Strong tunable coupling between two distant superconducting spin qubits

TL;DR

This paper demonstrates a strong, tunable supercurrent-mediated coupling between two distant superconducting spin qubits, enabling fast, high-fidelity two-qubit gates in hybrid quantum systems.

Contribution

It introduces a novel, gate- and flux-tunable coupling mechanism between remote Andreev spin qubits using supercurrent mediation.

Findings

Coupling strength up to 178 MHz achieved.

Coupling can be switched off in-situ with magnetic flux.

Demonstrates integration of spin states into superconducting circuits.

Abstract

Superconducting (or Andreev) spin qubits have recently emerged as an alternative qubit platform with realizations in semiconductor-superconductor hybrid nanowires. In these qubits, the spin degree of freedom is intrinsically coupled to the supercurrent across a Josephson junction via the spin-orbit interaction, which facilitates fast, high-fidelity spin readout using circuit quantum electrodynamics techniques. Moreover, this spin-supercurrent coupling has been predicted to facilitate inductive multi-qubit coupling. In this work, we demonstrate a strong supercurrent-mediated coupling between two distant Andreev spin qubits. This qubit-qubit interaction is of the longitudinal type and we show that it is both gate- and flux-tunable up to a coupling strength of 178 MHz. Finally, we find that the coupling can be switched off in-situ using a magnetic flux. Our results demonstrate that integrating microscopic spin states into a superconducting qubit architecture can combine the advantages of both semiconductors and superconducting circuits and pave the way to fast two-qubit gates between remote spins.