Charge sensing the parity of an Andreev molecule

TL;DR

This paper demonstrates a method to sense the charge parity of Andreev bound states and molecules in a hybrid nanowire, enabling non-invasive parity measurements relevant for topological quantum computing.

Contribution

It introduces a charge sensing technique using a quantum dot to measure the parity of Andreev states without disturbing them.

Findings

Charge sensing resolves even and odd parity states.

The method does not affect the quantum parity of the states.

Potential application in Majorana zero mode parity measurements.

Abstract

The proximity effect of superconductivity on confined states in semiconductors gives rise to various bound states such as Andreev bound states (ABSs), Andreev molecules and Majorana zero modes. While such bound states do not conserve charge, their Fermion parity is a good quantum number. One way to measure parity is to convert it to charge first, which is then sensed. In this work, we sense the charge of ABSs and Andreev molecules in an InSb-Al hybrid nanowire using an integrated quantum dot operated as a charge sensor. We show how charge sensing measurements can resolve the even and odd states of an Andreev molecule, without affecting the parity. Such an approach can be further utilized for parity measurements of Majorana zero modes in Kitaev chains based on quantum dots.