Pauli Decomposition via the Fast Walsh-Hadamard Transform v3

Scripts and data used to produce results for the paper "Pauli Decomposition via the Fast Walsh-Hadamard Transform" (https://arxiv.org/abs/2408.06206; Georges et al 2025 New J. Phys. https://doi.org/10.1088/1367-2630/adb44d) . 

In the previous version, there was a bug in generating kinetic energy matrix where one of the FFTs should have been transformed and not only conjugated. This did not practically change the timings but the input matrix was incorrect. Now it's fixed in "kinetic_energy_matrix.zip". All other files are the same as in the second version.