Spin Qubits and Spin Decoherence in Graphene Quantum Dots

石墨烯量子点中的自旋量子位和自旋退相干

• 批准号: 170792068
• 负责人: Professor Dr. Björn Trauzettel
• 金额: --
• 依托单位: Institut für Theoretische Physik und Astrophysik
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2010
• 资助国家: 德国
• 起止时间: 2009-12-31 至 2014-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/170792068?language=en
• 关键词: Spin; Qubits; Decoherence; Graphene; Quantum

Graphene quantum dots are a unique material system to study the quantum to classical crossover. The reason is the feasibility to actively reduce the bath degrees of freedom in this quantum dissipative system. A quantum dissipative system consists by definition of a small quantum system and a larger bath that are coupled to each other. In graphene quantum dots, the system could be the spin of a single electron (captured inside the dot) and the bath degrees of freedom would then be the nuclear spins of the 13C atoms of the host material. The coupling is mediated by the hyperfine interaction. At natural abundance of 1% 13C atoms, the number of bath degrees of freedom in a typically sized graphene quantum dot would still be quite large. However, isotopic purification enables us to reduce the 13C content with respect to the 12C content that does not carry any nuclear spin at all. Therefore, it is in principle possible to constantly reduce the bath degrees of freedom.We would like to study the dynamics of the electron spin as well as the nuclear spins in a graphene quantum dot. This analysis is interesting both from a quantum computing as well as a fundamental physics point of view. To do so, we will employ a combination of numerical methods (based on exact diagonalization) and analytical methods (based on the Nakajima-Zwanzig equation). We expect to discover interesting new physics especially in the crossover regime of an intermediate number of bath degrees of freedom, for instance, related to spin decoherence and relaxation.

石墨烯量子点是研究量子与经典交叉的独特材料系统。原因是在这个量子耗散系统中主动降低浴自由度的可行性。根据定义，量子耗散系统由相互耦合的小量子系统和较大的浴组成。在石墨烯量子点中，系统可以是单个电子的自旋（被捕获在点内），而浴自由度将是主体材料的 13C 原子的核自旋。耦合是由超精细相互作用介导的。在 1% 13C 原子的自然丰度下，典型尺寸的石墨烯量子点中的浴自由度数量仍然相当大。然而，同位素纯化使我们能够相对于根本不携带任何核自旋的 12C 含量减少 13C 含量。因此，原则上可以不断降低浴的自由度。我们想研究石墨烯量子点中电子自旋和核自旋的动力学。从量子计算和基础物理学的角度来看，这种分析都很有趣。为此，我们将采用数值方法（基于精确对角化）和分析方法（基于 Nakajima-Zwanzig 方程）的组合。我们期望发现有趣的新物理，特别是在中间数量的浴自由度的交叉区域中，例如，与自旋退相干和弛豫相关的交叉区域。