Cost_function

[Adwait-Naravane]

The way we measure Energy in PEPSKit is by building a localoperator for the Hamiltonian and applying all the local terms in this Hamiltonian on the reduced density matrix. The issue is that if I have many body terms in my hamiltonian (say 4 body), then the Hamiltonian stores it as a single tensor which acts on a patch of the PEPS (depending on the indices on which it acts). This is not really required if my many body operator is a product of single body operators or something simple. Is it possible to change this to allow for Hamiltonian LocalOperator to have PEPOs instead of just giant TensorMaps?

[Yue-Zhengyuan]

We have discussed this recently and before. Allowing finite MPO/PEPO in the terms of a LocalOperator is indeed a nice thing. We just haven't come up with an elegant way to do it... Anyway, I think @leburgel is going to tackle the simplest case where the term is just the tensor product of 1-site operators.