O. V. Astafiev

Tuneable on-demand single-photon source

  1. Z.H. Peng,
  2. J. S. Tsai,
  3. and O. V. Astafiev
An on-demand single photon source is a key element in a series of prospective quantum technologies and applications. We demonstrate the operation of a tuneable on-demand microwave photon
source based on a fully controllable superconducting artificial atom strongly coupled to an open-end transmission line (a 1D half-space). The atom emits a photon upon excitation by a short microwave π-pulse applied through a control line weakly coupled to the atom. The emission and control lines are well decoupled from each other, preventing the direct leakage of radiation from the π-pulses used for excitation. The estimated efficiency of the source is higher than 75\% and remains to be about 50\% or higher over a wide frequency range from 6.7 to 9.1 GHz continuously tuned by an external magnetic field.
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