Hello, Miles,

When I was using iqdmrg, I found there probably is an error in last site MPO in one dimensional spin model, when include external magnetic field as

$$

H = \sum h S^z

$$

It seems the magnetic term is missing for last site. Is it because of your way of constructing MPO? Thanks very much.

Best Regards

Wangwei

You are right, I did make a mistake by excluding the last site. I can't believe I made such a stupid mistake.

Please allow me to ask another trivial question though. In the construction of IQMPO, I notice that the quantum number for the link index is QN(), QN(2) and QN(-2), and the size of the Index is 3,1,1. However, is there a specific reason why the quantum number should be these numbers, and the degeneracy is 3, 1,1? Because the link index is going to be contracted finally, thus, my expectation would be that they are not from physics. Is that right?

Thanks very much for your patience.

Best Regards

Wangwei