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Dephasing of a superconducting qubit induced by photon noise

P. Bertet·I. Chiorescu·G. Burkard·K. Semba·C. J. P. M. Harmans·D. P. DiVincenzo·J. E. Mooij
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Abstract

We have studied the dephasing of a superconducting flux-qubit coupled to a DC-SQUID based oscillator. By varying the bias conditions of both circuits we were able to tune their effective coupling strength. This allowed us to measure the effect of such a controllable and well-characterized environment on the qubit coherence. We can quantitatively account for our data with a simple model in which thermal fluctuations of the photon number in the oscillator are the limiting factor. In particular, we observe a strong reduction of the dephasing rate whenever the coupling is tuned to zero. At the optimal point we find a large spin-echo decay time of $4 μs$.

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P. Bertet, I. Chiorescu, G. Burkard, K. Semba, C. J. P. M. Harmans, D. P. DiVincenzo, J. E. Mooij. 2005-12-18. Dephasing of a superconducting qubit induced by photon noise. https://doi.org/10.1103/physrevlett.95.257002

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