Pound-locking for characterization of superconducting microresonators.

We present a new application and implementation of the Pound-locking technique for the interrogation of superconducting microresonators. We discuss how by comparing against stable frequency sources this technique can be used to characterize properties of resonators that cannot be accessed using traditional methods. Specifically, by analyzing the noise spectra and the Allan deviation, we obtain valuable information about the nature of the noise in superconducting planar resonators. This technique also greatly improves the read-out accuracy and measurement throughput compared to conventional methods.