A phononic crystal coupled to a transmission line via an artificial atom

The interaction of superconducting qubits with surface acoustic wave resonators in quantum regime has been achieved recently. It opens a new field of research – quantum acoustodynamics – and allows developing new types of quantum devices. The main challenge in this direction is to manufacture acoustic resonators in the gigahertz range. Here, we demonstrate that the structure of a hybrid acoustodynamic device can be significantly simplified, if we replace an acoustic resonator with a phononic crystal. Our crystal consists of narrow metallic stripes on a quartz surface. The artificial atom in turn interacts with a microwave transmission line. Therefore, two degrees of freedom of different nature, acoustic and electromagnetic, are coupled with a single quantum object. A scattering spectrum of propagating electromagnetic waves on the artificial atom visualizes acoustic modes of the phononic crystal. Our geometry allows realizing effects of quantum acoustics on a simple and compact system.