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Why haven't quantum computers factored 21 yet?

(algassert.com)
335 points ingve | 1 comments | 31 Aug 25 12:14 UTC | HN request time: 0.2s | source
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NooneAtAll3 ◴[31 Aug 25 16:48 UTC] No.45084643[source]▶
> I think a more plausible amount of optimization would produce a circuit with 500x the cost of the factoring-15 circuit

I don't get this part

If author already produced "115x", how can optimizations make it worse?

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1. turtletontine ◴[31 Aug 25 17:11 UTC] No.45084872[source]▶
I think the idea is the minimal implementation will be unstable and unreliable. I don’t know the details, but there’s much work and thought on quantum error correcting qubits - where you hook up N qubits in a clever way to function as one very stable qubit. Terms such as “decoherence time” make appearances. You can imagine this quickly expands into an awful lot of qubits.