A Silicon Surface Code Architecture Resilient Against Leakage Errors
A Silicon Surface Code Architecture Resilient Against Leakage Errors
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DOI：
10.22331/q-2019-12-09-212
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发表时间：
2019-04
期刊：
影响因子：
6.4
通讯作者：
Z. Cai;M. Fogarty;S. Schaal;S. Patomäki;S. Benjamin;J. Morton
中科院分区：
文献类型：
--
作者：
Z. Cai;M. Fogarty;S. Schaal;S. Patomäki;S. Benjamin;J. Morton
硅量子点中的自旋量子比特由于其高的量子比特密度和与现有半导体技术的兼容性，是最有前途的大规模量子计算机的构建模块之一。高保真的单量子比特门已经被证明超过了像表面码那样的纠错码的门限，而两量子比特门的保真度已经达到98%，并且正在迅速提高。然而，还有其他类型的错误-例如电荷泄漏和传播-可能发生在量子点阵列中，无法通过量子纠错码进行纠正，即使在概率很小的情况下，它们也具有潜在的破坏性。我们提出了一种用于硅量子点自旋量子比特的表面代码结构，该结构通过结合多电子介质点对泄漏错误具有健壮性。量子比特点中的电荷泄漏通过电荷弛豫过程转移到介质点，然后使用连接到介体上的电荷库来去除。然后，针对我们的硬件进行优化的稳定器-检查周期消除了剩余物理误差之间的相关性。通过模拟，我们得到了电荷泄漏误差的表面编码阈值，并表明在我们的体系结构中，由于电荷泄漏误差造成的损害降低到与通常的去极化栅极噪声相似的水平。我们的体系结构中的自旋泄漏错误仅限于Ancilla量子比特，并且可以在量子纠错过程中通过Ancillae的重新初始化来消除，这也确保了我们的体系结构对自旋泄漏的健壮性。我们使用细长的介质点，在整个量子点阵列中为电荷库、测量设备和控制门创造了空间，提供了设计中的可扩展性。
Spin qubits in silicon quantum dots are one of the most promising building blocks for large scale quantum computers thanks to their high qubit density and compatibility with the existing semiconductor technologies. High fidelity single-qubit gates exceeding the threshold of error correction codes like the surface code have been demonstrated, while two-qubit gates have reached 98% fidelity and are improving rapidly. However, there are other types of error --- such as charge leakage and propagation --- that may occur in quantum dot arrays and which cannot be corrected by quantum error correction codes, making them potentially damaging even when their probability is small. We propose a surface code architecture for silicon quantum dot spin qubits that is robust against leakage errors by incorporating multi-electron mediator dots. Charge leakage in the qubit dots is transferred to the mediator dots via charge relaxation processes and then removed using charge reservoirs attached to the mediators. A stabiliser-check cycle, optimised for our hardware, then removes the correlations between the residual physical errors. Through simulations we obtain the surface code threshold for the charge leakage errors and show that in our architecture the damage due to charge leakage errors is reduced to a similar level to that of the usual depolarising gate noise. Spin leakage errors in our architecture are constrained to only ancilla qubits and can be removed during quantum error correction via reinitialisations of ancillae, which ensure the robustness of our architecture against spin leakage as well. Our use of an elongated mediator dots creates spaces throughout the quantum dot array for charge reservoirs, measuring devices and control gates, providing the scalability in the design.