Xueda Wen

Observation of the correspondence between Landau-Zener transition and Kibble-Zurek mechanism with a superconducting qubit system

  1. Ming Gong,
  2. Xueda Wen,
  3. Guozhu Sun,
  4. Dan-Wei Zhang,
  5. Yang Yu,
  6. Shi-Liang Zhu,
  7. and Siyuan Han
We present a direct experimental observation of the correspondence between Landau-Zener transition and Kibble-Zurek mechanism with a superconducting qubit system. We develop a time-resolved
approach to study quantum dynamics of the Landau-Zener transition. By using this method, we observe the key features of the correspondence between Landau-Zener transition and Kibble-Zurek mechanism, e.g., the boundary between the adiabatic and impulse regions, the freeze-out phenomenon in the impulse region. Remarkably, the scaling behavior of the population in the excited state, an analogical phenomenon originally predicted in Kibble-Zurek mechanism, is also observed in the Landau-Zener transition.
arxiv pdf

Entanglement dynamics of a superconducting phase qubit coupled to a two-level system

  1. Guozhu Sun,
  2. Zhongyuan Zhou,
  3. Bo Mao,
  4. Xueda Wen,
  5. Peiheng Wu,
  6. and Siyuan Han
We report the observation and quantitative characterization of driven and spontaneous oscillations of quantum entanglement, as measured by concurrence, in a bipartite system consisting
of a macroscopic Josephson phase qubit coupled to a microscopic two-level system. The data clearly show the behavior of entanglement dynamics such as sudden death and revival, and the effect of decoherence and ac driving on entanglement.
arxiv pdf