Characterization of low loss microstrip resonators as a building block for circuit QED in a 3D waveguide*

We perfomed microwave characterization on a new kind of microstrip resonator made from niobium and aluminum, by placing it in a rectangular waveguide. Our novel approach combines the low loss advantages of three dimensional structures with a compact planar design. The setup allows flexible coupling to the resonator, depending on its position within the waveguide. The waveguide represents a well defined microwave environment, which makes our setup appealing for testing materials. In the low temperature, low power regime, we measure a single photon internal quality factor of up to one million. The demonstrated quality factor is comparable to state of the art coplanar waveguide resonators, but does not require complex fabrication procedures. We measured the internal quality factor with increasing temperature, where our data shows good agreement with theoretical models predicting temperature dependent behavior.
We plan to use our microstrip resonators for qubit readout in a novel waveguide Quantum-Electro-Dynamics architecture. This represents an ideal platform for analogue quantum simulation of spin models.