Light, Symmetry Breaking, and Nonreciprocal Quantum Control

Time reversal symmetry is critical in controlling and harnessing nonreciprocal quantum phenomena, and superconducting circuits provide a platform to probe and control TRSB. First, I will discuss an integrated device where a transmon qubit is capacitively coupled to a microwave cross-resonator. The transmon acts as both control element and detector while the resonator couples to the quantum material, with access to TRSB. I will show how the electromagnetic properties of matter are encoded in the dynamics of the photonic states and formulate a measuring protocol that can be used to sensitively measure small nonreciprocal responses in the material, e.g., through magnetic or chiral topological order. Our process tomography method utilizes the quantum geometry of photonic wavefunctions. Building on this, I will present how a superconducting multimode ring resonator would couple and using a driven-dissipative analysis, how to map the nonlinear dynamics of a two-mode circuit with self- and cross-Kerr interactions beyond the bifurcation threshold. The critical behavior of the system serves as a highly sensitive detection method, and by mapping out the optimal parameter regions, the photon occupation numbers exhibit bistability where the relative photon occupations significantly change according to the strength of the interaction. This work forms the foundation for studies into the detection of TRSB and other symmetry-breaking phenomena in correlated quantum materials.