Qubit based on spin-singlet Yu-Shiba-Rusinov states

TL;DR

This paper explores a qubit based on spin-singlet Yu-Shiba-Rusinov states in a quantum dot system, demonstrating the potential for coherent manipulation using electric fields, with implications for quantum computing technology.

Contribution

It introduces a novel YSR-based qubit system with controllable subgap states in a quantum dot setup, feasible with current technology.

Findings

Identification of two distinct spin-singlet subgap states

Demonstration of coherent superposition and manipulation of YSR states

Proposal for implementing YSR qubits with existing experimental techniques

Abstract

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 YSR qubit could be implemented using present-day technology.