The iterative qubit coupled cluster (iQCC) method is a systematic variational approach to solve the electronic structure problem on universal quantum computers. It is able to use arbitrarily shallow quantum circuits at expense of iterative canonical transformation of the Hamiltonian and rebuilding a circuit. Here we present a variety of a posteriori corrections to the iQCC energies to reduce the number of iterations to achieve the desired accuracy. Our energy corrections are based on a low-order perturbation theory series that can be efficiently evaluated on a classical computer. Moreover, capturing a part of the total energy perturbatively, allows us to formulate the qubit active-space concept, in which only a subset of all qubits is treated variationally. As a result, further reduction of quantum resource requirements is achieved. We demonstrate the utility and efficiency of our approach numerically on the examples of 10-qubit N₂ molecule dissociation, the 24-qubit H₂O symmetric stretch, and 56-qubit singlet-triplet gap calculations for the technologically important complex, tris-(2-phenylpyridine)iridium(III) Ir(ppy)₃.

迭代量子位耦合簇 (iQCC) 方法是解决通用量子计算机上电子结构问题的系统变分方法。它能够使用任意浅层量子电路，代价是哈密顿量的迭代规范变换和重建电路。在这里，我们提出了各种后验对 iQCC 能量进行修正，以减少迭代次数以达到所需的精度。我们的能量修正基于可以在经典计算机上有效评估的低阶微扰理论系列。此外，通过微扰捕获总能量的一部分，我们可以制定量子位活动空间概念，其中仅对所有量子位的一个子集进行可变处理。结果，实现了量子资源需求的进一步减少。我们在 10 量子位 N ₂分子解离、24 量子位 H ₂ O 对称拉伸和 56 量子位单线态-三线态间隙计算的示例中以数值方式证明了我们的方法的实用性和效率，用于技术上重要的复合物 tris-( 2-苯基吡啶)铱(III) Ir(ppy)₃ .