论文标题
具有广义的两体群集操作员的统一耦合群集方法的功能和限制
Capabilities and Limits of the Unitary Coupled-cluster Approach with Generalized Two-body Cluster Operators
论文作者
论文摘要
电子波功能的单一簇扩展最近引起了人们的极大兴趣，因为它们与量子算法结合使用。在这项贡献中，我们使用广义的两体激发算子研究了ANSATZ的某些方面，这在最近的一些有关量子化学量子算法的著作中被考虑。我们的数值结果表明，尤其是与通常的粒子孔双激发算子相关的有效粒子孔激发水平的两体算子导致波函数的非常准确但紧凑的表示。具有有效激发等级零的广义两体操作员的效果明显差得多。我们将与标准和统一耦合群集的扩展进行比较，并表明上述方法匹配甚至超过了三体粒子孔激发的膨胀精度，尤其是在强相关开始时。该方法的一个缺点是，将其严格地将其汇合到最小值是相当困难的。
Unitary cluster expansions of the electronic wavefunction have recently gained much interest because of their use in conjunction with quantum algorithms. In this contribution, we investigate some aspects of an ansatz using generalized two-body excitations operators, which has been considered in some recent works on quantum algorithms for quantum chemistry. Our numerical results show that in particular two-body operators with effective particle-hole excitation level of one in connection with the usual particle-hole double excitation operators lead to a very accurate yet compact representation of the wavefunction. Generalized two-body operators with effective excitation rank zero have a considerably less pronounced effect. We compare to standard and unitary coupled-cluster expansions and show that the above mentioned approach matches or even surpasses the accuracy of expansions with three-body particle-hole excitations, in particular at the onset of strong correlation. A downside of the approach is that it is rather difficult to rigorously converge it to its variational minimum.
