A ballistic graphene superconducting microwave circuit

TL;DR

This paper demonstrates a microwave circuit using a ballistic graphene Josephson junction embedded in a superconducting cavity, revealing its tunable inductance and microwave losses, and highlighting its potential for quantum circuit applications.

Contribution

It provides the first detailed microwave characterization of ballistic graphene Josephson junctions within a superconducting circuit, showing their feasibility for quantum technologies.

Findings

Gate-tunable Josephson inductance observed

Microwave losses characterized and linked to sub-gap resistance

Graphene JJs show potential for coherent quantum circuits

Abstract

Josephson junctions (JJ) are a fundamental component of microwave quantum circuits, such as tunable cavities, qubits and parametric amplifiers. Recently developed encapsulated graphene JJs, with supercurrents extending over micron distance scales, have exciting potential applications as a new building block for quantum circuits. Despite this, the microwave performance of this technology has not been explored. Here, we demonstrate a microwave circuit based on a ballistic graphene JJ embedded in a superconducting cavity. We directly observe a gate-tunable Josephson inductance through the resonance frequency of the device and, using a detailed RF model, we extract this inductance quantitatively. We also observe the microwave losses of the device, and translate this into sub-gap resistances of the junction at {\mu}eV energy scales, not accessible in DC measurements. The microwave performance we observe here suggests that graphene Josephson junctions are a feasible platform for implementing coherent quantum circuits.