Coherent few-electron spin-states in graphene nanoribbons from ab initio

石墨烯纳米带（GNR）为实现基于自旋的量子寄存器系统提供了多种有前途的途径。一是量子点的制备。除了孤立量子点中的单电子态外，耦合双量子点系统中的双电子单重态-三重态也代表了合适的两能级量子比特实现。在任何情况下，自旋相干过程对量子门的操作起着至关重要的作用。该项目解决了这一问题，主要针对耦合量子点结构中自旋态及其动力学的理论理解。在这里，我们重点研究了一个基于一维结构的少电子原型系统，该系统被实现为石墨烯纳米带。作为一种新颖的方法，现实的纳米器件模拟正在进行，结合了用于确定矩阵元素的ab-initio理论（密度泛函理论，DFT）和随后在相关子空间中的对角化（“组态相互作用”，CI）。因此，考虑到所考虑的纳米电子系统的材料和几何特定方面。由于将包括激发的多体态，因此可以计算少电子自旋系统的实时响应-固有地考虑相干和多体相关方面。

Graphene nanoribbons (GNR) offer various promising paths towards the realization of spin-based quantum register systems. One is the preparation of quantum dots. Besides single-electron states in an isolated quantum dot, two-electron singlet-triplet states of a coupled double-quantum-dot system represent suitable two-level quantum- bit realizations. In any case, spin coherence processes play a crucial role for the operation of a quantum gate. The project addresses this realization, aiming predominantly at the theoretical understanding of spin states and their dynamics in coupled quantum-dot structures. Here, we focus on a few-electron prototype system, based on a one-dimensional structure, which is realized as a graphene nanoribbon. As a novel approach, realistic nanodevice simulations are being carried out, combining an ab-initio theory (density-functional theory, DFT) for the determination of the matrix elements with a subsequent diagonalization in the relevant subspace (“configuration interaction”, CI). Hence, material- and geometry-specific aspects of the considered nanoelectronic system are taken into account. Since excited many-body states will be included, the real-time response of the few electron spin system can be calculated – inherently considering coherence and many-body correlation aspects.