Hi, I am new to itensor and MPS/MPO in general and I have the following question:

I have a chain of spin-1/2 and a 4x4 matrix U that couples two adjacent spins i and i+1. How can I form the MPO in itensor:

U*1,2 + U*3,4 + U_5,6 + ...

If all of the Us are the same but just operate on different sites and similarly if all of the Us are different.

I hope my question is clear. Thank you in advance.