Ultralinear Magnetic-Flux-To-Voltage Conversion in Superconducting Quantum Interference Proximity Transistors

Superconducting interferometers are quantum devices able to transduce a magnetic flux into an elec-trical output with excellent sensitivity, integrability, and power consumption. Yet, their voltage response is intrinsically nonlinear, a limitation which is conventionally circumvented through the introduction of compensation inductances or by the construction of complex device arrays. Here we propose an intrinsi-cally linear flux-to-voltage mesoscopic transducer, exploiting the superconducting quantum interference proximity transistor (SQUIPT) as a fundamental building block, called bi-SQUIPT. It provides a voltage -noise spectral density as low as approximately 10-16 V/Hz1/2 and, more interestingly, under a proper operation parameter selection, exhibits a spur-free dynamic range as large as approximately 60 dB, a value on par with that obtained with state-of-the-art linear flux-to-voltage superconducting transducers based on superconducting quantum interference devices (SQUIDs). Furthermore, thanks to its peculiar measurement configuration, the bi-SQUIPT is tolerant to imperfections and nonidealities in general. For the above reasons, we believe that the bi-SQUIPT could provide a relevant step beyond in the field of low-dissipation and low-noise current amplification with a special emphasis on applications in cryogenic quantum electronics.