Circuit Quantum Electrodynamic Spectroscope: a new superconducting microwave quantum sensor

Superconductivity is a remarkable phase of matter which has advanced a wide variety of fields, including particle accelerators, biomedical imaging tools, and quantum computers.

However, there are fundamental open questions about the nature of the superconducting state in many materials, with new ones being discovered every year.

Understanding their structure can help unravel the dynamics of interacting many-body quantum systems, and lead to a next generation of technological innovations.Superconducting circuits are macroscopic tunable quantum devices which can interact strongly while maintaining high coherence, making them a leading quantum computing platform.

These advantages also make them excellent quantum sensors, and as they are entirely superconductor-based and operate at microwave frequencies well below the gap energy of most materials, superconducting circuits are ideally suited for the exploration of novel superconductors.cQEDscope will utilize superconducting circuits to expand our understanding of superconductivity in three ways: 1) using strong coupling to kinetic inductance, we will probe the structure of the superconducting order parameter in micron-sized samples (such as flakes of layered materials), orders of magnitude below current techniques; 2) using nonlinearity, we will implement a microwave analogue of Raman spectroscopy, allowing us to probe a wide frequency range and observe collective modes within the superconducting phase; 3) using quantum coherence, our circuit will interact with the Higgs collective mode to create the first Higgs-polariton, a novel quantum system by itself and a new path to study the superconducting structure.

In addition to our contribution to the understanding of novel superconductors, cQEDscope will also develop a new quantum sensing tool for material exploration, and a promising new class of hybrid superconducting circuits with potential quantum technology applications.