S. N. Shevchenko

Mirror, mirror: Landau-Zener-Stuckelberg-Majorana interferometry of a superconducting qubit in front of a mirror

  1. P. Y. Wen,
  2. O. V. Ivakhnenko,
  3. M. A. Nakonechnyi,
  4. B. Suri,
  5. J.-J. Lin,
  6. W.-J. Lin,
  7. J. C. Chen,
  8. S. N. Shevchenko,
  9. Franco Nori,
  10. and I.-C. Hoi
We investigate the Landau-Zener-Stuckelberg-Majorana interferometry of a superconducting qubit in a semi-infinite transmission line terminated by a mirror. The transmon-type qubit is
at the node of the resonant electromagnetic (EM) field, hiding from the EM field. „Mirror, mirror“ briefly describes this system, because the qubit acts as another mirror. We modulate the resonant frequency of the qubit by applying a sinusoidal flux pump. We probe the spectroscopy by measuring the reflection coefficient of a weak probe in the system. Remarkable interference patterns emerge in the spectrum, which can be interpreted as multi-photon resonances in the dressed qubit. Our calculations agree well with the experiments.
arxiv pdf

Landau-Zener-Stückelberg-Majorana lasing in circuit QED

  1. P. Neilinger,
  2. S. N. Shevchenko,
  3. J. Bogár,
  4. M. Rehák,
  5. G. Oelsner,
  6. D. S. Karpov,
  7. O. Astafiev,
  8. M. Grajcar,
  9. and E. Il'ichev
We demonstrate amplification (and attenuation) of a probe signal by a driven two-level quantum system in the Landau-Zener regime. In the experiment, a superconducting qubit was strongly
coupled to a microwave cavity, the conventional arrangement of circuit quantum electrodynamics. Two different types of flux qubits show a similar result, lasing at the points where amplification takes place. The experimental data are explained by the interaction of the probe signal with Rabi-like oscillations. The latter are created by constructive interference of Landau-Zener-St\“{u}ckelberg-Majorana (LZSM) transitions during the driving period of the qubit. A detailed description of the occurrence of these oscillations and a comparison of obtained data with both analytic and numerical calculations are given.
arxiv pdf