Post-fabrication adjustment of Josephson junctions - materials and techniques

The requirements on frequency allocation of superconducting qubits requires greater precision in the manufacture of Josephson junctions than the current state of the art. The amorphous, inhomogeneous nature of the AlOx barrier core to Josephson junctions, may indeed mean that current lift-off based technologies cannot achieve the requisite precision. Technologies to alter the Josephson junction properties post-manufacture are therefore becoming important in order to build high-quality large-scale quantum computers by enabling corrections to be made to as-manufactured junction properties. Here we consider how tunnel junctions can be modified, assessing the process against key parameters such as yield. We interrogate the barrier materials developing models which explain the ability to tune and give greater insight into the processes used.