AI 中文总结
本文提出一种基于少量固定序列的单量子比特门黑箱认证协议，在囚禁离子处理器上实验验证其对态制备和测量误差的鲁棒性，实现无需可信参考等条件的高效可靠量子门认证。
AI 中文摘要
当未表征的态制备和测量误差占主导时，能否对高质量量子门进行认证？能否以较低的实验开销实现这一点？本文提出一种基于少量固定确定性序列的单量子比特门的可靠黑箱认证协议。该协议从数据中推导出门的旋转本征值的有限样本界，这是一种规范不变性质。其相位反映旋转角的精度，模则量化重复门操作下的相干性损失。我们在$^{40}\text{Ca}^+$囚禁离子处理器上实现该协议，使用22000次电路执行对$\text{√X}$门的旋转本征值进行认证，并通过刻意降低读出质量，证明该认证对态制备和测量误差的鲁棒性。最后，我们证明这些谱约束在物理上有意义的幺正基变换下，对所有与数据兼容的时不变量子比特模型，蕴含严格的平均门保真度下界。在两种读出设置下，谱约束均给出99.94(3)%的相同保真度认证，置信度为99%。我们的结果通过结合可靠性与实验效率，为量子门认证建立了新的标准，无需可信参考操作、随机化电路或模型拟合。
英文摘要
Can a high-quality quantum gate be certified when uncharacterized state-preparation and measurement errors are dominant? Can this be achieved with low experimental overhead? Here, we introduce a sound black-box certification protocol for a single-qubit gate based on a small set of fixed, deterministic sequences. From the data, the protocol derives finite-sample bounds on the gate's rotation eigenvalue, a gauge-invariant property. Its phase reveals the accuracy of the rotation angle, while its modulus quantifies the loss of coherence under repeated gate applications. We implement the protocol on a $^{40}\mathrm{Ca}^{+}$ trapped-ion processor and certify the $\sqrt{\mathrm{X}}$-gate rotation eigenvalue using $22\,000$ circuit executions, and demonstrate the robustness of certification to state-preparation and measurement errors by deliberately degrading the readout. Finally, we prove that these spectral constraints imply, up to a physically meaningful unitary change of basis, a rigorous average gate-fidelity lower bound for every time-independent qubit model compatible with the data. In both readout settings, the spectral bounds yield the same fidelity certificate of $99.94(3)\%$ with $99\%$ confidence. Our results establish a new standard for quantum-gate certification by combining soundness and experimental efficiency without requiring trusted reference operations, randomized circuits, or model fitting.
Comments27 pages, 4 figures, comments welcome
