基于动力学不变量的芯片阱上高保真度快速离子输运研究

Fast ion separation, merging and moving operations on a chip trap without final state excitation are key steps for scaling up the quantum computing system based on trapped ion. Two-ion separation and single-ion moving in non-rigid traps play a fundamental role in complex transport operations involving non-harmonic potential and Coulomb interaction. At present, these two kind of transport operations haven’t be realized with the final state phonon number excitation less than 2. In theory, the reverse engineering method based on Lewis-Riesenfeld invariant provides a new scheme for solving the control potential in the two transport processes. But they are not applicable to experiments. On the basis of this theoretical scheme, we intend to further study the transport scheme which satisfies the experimental conditions and has better parameter fault tolerance. By studying the dynamic behavior of transport process, we will analyze the key components of transport potential, and provide the basis for improving the transport fidelity by using optimization strategy in experiments. We also intend to realize the two-ion separation and the single-ion movement in non-rigid trap, in microsecond scale with phonon excitation number less than 0.2 experimentally, and the robustness of the parameters will be tested. This research will make a thorough study on the three links of theory, experiment and the bridge between theory and experiment, in order to break through the bottleneck of experimental research and lay a foundation for the scaling of the trapped ion system.

芯片阱上快速且无声子激发的离子分离、合并和移动操作是囚禁离子量子计算系统进行规模扩展的关键步骤。两离子分离和非刚性阱中单离子移动操作在涉及到非谐势和库仑相互作用的复杂输运操作中处于基础地位。目前实验上还没有实现末态声子激发数小于2的这两种输运操作。理论方面，采用基于Lewis-Riesenfeld不变量的逆向工程法，为这两个输运过程中控制电势的求解提供了新方案，但是还无法应用于实验。我们拟在此理论方案的基础上更进一步，研究满足实验条件并具有较好的参数容错性的输运方案；通过研究输运过程的动力学行为分析输运电势的关键成分，为实验上采用优化策略提高输运保真度提供依据。还将在实验上实现微秒量级内的、声子激发数小于0.2的两离子分离和非刚性阱中单离子移动操作，并进行参数鲁棒性检验。该项研究将从理论、实验和理论连接实验这三个环节进行深入研究，力求突破实验研究的瓶颈，为实现囚禁离子系统的扩展奠定基础。

芯片阱上快速且无声子激发的离子分离、合并和移动操作是囚禁离子量子计算系统进行规模扩展的关键步骤。本项目以动力学不变量为依据，对快速且无声子激发的离子输运操作进行了系统的研究。理论上获得了在3个离子振动周期内可以完成，在离子振动频率发生5%以内波动时振动量子数激发均能小于0.15的输运路径，根据实验约束条件设计了易于扩展的三步分离方案。项目找到了参数化电极空间电势表达式，并通过大量采集多维数据拟合参数模型，获得了振动频率预测误差小于0.5%的势阱模型，且发展了针对滤波电路的电压波形预补偿技术，实现了输运路径从理论设计到实验实施的全程精确控制。结合上述技术，项目演示了多至5离子的线性输运和两离子分离操作。针对离子输运的研究，项目还发展了多项针对表面电极离子阱的优化技术，包括：通过测量电极间的电容变化实时监控芯片离子阱的剩余寿命、多层金属电极离子阱和复杂结构离子阱的参数优化技术、表面粗糙度小于6.2nm的厚膜金电极制备技术、冷却带宽覆盖4MHz的并行EIT冷却等方面的理论和实验研究。此外，项目还发展了包括射频相位失配引起的附加微运动补偿技术、基于离子探针的超窄线宽激光相位噪声测量技术和激光噪声抑制技术等在内的离子阱操控共性技术。本项目的实施提高了对芯片上离子输运过程的理解，有效提高了囚禁离子体系的操控能力，为进一步发展基于囚禁离子体系的量子信息处理和量子精密测量技术打下了良好的基础。

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