Voltage-Tunable Coupling to a Coplanar Waveguide Resonator Mediated by a Josephson Junction Field Effect Transistor—Part I

Superconducting qubit circuits could benefit immensely from a low power and fast tunability mechanism. This tunability can mediate microwave photon storage for quantum memory, as well as dynamically control qubit-qubit coupling. However, many current implementations of a tunable coupler for superconducting qubits are based on Al-AlOx-Al Josephson tunnel junctions arranged in a loop controlled via an applied flux through the loop generated by a current on the order of a milliampere. As the system size scales up, the additional heat load will scale as the square of the number of flux lines. Low-power voltage-controlled Josephson junction field effect transistors (JJ-FET) fabricated on superconductor-semiconductor heterostructures have been utilized to make tunable qubits. We present a gate voltage tunable Josephson junction field effect transistor fabricated on an Al-InAs heterostructure embedded in a coplanar waveguide resonator.<br/>We show how the properties of this device make it a viable option for a tunable coupler. We show measurements of the internal quality factor of the materials stack and find that the loss is dominated by the InAlAs buffer layer. By varying the inductance of the junction via a gate voltage tunable critical current, we find that the resonant frequency and external quality factor can be tuned. By completely suppressing the supercurrent flowing through the junction, the coupler can provide full isolation. Electromagnetic field simulations are utilized to understand and solve for the lowest frequency eigenmodes as a function of the Josephson inductance.<br/>*This abstract is the first part of a two-part abstract. The second abstract will be presented by Bassel Heiba Elfeky.