Reduction of low-frequency excess noise in superconducting quantum interference devices by applying high-frequency magnetic fields

Abstract

We have investigated a possible reduction of low-frequency excess noise and the dependence of the flux signal on temperature changes in direct current superconducting quantum interference devices, dc SQUIDs, generated by trapped flux. Niobium thin film dc SQUIDs, carefully cooled down in a well shielded environment, have been exposed to switching transients. The thereby generated low-frequency excess noise and in some case an excess white noise, could substantially be reduced by applying a rf magnetic field of sufficiently high frequency to the SQUID. The temperature dependence of the flux signal of the SQUID and the magnetic field dependence of the drift could also be reduced in these cases, where the drift is caused by movement of trapped vortices.