Critical current noise investigations in underdamped Josephson devices

Abstract

An experimental investigation of the critical current noise in underdamped niobium based Josephson devices [junctions and Superconducting Quantum Interference Device (SQUID)] by a technique based on the switching current measurements is reported. By sweeping the junction with a current ramp we measure the critical current switching using the standard time of flight technique and analyze the data to extract the current noise. Measurements on Josephson junctions having an area ranging from (4 \ifmmode\times\else\texttimes\fi{} 4) to (40 \ifmmode\times\else\texttimes\fi{} 40) \ensuremath{\mu}m${}^{2}$ in the temperature range from 4.2 to 1.2 K are reported. The experimental results show a linear behavior of the current white noise from both the junction area and the temperature. These measurements provide very useful information about the intrinsic noise of Josephson devices involving SQUIDs and qubits.