Open quantum dynamics of spin qubits on graphene nanoribbons

石墨烯纳米带上自旋量子位的开放量子动力学

• 批准号: 2744947
• 金额: --
• 依托单位: University of Bristol
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2022
• 资助国家: 英国
• 起止时间: 2022 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2744947
• 关键词: Open; quantum; dynamics; spin; qubits; Open; quantum; dynamics; spin; qubits

The next generation of quantum computers will need to make use of new materials to realise higher temperature operation and all-electrical control of qubits. Strong contenders for achieving these goals are atomically precise graphene nanoribbons, whose true potential has only recently been uncovered with ground-breaking developments in nanofabrication. Due to their molecular precision, these auspicious graphene nanoribbons boast spin relaxation times on the order of milliseconds at temperatures as large as 10 K [1], offering exciting prospects for further investigations. This project will investigate a spin-qubit framework that exploits proximity effects to enable ultra-fast all-electrical single-qubit control with Rabi frequencies breaking the GHz barrier [2]. The overall aim is to understand the effects of spin-phonon coupling upon qubit stability by using a combination of theoretical and numerical methods. The ability to identify and characterise the spin decoherence channels will provide a stepping stone to understand the resilience of spin-qubit encoding strategies in graphene nanoribbons. The main objectives are to determine the effects of electron-phonon coupling and common random sources of elastic scattering upon qubit stability and model the open quantum dynamics of proximitised graphene nanoribbons(GNRs). Benefiting from the team's expertise, we will use many-body perturbation theory and numerically exact methods to obtain a robust microscopic theory applicable to realistic systems. The following effects will be considered. (i) Spin-phonon coupling. Electron-phonon coupling is the main charge relaxation mechanism in gate-defined graphene quantum dots [3] and is likely to be the main factor in setting the spin coherence time in bottom-up GNRs as evidenced by pulse electron paramagnetic resonance experiments [4]. (ii) Disorder. The most common imperfection in bottom-up GNRs are "bite defects" (i.e. missing C rings) at the edge [5]. We shall map out the open dephasing channels for (i) and (ii), calculating the microscopic relaxation times and the ensuing T1 and T2 times. The secondary objectives are: (1) characterise spin-phonon relaxation processes due to spin-orbit admixture; and (2) determine the impact of magnetic noise.

下一代量子计算机将需要利用新材料来实现较高的温度操作和量子的全电动控制。实现这些目标的强大竞争者是原子上精确的石墨烯纳米骨本，其真正的潜力直到最近才被纳米制动的开创性发展所揭示。由于它们的分子精度，这些吉祥的石墨烯纳米纤维在温度至10 k的温度下在毫秒的级数上具有自旋松弛时间[1]，为进一步研究提供了令人兴奋的前景。该项目将研究一个自旋量子框架，该框架利用近距离效应，以使超快速的全电动单量子控制能够打破GHz屏障[2]。总体目的是通过使用理论和数值方法的组合来了解自旋 - 光子耦合对量子稳定性的影响。识别和表征旋转分解通道和表征的能力将提供垫脚石，以了解石墨烯纳米纤维中自旋量子编码策略的弹性。主要目的是确定电子 - 音波耦合和弹性散射对量子稳定性的常见随机来源的影响，并建模邻近石墨烯纳米纤维（GNRS）的开放量子动力学。从团队的专业知识中受益，我们将使用多体扰动理论和数值精确的方法来获得适用于现实系统的强大显微镜理论。将考虑以下效果。 （i）旋转偶联。电子 - 音波耦合是栅极定义的石墨烯量子点中的主要电荷松弛机制[3]，并且可能是设置自下而上GNR中自旋相干时间的主要因素，如脉冲电子顺磁共振共振实验所证明的那样[4]。 （ii）混乱。自下而上的GNR中最常见的不完美是边缘[5]处的“咬合缺陷”（即缺失的c环）。我们将绘制出（i）和（ii）的开放式驱动通道，计算微观放松时间以及随后的T1和T2次。次要目标是：（1）表征由于自旋轨道混合而引起的自旋光子弛豫过程； （2）确定磁噪声的影响。