  The emerging field of quantum sensors and electronics for fundamental physics
is introduced, emphasising the role of thin-film superconducting devices.
Although the next generation of ground-based and space-based experiments
requires the development of advanced technology across the whole of the
electromagnetic spectrum, this article focuses on ultra-low-noise techniques
for radio to far-infrared wavelengths, where existing devices fall short of
theoretical limits. Passive circuits, detectors and amplifiers are described
from classical and quantum perspectives, and the sensitivities of
detector-based and amplifier-based instruments discussed. Advances will be
achieved through refinements in existing technology, but innovation is
essential. The needed developments go beyond engineering and relate to
theoretical studies that bring together concepts from quantum information
theory, quantum field theory, classical circuit theory, and device physics.
This article has been written to introduce graduate-level scientists to quantum
sensor physics, rather than as a formal review.
