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arXiv:2409.16634 · Physical Review A

Trotter error timescaling separation via commutant decomposition

Yi‐Hsiang Chen

Published Feb 11, 2025• 1 citation
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Abstract

Suppressing the Trotter error in dynamical quantum simulation typically requires running deeper circuits, posing a great challenge for noisy near-term quantum devices. Studies have shown that the empirical error is usually much smaller than the one suggested by existing bounds, implying the actual circuit cost required is much less than the ones based on those bounds. Here, we improve the estimate of the Trotter error over existing bounds, by introducing a general framework of commutant decomposition that separates disjoint error components that have fundamentally different scaling with time. In particular we identify two error components that each scale as $O({\ensuremath{\tau}}^{p}t)$ and $O({\ensuremath{\tau}}^{p})$ for a $p\mathrm{th}$-order product formula evolving to time $t$ using a fixed step size $\ensuremath{\tau}$, implying one would scale linearly with time $t$ and the other would be a constant of $t$. We show that this formalism not only straightforwardly reproduces previous results but also provides a better error estimate for higher-order product formulas. We demonstrate the improvement both analytically and numerically. We also apply the analysis to observable error relating to the heating in Floquet dynamics and thermalization, which is of independent interest.

DOI
10.1103/physreva.111.022612

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Trotter decomposition provides a simple approach to simulating open quantum systems by decomposing the Lindbladian into a sum of individual terms. While it is established that Trotter errors in Hamiltonian simulation depend on nested commutators of the summands, such a relationship remains poorly understood for Lindbladian dynamics. In this Letter, we derive commutator-based Trotter error bounds for Lindbladian simulation, yielding an O(N)O(\sqrt{N})O(N​) scaling in the number of Trotter steps for locally interacting systems on NNN sites. When estimating observable averages, we apply Richardson extrapolation to achieve polylogarithmic precision while maintaining the commutator scaling. To bound the extrapolation remainder, we develop a general truncation bound for the Baker-Campbell-Hausdorff expansion that bypasses common convergence issues in physically relevant systems. For local Lindbladians, our results demonstrate that the Trotter-based methods outperform prior simulation techniques in system-size scaling while requiring only O(1)O(1)O(1) ancillas. Numerical simulations further validate the predicted system-size and precision scaling.