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arXiv · 1206.6946

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

D. H. Slichter·R. Vijay·S. J. Weber·S. Boutin·M. Boissonneault·J. M. Gambetta·A. Blais·I. Siddiqi
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Abstract

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 $1/f^α$ fit to the measured flux noise spectral density below 1 Hz.

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D. H. Slichter, R. Vijay, S. J. Weber, S. Boutin, M. Boissonneault, J. M. Gambetta, A. Blais, I. Siddiqi. 2012-10-12. Measurement-induced qubit state mixing in circuit QED from up-converted dephasing noise. https://doi.org/10.1103/physrevlett.109.153601

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