Room temperature resistance measurements of metallic thin films using microwave cavities

A necessary element of superconducting qubits are LC resonator circuits responsible for manipulating the qubit’s quantum states and facilitating qubit readout. It is therefore of great interest to minimize the physical size of the linear capacitors and inductors within these circuits to optimize the limited real estate of a qubit architecture. We therefore look towards superconducting materials that have an intrinsic inductance associated with the inertia of charge carriers. This so-called “kinetic inductance” has proven to be orders of magnitude larger than geometric inductance and has the potential to reduce the size of qubits.

Still, before using these materials within a qubit, it is necessary to characterize the film parameters. The kinetic inductance of a type-I superconductor can be calculated from its sheet resistance; however, traditional I - V measurements should be avoided because contact from the probe can damage the fragile surface of the thin film. This project therefore explores the precision of contactless resistance measurements that can be achieved using microwave cavities. The insertion of a sample into a cavity will introduce new losses, therefore making it possible to extract the resistance of the sample from the change in the quality factor of the cavity. These losses are simulated using finite element analysis software and show that sufficient precision can be obtained.