The accelerated progress in manufacturing noisy intermediate-scale quantum (NISQ) computing hardware has opened the possibility of exploring its application in transforming approaches to solving computationally challenging problems. The important limitations common among all NISQ computing technologies are the absence of error correction and the short coherence time, which limit the computational power of these systems. Shortening the required time of a single run of a quantum algorithm is essential for reducing environment-induced errors and for the efficiency of the computation. We have investigated the ability of a variational version of adiabatic quantum computation (AQC) to generate an accurate state more efficiently compared to existing adiabatic methods. The standard AQC method uses a time-dependent Hamiltonian, connecting the initial Hamiltonian with the final Hamiltonian. In the current approach, a navigator Hamiltonian is introduced which has a non-zero amplitude only in the middle of the annealing process. Both the initial and navigator Hamiltonians are determined using variational methods. A hermitian cluster operator, inspired by coupled-cluster theory and truncated to single and double excitations/de-excitations, is used as a navigator Hamiltonian. A comparative study of our variational algorithm (VanQver) with that of standard AQC, starting with a Hartree--Fock Hamiltonian, is presented. The results indicate that the introduction of the navigator Hamiltonian significantly improves the annealing time required to achieve chemical accuracy by two to three orders of magnitude. The efficiency of the method is demonstrated in the ground-state energy estimation of molecular systems, namely, H$_2$, P4, and LiH.

中文翻译：

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VanQver：变分和绝热导航的量子特征求解器

制造嘈杂的中尺度量子 (NISQ) 计算硬件的加速进展为探索其在转换方法以解决计算挑战性问题中的应用开辟了可能性。所有 NISQ 计算技术的共同重要限制是没有纠错和短相干时间，这限制了这些系统的计算能力。缩短量子算法单次运行所需的时间对于减少环境引起的错误和计算效率至关重要。与现有的绝热方法相比，我们研究了变分版本的绝热量子计算 (AQC) 更有效地生成准确状态的能力。标准的 AQC 方法使用时间相关的哈密顿量，连接初始哈密顿量和最终哈密顿量。在当前的方法中，引入了一个导航哈密顿量，它仅在退火过程的中间具有非零幅度。初始哈密顿量和导航哈密顿量都是使用变分方法确定的。受耦合簇理论启发并被截断为单和双激发/去激发的厄密聚类算子被用作导航哈密顿量。我们的变分算法 (VanQver) 与标准 AQC 的变分算法的比较研究，从 Hartree--Fock Hamiltonian 开始。结果表明，导航器哈密顿量的引入将实现化学精度所需的退火时间显着提高了两到三个数量级。