通过低频电荷驱动实现动态保护的擦除量子比特
Dynamically protected erasure qubit via low-frequency charge driving
- University of California at Berkeley（加州大学伯克利分校）
- Lawrence Berkeley National Laboratory（劳伦斯伯克利国家实验室）
- Chapman University（查普曼大学）
- University of Rochester（罗切斯特大学）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
本文提出利用亚GHz电荷驱动超导Kerr振荡器，在激活快速参数相互作用的同时保护量子比特免受低频噪声，实现快速冷却、双轨擦除量子比特逻辑控制及低错误率。
AI中文摘要：
通过强驱动实现的动态保护可以使量子处理在非理想的物理硬件上具有鲁棒性。然而，此类方案的实际效用常常受到诸如驱动引起的退相和泄漏等寄生过程的限制。在此，我们证明在transmon区域中对超导Kerr振荡器（KOs）进行亚GHz电荷驱动可以规避这种权衡，同时激活快速参数相互作用并保护编码量子比特免受低频噪声的影响。关键在于电荷灵敏度的频率依赖性：使用AC Stark位移作为探针，我们发现KO对电荷驱动的频率灵敏度随驱动频率和振幅的平方增长，这使得振荡器对$1/f$电荷噪声弱敏感，但对接近1~GHz的驱动强耦合。利用这一点，我们首先展示了在82~ns内对KO进行冷却和重置，残余布居低于$0.7\%$，低于其$2.5\%$的稳态热布居。接下来，使用两个KO，我们展示了双轨量子比特的逻辑控制和动态保护，具有近四倍的擦除偏置。最后，使用单个电路末端擦除检查，我们实现了每Clifford误差为$5.6\ imes10^{-4}$，经过后选择后降至$1.5\ imes10^{-4}$，门时间为25~ns。
英文摘要：
Dynamical protection via strong driving can enable resilient quantum processing on imperfect physical hardware. However, the practical utility of such schemes is frequently limited by parasitic processes such as drive-induced dephasing and leakage. Here, we demonstrate that sub-GHz charge driving of superconducting Kerr oscillators (KOs) in the transmon regime circumvents this trade-off, simultaneously activating fast parametric interactions and protecting the encoded qubit from low-frequency noise. The key is the frequency dependence of the charge sensitivity: using the AC Stark shift as a probe, we find that the KO frequency sensitivity to a charge drive grows quadratically with both drive frequency and amplitude, making the oscillator weakly sensitive to $1/f$ charge noise yet strongly coupled to drives near 1~GHz. Exploiting this, we first demonstrate cooling and reset of the KO in 82~ns, to a residual population below $0.7\%$---lower than its $2.5\%$ steady-state thermal population. Next, using two KOs, we demonstrate logical control and dynamical protection of a dual-rail qubit with nearly fourfold erasure bias. Finally, using a single end-of-circuit erasure check, we achieve an error per Clifford of $5.6\times10^{-4}$, which falls to $1.5\times10^{-4}$ after post-selection, with 25~ns gates.
