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 4μs.
@article{arxiv.cond-mat/0512428,
title = {Dephasing of a superconducting qubit induced by photon noise},
author = {P. Bertet and I. Chiorescu and G. Burkard and K. Semba and C. J. P. M. Harmans and D. P. DiVincenzo and J. E. Mooij},
journal= {arXiv preprint arXiv:cond-mat/0512428},
year = {2007}
}
Comments
New version of earlier paper arXiv/0507290 after in-depth rewriting