论文标题

用于连贯的中端量子乘以SI/SIGE/SIE/SIO $ _2 $的可伸缩自旋量子乘坐乘坐乘坐乘坐乘坐乘坐的蓝图

Blueprint of a scalable spin qubit shuttle device for coherent mid-range qubit transfer in disordered Si/SiGe/SiO$_2$

论文作者

Langrock, Veit, Krzywda, Jan A., Focke, Niels, Seidler, Inga, Schreiber, Lars R., Cywiński, Łukasz

论文摘要

硅自旋量子台由于其很长的相干时间,与工业制造的兼容性以及整合经典控制电子产品的前景而脱颖而出。为了实现真正可扩展的体系结构,已经建议将Qubit寄存器之间的电子移动的连贯的中端链路解决信号风扇输出问题。在这里,我们提出了这样的$ \ 10 \,μ$ m长的蓝图,称为旋转量子班车,它基于将一系列门连接到少数集合中。为了控制这些集合,仅需要几个电压控制线,并且这些集合的数量以及所需的控制信号的数量与此链接的长度无关。我们讨论了旋转量子乘坐的两种不同的操作模式:乘量子传送带,即平稳移动的潜在最小值,以及一个桶式旅,其中电子通过绝热通道通过一系列隧道耦合的量子点传输。我们发现,考虑到现实的SI/SIGE设备,包括来自Si/Sio $ _2 $层的带电缺陷以及典型的充电噪声的潜在疾病,这是前一个方法更有希望的。为了关注输送机穿梭模式下的量子转移保真度,我们详细讨论了运动变窄,轨道和山谷激发之间的相互作用以及依赖于电子的轨道和山谷状态的$ g $ factor的相互作用以及旋转孔的效果。我们发现,如果平均山谷分裂及其不均匀性在现实界限内,则以$ \ sim $ 10 m/s的速度在Si/Sige中的转移保真度可行。在低全球磁场上的操作$ \ \ \ 20 $ MT,材料工程在高谷拆分方面有利于达到高忠诚的转移。

Silicon spin qubits stand out due to their very long coherence times, compatibility with industrial fabrication, and prospect to integrate classical control electronics. To achieve a truly scalable architecture, a coherent mid-range link that moves the electrons between qubit registers has been suggested to solve the signal fan-out problem. Here, we present a blueprint of such a $\approx 10\,μ$m long link, called a spin qubit shuttle, which is based on connecting an array of gates into a small number of sets. To control these sets, only a few voltage control lines are needed and the number of these sets and thus the number of required control signals is independent of the length of this link. We discuss two different operation modes for the spin qubit shuttle: A qubit conveyor, i.e. a potential minimum that smoothly moves laterally, and a bucket brigade, in which the electron is transported through a series of tunnel-coupled quantum dots by adiabatic passage. We find the former approach more promising considering a realistic Si/SiGe device including potential disorder from the charged defects at the Si/SiO$_2$ layer, as well as typical charge noise. Focusing on the qubit transfer fidelity in the conveyor shuttling mode, we discuss in detail motional narrowing, the interplay between orbital and valley excitation and relaxation in presence of $g$-factors that depend on orbital and valley state of the electron, and effects from spin-hotspots. We find that a transfer fidelity of 99.9 \% is feasible in Si/SiGe at a speed of $\sim$10 m/s, if the average valley splitting and its inhomogeneity stay within realistic bounds. Operation at low global magnetic field $\approx 20$ mT and material engineering towards high valley splitting is favourable for reaching high fidelities of transfer.

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