We demonstrate a highly linear superconducting quantum interference device (SQUID) amplifier based on a double-loop (Bi-SQUID) architecture incorporating three superconductor-normal metal-superconductor (S-N-S) junctions. Fabricated using niobium-gold technology, the device exhibits robust operation at liquid helium temperatures, with a superconducting transition temperature of 8.5 K. The flux-to-voltage transfer function demonstrates sharp, symmetric, and highly linear behavior at temperatures up to 5 K. Bi-SQUIDs featuring our single-element S-N-S design represent an interesting and original approach to this field, as they demonstrate a numerically estimated spurious-free dynamic range (SFDR) linearity exceeding 60 dB, achieved in a single element, simplifying the requirements in terms of arrays containing hundreds of junctions. These results highlight the potential of proximity-based Bi-SQUIDs for compact, low-noise, and highly linear cryogenic amplifiers in quantum sensing, magnetometry, and biomedical diagnostics.
@article{arxiv.2510.02923,
title = {Highly-Linear Proximity-Based Bi-SQUID Operating above 4 K},
author = {G. Trupiano and E. Riccardi and C. Puglia and M. Kiczynski and A. Gardin and G. De Simoni and G. C. Tettamanzi and F. Giazotto},
journal= {arXiv preprint arXiv:2510.02923},
year = {2025}
}