U. Huebner

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

Broadband Sample Holder for Microwave Spectroscopy of Superconducting Qubits

  1. A.S. Averkin,
  2. A. Karpov,
  3. K. Shulga,
  4. E. Glushkov,
  5. N. Abramov,
  6. U. Huebner,
  7. E. Il'ichev,
  8. and A. V. Ustinov
We present a practical design and implementation of a broadband sample holder suitable for microwave experiments with superconducting integrated circuits at millikelvin temperatures.
Proposed design can be easily integrated in standard dilution cryostats, has flat pass band response in a frequency range from 0 to 32 GHz, allowing the RF testing of the samples with substrate size up to 4×4 mm. The parasitic higher modes interference in the holder structure is analyzed and prevented via design considerations. The developed setup can be used for characterization of superconducting parametric amplifiers, bolometers and qubits. We tested the designed sample holder by characterizing of a superconducting flux qubit at 20 mK temperature.
arxiv pdf