  The fragment molecular orbital (FMO) scheme is one of the popular
fragmentation-based methods and has the potential advantage of making the
circuit flat in quantum chemical calculations on quantum computers. In this
study, we used a GPU-accelerated quantum simulator (cuQuantum) to perform the
electron correlation part of the FMO calculation as unitary coupled-cluster
singles and doubles (UCCSD) with the variational quantum eigensolver (VQE) for
hydrogen-bonded (FH)$_3$ and (FH)$_2$-H$_2$O systems with the STO-3G basis set.
VQE-UCCD calculations were performed using both canonical and localized MO
sets, and the results were examined from the point of view of size-consistency
and orbital-invariance affected by the Trotter error. It was found that the use
of localized MO leads to better results, especially for (FH)$_2$-H$_2$O. The
GPU acceleration was substantial for the simulations with larger numbers of
qubits, and was about a factor of 6.7--7.7 for 18 qubit systems.
