By driving a 3D transmon with microwave fields, we generate an effective avoided energy-level crossing. Then we chirp microwave frequency, which is equivalent to driving the systemthrough the avoided energy-level crossing by sweeping the avoided crossing. A double-passage chirp produces Landau-Zener-St\“uckelberg-Majorana interference that agree well with the numerical results. Our method is fully applicable to other quantum systems that contain no intrinsic avoided level crossing, providing an alternative approach for quantum control and quantum simulation.
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-resolvedapproach 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.
We report the observation and quantitative characterization of driven and
spontaneous oscillations of quantum entanglement, as measured by concurrence,
in a bipartite system consistingof 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.