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Low-frequency Noise in Josephson Junctions for Superconducting Qubits

J. Eroms·L. C. van Schaarenburg·E. F. C. Driessen·J. H. Plantenberg·K. Huizinga·R. N. Schouten·A. H. Verbruggen·C. J. P. M. Harmans·J. E. Mooij
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Abstract

We have studied low-frequency resistance fluctuations in shadow-evaporated Al/AlOx/Al tunnel junctions. Between 300 K and 5 K the spectral density follows a 1/f-law. Below 5 K, individual defects distort the 1/f-shape of the spectrum. The spectral density decreases linearly with temperature between 150 K and 1 K and saturates below 0.8 K. At 4.2 K, the spectral density is about two orders of magnitude lower than expected from a recent survey [D. J. Van Harlingen et al., Phys. Rev. B 70, 064510 (2004)]. Due to the saturation below 0.8 K the estimated qubit dephasing times at 100 mK are only about two times longer than calculated by Van Harlingen et al.

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J. Eroms, L. C. van Schaarenburg, E. F. C. Driessen, J. H. Plantenberg, K. Huizinga, R. N. Schouten, A. H. Verbruggen, C. J. P. M. Harmans, J. E. Mooij. 2006-10-03. Low-frequency Noise in Josephson Junctions for Superconducting Qubits. https://doi.org/10.1063/1.2357010

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