cQEDscope is divided into 3 milestones that highlight different geometries of the hybrid microwave circuit as well as measurement techniques of growing complexity.
Here we will highlight the main achievements so far, focusing on milestones 1 and 3.
Milestone 1: Hybrid microwave resonators for studying the gap structure of micron-sized samples
The main objectives of Milestone 1 are the fabrication and measurement of microwave resonators which combine a novel superconductor as part of the circuit. We have initially focused on van-der-Waals superconductors. In the first two years of the project, we have developed a process for fabricating a thin film resonator and hybridizing it with a van-der-Waals superconducting flake by a capacitive link through a thin oxide barrier. We have shown that we can generate high quality circuits and maintain the pristine quality of the material. This method is now commonly used in the research group to create devices and explore various van-der-Waals materials, and is starting to be utilized by additional groups as well.
Our first hybrid circuits incorporated a flake of the cuprate superconductor Bi2Sr2CaCu2O8+x, and our measurements have observed strong coupling to a nonlinear mode, a surprising result that be useful both to understand the superconductivity in these materials and for future devices for quantum technology. These results have been recently published in Jin et al., Nano Letters (2025).
Milestone 3: Superconducting qubit based on effects in novel superconductors
The objective of Milestone 3 is to design a novel superconducting qubit based on the interaction between the models of novel superconductor with the microwave circuits. While considering the design of this circuit, we have made a theoretical breakthrough that led to a new type of superconducting circuit that is protected by the unique "d-wave" symmetry which appears in a certain class of novel superconductors. This new design can protect the underlying quantum state from noise in the environment - a key limited of current quantum devices. These results have been published in Brosco et al. Phys. Rev. Lett (2024).
This circuit, which we nicknamed "flowermon", can be seen as the first of a new class of circuits that utilize the effects of novel superconductors. We have begun the first theoretical steps in exploring this class of qubits, and this work is published in Coppo et al. Appl. Phys. Lett. (2024).
