Ratini Leonardo, Capecci Chiara, Guidoni Leonardo
Dipartimento di Scienze Fisiche e Chimiche, Università degli Studi dell'Aquila, Coppito, L'Aquila, 67100 Italy.
Dipartimento di Ingegneria e Scienze dell'Informazione e Matematica, Università degli Studi dell'Aquila, Coppito, L'Aquila, 67100 Italy.
J Chem Theory Comput. 2024 May 14;20(9):3535-3542. doi: 10.1021/acs.jctc.3c01325. Epub 2024 Apr 24.
Natural orbitals, defined in electronic structure and quantum chemistry as the molecular orbitals diagonalizing the one-particle reduced density matrix of the ground state, have been conjectured for decades to be the perfect reference orbitals to describe electron correlation. In the present work we applied the Wave function-Adapted Hamiltonian Through Orbital Rotation (WAHTOR) method to study correlated empirical ansätze for quantum computing. In all representative molecules considered, we show that the converged orbitals are coinciding with natural orbitals. Interestingly, the resulting quantum mutual information matrix built on such orbitals is also maximally sparse, providing a clear picture that such orbital choice is indeed able to provide the optimal basis to describe electron correlation. The correlation is therefore encoded in a smaller number of qubit pairs contributing to the quantum mutual information matrix.
自然轨道在电子结构和量子化学中被定义为使基态单粒子约化密度矩阵对角化的分子轨道，几十年来一直被推测为描述电子关联的理想参考轨道。在本工作中，我们应用了通过轨道旋转的波函数自适应哈密顿量（WAHTOR）方法来研究量子计算的相关经验近似。在所有考虑的代表性分子中，我们表明收敛轨道与自然轨道重合。有趣的是，基于这些轨道构建的量子互信息矩阵也是最大程度稀疏的，这清楚地表明这种轨道选择确实能够提供描述电子关联的最优基。因此，关联被编码在对量子互信息矩阵有贡献的较少数量的量子比特对中。
