0−π qubit with one Josephson junction

Quantum states are usually fragile, making quantum computation less stable than classical computation. Quantum correction codes can protect quantum states but need many physical qubits to encode a single logical qubit. Alternatively, protecting quantum states at the hardware level has been recently developed to maintain the coherence of the quantum information by using symmetry. However, it generally has to pay the expense of increasing the complexity of the quantum devices. In this work, we propose to approach the protection of quantum states at the hardware level without increasing the complexity of the devices. The interplay between the spin-orbit coupling and the Zeeman splitting in the semiconductor allows us to tune the Josephson coupling in terms of the spin degree of freedom of Cooper pairs, the hallmark of the superconducting spintronics. This leads to the implementation of the parity-protected 0-$\ensuremath{\pi}$ superconducting qubit with only one highly transparent superconductor-semiconductor Josephson junction, which makes our proposal immune from the various fabrication imperfections.