Hi all,

I am trying to implement the AKLT Hamiltonian for the Spin-2 case.

Having computed with Mathematica the power (S*i * S*j)^3 and (S*i * S*j)^4 (that are contained in the Hamiltonian) as a function of the operators S+ and S-, I have terms of the form

```
ampo += 1.0, "Sz*S+*S+",indices_prime[i],"Sz*S-*S-",indices_prime[i+1];
```

and

```
ampo += 1.0, "S+*S-*Sz*Sz",indices_prime[i],"S-*S+*Sz*Sz",indices_prime[i+1];
```

with products of three or four operators on each site. I compile the code, but when I try to run it, I obtain the following error:

"Operator S- name not recognized".

Actually, the code seems to recognise the operator "S-", because, if I put only two operators for each site (for instance, "S+S-" and "S-S+"), it works. I think the error it is due to the fact that I am using more than two operators in the product on each site.

Any advice?

Thank you very much.