Add nsteps for Trotter expansion based on propagator error#1371
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arettig wants to merge 4 commits into
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Add nsteps for Trotter expansion based on propagator error#1371arettig wants to merge 4 commits into
arettig wants to merge 4 commits into
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The current implementation computes the number of steps needed in a Trotter expansion to reach an error in the ground state energy. This commit adds functionality to compute the number of steps determined by the error in the propagator itself.
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This pull request introduces trotter_steps_required_propagator to calculate the number of Trotter steps required for accurate state evolution, updates trotter_steps_required to handle negative times correctly, and adds corresponding unit tests. The reviewer suggested adding input validation to both functions to prevent division-by-zero errors when precision parameters are non-positive, and ensuring that at least one step is returned for any non-zero simulation time when the error bound is zero.
Added checks to ensure the parameters and therefore output of trotter_steps_required functions are physically meaningful. Added several tests for edge cases of these functions.
mhucka
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Jun 23, 2026
mhucka
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IMHO it would benefit for just a couple of small additions to value testing. Otherwise it looks good!
The parameter trotter_error_bound is checked within the trotter_steps_required function and a ValueError is raised if a negative value is provided.
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Fixes #820. Currently we compute the number of steps in a Trotter expansion based on the desired error in the ground state energy. This PR adds a function to compute the number of steps based on the desired error in the propagator$U$ (which is different). This could be useful for certain use cases like dynamics.
New tests are also added to cover this new function.