Multiplexed microwave resonators by frequency comb spectroscopy

TL;DR

This paper demonstrates the use of a broadband microwave frequency comb generated by a superconducting device to perform multiplexed spectroscopy of coplanar microwave resonators, enabling simultaneous measurement and analysis.

Contribution

It introduces a novel method of using a superconducting quantum interference device (SQUID) driven frequency comb for spectroscopic probing of multiple microwave resonators.

Findings

Resonator quality factors estimated accurately with the comb source

Effective multiplexing of multiple resonators via dense frequency comb

Comparable results between room temperature electronics and cryogenic source

Abstract

Coplanar waveguide resonators are central to the thriving field of circuit quantum electrodynamics. Recently, we have demonstrated the generation of a broadband microwave-frequency comb spectrum using a superconducting quantum interference device (SQUID) driven by a time-dependent magnetic field. Here, the frequency comb is used to spectroscopically probe a bank of coplanar microwave resonators, inductively coupled to a common transmission line, a standard circuit with a variety of applications. We compare the resonator line shape obtained from signals synthesized at room temperature using conventional electronics with the radiation produced in the cryogenic environment by our source, showing substantial equivalence in the estimation of the resonator quality factors. To measure non-uniformly spaced resonant frequencies, we drive the generator with a bi-chromatic tone to generate intermodulation products. Such a dense frequency comb spectrum enables simultaneous addressing of a few resonators via frequency multiplexing. Finally, we discuss the criteria for achieving effective spectroscopic coverage of a given frequency bandwidth.