In the meantime, however, the adaptive feature of ADAPT-VQE requires much more number of iterations than the UCCSD Ansätze. Anyway, compared to the infeasibility of UCCSD Ansätze since it consists of a long sequence of operators on NISQ devices, the additional computational cost introduced by ADAPT-VQE is completely acceptable. Like every coin has two sides, the adaptive feature makes the Ansätze compact and well-ordered but time-consuming. The sheer number of measurements might be an insurmountable obstacle in practice for the simulations of large molecular systems. For a practical VQE simulation process, the task of quantum computers is to generate the expectation values of various observable operators such as the Hamiltonian and commutators of Hamiltonian in each adaptive iteration. Assuming that there are totally N T expectation values generated by quantum computers throughout the simulation, the total number of measurements N tot is