ffsim.multireference_state¶

ffsim.multireference_state(hamiltonian, ansatz_operator, reference_occupations, norb, nelec, root=0)[source]¶

Compute multireference energy and state.

Parameters:

hamiltonian (LinearOperator | SupportsLinearOperator) – The Hamiltonian.
ansatz_operator (SupportsApplyUnitary) – The ansatz operator.
reference_occupations (Sequence[tuple[Sequence[int], Sequence[int]]]) – The orbital occupations of the reference states.
norb (int) – The number of spatial orbitals.
nelec (tuple[int, int]) – The number of alpha and beta electrons.
root (int) – The index of the desired eigenvector. Defaults to 0, which yields the lowest-energy state.

Return type:

tuple[float, ndarray]

Returns:

The energy of the multireference state, and the state itself.