P. Neilinger

The transition regime between traveling-wave and resonant parametric amplifier

  1. S. Kern,
  2. P. Neilinger,
  3. E. Il'ichev,
  4. A. Sultanov,
  5. M. Schmelz,
  6. S. Linzen,
  7. J. Kunert,
  8. G. Oelsner,
  9. R. Stolz,
  10. A. Danilov,
  11. S. Mahashabde,
  12. A. Jayaraman,
  13. V. Antonov,
  14. S. Kubatkin,
  15. and M. Grajcar
Traveling wave parametric amplifiers based on kinetic or Josephson nonlinear inductance are known to be microwave quantum limited amplifiers. Usually, a perfectly impedance-matched
model is used to describe their characteristics in terms of standard coupled mode theory. In practice, the amplifiers are unmatched nonlinear devices with finite length, exhibiting ripples in the transmission. Since commonly used models fail to describe the ripples of real parametric amplifiers, here we are introducing a theoretical approach with non-negligible reflections, which provides their gain and bandwidth properly for both 3-wave and 4-wave mixing. Predictions of the model are experimentally demonstrated on two types of TWPA, based on coplanar waveguides with a central wire consisting of i) high kinetic inductance superconductor, and ii) array of 2000 Josephson junctions.
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

Experimental system design for the integration of trapped-ion and superconducting qubit systems

  1. D. De Motte,
  2. A. R. Grounds,
  3. M. Rehák,
  4. A. Rodriguez Blanco,
  5. B. Lekitsch,
  6. G. S. Giri,
  7. P. Neilinger,
  8. G. Oelsner,
  9. E. Il'ichev,
  10. M. Grajcar,
  11. and W. K. Hensinger
We present a design for the experimental integration of ion trapping and superconducting qubit systems as a step towards the realization of a quantum hybrid system. The scheme addresses
two key difficulties in realizing such a system; a combined microfabricated ion trap and superconducting qubit architecture, and the experimental infrastructure to facilitate both technologies. Developing upon work by Kielpinski et al. [1] we describe the design, simulation and fabrication process for a microfabricated ion trap capable of coupling an ion to a superconducting microwave LC circuit with a coupling strength in the tens of kHz. We also describe existing difficulties in combining the experimental infrastructure of an ion trapping setup into a dilution fridge with superconducting qubits and present solutions that can be immediately implemented using current technology.
arxiv pdf

Two-photon lasing by a superconducting qubit

  1. P. Neilinger,
  2. M. Rehák,
  3. M. Grajcar,
  4. G. Oelsner,
  5. U. Hübner,
  6. and E. Il'ichev
We study the response of a magnetic-field-driven superconducting qubit strongly coupled to a superconducting coplanar waveguide resonator. We observed a strong amplification/damping
of a probing signal at different resonance points corresponding to a one and two-photon emission/absorption. The sign of the detuning between the qubit frequency and the probe determines whether amplification or damping is observed. The larger blue detuned driving leads to two-photon lasing while the larger red detuning cools the resonator. Our experimental results are in good agreement with the theoretical model of qubit lasing and cooling at the Rabi frequency.
arxiv pdf

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