  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.
