Building a minimal Kitaev chain using proximitized quantum dots at the charge-neutral sweet spot

A Poor Man’s Majorana platform can generate two isolated Majorana zero modes at a parameter sweet spot by controllably coupling two ordinary fermions. Starting from electrons in quantum dots that have charge –e and spin ½, tunnel coupling mixes them to produce chargeless, spinless Majorana zero modes. In comparison, an Andreev bound state can also have zero charge at a critical coupling rate to a superconductor, although its spin remains ½. Following the general recipe for obtaining Poor Man’s Majorana zero modes, we couple two such chargless Andreev bound states in two proximitized quantum dots and study the system under a two-fold sweet spot. The inter-dot coupling sweet spot eliminates both charge and spin, while the intra-dot superconducting coupling further removes any dependence of local charge on the electrostatic environment. We discuss the practical implications on this system’s immunity to noise and perturbations.