MariaSapova

@ikkoham Hello! Aer for statevector simulator provides the same results as BasicAer and they are equal to exact diagonalization results. But still there is some problem with qasm.

Hello @yaelbh! I use `include_custom = True` with qasm simulator. Still excited state energies deviate greatly.  And also there is some obvious error in matrix element calculations. 

Hello @paulineollitrault ! Could you please provide any insights on how to deal with this inconsistence in qasm results?

@paulineollitrault as far as I can see this commit fixes the normalization of the matrix elements, but what about differences in q_0_0, q_1_1, q_2_2 values? I guess the energies differ...

@woodsp-ibm @paulineollitrault Hello! I actually already opened another issue which is more general Qiskit/qiskit-aqua#1510. I found out that evaluate_operators() in GroundStateEigensolvers produces incorrect expectation values when using qasm. With rewriting...