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arXiv · 2607.19852

Optimal Lower Bounds for Hamiltonian Simulation

Alexander Zlokapa·Richard R. Allen·Aram W. Harrow
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Abstract

For Hamiltonian $H = \sum_j h_j$, we prove asymptotically tight lower bounds on the gate and query complexities of simulating time evolution on a quantum computer. Our bounds hold for arbitrary term norms $\|h_j\|$, time $t$, and trace-distance error $\epsilon$. The matching upper bound (known as composite qDRIFT) consists of high-order Trotterization of the large terms and a randomized first-order Trotterization of the small terms. Unlike prior work that chooses worst-case $\|h_j\|$ to encode the computation of parity or other Boolean functions in time evolution, our proof is elementary and based on a local, bounded-degree classical Hamiltonian. Our work suggests that for many physical systems (e.g., power-law interactions), gate count must scale polynomially in $1/\epsilon$, contrary to the complexity suggested by counting coherent oracle queries such as those in the block-encoding model.

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Alexander Zlokapa, Richard R. Allen, Aram W. Harrow. 2026-07-22. Optimal Lower Bounds for Hamiltonian Simulation. https://arxiv.org/abs/2607.19852

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