Strengths and Weaknesses of Quantum Computing · HackerPapers discussions

Strengths and Weaknesses of Quantum Computing — mentioned by amluto

Tue, 21 Apr 2026 00:17:06 GMT

Yes and no. Grover's algorithm is provably optimal [0]. No quantum algorithm will ever find an n-bit key by queries to any reasonable sort of oracle faster than Grover's algorithm, and Grover's algorithm is way too slow to be a serious problem. But symmetric ciphers are not black boxes. They're mostly built on some variant of a Feistel network, which is a very nice construction for turning a messy function into an invertible function that, in a potentially very strong sense, acts like a cryptographically secure permutation. When I was in grad school, one project I contemplated but never spent…

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Strengths and Weaknesses of Quantum Computing — mentioned by michael_nielsen

Sat, 23 Dec 2023 23:58:15 GMT

Quantum computers won't search unordered databases with fewer than ~ sqrt(N) queries. Proved in: https://arxiv.org/abs/quant-ph/9701001

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Strengths and Weaknesses of Quantum Computing — mentioned by bshanks

Wed, 21 Sep 2016 05:30:52 GMT

The paper on lower bounds for black-box quantum algorithms trying to solve NP appears to be https://arxiv.org/pdf/quant-ph/9701001.pdf (?)

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Strengths and Weaknesses of Quantum Computing — mentioned by michael_nielsen

Fri, 04 Jun 2010 01:27:24 GMT

Hard to say. My first instinct is probably not a whole lot. It's more or less conventional wisdom in the field that quantum computers are unlikely to be able to solve NP-complete problems in polynomial time. The argument for this conventional wisdom is heuristic (and certainly open to doubt, maybe most people are wrong), and it's in this paper: http://arxiv.org/abs/quant-ph/9701001 But in any case, it's one thing for something to be widely believed, and another thing to have hard evidence. People might respond quite dramatically to such evidence.

Paper and discussion history. A mention is not an endorsement.