SQUIRREL: An open-source software suite for quantum dynamics calculations on complex geometries with time-dependent electric/magnetic fields

We present a general-purpose, open-source software suite, SQUIRREL (Streamlined Quantum Unified Interface for Researching Real-time Excitations with Light), for propagating the time-dependent Schrödinger equation on complex geometries in the presence of time-dependent electric and/or magnetic fields. To handle large systems that can be executed on a conventional desktop computer, the SQUIRREL software suite uses a suite of efficient propagation methods for various quantum dynamics applications, including a new perturbation-based element-dropping algorithm that improves computational performance with minimal loss of accuracy. We analyze the efficacy of these optimizations for Crank-Nicolson, scaled Taylor series approximation, and split-operator propagation methods and discuss the range of their applicability to a variety of quantum dynamics problems. In addition, we provide several examples of time-dependent dynamics calculations and extensive documentation for generating custom geometries, potentials, and time-propagation approaches. Our numerical benchmarks and results demonstrate the versatility of the SQUIRREL software suite for efficiently calculating quantum dynamics in complex nanoscale geometries, particularly in the presence of time-dependent magnetic fields, which have received less attention in previous quantum dynamics studies.我们推出一款通用开源软件套件SQUIRREL（全称：Streamlined Quantum Unified Interface for Researching Real-time Excitations with Light，即面向光致实时激发研究的精简量子统一接口），该套件可用于在含时电场和/或磁场存在的复杂几何结构中求解含时薛定谔方程（time-dependent Schrödinger equation）。为了能在普通台式机上运行大规模体系的计算，SQUIRREL软件套件针对各类量子动力学应用场景集成了一系列高效传播算法，其中包含一种基于微扰的元素丢弃算法，可在精度损失极小的前提下提升计算性能。我们针对克兰克-尼科尔森法（Crank-Nicolson）、缩放泰勒级数近似法（scaled Taylor series approximation）以及分裂算符传播法（split-operator propagation）这三种方法，分析了上述优化策略的有效性，并探讨了它们在各类量子动力学问题中的适用范围。此外，我们还提供了若干含时动力学计算案例，以及用于自定义几何结构、势场与时间传播方案的详尽文档。我们的数值基准测试与结果证明，SQUIRREL软件套件可高效计算复杂纳米级几何结构中的量子动力学过程，尤其适用于含时磁场场景——这类场景在过往的量子动力学研究中尚未得到足够关注。