Uniform semiclassical observable error bound of Trotter-Suzuki splitting: a simple algebraic proof

TL;DR

This paper provides a simple algebraic proof that certain observables in semiclassical Schrödinger equation simulations have error bounds independent of the semiclassical parameter, applicable to high-order Trotter schemes.

Contribution

It introduces a new algebraic proof for uniform-in-$h$ error bounds of Trotterization, avoiding complex semiclassical analysis and extending to high-order schemes.

Findings

Uniform error bounds for observables independent of $h$

Applicable to arbitrarily high-order Trotter schemes

Proof relies solely on algebraic operator structure

Abstract

Efficient simulation of the semiclassical Schr\"odinger equation has garnered significant attention in the numerical analysis community. While controlling the error in the unitary evolution or the wavefunction typically requires the time step size to shrink as the semiclassical parameter $h$ decreases, it has been observed -- and proved for first- and second-order Trotterization schemes -- that the error in certain classes of observables admits a time step size independent of $h$. In this work, we explicitly characterize this class of observables and present a new, simple algebraic proof of uniform-in-$h$ error bounds for arbitrarily high-order Trotterization schemes. Our proof relies solely on the algebraic structure of the underlying operators in both the continuous and discrete settings. Unlike previous analyses, it avoids Egorov-type theorems and bypasses heavy semiclassical machinery. To our knowledge, this is the first proof of uniform-in-$h$ observable error bounds for Trotterization in the semiclassical regime that relies only on algebraic structure, without invoking the semiclassical limit.