  We consider how superconducting microwave detector technology might be
applied to the readout of cavity-axion haloscopes and similar fundamental
physics experiments. Expressions for the sensitivity of two detection schemes
are derived: 1) a dispersive spectrometer, and 2) a direct-conversion/homodyne
receiver using detectors as mixing elements. In both cases the
semi-classical/Poisson-mixture approach is used to account for quantum effects.
Preliminary sensitivity calculations are performed to guide future development
work. These suggest the homodyne scheme offers a near-term solution for
realising near-quantum-noise limited receivers with improved usability compared
with parametric amplifiers. Similarly, they show that the dispersive
spectrometer offers a potential way to beat the quantum noise limit, but that
significant technological development work is needed to do so.
