Weak qubit measurement with a nonlinear cavity: beyond perturbation theory.

  title={Weak qubit measurement with a nonlinear cavity: beyond perturbation theory.},
  author={Catherine Laflamme and Aashish A Clerk},
  journal={Physical review letters},
  volume={109 12},
We analyze the use of a driven nonlinear cavity to make a weak continuous measurement of a dispersively coupled qubit. We calculate the backaction dephasing rate and measurement rate beyond leading-order perturbation theory using a phase-space approach which accounts for cavity noise squeezing. Surprisingly, we find that increasing the coupling strength beyond the regime describable by leading-order perturbation theory (i.e., linear response) allows one to come significantly closer to the… 

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