Variational quantum eigensolver (VQE) for electronic structure calculations is believed to be one major potential application of near term quantum computing. Among all proposed VQE algorithms, the unitary coupled cluster singles and doubles excitations (UCCSD) VQE ansatz has achieved high accuracy and received a lot of research interest. However, the UCCSD VQE based on fermionic excitations needs extra terms for the parity when using Jordan–Wigner transformation. Here we introduce a new VQE ansatz based on the particle preserving exchange gate to achieve qubit excitations. The proposed VQE ansatz has gate complexity up-bounded to O ( n 4 ) for all-to-all connectivity where n is the number of qubits of the Hamiltonian. Numerical results of simple molecular systems such as BeH 2 , H 2 O, N 2 , H 4 and H 6 using the proposed VQE ansatz gives very accurate results within errors about 10 −3 Hartree....

中文翻译：

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Qubit耦合簇单双态变分量子本征求解器ansatz用于电子结构计算

用于电子结构计算的变分量子本征求解器（VQE）被认为是近期量子计算的主要潜在应用之一。在所有提出的VQE算法中，整体耦合簇单双激发（UCCSD）VQE ansatz已实现了高精度，并引起了很多研究兴趣。但是，当使用约旦-维格纳变换时，基于铁离子激发的UCCSD VQE需要额外的奇偶校验条件。在这里，我们介绍了一种基于保留粒子交换门的新型VQE ansatz，以实现量子比特激发。拟议的VQE ansatz对于所有到所有的连接，门的复杂度上升到O（n 4），其中n是哈密顿量的量子位数。简单分子系统（例如BeH 2，H 2 O，N 2，