# Heteroatomic Andreev Molecule in a Superconducting Island–Double Quantum Dot Hybrid

## TL;DR

Researchers created a new type of superconducting molecule that could help in building fault-tolerant quantum hardware.

## Contribution

The novel contribution is the demonstration of a tunable heteroatomic Andreev molecule using a superconducting island and quantum dots.

## Key findings

- A three-electron-based molecular state is formed by coupling two quantum dots through a superconducting island.
- DMRG calculations confirm the robust binding of electrons in the system.
- Electrical gating enables a quantum phase transition between antiferromagnetic and ferromagnetic coupling states.

## Abstract

Topological superconductors
(SCs) hold great promise for fault-tolerant
quantum hardware; however, their experimental realization is very
challenging. Recently, superconducting artificial molecules (Andreev
molecules) have opened new avenues to engineer topological superconducting
materials. In this work, we demonstrate a heteroatomic Andreev molecule,
where two normal artificial atoms realized by quantum dots (QDs) are
coupled by a superconducting island (SCI). We show that the two normal
atoms hybridize and form a three-electron-based molecular state. Our
density matrix renormalization group (DMRG) calculations explain quantitatively
the robust binding of electrons. The tunability of the structure allows
us to drive a quantum phase transition from an antiferromagnetic Andreev
molecular state to a heteroatomic Andreev molecule with ferromagnetically
coupled QDs using simple electrical gating.