Exascale-Efficient Optimization for Variational Quantum Eigensolvers - Codes and Data

This repository contains the full implementation supporting the paper "Exascale-Efficient Optimization for Variational Quantum Eigensolvers Using Fractal-Based Decomposition" (El-Khadiri, Cruz-Duarte, and Talbi, University of Lille / CRIStAL / Inria). Contents The repository includes the following source files: CMakeLists.txt — CMake build configuration for the C++/MPI/Kokkos/HIP application GPfunctions.cpp / GPfunctions.hpp — General-purpose utility functions HPCfunctions.cpp / HPCfunctions.hpp — HPC-level parallelism and Kokkos integration oldmain1.cpp — Main entry point for the PFDA-BS optimizer py_vqe_shim.cpp / py_vqe_shim.hpp — C++/Python binding layer (pybind11) interfacing the optimizer with the VQE objective vqe_bridge.py — Python driver constructing the qubit Hamiltonian and UCCSD circuit via PennyLane and JAX vqe_cost_reference.py — Reference cost function and benchmarking utilities README.md — Step-by-step instructions for building, configuring, and running all experiments on LUMI-G System and dependencies The code targets the LUMI-G partition (AMD MI250X GPUs, 8 GCDs per node). Dependencies include MPI (Cray toolchain), Kokkos with HIP backend, ROCm, JAX (via a Singularity/Apptainer container), PennyLane ≥ 0.41 with the lightning-kokkos backend, and pybind11. Full module load commands and container paths are documented in README.md. Reproducibility The repository provides all configurations required to reproduce the strong-scaling experiments (1–1000 nodes, LUMI-G) and the solution-quality benchmarks across nine molecular systems (HeH⁺, H₃⁺, H₄, OH⁻, NeH⁺, HF, LiH, BH₃, CH₄) in the STO-3G basis, as reported in the manuscript. Molecular data are prefetched from the PennyLane quantum chemistry dataset via the included prefetch script. Keywords Variational Quantum Eigensolver, UCCSD, fractal decomposition, derivative-free optimization, MPI, Kokkos, JAX, PennyLane, AMD MI250X, LUMI, exascale, high-performance computing, quantum chemistry