Quantum Sensing with Circuit QED Photonics

Quantum sensing has emerged as a transformative tool in the exploration and manipulation of quantum materials, pushing the boundaries of precision and sensitivity far beyond what classical approaches can achieve. The convergence of quantum sensing with advanced technologies like superconducting circuits and NV centers has revolutionized the ability to probe and understand the fundamental properties of quantum matter. Here, we present an integrated quantum photonic device where a transmon qubit is capacitively coupled to a microwave cross-resonator. In this sensing scheme, the transmon qubit plays a dual role as both a control element and a passive detector, while the cross-resonator interacts with matter. By tuning the coupling strength and phase between the transmon and the cross-resonator, the device allows selective control over the interaction dynamics and leads to a highly sensitive detection method that can be compactly described and understood via the quantum metric. This serves as an effective measurement approach that enables access to elusive aspects of correlated quantum matter, such as the detection of time reversal symmetry signatures in superconductors, or the magnetic nature of twisted bilayer graphene.