In the page on Jordan-Wigner strings, it says
Even though AutoMPO will produce a correct MPO, if you use this MPO in DMRG, for example, to find a ground state of a fermionic system, when measuring correlation functions such as @@⟨c_i^\dagger c_j⟩@@ it is still required that you insert the necessary Jordan-Wigner string operators yourself.
I don't understand this. If I do something like
auto ampo = AutoMPO(sites);
auto mpo = MPO(ampo);
auto answer = overlap(psi,mpo,psi);
will this not give the correct answer automatically? I thought the whole point of AutoMPO was that it generated the exact right thing for fermions.
Or am I misinterpreting something?