Dong He

Dynamics and Resonance Fluorescence from a Superconducting Artificial Atom Doubly Driven by Quantized and Classical Fields

  1. Xinhui Ruan,
  2. Jia-Heng Wang,
  3. Dong He,
  4. Pengtao Song,
  5. Shengyong Li,
  6. Qianchuan Zhao,
  7. L.M. Kuang,
  8. Jaw-Shen Tsai,
  9. Chang-Ling Zou,
  10. Jing Zhang,
  11. Dongning Zheng,
  12. O. V. Astafiev,
  13. Yu-xi Liu,
  14. and Zhihui Peng
We report an experimental demonstration of resonance fluorescence in a two-level superconducting artificial atom under two driving fields coupled to a detuned cavity. One of the fields
is classical and the other is varied from quantum (vacuum fluctuations) to classical one by controlling the photon number inside the cavity. The device consists of a transmon qubit strongly coupled to a one-dimensional transmission line and a coplanar waveguide resonator. We observe a sideband anti-crossing and asymmetry in the emission spectra of the system through a one-dimensional transmission line, which is fundamentally different from the weak coupling case. By changing the photon number inside the cavity, the emission spectrum of our doubly driven system approaches to the case when the atom is driven by two classical bichromatic fields. We also measure the dynamical evolution of the system through the transmission line and study the properties of the first-order correlation function, Rabi oscillations and energy relaxation in the system. The study of resonance fluorescence from an atom driven by two fields promotes understanding decoherence in superconducting quantum circuits and may find applications in superconducting quantum computing and quantum networks.
arxiv pdf

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.
arxiv pdf