We investigate the transport characteristics induced by the serially coupling of two pairs of Majorana bound states (MBSs) in two topological-superconducting nanowires. By considering the direct and indirect couplings of the MBSs via an embedded quantum dot (QD), we find that the coupling manner has an important influence on the nonlocality of MBSs. This is manifested as the change of conductance and Fano factors following the variation of the MBS-lead couplings, inter-MBS couplings, superconducting phase difference and the QD level, respectively. What is important is that the relationship of Fano factors can be altered by adjusting the coupling manner of the neighboring MBSs in the two nanowires. This indicates that the nonlocality of MBSs can be modulated by changing the inter-MBS couplings.

我们研究了两条拓扑超导纳米线中两对马约拉纳束缚态 (MBS) 串联耦合引起的传输特性。通过考虑MBS通过嵌入式量子点（QD）的直接和间接耦合，我们发现耦合方式对MBS的非定域性有重要影响。这表现为分别随着MBS-引线耦合、MBS间耦合、超导相位差和QD能级变化的电导和Fano因子的变化。重要的是，可以通过调整两条纳米线中相邻 MBS 的耦合方式来改变 Fano 因子的关系。这表明可以通过改变 MBS 间的耦合来调制 MBS 的非定域性。