  Introducing an active space approximation is inevitable for the quantum
computations of chemical systems. However, this approximation ignores the
electron correlations related to non-active orbitals. Here, we propose a
computational method for correcting quantum computing results using a
well-established classical theory called coupled cluster theory. Our approach
efficiently extracts the quantum state from a quantum device by computational
basis tomography. The extracted expansion coefficients of the quantum state are
embedded into the coupled cluster ansatz within the framework of the tailored
coupled cluster method. We demonstrate the performance of our method by
verifying the potential energy curves of LiH, H2O, and N2 with a
correlation-energy correction scheme. Our method demonstrates reasonable
potential energy curves even when the standard coupled cluster fails. The
sufficient numbers of measurements for tomography were also investigated.
Furthermore, this method successfully estimated the activation energy of the
Cope rearrangement reaction of 1,5-hexadiene together with perturbative triples
correction. These demonstrations suggest that our approach has the potential
for practical quantum chemical calculations using quantum computers.
