Strong tunable coupling between two distant superconducting spin qubits

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 of a quasiparticle trapped in a Josephson junction is intrinsically spin–orbit coupled to the supercurrent across the junction. This interaction has previously been used to perform spin readout, but it has also been predicted to facilitate inductive multi-qubit coupling. Here we demonstrate a strong supercurrent-mediated longitudinal coupling between two distant Andreev spin qubits. We show that it is both gate- and flux-tunable into the strong coupling regime and, furthermore, that magnetic flux can be used to switch off the coupling in situ. 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 distant spins. The hybrid architecture of Andreev spin qubits made using semiconductor–superconductor nanowires means that supercurrents can be used to inductively couple qubits over long distances.