I was wondering if you could help me with the following problem I ran into when using the Julia version of ITensor. When I define a composite on-site operator in the autoMPO of a Hamiltonian such as writing $C^\dagger*{up} C*{up}$ instead of $N_{up}$ when using "Electron" site types, I get unphysical results for the energy and ground state properties.

I have included a minimal code (based on your example of the Hubbard model) showing the problem I am having. It would be great if you could let me know how I can avoid this problem. In particular how can I avoid this problem in four Fermi terms where two fermi operators belong to one site.

Thank you.

============================================================

```
using ITensors
N = 5
Npart = 3
t1 = 1.0
sites = siteinds("Electron",N; conserve_qns=true);
ampo = AutoMPO()
for b=1:N-1
ampo += -t1,"Cdagup",b,"Cup",b+1
ampo += -t1,"Cdagup",b+1,"Cup",b
ampo += -t1,"Cdagdn",b,"Cdn",b+1
ampo += -t1,"Cdagdn",b+1,"Cdn",b
end
## The following two choices for including an on-site potential result in two different results for the energy and ground state properties. In particular the second choice seems defective.
## Choice 1:
ampo += 1000.,"Nup",1
ampo += 1000.,"Ndn",1
## Choice 2:
# ampo += 1000.,"Cdagup",1,"Cup",1
# ampo += 1000.,"Cdagdn",1,"Cdn",1
H = MPO(ampo,sites);
```