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arXiv · 1504.08075

Candidate source of flux noise in SQUIDs: adsorbed oxygen molecules

Hui Wang·Chuntai Shi·Jun Hu·Sungho Han·Clare C. Yu·R. Q. Wu
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Abstract

A major obstacle to using SQUIDs as qubits is flux noise. We propose that the heretofore mysterious spins producing flux noise could be $O_2$ molecules adsorbed on the surface. Using density functional theory calculations, we find that an $O_2$ molecule adsorbed on an {\alpha}-alumina surface has a magnetic moment of ~1.8 {\mu}B. When the spin is oriented perpendicular to the axis of the O-O bond, the barrier to spin rotations is about 10 mK. Monte Carlo simulations of ferromagnetically coupled, anisotropic XY spins on a square lattice find 1/f magnetization noise, consistent with flux noise in Al SQUIDs.

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Hui Wang, Chuntai Shi, Jun Hu, Sungho Han, Clare C. Yu, R. Q. Wu. 2015-04-30. Candidate source of flux noise in SQUIDs: adsorbed oxygen molecules. https://doi.org/10.1103/physrevlett.115.077002

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