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

  1. Aleksey N. Bolgar,
  2. Daniil D. Kirichenko,
  3. Rais. S. Shaikhaidarov,
  4. Shtefan V. Sanduleanu,
  5. Alexander V. Semenov,
  6. Aleksey Yu. Dmitriev,
  7. and Oleg V. Astafiev
We study a phononic crystal interacting with an artificial atom { a superconducting quantum system { in the quantum regime. The phononic crystal is made of a long lattice of narrow
metallic stripes on a quatz surface. The artificial atom in turn interacts with a 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. We simulate the system and found quasinormal modes of our phononic crystal and their properties. The calculations are consistent with the experimentally found modes, which are fitted to the dispersion branches of the phononic crystal near the first Brillouin zone edge. Our geometry allows to realize effects of quantum acoustics on a simple and compact phononic crystal.

Quantum versus Classical Regime in Circuit Quantum Acoustodynamics

  1. Gang-hui Zeng,
  2. Yang Zhang,
  3. Aleksey N. Bolgar,
  4. Dong He,
  5. Bin Li,
  6. Xin-hui Ruan,
  7. Lan Zhou,
  8. Le-Mang Kuang,
  9. Oleg V. Astafiev,
  10. Yu-xi Liu,
  11. and Z.H. Peng
We experimentally study a circuit quantum acoustodynamics system, which consists of a superconducting artificial atom, coupled to both a two-dimensional surface acoustic wave resonator
and a one-dimensional microwave transmission line. The strong coupling between the artificial atom and the acoustic wave resonator is confirmed by the observation of the vacuum Rabi splitting at the base temperature of dilution refrigerator. We show that the propagation of microwave photons in the microwave transmission line can be controlled by a few phonons in the acoustic wave resonator. Furthermore, we demonstrate the temperature effect on the measurements of the Rabi splitting and temperature induced transitions from high excited dressed states. We find that the spectrum structure of two-peak for the Rabi splitting becomes into those of several peaks, and gradually disappears with the increase of the environmental temperature T. The quantum-to-classical transition is observed around the crossover temperature Tc, which is determined via the thermal fluctuation energy kBT and the characteristic energy level spacing of the coupled system. Experimental results agree well with the theoretical simulations via the master equation of the coupled system at different effective temperatures.