论文标题
使用线性组合来定制电子结构计算的截断
Tailoring Term Truncations for Electronic Structure Calculations Using a Linear Combination of Unitaries
论文作者
论文摘要
备受期待的量子计算机的使用是模拟复杂的量子系统，包括分子和其他多体系统。一种有前途的方法涉及直接应用单位（LCU）的线性组合来近似泰勒级数，以截断一定的顺序。在这里，我们提出了该方法的适应，该方法针对具有广泛变化的术语的哈密顿量优化，就像电子结构计算中通常情况一样。我们表明，使用截断，该截断保留了由迭代程序确定的较大的幅度项，将LCU施加更有效。我们获得了这种广义截短的泰勒方法的模拟误差的边界，对于一系列分子模拟，我们报告了这些界限以及确切的数值结果。我们发现，对于给定的电路深度，我们的自适应方法通常可以通过数量级提高模拟精度。
A highly anticipated use of quantum computers is the simulation of complex quantum systems including molecules and other many-body systems. One promising method involves directly applying a linear combination of unitaries (LCU) to approximate a Taylor series by truncating after some order. Here we present an adaptation of that method, optimized for Hamiltonians with terms of widely varying magnitude, as is commonly the case in electronic structure calculations. We show that it is more efficient to apply LCU using a truncation that retains larger magnitude terms as determined by an iterative procedure. We obtain bounds on the simulation error for this generalized truncated Taylor method, and for a range of molecular simulations, we report these bounds as well as exact numerical results. We find that our adaptive method can typically improve the simulation accuracy by an order of magnitude, for a given circuit depth.
