CUDA-Q Algorithms

CUDA-Q Algorithms is a primitive-first algorithms library built on CUDA-Q, focused on fault-tolerant quantum computing (FTQC) primitives: block encodings, qubitization, quantum singular value transformation, product formulas, and the state-preparation and fermion-to-qubit building blocks they compose with.

NISQ-era application workflows such as VQE, ADAPT-VQE, QAOA, GQE, and optimizer loops are intentionally out of scope.

Python primitives

cudaq_algorithms is a pure-Python package implemented as CUDA-Q Python kernels and host-side helpers (the only runtime requirement is the cudaq Python package):

• fermion-to-qubit transforms (fermion.jordan_wigner, fermion.bravyi_kitaev)
• state-preparation kernels and operator pools (stateprep)
• Pauli LCU block encoding (PauliLCU, plus prepare/select/apply kernels)
• qubitization walks and Chebyshev moment measurement (Walk)
• QSVT phase sequences (QSVT, PhaseSequence)
• Suzuki-Trotter product formulas (trotter.Trotter, orders 1/2/4)
• chemistry input bridges (chemistry.from_pyscf, chemistry.from_psi4, chemistry.from_fcidump)

Simulation-only helpers (statevector access) are isolated in cudaq_algorithms.sim_utils; everything else is hardware-shaped. The documentation is a Sphinx site under docs/ (build instructions in docs/README.md); the runnable, self-verifying examples live in docs/sphinx/examples/python/.

Classical chemistry preprocessing ships as a peer pure-Python module: double factorization of two-electron integrals (X-DF and C-DF/RC-DF) on NumPy/SciPy with optional CuPy GPU acceleration — see the preprocessing guide in the Sphinx docs.

Chemistry Inputs

The library APIs operate on reusable algorithmic inputs: one- and two-body tensors, qubit Hamiltonians, Pauli words, and state-preparation operator pools. The chemistry module provides bridges that produce those inputs from electronic-structure packages — from_pyscf and from_psi4 extract molecular-orbital integrals from a converged mean-field calculation, and from_fcidump parses the standard FCIDUMP interchange format. The electronic-structure packages themselves are optional and never imported at package-import time; everything downstream of the integrals runs without them.

License

The code in this repository is licensed under the Apache License 2.0. Dependency license references and attributions are listed in NOTICE.

See CONTRIBUTING.md for contribution requirements, including Developer Certificate of Origin (DCO) sign-off.