After multiple fixes in Qiskit Nature, this PR now also adds support for computing S^z and S^2 in the PySCFGroundStateSolver.
Details and comments
Supporting the correct AngularMomentum with taking the alpha-beta overlap into account during the QiskitSolver is currently not possible because of the API workflow. In other words: the kernel method is not provided the information from which we can reconstruct this overlap matrix during the construction of the AngularMomentum property.
We also cannot really compute it up-front and inject it into the QiskitSolver as an attribute, because this would require a-priori knowledge of the active MOs (which we do not have at that point).
This will need to be sorted together with the PySCF team, once I have raised the problem discussed here to them, since this affects their UCASCI and UCASSCF methods, too.
Summary
After multiple fixes in Qiskit Nature, this PR now also adds support for computing
S^z
andS^2
in thePySCFGroundStateSolver
.Details and comments
Supporting the correct
AngularMomentum
with taking the alpha-beta overlap into account during theQiskitSolver
is currently not possible because of the API workflow. In other words: thekernel
method is not provided the information from which we can reconstruct this overlap matrix during the construction of theAngularMomentum
property. We also cannot really compute it up-front and inject it into theQiskitSolver
as an attribute, because this would require a-priori knowledge of the active MOs (which we do not have at that point).This will need to be sorted together with the PySCF team, once I have raised the problem discussed here to them, since this affects their UCASCI and UCASSCF methods, too.