openfermion.hamiltonians.s_squared_operator

Return the s^{2} operator.

openfermion.hamiltonians.s_squared_operator(
    n_spatial_orbitals: int
) -> openfermion.ops.FermionOperator

\[ \begin{align} S^{2} = S^{-} S^{+} + S^{z}( S^{z} + 1) \end{align} \]

n_spatial_orbitals number of spatial orbitals (n_qubits + 1 // 2).

operator FermionOperator

corresponding to the s+ operator over n_spatial_orbitals.

The indexing convention used is that even indices correspond to spin-up (alpha) modes and odd indices correspond to spin-down (beta) modes.