Photon-mediated Collective Effects Between Systems of Closely Packed 3D Transmons

Collective effects in many-body quantum systems were extensively studied theoretically and experimentally over the last decade. So far experiments were mainly relying on a single dominant coupling mechanism, either direct or photon-mediated. In this talk we present our experimental results with a system where both types of interaction are present and comparable in strength. We enter this regime with a 3D circuit QED platform, making use of the large, engineerable direct dipole-dipole interaction between qubits and a strong coupling to the fundamental mode of 3D rectangular waveguide. In particular we report on the collective dynamics of well separated pairs of closely packed 3D transmon qubits.