Huang Peihao, Bryant Garnett W
Joint Quantum Institute, National Institute of Standards and Technology and University of Maryland, Maryland 20899, USA.
Quantum Measurement Division, National Institute of Standards and Technology, Maryland 20899, USA.
Phys Rev B. 2018 Nov;98(19). doi: 10.1103/physrevb.98.195307.
An electron spin qubit in a silicon donor atom is a promising candidate for quantum information processing because of its long coherence time. To be sensed with a single-electron transistor, the donor atom is usually located near an interface, where the donor states can be coupled with interface states. Here we study the phonon-assisted spin-relaxation mechanisms when a donor is coupled to confined (quantum-dot-like) interface states. We find that both Zeeman interaction and spin-orbit interaction can hybridize spin and orbital states, each contributing to phonon-assisted spin relaxation in addition to the spin relaxation for a bulk donor or a quantum dot. When the applied magnetic field is weak (compared to orbital spacing), the phonon assisted spin relaxation shows the dependence. We find that there are peaks (hot spots) in the -dependent and detuning dependent spin relaxation due to strong hybridization of orbital states with opposite spin. We also find spin relaxation dips (cool spots) due to the interference of different relaxation channels. Qubit operations near spin relaxation hot spots can be useful for the fast spin initialization and near cool spots for the preservation of quantum information during the transfer of spin qubits.
硅施主原子中的电子自旋量子比特因其长相干时间而成为量子信息处理的一个有前途的候选者。为了能用单电子晶体管进行探测，施主原子通常位于界面附近，在那里施主态可以与界面态耦合。在此，我们研究当施主与受限（类量子点）界面态耦合时的声子辅助自旋弛豫机制。我们发现塞曼相互作用和自旋轨道相互作用都能使自旋态和轨道态杂化，除了体施主或量子点的自旋弛豫外，它们各自都对声子辅助自旋弛豫有贡献。当外加磁场较弱（与轨道间距相比）时，声子辅助自旋弛豫呈现出 依赖性。我们发现，由于具有相反自旋的轨道态的强杂化，在依赖于 和失谐的自旋弛豫中存在峰值（热点）。我们还发现由于不同弛豫通道的干涉导致自旋弛豫出现凹陷（冷点）。在自旋弛豫热点附近进行量子比特操作对于快速自旋初始化可能是有用的，而在冷点附近进行操作则有助于在自旋量子比特转移过程中保存量子信息。
