A Superconducting Harper-Hofstadter Lattice for Microwave Photons*

We present the latest progress in developing a novel architecture for exploration of topological matter. We construct photonic lattices from tunnel-coupled, time-reversal-broken microwave cavities that are both low loss and compatible with Josephson junction-mediated particle-particle interactions, allowing us access to topological phenomena such as the fractional quantum Hall effect. We employ seamless 3D microwave cavities all machined from a single block of high purity superconductor, along with Yttrium-Iron-Garnet (YIG) spheres magnetically biased below the critical field so our meta-material is scalable and directly compatible with the circuit QED toolbox. After demonstrating the essential properties of a time-reversal broken topological insulator at room temperature without interactions, we now push towards coupling Josephson junction qubits to a cryo-compatible superconducting lattice.