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Spectroscopy of low-frequency noise and its temperature dependence in a superconducting qubit

F. Yan ; Jonas Bylander (Institutionen för mikroteknologi och nanovetenskap, Kvantkomponentfysik) ; S. Gustavsson ; F. Yoshihara ; K. Harrabi ; D.G. Cory ; T.P. Orlando ; Y. Nakamura ; J.S. Tsai ; W.D. Oliver
Physical Review B - Condensed Matter and Materials Physics (1098-0121). Vol. 85 (2012), 17, p. 174521.
[Artikel, refereegranskad vetenskaplig]

We report a direct measurement of the low-frequency noise spectrum in a superconducting flux qubit. Our method uses the noise sensitivity of a free-induction Ramsey interference experiment, comprising free evolution in the presence of noise for a fixed period of time followed by single-shot qubit-state measurement. Repeating this procedure enables Fourier-transform noise spectroscopy with access to frequencies up to the achievable repetition rate, a regime relevant to dephasing in ensemble-averaged time-domain measurements such as Ramsey interferometry. Rotating the qubit's quantization axis allows us to measure two types of noise: effective flux noise and effective critical-current or charge noise. For both noise sources, we observe that the very same 1/f-type power laws measured at considerably higher frequencies (0.2-20 MHz) are consistent with the noise in the 0.01-100-Hz range measured here. We find no evidence of temperature dependence of the noises over 65-200 mK, and also no evidence of time-domain correlations between the two noises. These methods and results are pertinent to the dephasing of all superconducting qubits. © 2012 American Physical Society.



Denna post skapades 2016-07-27. Senast ändrad 2016-08-15.
CPL Pubid: 239580

 

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