qiskit/crates/accelerate/README.md

qiskit-accelerate

This crate provides a bits-and-pieces Rust libary for small, self-contained functions that are used by the main Python-space components to accelerate certain tasks. If you're trying to speed up one particular Python function by replacing its innards with a Rust one, this is the best place to put the code. This is usually the right place to put new Rust/Python code.

The qiskit-pyext crate is what actually builds the C extension modules. Modules in here should define themselves has being submodules of qiskit._accelerate, and then the qiskit-pyext crate should bind them into its fn _accelerate when it's making the C extension.