标题： 反应化学量子计算的电子结构分类和状态制备 显示英文标题

标题： Classification of electronic structures and state preparation for quantum computation of reaction chemistry

摘要： 量子计算在化学问题中的应用将需要构建与目标状态具有足够重叠的引导态。 由于易于获取和初始化的平均场态对于多组态电子结构的重叠较低，甚至随着系统尺寸的增长而消失，我们在此研究反应化学中状态制备的严重性。 我们强调当前传统方法的弱点（即使对于弱关联分子也是如此），并突出量子相位估计算法的优势。 一个重要结果是基于轨道纠缠信息引入了电子结构的新分类方案。 我们识别出两类多组态分子。 虽然第一类分子主要由很少的决定式主导，并且常出现在反应化学中，但第二类分子无法选出一个合理数量的重要决定式。 后者对于传统方法特别困难，是量子计算的最终目标。 一些开放壳层铁-硫簇属于第二类。 我们讨论分子轨道基组的作用，并表明真正的第二类分子无论选择何种轨道基组都保持在该类中，固氮酶的铁-钼辅因子是一个典型例子。 我们强调，第二类分子可以系统地从开放壳中心或不饱和碳原子构建而成。 我们的关键结果是，基于初始低成本的近似电子结构信息，总是可以在基态中初始化用于化学反应化学的引导态，这得益于所考虑的原子结构的有限尺寸。 显示英文摘要

摘要： Quantum computation for chemical problems will require the construction of guiding states with sufficient overlap with a target state. Since easily available and initializable mean-field states are characterized by an overlap that is reduced for multi-configurational electronic structures and even vanishes with growing system size, we here investigate the severity of state preparation for reaction chemistry. We emphasize weaknesses in current traditional approaches (even for weakly correlated molecules) and highlight the advantage of quantum phase estimation algorithms. An important result is the introduction of a new classification scheme for electronic structures based on orbital entanglement information. We identify two categories of multi-configurational molecules. Whereas class-1 molecules are dominated by very few determinants and often found in reaction chemistry, class-2 molecules do not allow one to single out a reasonably sized number of important determinants. The latter are particularly hard for traditional approaches and an ultimate target for quantum computation. Some open-shell iron-sulfur clusters belong to class 2. We discuss the role of the molecular orbital basis set and show that true class-2 molecules remain in this class independent of the choice of the orbital basis, with the iron-molybdenum cofactor of nitrogenase being a prototypical example. We stress that class-2 molecules can be build in a systematic fashion from open-shell centers or unsaturated carbon atoms. Our key result is that it will always be possible to initialize a guiding state for chemical reaction chemistry in the ground state based on initial low-cost approximate electronic structure information, which is facilitated by the finite size of the atomistic structures to be considered.