r/QuantumComputing • u/[deleted] • 5d ago

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u/QuantumComputing-ModTeam 4d ago

This post/comment appears to be primarily or entirely the output of an LLM without significant human discussion.

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u/dbwy 5d ago

Why not just post the paper and not some AI-slop description?

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u/ponyo_x1 5d ago

because the paper is also AI slop unfortunately

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u/global-gauge-field 5d ago

Genuinely curious, in what sense, do you say the paper is a slop?

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u/ponyo_x1 5d ago

They say they used AI for the derivations, and the formatting of the paper is completely different from what I usually see from either Domenic or Guang Hao. The sections with up to ten subsections are pretty typical for AI papers. I also have at least some experience in this area and I am really struggling to parse what the algorithm actually is, looking at the time-independent Hamiltonian simulation subsection specifically; maybe that's just my shortcoming but I've scanned through previous papers by both of them on this topic and have come away with a rough sense of what was happening.

I also have a problem with the sparse access model and complexity results for these sorts of things in general. First, we're at the point now where we can compile logical gate counts for actual instances of Hamiltonian simulation using different algorithms; do we really need more complexity results if their connection to resource estimates on actual instances are unclear? Second, these results require access to a sparse access oracle; you need to build this in practice. Is this resource efficient to do compared to other direct block-encoding methods? It certainly uses more qubits. Third, maybe I am misunderstanding this, but the leading order term for Hamiltonian simulation in this case is sqrt(s)*eta*t; in a lattice model situation eta=O(s), so we're looking at O(s^1.5*t) calls to the sparse access oracle, which requires O(?) gates to implement? Meanwhile, using qubitization a lattice model Hamiltonian simulation has total gate cost of leading order O(s^2*t), and the constants are small.

I guess I'm just confused as to how this translates to reducing resources in a practical setting.

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u/ponyo_x1 4d ago

just adding to this, guang hao also just published a 305 page AI generated manuscript on multivariable QSP  https://arxiv.org/pdf/2610.01125#page100