论文标题
计算非绝热耦合和通过变量量子本素的阶段
Calculating nonadiabatic couplings and Berry's phase by variational quantum eigensolvers
论文作者
论文摘要
变异量子本素（VQE）是一种算法，可在量子化学和量子多体物理学中找到系统的特征力和本征态。 VQE是研究此类系统的近期量子设备最有前途的应用之一。在这里，我们提出了VQE的扩展，以计算量子化学系统中分子的非绝热耦合以及量子多体系统中的贝里相。这两种数量都起着重要的作用，可以理解超出天真绝热图片的系统的性质，例如非绝热动态和物质的拓扑阶段。我们提供量子电路和经典后处理，以计算非绝热耦合和贝瑞的阶段。具体而言，我们表明，对非绝热耦合的评估减少到可观察到的期望值，而贝瑞阶段的耦合值也需要一个额外的Hadamard测试。此外，我们使用在实际量子装置上评估的非绝热耦合模拟氟化锂分子的光解离动力学。我们的建议扩大了VQE的适用性以及近期量子设备研究分子和量子多体系统的可能性。
The variational quantum eigensolver (VQE) is an algorithm to find eigenenergies and eigenstates of systems in quantum chemistry and quantum many-body physics. The VQE is one of the most promising applications of near-term quantum devices to investigate such systems. Here we propose an extension of the VQE to calculate the nonadiabatic couplings of molecules in quantum chemical systems and Berry's phase in quantum many-body systems. Both quantities play an important role to understand the properties of a system beyond the naive adiabatic picture, e.g., nonadiabatic dynamics and topological phase of matter. We provide quantum circuits and classical post-processings to calculate the nonadiabatic couplings and Berry's phase. Specifically, we show that the evaluation of the nonadiabatic couplings reduces to that of expectation values of observables while that of Berry's phase also requires one additional Hadamard test. Furthermore, we simulate the photodissociation dynamics of a lithium fluoride molecule using the nonadiabatic couplings evaluated on a real quantum device. Our proposal widens the applicability of the VQE and the possibility of near-term quantum devices to study molecules and quantum many-body systems.
