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arXiv · 1206.4757

Weak Qubit Measurement with a Nonlinear Cavity: Beyond Perturbation Theory

Catherine Laflamme·Aashish A. Clerk
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Abstract

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 quantum limit on the measurement efficiency. We interpret this behaviour in terms of the non-Gaussian photon number fluctuations of the nonlinear cavity. Our results are relevant to recent experiments using superconducting microwave circuits to study quantum measurement.

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Catherine Laflamme, Aashish A. Clerk. 2012-06-21. Weak Qubit Measurement with a Nonlinear Cavity: Beyond Perturbation Theory. https://doi.org/10.1103/physrevlett.109.123602

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