Rare-earth nitride π-Josephson junctions as elements in superconducting quantum logic circuits

The overall goal of this project is to demonstrate new functionality in superconducting logic by introducing π-Josephson junctions (π-JJs) into superconducting electronic circuits. Josephson junctions (JJs) are widely used to make quantum logic circuits, and π-JJs are considered a viable way to introduce new functionalities to these circuits and to reduce their need for biasing electrical currents, improving speed and energy efficiency.  Rare-earth nitrides (RENs) are semiconducting materials with highly tuneable magnetic and conductivity properties and are well suited for producing π-JJs. The team will draw on its knowledge of the growth and properties of RENs to fabricate superconductor-REN-superconductor junctions, controlling the REN properties and interface quality to produce the desired π-JJs.

The project objectives are threefold: to produce π-Josephson junctions from REN alloys and to determine their critical current and voltage characteristics; to prove the potential of the technology by producing a proof-of-concept superconducting electronic circuit with a REN-π-JJ element; and to investigate other uses for π-JJs in quantum logic circuits, such as amplifiers, ferrotransmons (a type of qubit), superconducting diodes, or superconducting rectifiers. The applications are anywhere a superconducting circuit can be used, such as for high-speed communications, superconducting sensors, in quantum computing or for energy-efficient AI systems.

This work is led by Affiliate Member Dr Simon Granville, with Professor Ben Ruck. They will collaborate with Nagoya University and Yokohama National University in Japan to construct the circuits using π-Josephson junctions.