论文标题
硅量子点中的模拟相干电子穿梭
Simulated coherent electron shuttling in silicon quantum dots
论文作者
论文摘要
在栅极定义的硅量子点中的单电子穿梭是数值模拟的。引入了无显式隧道屏障门的最小栅极几何形状，并用于定义一系列累积模式量子点，每个点由单个栅极电压控制。一维电位来自三维静电模型，用于构建有效的哈密顿量以进行有效的模拟。控制脉冲序列是通过保持固定绝热性来设计的，因此可以系统地比较不同的穿梭条件。我们首先使用这些工具来优化设备的几何形状以最大程度的传输速度，考虑到轨道状态并忽略了山谷和自由度的自由度。考虑现实的几何约束，充电速度高达$ \ sim $ 300 m/s保存绝热。通过在有效的哈密顿量中包括旋转轨道和山谷的术语来模拟连贯的自旋运输，从而将一对单线对的一名成员穿梭并跟踪纠缠忠诚度。使用逼真的设备和材料参数，当隧道能量超过Zeeman Energy时，可以在10-100 m/s的范围内获得具有高自旋纠缠储备的航班速度。高保真度还需要跨点谷相差，低于隧道和Zeeman Energies的比率低于阈值，以使Spin-Valley-Orbit混合较弱。在这种制度中，我们发现不忠的主要来源是一种相干的自旋旋转，原则上是可纠正的。结果与同位素纯化的硅中的大规模自旋量子量处理器的提案有关，该硅依赖于旋转的相干穿梭以在计算节点之间快速分布量子信息。
Shuttling of single electrons in gate-defined silicon quantum dots is numerically simulated. A minimal gate geometry without explicit tunnel barrier gates is introduced, and used to define a chain of accumulation mode quantum dots, each controlled by a single gate voltage. One-dimensional potentials are derived from a three-dimensional electrostatic model, and used to construct an effective Hamiltonian for efficient simulation. Control pulse sequences are designed by maintaining a fixed adiabaticity, so that different shuttling conditions can be systematically compared. We first use these tools to optimize the device geometry for maximum transport velocity, considering only orbital states and neglecting valley and spin degrees of freedom. Taking realistic geometrical constraints into account, charge shuttling speeds up to $\sim$300 m/s preserve adiabaticity. Coherent spin transport is simulated by including spin-orbit and valley terms in an effective Hamiltonian, shuttling one member of a singlet pair and tracking the entanglement fidelity. With realistic device and material parameters, shuttle speeds in the range 10-100 m/s with high spin entanglement fidelities are obtained when the tunneling energy exceeds the Zeeman energy. High fidelity also requires the inter-dot valley phase difference to be below a threshold determined by the ratio of tunneling and Zeeman energies, so that spin-valley-orbit mixing is weak. In this regime, we find that the primary source of infidelity is a coherent spin rotation that is correctable, in principle. The results pertain to proposals for large-scale spin qubit processors in isotopically purified silicon that rely on coherent shuttling of spins to rapidly distribute quantum information between computational nodes.
