S. Boutin

Resonance fluorescence from an artificial atom in squeezed vacuum

  1. D.M. Toyli,
  2. A.W. Eddins,
  3. S. Boutin,
  4. S. Puri,
  5. D. Hover,
  6. V. Bolkhovsky,
  7. W. D. Oliver,
  8. A. Blais,
  9. and I. Siddiqi
We present an experimental realization of resonance fluorescence in squeezed vacuum. We strongly couple microwave-frequency squeezed light to a superconducting artificial atom and detect
the resulting fluorescence with high resolution enabled by a broadband traveling-wave parametric amplifier. We investigate the fluorescence spectra in the weak and strong driving regimes, observing up to 3.1 dB of reduction of the fluorescence linewidth below the ordinary vacuum level and a dramatic dependence of the Mollow triplet spectrum on the relative phase of the driving and squeezed vacuum fields. Our results are in excellent agreement with predictions for spectra produced by a two-level atom in squeezed vacuum [Phys. Rev. Lett. \textbf{58}, 2539-2542 (1987)], demonstrating that resonance fluorescence offers a resource-efficient means to characterize squeezing in cryogenic environments.
arxiv pdf

Measurement-induced qubit state mixing in circuit QED from up-converted dephasing noise

  1. D. H. Slichter,
  2. R. Vijay,
  3. S. J. Weber,
  4. S. Boutin,
  5. M. Boissonneault,
  6. J. M. Gambetta,
  7. A. Blais,
  8. and I. Siddiqi
We observe measurement-induced qubit state mixing in a transmon qubit dispersively coupled to a planar readout cavity. Our results indicate that dephasing noise at the qubit-readout
detuning frequency is up-converted by readout photons to cause spurious qubit state transitions, thus limiting the nondemolition character of the readout. Furthermore, we use the qubit transition rate as a tool to extract an equivalent flux noise spectral density at f ~ 1 GHz and find agreement with values extrapolated from a $1/f^alpha$ fit to the measured flux noise spectral density below 1 Hz.
arxiv pdf