H.-G. Meyer

Parametric amplification by coupled flux qubits

  1. M. Rehak,
  2. P. Neilinger,
  3. M. Grajcar,
  4. G. Oelsner,
  5. U. Hubner,
  6. E. Il'ichev,
  7. and H.-G. Meyer
We report the parametric amplification of a microwave signal in a Kerr medium formed from superconducting qubits. Two mutually coupled flux qubits, embedded in the current antinode
of a superconducting coplanar waveguide resonator, are used as a nonlinear element. Shared Josephson junctions provide the qubit-resonator coupling, resulting in a device with a measured gain of about 20 dB. We argue, that this arrangement represents a unit cell which can be straightforwardly extended to a quasi one-dimensional quantum metamaterial with a large tunable Kerr nonlinearity.
arxiv pdf

Dressed-state amplification by a superconducting qubit

  1. G. Oelsner,
  2. P. Macha,
  3. O. V. Astafiev,
  4. E. Il'ichev,
  5. M. Grajcar,
  6. U. Hübner,
  7. B. I. Ivanov,
  8. P. Neilinger,
  9. and H.-G. Meyer
We demonstrate amplification of a microwave signal by a strongly driven two-level system in a coplanar waveguide resonator. The effect known from optics as dressed-state lasing is observed
with a single quantum system formed by a persistent current (flux) qubit. The transmission through the resonator is enhanced when the Rabi frequency of the driven qubit is tuned into resonance with one of the resonator modes. Amplification as well as linewidth narrowing of a weak probe signal has been observed. The laser emission at the resonator’s fundamental mode has been studied by measuring the emission spectrum. We analyzed our system and found an excellent agreement between the experimental results and the theoretical predictions obtained in the dressed-state model.
arxiv pdf