Nonlocal Josephson effect in Andreev molecules

TL;DR

This paper introduces the concept of Andreev molecules, systems of two coupled Josephson junctions where supercurrent depends on phase differences across both junctions, with potential applications in quantum tech.

Contribution

It presents the theoretical framework for Andreev molecules, showing how coupling via Andreev Bound States leads to nonlocal supercurrent effects and proposing experimental verification methods.

Findings

Derivation of energy spectrum and current-phase relations for Andreev molecules.

Prediction of creating a $$-junction with nonlocal supercurrent.

Potential applications in quantum information and sensing.

Abstract

We propose the "Andreev molecule", an artificial quantum system composed of two closely spaced Josephson junctions. The coupling between Josephson junctions in an Andreev molecule occurs through the overlap and hybridization of the junction's "atomic" orbitals, Andreev Bound States. A striking consequence is that the supercurrent flowing through one junction depends on the superconducting phase difference across the other junction. Using the Bogolubiov-de-Gennes formalism, we derive the energy spectrum and non-local current-phase relation for arbitrary separation. We demonstrate the possibility of creating a $\varphi$-junction and propose experiments to verify our predictions. Andreev molecules may have potential applications in quantum information, metrology, sensing, and molecular simulation.