The local magnetic moment of an interacting quantum dot occupied by a single electron can be screened by binding a Bogoliubov quasiparticle from a nearby superconductor. This gives rise to a long-lived discrete spin-singlet state inside the superconducting gap, known as the Yu-Shiba-Rusinov (YSR) state. We study the nature of the subgap states induced by a quantum dot embedded between two small superconducting islands. We show that this system has two spin-singlet subgap states with different spatial charge distributions. These states can be put in a linear superposition and coherently manipulated using electric-field pulses applied on the gate electrode. Such a YSR qubit could be implemented using present-day technology.

• Received 2 December 2021
• Revised 7 February 2022
• Accepted 7 February 2022

DOI:https://doi.org/10.1103/PhysRevB.105.075129