We assess the prospects for algorithms within the general framework of
quantum annealing (QA) to achieve a quantum speedup relative to classical state
of the art methods in combinatorial optimization and related sampling tasks. We
argue for continued exploration and interest in the QA framework on the basis
that improved coherence times and control capabilities will enable the
near-term exploration of several heuristic quantum optimization algorithms that
have been introduced in the literature. These continuous-time Hamiltonian
computation algorithms rely on control protocols that are more advanced than
those in traditional ground-state QA, while still being considerably simpler
than those used in gate-model implementations. The inclusion of coherent
diabatic transitions to excited states results in a generalization called
diabatic quantum annealing (DQA), which we argue for as the most promising
route to quantum enhancement within this framework. Other promising variants of
traditional QA include reverse annealing and continuous-time quantum walks, as
well as analog analogues of parameterized quantum circuit ansatzes for machine
learning. Most of these algorithms have no known (or likely to be discovered)
efficient classical simulations, and in many cases have promising (but limited)
early signs for the possibility of quantum speedups, making them worthy of
further investigation with quantum hardware in the intermediate-scale regime.
We argue that all of these protocols can be explored in a state-of-the-art
manner by embracing the full range of novel out-of-equilibrium quantum dynamics
generated by time-dependent effective transverse-field Ising Hamiltonians that
can be natively implemented by, e.g., inductively-coupled flux qubits, both
existing and projected at application scale.

本文研究了量子退火算法在组合优化和相关抽样任务中相对于经典最新方法实现量子加速的前景，并且基于对既有文献中引入的多种启发式量子优化算法的改进相干时间以及控制能力的持续探索和兴趣，提出了包括连续时间哈密顿计算算法、反向退火和连续时间量子行走在内的 QA 有前途的变体，同时就机器学习的参数化量子电路的模拟提出了类比算法，这些算法大多没有（或被认为不可能有）已知的高效古典模拟，其中大多数算法的 “中等规模” 实验可能存在量子加速的可行可能性。建议通过在使能交换耦合通量量子比特时实现的时间依赖有效横向场伊辛哈密顿量生成的新型量子动力学的全面研究来实现更先进的控制协议以及 DQA 的最有前途的路径。