石墨烯量子点和量子比特

本文主要回顾了石墨烯量子点的制备以及基于石墨烯量子点自旋和电荷量子比特操作的研究进展,由于石墨烯材料相对较轻的原子重量使其具有较小的自旋轨道相互作用,另外含有核自旋的碳同位素13C在自然界中的含量大约只占1%,这使得超精细相互作用(即核自旋和电子自旋相互作用)较弱,所以石墨烯比其他材料具有较长的自旋退相干时间,在量子计算和量子信息中有非常好的应用前景.本文计算了5种静电约束制备的石墨烯量子点:1)扶手型单层石墨烯纳米条带,2)单层石墨烯圆盘,3)双层石墨烯圆盘,4)ABC堆积型三层石墨烯圆盘,5)ABA堆积型三层石墨烯圆盘.石墨烯量子点中自旋比特应用的关键是破坏谷简并,在1)中,主要是利用边界条件破坏谷简并,而2)–5)中是利用外磁场破坏谷简并.文章进一步介绍了自旋轨道相互作用和超精细相互作用对石墨烯量子点中自旋操作的影响.

Graphene quantum dots and qubits

This paper reviews the progress of preparation of graphene quantum dots (GQD) and the operation of spin qubits and charge qubits based on GQD. Since the graphene material has a relatively light atomic weight resulting to a smaller spin orbital interaction, and the 13C of carbon isotope containing the nuclear spin accounts for only about 1% in the nature world, the ultra-fine interaction (i.e., nuclear spin and electron spin interaction) is weaker, which means graphene has longer spin decoherence time than other materials. Therefore, graphene has promising application in quantum computation and quantum information. This paper calculates five different types of graphene quantum dots prepared by electrostatic confinement: 1) graphene nanoribbons with armchair, 2) a disc in monolayer graphene, 3) a disc in bilayer graphene, 4) a disc in trilayer graphene of ABC stacking, 5) a disc in trilayer graphene of ABA stacking. The key to application of spin qubits in the graphene quantum dots is the destruction of valley degeneracy. In the first scenario, boundary condition is used to destroy valley degeneracy, while in other cases, valley degeneracy is destroyed by external magnetic field. Further, the effect of spin-orbit interaction and hyperfine interaction on operation of spin is introduced in graphene quantum dots.