The PennyLane quantum chemistry library.


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.


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.


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).


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.