to_chemist_ordering#

to_chemist_ordering(two_body_tensor, *, index_order=None)[source]#

Convert a two-body tensor to chemists’ index order.

Coverts the rank-four tensor two-body tensor representing two-body integrals from physicists’, or intermediate, index order to chemists’ index order: i,j,k,l -> i,l,j,k

Parameters:

  • two_body_tensor (np.ndarray | SparseArray) – the rank-four tensor to be converted.

  • index_order (IndexType | None) – when supplied this will hard-code the IndexType value. If None (the default), the index_order will be determined automatically based on the symmetries of the two_body_tensor.

Returns:

The same rank-four tensor, now in chemists’ index order.

Raises:

QiskitNatureError – when an unknown index type is encountered.

Return type:

np.ndarray | SparseArray