Circuit optimization of Hamiltonian simulation by simultaneous diagonalization of Pauli clusters

This code is provided to allow reproducibility of the results in the paper:

E. van den Berg, K. Temme, "Circuit optimization of Hamiltonian simulation by simultaneous diagonalization of Pauli clusters," Quantum 4, 322 (2020).

The cache directory contains all pre-computed results. Files in this directory can be deleted and will be regenerated as needed. The Hamiltonian directory contains data files (Pauli lists and coefficients) kindly provided by Antonio Mezzacaco along with derived partitions; see also the relevant publication or preprint: Kenny Choo, Antonio Mezzacapo, and Giuseppe Carleo "Fermionic neural-network states for ab-initio electronic structure", Nature Communications volume 11, Article number: 2368 (2020).

The code has a number of external dependences. It uses the NetworkX and Matplotlib python packages and calls pdfcrop to crop the generated figures. The cl.py file contains routines for Paulis, tableau operations, and diagonalization; cl_methods.py generates exponentiation circuits; cl_qiskit.py provides code to generate Qiskit circuits; and cl_chemistry.py contains routines for dealing with the chemistry data. (Running the experiment_chemistry.py code may generate warnings for missing files, these correspond to partitions that took too long to generate.)