L.M. Kuang

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

Vacuum induced Aulter-Townes splitting in a superconducting artificial atom

  1. Z.H. Peng,
  2. J.H. Ding,
  3. Y. Zhou,
  4. L.L. Ying,
  5. Z. Wang,
  6. L. Zhou,
  7. L.M. Kuang,
  8. Yu-xi Liu,
  9. O. Astfiev,
  10. and J. S. Tsai
We study experimentally a vacuum induced Aulter-Townes doublet in a superconducting three-level artificial atom strongly coupled to a coplanar waveguide resonator and simultaneously
to a transmission line. The Aulter-Townes splitting is observed in the reflection spectrum of the three-level atom when the transition between two excited states is resonant with the resonator. By varying an amplitude of the driving field applied to the resonator, we observe quantum-to-classical transition of the Aulter-Townes splitting. Our results may pave the way for the control of microwaves by single photons.
arxiv pdf