Putting a Spin on the Josephson Effect

The Josephson “weak link”—a common element in quantum devices and sensitive magnetometers—consists of a nonsuperconducting material, such as a semiconducting nanowire, sandwiched between two superconductors. A supercurrent can flow through the wire, mediated by localized electronic states called Andreev bound states. Theory predicts that the energies of these states are influenced by the spins of the electrons and holes that give rise to these states. Now experiments by Leandro Tosi of the French Atomic Energy Commission (CEA) in Saclay, France, and his colleagues confirm these predictions. This spin degree of freedom could be used to manipulate the bound states for quantum computing applications.