Collective effects based on direct dipole-dipole interaction in closely packed 3D transmon systems.

Collective effects, including subradiance and superradiance, in many-body quantum systems were extensively studied theoretically since the seminal work of Dicke. Experimental studies in this area were initially performed in atomic physics experiments with a cavity mediated interaction between atoms. More recently similar experiments with two superconducting qubits have been performed using on-chip circuit QED architectures.
Here we report on experiments utilizing a 3D circuit QED architecture, which is a promising experimental platform to study collective effects appearing due to direct dipole-dipole interaction. We exploit the advantages of superconducting transmon qubits, which can be easily engineered to have large transition dipole moments, tunable frequency and predefined coupling. We present the experimental results on the collective dynamics of a closely packed multi-qubit system embedded into a 3D rectangular waveguide.