# qml.qchem¶

The PennyLane quantum chemistry library.

Note

To access the qml.qchem package, pennylane-qchem must be installed via pip:

pip install pennylane-qchem


The PennyLane quantum chemistry package. Supports OpenFermion, PySCF, and Psi4 for quantum chemistry calculations using PennyLane.

## Functions¶

 read_structure(filepath[, outpath]) Reads the molecular structure from a file and creates a list containing the symbol and Cartesian coordinates of the atomic species. meanfield_data(mol_name, geometry, charge, …) Launches the meanfield (Hartree-Fock) electronic structure calculation. active_space(mol_name, hf_data[, …]) Builds the active space by partitioning the set of Hartree-Fock molecular orbitals. decompose_hamiltonian(mol_name, hf_data[, …]) Decomposes the electronic Hamiltonian into a linear combination of Pauli operators using OpenFermion tools. _qubit_operator_to_terms(qubit_operator) Converts OpenFermion QubitOperator to a 2-tuple of coefficients and PennyLane Pauli observables. _terms_to_qubit_operator(coeffs, ops) Converts a 2-tuple of complex coefficients and PennyLane operations to OpenFermion QubitOperator. Checks equivalence between OpenFermion QubitOperator and Pennylane VQE Hamiltonian (Tensor product of Pauli matrices). convert_observable(qubit_observable) Converts an OpenFermion QubitOperator operator to a Pennylane VQE observable generate_hamiltonian(mol_name, mol_geo_file, …) Generates the qubit Hamiltonian based on geometry and mean field electronic structure. sd_excitations(n_electrons, n_orbitals[, …]) Generates single and double excitations from a Hartree-Fock (HF) reference state. hf_state(n_electrons, m_spin_orbitals) Generates the occupation-number vector representing the Hartree-Fock (HF) state of $$N$$ electrons in a basis of $$M$$ spin orbitals.