Magnetic Sensors Based on Long Josephson Tunnel Junctions - An Alternative to SQUIDs

TL;DR

This paper introduces a new type of superconducting magnetic sensor based on long Josephson tunnel junctions, offering a linear response over a wide range and potential advantages over traditional SQUIDs.

Contribution

It proposes a novel, robust magnetic sensing device using long Josephson junctions that does not rely on quantum interference, with improved linearity and potential noise benefits.

Findings

Linear response to magnetic flux over a wide range

Enhanced robustness without quantum interference

Potential for improved noise performance

Abstract

The properties of Josephson devices are strongly affected by geometrical effects. A loop-shaped superconducting electrode tightly couples a long Josephson tunnel junction with the surrounding electromagnetic field. Due to the fluxoid conservation, any change of the magnetic flux linked to the loop results in a variation of the shielding current circulating around the loop, which, in turn, affects the critical current of the Josephson junction. This method allows the realization of a novel family of robust superconducting devices (not based on the quantum interference) which can function as a general-purpose magnetic sensors. The best performance is accomplished without compromising the noise performance by employing an in-line-type junction few times longer than its Josephson penetration length. The linear (rather than periodic) response to magnetic flux changes over a wide range is just one of its several advantages compared to the most sensitive magnetic detectors currently available, namely the Superconducting Quantum Interference Devices (SQUID). We will also comment on the drawbacks of the proposed system and speculate on its noise properties.