Tuning non-reciprocity between two circuit QED modules I - linear interactions

In a modular quantum information processing architecture, it is highly desirable to have low-loss directional transmission channels to control the information flow while maintaining high fidelity. Using single crystalline yttrium iron garnet (YIG) in a waveguide-based package, we directly integrate a pair of shielded superconducting cavities with a low-loss custom-designed circulator, which has insertion loss of ~1% and isolation of >20 dB in the quantum region. By adjusting external magnetic field, we can tune the cavity-cavity interaction in-situ between the reciprocal (hybridized) regime and the directional (cascaded) regime. Based on a 4 mode model derived using input output theory, the predicted spectrum of transmission measurements over fields is in good agreement with experimental results. Furthermore, we integrate qubits to our superconducting cavities to explore interactions between the cavities and qubits with varying degrees of non-reciprocity.