Experimental demonstrations of high-Q superconducting coplanar waveguide resonators

TL;DR

This paper reports the design, fabrication, and measurement of high-Q superconducting coplanar waveguide resonators made from Niobium, demonstrating their potential for quantum computing and photon detection applications.

Contribution

It introduces a novel absorption-type CPW resonator with high quality factors and characterizes its temperature-dependent behavior at ultra-low temperatures.

Findings

Loaded quality factors up to 10^6 achieved

Resonance frequencies blue shift with temperature increase

Resonators show potential for quantum information and photon detection

Abstract

We designed and successfully fabricated an absorption-type of superconducting coplanar waveguide (CPW) resonators. The resonators are made from a Niobium film (about 160 nm thick) on a high-resistance Si substrate, and each resonator is fabricated as a meandered quarter-wavelength transmission line (one end shorts to the ground and another end is capacitively coupled to a through feedline). With a vector network analyzer we measured the transmissions of the applied microwave through the resonators at ultra-low temperature (e.g., at 20 mK), and found that their loaded quality factors are significantly high, i.e., up to 10^6. With the temperature increases slowly from the base temperature (i.e., 20 mK), we observed the resonance frequencies of the resonators are blue shifted and the quality factors are lowered slightly. In principle, this type of CPW-device can integrate a series of resonators with a common feedline, making it a promising candidate of either the data bus for coupling the distant solid-state qubits or the sensitive detector of single photons.