Optimization of superconducting quantum interference device performance through use of a "quick noise" measurement circuit

Voiceover

Presenter(s)

Jennifer Lofgren

Abstract or Description

Through the unique properties of superconducting materials and interactions with magnetic fields, superconducting quantum interference devices (SQUIDs) are highly sensitive magnetometers. Characterizing this sensitivity is an important aspect of our group's research. In this application, a SQUID in its superconducting state produces a current dependent on the magnetic flux through its area. By reducing the area of a SQUID to the nanoscale, the nanoSQUID is able to detect magnetic fluctuations as small as the magnetic moment of a single electron. Because of this extreme sensitivity, the instrumentation for measuring the SQUID output must also have proportional sensitivity. Measuring the intrinsic noise of the nanoSQUID is necessary for evaluating the SQUID performance, since high levels of intrinsic noise reduce the sensitivity of the SQUID. The present method of measuring this noise using a fast Fourier transform (FFT) spectrum analyzer is time consuming, inhibiting our ability to characterize SQUIDs efficiently. To solve this issue, I developed a "quick noise" measurement circuit through a combination of analog filters and an amplifier. This circuit will measure the noise at a representative frequency without the need of a time-consuming FFT. I will present the design of the circuit and describe its performance.