I am struggling with understanding the differences between OpenFermion and Qiskit libraries when it comes to Molecular Data, two body integrals.
For example, I am working with the following [('H',[0,0,0]),('H',[0,0,1.595])] Basis: 6-31G.
For Qiskit I am using the second_q_ops() function from ElectronicStructureProblem class. While for Openfermion I just load the molecular data and then use the two_body_integrals attribute. There is some difference in the numbers I see for the 2-body integral 4D tensor between the classes. For example, for the creation, annihilation operators [0,0,0,0] Qiskit gives me the following: ('+_0 +_0 -_0 -_0', -0.231966689269309), while OpenFermion the following value 0.46393337853861794. I thought that it might be a factor of -2 (Qiskit values are -2 times smaller than Openfermion), but simply multiplying the whole 4D Qiskit tensor by a factor did not make both 4D tensors equal.
I would like to ask if someone can explain the differences, is it related to convention or ordering of alpha/beta orbitals? Thank you.
