Quantum versus classical regime in circuit quantum acoustodynamics

We experimentally study a circuit quantum acoustodynamics system with 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 could become into those of several peaks under some special experimental conditions, and gradually disappears with the increase of the environmental temperature T. The continuous quantum-to-classical crossover is observed around the crossover temperature T (c), which is determined via the thermal fluctuation energy k (B) T 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.

Automated summary

In this experiment, a circuit quantum acoustodynamics system was studied with a superconducting artificial atom coupled to both a 2D surface acoustic wave resonator and a 1D microwave transmission line. Strong coupling between the artificial atom and the acoustic wave resonator was confirmed, and the impact of temperature on the system was demonstrated. The spectrum structure of the Rabi splitting changed under specific experimental conditions and gradually disappeared with increasing environmental temperature. Additionally, a continuous quantum-to-classical crossover was observed around a crossover temperature T(c).