Poor Man's Majoranas and 3-site chains in a QD-ABS system

Because of their non-abelian exchange statistics, Majorana zero modes are highly promising candidates for topological quantum computing. While these quasiparticles have been predicted to arise in semiconducting nanowires coupled to superconductors, their experimental observation has proven to be quite elusive. In a different approach, the first physical implementation of a minimal Kitaev chain has recently demonstrated the ability to instead create so-called Poor Man's Majorana zero modes [1]. This is enabled via the coupling of two quantum dots via an Andreev Bound State in a short proximitized semiconductor. In this talk, we demonstrate that this state itself can also form one of the sites of a Kitaev chain and show that Poor Man's Majorana bound states arise in this coupled Andreev Bound State - quantum dot system [2]. Moreover, we introduce an auxiliary quantum dot to the system, whose coupling invokes a splitting of the zero energy modes. This splitting is an important metric to gauge the Majorana polarization of a Kitaev chain. The auxiliary quantum dot can also participate in the Kitaev chain when the coupling is tuned appropriately. This enables the creation of a three-site chain, forming an attractive approach to scale up the length of these artificial Kitaev chains and thereby increasing the robustness of the Majorana zero modes.

[1] Dvir, Tom, et al. "Realization of a minimal Kitaev chain in coupled quantum dots." Nature 614.7948 (2023): 445-450.

[2] Miles, Sebastian, et al. “Efficient simulation of Kitaev chain in an alternating quantum dot-Andreev bound state array.” arXiv:2309.15777 (2023)