Nick van Loo

Owing to their non-abelian exchange statistics, Majorana zero modes are promising candidates to realize topological quantum bits. Such quasiparticles were initially predicted to form in semiconducting nanowires coupled to superconductors, though they remain elusive to experimental detection. In a recent breakthrough experiment [1], it was demonstrated that instead two quantum dots coupled via a short superconducting segment can be used to emulate a minimal Kitaev chain. Such a chain, despite not being topological, hosts a pair of separated Majorana modes in the two quantum dots. In order to move towards quantum information experiments and demonstrate the non-abelian nature of these quasiparticles, it is necessary to read out the joint Fermion parity of a pair of Majorana zero modes. In this work, we demonstrate such parity readout in a minimal Kitaev chain. For this purpose, we connect the superconducting segment to a resonator circuit in a reflectometry setup. When the Majorana pair is in the even parity ground state, the system supports the splitting and forming of Cooper pairs between the superconductor and the two quantum dots. However, this is not the case for the odd parity ground state. These two ground states are thus distinguishable in the reflected signal on the superconducting lead. We further show that quasiparticle poisoning induces parity flips with lifetimes exceeding 1 ms and are able to detemine the parity state in a single-shot readout within 1 $\mu$s.
[1] T. Dvir, G. Wang, N. van Loo, et al. "Realization of a minimal Kitaev chain in coupled quantum dots." Nature 614.7948 (2023): 445-450