Magnetism in SQUIDs at Millikelvin Temperatures

Abstract

We have characterized the temperature dependence of the flux threading dc SQUIDs cooled to millikelvin temperatures. The flux increases as 1/T as temperature is lowered; moreover, the flux change is proportional to the density of trapped vortices. The data is compatible with the thermal polarization of surface spins in the trapped fields of the vortices. In the absence of trapped flux, we observe evidence of spin-glass freezing at low temperature. These results suggest an explanation for the "universal" 1/f flux noise in SQUIDs and superconducting qubits.

4 pages, 4 figures

References in corpus (5)

• Model for l/f Flux Noise in SQUIDs and Qubits
• 1/f Flux Noise in Josephson Phase Qubits
• Dephasing of a superconducting flux qubit
• Microscopic origin of low frequency flux noise in Josephson circuits
• Dangling-bond spin relaxation and magnetic 1/f noise from the amorphous-semiconductor/oxide interface: Theory

Cited by in corpus (8)

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• Microscopic origin of low frequency flux noise in Josephson circuits
• Geometrical dependence of low frequency noise in superconducting flux qubits
• Spin-like susceptibility of metallic and insulating thin films at low temperature
• Enhancement of quasiparticle recombination in Ta and Al superconductors by implantation of magnetic and nonmagnetic atoms
• Relaxation of Josephson qubits due to strong coupling to two-level systems
• Observation of Josephson coupling through an interlayer of antiferromagnetically ordered chromium