Coherent Multispin Exchange Coupling in a Quantum-Dot Spin Chain
Coherent Multispin Exchange Coupling in a Quantum-Dot Spin Chain
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DOI：
10.1103/physrevx.10.031006
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发表时间：
2020-07-08
影响因子：
12.5
通讯作者：
Nichol, John M.
中科院分区：
文献类型：
--
作者：
Qiao, Haifeng;Kandel, Yadav P.;Nichol, John M.
半导体量子点中相邻电子自旋之间的海森堡交换耦合为量子信息处理和模拟提供了强有力的工具。虽然到目前为止还没有实现，扩展海森堡自旋链可以实现长距离量子信息传输和非平衡量子态的产生。在这项工作中，我们实现了四重量子点中所有最近邻自旋对之间的同步相干交换耦合。实现同步交换耦合的主要挑战是交换耦合对栅极电压的非线性和非局部依赖性。通过结合静电模拟和理论建模，我们表明，这一挑战主要是由于量子点在门脉冲的横向位移。基于这一认识，我们开发了两种模型，可用于预测所需的一组交换耦合的限制栅电压。虽然模型参数取决于所需的交换耦合的数量（这表明除了横向波函数位移的影响是重要的），模型足以使所有三个交换耦合在一个四重量子点的同时和独立的控制。我们证明了两个，三个和四个自旋交换振荡，我们的数据与模拟一致。
Heisenberg exchange coupling between neighboring electron spins in semiconductor quantum dots provides a powerful tool for quantum information processing and simulation. Although so far unrealized, extended Heisenberg spin chains can enable long-distance quantum information transfer and the generation of nonequilibrium quantum states. In this work, we implement simultaneous, coherent exchange coupling between all nearest-neighbor pairs of spins in a quadruple quantum dot. The main challenge in implementing simultaneous exchange couplings is the nonlinear and nonlocal dependence of the exchange couplings on gate voltages. Through a combination of electrostatic simulation and theoretical modeling, we show that this challenge arises primarily due to lateral shifts of the quantum dots during gate pulses. Building on this insight, we develop two models that can be used to predict the confinement gate voltages for a desired set of exchange couplings. Although the model parameters depend on the number of exchange couplings desired (suggesting that effects in addition to lateral wave-function shifts are important), the models are sufficient to enable simultaneous and independent control of all three exchange couplings in a quadruple quantum dot. We demonstrate two-, three-, and four-spin exchange oscillations, and our data agree with simulations.