Ballistic supercurrent discretization and micrometer-long Josephson coupling in germanium

Abstract

Germanium quantum wells have long been considered to form an excellent host for spin, superconducting, and topological quantum circuits. As a first experimental step towards planar germanium hybrids, the authors demonstrate gate-tunable Josephson supercurrent that can extend over several micrometers. The supercurrent is observed to become discretized in quantum point contacts due to the quantization of the current carrying modes. These demonstrations provide scope for novel hole-based quantum technologies with control down to the last hole.