  In this study, we utilize the many-body expansion (MBE) framework to
decompose electronic structures into fragments by incrementing the virtual
orbitals. Our work aims to accurately solve the ground and excited state
energies of each fragment using the variational quantum eigensolver and
deflation algorithms. Although our approach is primarily based on unitary
coupled cluster singles and doubles (UCCSD) and a generalization thereof, we
also introduce modifications and approximations to conserve quantum resources
in MBE by partially generalizing the UCCSD operator and neglecting the
relaxation of the reference states. As a proof of concept, we investigate the
potential energy surfaces for the bond-breaking processes of the ground state
of two molecules ($\rm H_2O$ and $\rm N_2$) and calculate the ground and
excited state energies of three molecules (LiH, CH$^+$, and $\rm H_2O$). The
results demonstrate that our approach can, in principle, provide reliable
descriptions in all tests, including strongly correlated systems, when
appropriate approximations are chosen. Additionally, we perform model
simulations to investigate the impact of shot noise on the total MBE energy and
show that precise energy estimation is crucial for lower-order MBE fragments.
