computers are here, but aren’t yet particularly useful

John D/Getty Images

Quantum computers have long promised to solve certain problems faster than any ordinary, or classical, computer can. In fact, Google delivered on this promise in 2019, when it declared that its quantum computer had achieved quantum supremacy, performing a calculation impossible for the best classical computers of the day. As New Scientist said at the time, Google had “secured yet another place in the history books”.

Yet the next chapter of the quantum revolution is struggling to be written. Since …

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