论文标题
早期容忍量子计算的状态准备助推器
State Preparation Boosters for Early Fault-Tolerant Quantum Computation
论文作者
论文摘要
在各种应用中,量子计算对于化学和材料的模拟特别有用。近年来,用于用于量子模拟的近期量子算法的发展,包括VQE及其许多变体。但是,为了使这种算法有用,它们需要克服几个关键障碍,包括无法准备基态的高质量近似。当前对国家准备的挑战,包括贫瘠的高原和优化景观的高维度,使国家制备通过ANSATZ优化不可靠。在这项工作中,我们介绍了基态增强方法,该方法使用有限的深入量子电路可靠地增加与基态的重叠。我们称之为助推器的电路可用于从VQE增强ANSATZ或用作独立状态准备方法。助推器以可控制的方式将电路深度转换为基态重叠。我们通过模拟特定类型的助推器的性能,即高斯助推器来准备$ n_2 $分子系统的基础状态,从而证明了助推器的功能。除了基态制备作为直接目标之外,许多量子算法(例如量子相估计)依赖于高质量的状态制备作为子例程。因此,我们预见到基础状态的增强和类似的方法,即作为使用早期耐断层量子计算机的现场转变,成为必不可少的算法成分。
Quantum computing is believed to be particularly useful for the simulation of chemistry and materials, among the various applications. In recent years, there have been significant advancements in the development of near-term quantum algorithms for quantum simulation, including VQE and many of its variants. However, for such algorithms to be useful, they need to overcome several critical barriers including the inability to prepare high-quality approximations of the ground state. Current challenges to state preparation, including barren plateaus and the high-dimensionality of the optimization landscape, make state preparation through ansatz optimization unreliable. In this work, we introduce the method of ground state boosting, which uses a limited-depth quantum circuit to reliably increase the overlap with the ground state. This circuit, which we call a booster, can be used to augment an ansatz from VQE or be used as a stand-alone state preparation method. The booster converts circuit depth into ground state overlap in a controllable manner. We numerically demonstrate the capabilities of boosters by simulating the performance of a particular type of booster, namely the Gaussian booster, for preparing the ground state of $N_2$ molecular system. Beyond ground state preparation as a direct objective, many quantum algorithms, such as quantum phase estimation, rely on high-quality state preparation as a subroutine. Therefore, we foresee ground state boosting and similar methods as becoming essential algorithmic components as the field transitions into using early fault-tolerant quantum computers.