High-fidelity operation of quantum computers requires precise knowledge of the physical system through characterization. For motion-mediated entanglement generation in trapped ions, it is crucial to have precise knowledge of the motional-mode parameters such as the mode frequencies and the Lamb–Dicke parameters. Unfortunately, the state-of-the-art mode-characterization schemes do not easily render the mode parameters in a sufficiently accurate and efficient fashion for large-scale devices, due to the unwanted excitation of adjacent modes in the frequency space when targeting a single mode, an effect known as the cross-mode coupling. Here, we develop an alternative scheme that leverages the degrees of freedom in pulse design for the characterization experiment such that the effects of the cross-mode coupling is actively silenced. Further, we devise stabilization methods to accurately characterize the Lamb–Dicke parameters even when the mode frequencies are not precisely known due to experimental drifts or characterization inaccuracies. We extensively benchmark our scheme in simulations of a three-ion chain and discuss the parameter regimes in which the shaped pulses significantly outperform the traditional square pulses.

中文翻译：

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俘获离子量子计算机中高精度运动模式表征的脉冲优化

量子计算机的高保真操作需要通过表征获得对物理系统的精确了解。对于捕获离子中运动介导的纠缠生成，精确了解运动模式参数（例如模式频率和兰姆-迪克参数）至关重要。不幸的是，最先进的模式表征方案不容易以足够准确和有效的方式为大型设备呈现模式参数，因为当针对单个模式，这种效应称为交叉模式耦合。在这里，我们开发了一种替代方案，利用脉冲设计的自由度进行表征实验，从而主动消除交叉模式耦合的影响。此外，我们设计了稳定方法来准确表征兰姆-迪克参数，即使由于实验漂移或表征不准确而无法精确了解模式频率。我们在三离子链的模拟中对我们的方案进行了广泛的基准测试，并讨论了整形脉冲明显优于传统方波脉冲的参数范围。