Ultra linear magnetic flux-to-voltage conversion in superconducting quantum interference proximity transistors

TL;DR

This paper introduces the bi-SQUIPT, a superconducting device that achieves intrinsically linear magnetic flux-to-voltage conversion with low noise and high dynamic range, suitable for quantum electronics applications.

Contribution

The paper presents the bi-SQUIPT, a novel superconducting transducer with intrinsic linearity and high dynamic range, reducing the need for complex compensation circuitry.

Findings

Voltage-noise spectral density as low as 10^{-16} V/Hz^{1/2}

Dynamic range up to 60 dB, comparable to state-of-the-art SQUIDs

Tolerance to device imperfections and non-idealities

Abstract

Superconducting interferometers are quantum devices able to transduce a magnetic flux into an electrical output with excellent sensitivity, integrability and power consumption. Yet, their voltage response is intrinsically non-linear, a limitation which is conventionally circumvented through the introduction of compensation inductances or by the construction of complex device arrays. Here we propose an intrinsically-linear flux-to-voltage mesoscopic transducer, called bi-SQUIPT, based on the superconducting quantum interference proximity transistor as fundamental building block. The bi-SQUIPT provides a voltage-noise spectral density as low as $\sim10^{-16}$ V/Hz$^{1/2}$ and, more interestingly, under a proper operation parameter selection, exhibits a spur-free dynamic range as large as $\sim60$ dB, a value on par with that obtained with state-of-the-art SQUID-based linear flux-to-voltage superconducting transducers. Furthermore, thanks to its peculiar measurement configuration, the bi-SQUIPT is tolerant to imperfections and non-idealities 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.