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arXiv · 2610.02146

Polynomial-time additive-error estimation of output probabilities for shallow quantum circuits

Matthew Coudron·Michael J. Gullans·Jon Nelson·Joel Rajakumar·Shi Jie Samuel Tan
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Abstract

We give a deterministic classical algorithm that estimates $|\langle x|U|0^n\rangle|^2$ to additive error $\varepsilon$ in $\mathrm{poly}(n, 1/\varepsilon)$ time, where $U$ is a constant-depth quantum circuit comprised of gates with bounded fan-in and arbitrary connectivity, and $x$ is an arbitrary $n$-bit output string. This improves over prior state-of-the-art algorithms that takes $n^{O(log(n))}$ time for the same task, $n^{O(log(log(n))}$ when $U$ is geometrically local, and $n^{O(1)}$ for 2D geometrically-local circuits.

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Matthew Coudron, Michael J. Gullans, Jon Nelson, Joel Rajakumar, Shi Jie Samuel Tan. 2026-10-01. Polynomial-time additive-error estimation of output probabilities for shallow quantum circuits. https://arxiv.org/abs/2610.02146

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