Elektrische Dipol-Spin-Resonanz in Graphen-Quantenpunkten

该项目的主要目标是探索石墨烯量子点中的自旋态和自旋退相干时间。特别是，我们将专注于测试最先进的石墨烯量子点中的电偶极自旋共振（EDSR），以研究这些碳基量子器件中自旋寿命的限制。石墨烯量子点已被确定为托管固态量子比特的有吸引力的候选者，因为由于预测的弱自旋轨道和超精细相互作用，它们可能允许具有长相干时间的自旋量子比特。刻蚀石墨烯量子点的激发光谱、自旋填充序列和电子-空穴交叉已经被广泛研究。然而，它们的自旋弛豫动力学仍然在很大程度上未被探索。这主要是由于器件制造中的挑战，特别是关于载流子限制的控制和隧穿势垒的可调谐性，这两者对于实验研究退相干时间至关重要。最近，我们展示了先进的石墨烯量子点设备上的脉冲门实验，其中瞬态电流测量允许估计电荷弛豫时间的下限。为了实现自旋弛豫实验，我们建议在我们最先进的石墨烯量子点上研究EDSR，最终目标是控制各个自旋状态。这种技术已经被证明在没有保利自旋封锁的情况下也能工作，而保利自旋封锁到目前为止还没有在石墨烯量子点中观察到。

The main goal of this project is to explore spin states and spin decoherence times in graphene quantum dots. In particular, we will focus on testing electric dipole spin resonance (EDSR) in state-of-the-art graphene quantum dots for investigating the limitations of spin lifetimes in these carbon-based quantum devices. Graphene quantum dots have been identified as attractive candidates for hosting solid-state quantum bits because, thanks to the predicted weak spin-orbit and hyperfine interaction, they might allow spin qubits with long coherence times. Etched graphene quantum dots have been extensively investigated with respect to their excitation spectrum, spin-filling sequence and electron-hole crossover. However, their spin relaxation dynamics remain largely unexplored. This is mainly due to challenges in device fabrication, in particular concerning the control of carrier confinement and the tunability of the tunnelling barriers, both crucial to experimentally investigate decoherence times. Recently, we demonstrated pulse-gate experiments on advanced graphene quantum dot devices, where transient current measurements allowed estimating a lower bound for the charge relaxation time. For moving towards spin relaxation experiments we propose to investigate EDSR on our most advanced graphene quantum dots, with the ultimate goal of controlling individual spin states. This technique has been shown to work also without Pauli-spin-blockade, which so far has not been observed in graphene quantum dots.