Title: Extension of the Trotterized Unitary Coupled Cluster to Triple Excitations Show Chinese title

Title: Trotter化单重耦合簇方法在三重激发的扩展

Abstract: The Trotterized Unitary Coupled Cluster Single and Double (UCCSD) ansatz has recently attracted interest due to its use in Variation Quantum Eigensolver (VQE) molecular simulations on quantum computers. However, when the size of molecules increases, UCCSD becomes less interesting as it cannot achieve sufficient accuracy. Including higher-order excitations is therefore mandatory to recover the UCC's missing correlation effects. In this Letter, we extend the Trotterized UCC approach via the addition of (true) Triple T excitations introducing UCCSDT. We also include both spin and orbital symmetries. Indeed, in practice, these later help to reduce unnecessarily circuit excitations and thus accelerate the optimization process enabling to tackle larger molecules. Our initial numerical tests (12-14 qubits) show that UCCSDT improves the overall accuracy by at least two-orders of magnitudes with respect to standard UCCSD. Overall, the UCCSDT ansatz is shown to reach chemical accuracy and to be competitive with the CCSD(T) gold-standard classical method of quantum chemistry. Show Chinese abstract

Abstract: Trotter化单双激发单位耦合簇（UCCSD）假设由于在量子计算机上的变分量子本征求解器（VQE）分子模拟中的应用而最近引起了关注。 然而，当分子尺寸增大时，UCCSD变得不那么有吸引力，因为它无法达到足够的准确性。 因此，包括高阶激发是恢复UCC缺失的相关效应的必要条件。 在本文中，我们通过添加（真实）三重T激发扩展了Trotter化UCC方法，引入了UCCSDT。 我们还包含了自旋和轨道对称性。 实际上，在实践中，这些有助于减少不必要的电路激发，从而加速优化过程，使能够处理更大的分子。 我们的初步数值测试（12-14个量子比特）显示，与标准UCCSD相比，UCCSDT的总体准确性至少提高了两个数量级。 总体而言，UCCSDT假设被证明可以达到化学精度，并且与量子化学中的CCSD(T)黄金标准经典方法具有竞争力。