Could you please clarify about QN conserving tensors and how to use it?
After defining the hamiltonian
auto H = IQMPO(ampo);
I write the state as follows
auto psi0 = InitState(sites, "Emp");
auto psi = IQMPS(psi0);
(3 up and 1 down particles).
I verified the ground state for small system with the exact value and noticed that the values are slightly different.
For example, -7.34478928869732605733
instead of the correct answer -7.46410162