ExchangeTerm Type
A two-body exchange term with indices i, j, k, l representing the operator
a†_i a†_j a_k a_l (annihilators in the order k then l).
The coefficient supplied to this internal helper for key "i,j,k,l" is the
FULL WEIGHTED prefactor of this operator string and is applied verbatim — the
weighted core folds in the ½ of the two-body Hamiltonian term
½·Σ g_pqrs a†_p a†_q a_r a_s; no additional ½ is applied here. The raw-physicist
primary builders reach this helper via the internal raw→weighted mapping (½ and
r↔s swap), so a raw ⟨pq|rs⟩ factory is supplied to
computeHamiltonianWith directly. The Fcidump
adapters produce a conforming raw factory.