Single-shot readout of Majorana parity in a minimal Kitaev chain

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 introduce a single Cooper pair splitter as a new tool to measure the joint parity. 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. In the odd parity ground state however, Cooper pair splitting is forbidden. As a result, the two ground states are distinguishable with the single Cooper pair splitter. In addition, we connect the minimal chain to an auxilliary quantum dot operated as a single electron box charge sensor. The charge sensor only detects local charge, and we demonstrate that it us thus insensitive to the two parity states of the Majorana pair. We further show that quasiparticle poisoning induces parity flips, with a parity lifetime that exceeds milliseconds. Finally, we demonstrate the ability to determine the parity state in a single-shot readout within microseconds.

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