Quantum annealers require accurate control and optimized operation schemes to reduce noise levels, in order to eventually demonstrate a computational advantage over classical algorithms. We study a high coherence four-junction capacitively shunted flux qubit (CSFQ), using dispersive measurements to extract system parameters and model the device. Josephson junction asymmetry inherent to the device causes a deleterious nonlinear cross-talk when annealing the qubit. We implement a nonlinear annealing path to correct the asymmetry in situ, resulting in a substantial increase in the probability of the qubit being in the correct state given an applied flux bias. We also confirm the multi-level structure of our CSFQ circuit model by annealing it through small spectral gaps and observing quantum signatures of energy level crossings. Our results demonstrate an anneal-path correction scheme designed and implemented to improve control accuracy for high-coherence and high-control quantum annealers, which leads to an enhancement of success probability in annealing protocols.

量子退火器需要精确的控制和优化的操作方案来降低噪声水平，以便最终展示出优于传统算法的计算优势。我们使用色散测量来提取系统参数并对设备进行建模，从而研究了高相干四结电容分流通量量子位（CSFQ）。器件固有的约瑟夫逊结不对称性会导致量子比特退火时产生有害的非线性串扰。我们实施了非线性退火路径来原位校正不对称性，从而在给定的磁通量偏置下，导致量子位处于正确状态的概率大大增加。我们还通过对CSFQ电路模型进行小光谱隙退火并观察能级交叉的量子特征来确认其多级结构。