  Variational Quantum Eigensolver (VQE) method is the way to derive the wave
functions from their eigen energies using quantum computers. But, the methods
to utilize the superposition states between them haven't been developed yet.
The method to calculate the off diagonal element of observables between two
states derived by VQE method requires large numbers of gate operations for
Noisy Intermediate Scale Quantum (NISQ) devices. We proposed the novel method
to drive the superposition state between the states the derived by VQE method.
We call it Frame superposition cluster (FSC) method. Using the method, we
confirmed that dipole transition moment could be calculated with the highest
accuracy compared to other methods.
