Analysis of single-photon and linear amplifier detectors for microwave cavity dark matter axion searches

We show that at higher frequencies, and thus higher axion masses, single-photon detectors become competitive and ultimately favored, when compared to quantum-limited linear amplifiers, as the detector technology in microwave cavity experimental searches for galactic halo dark matter axions. The crossover point in this comparison is of order 10 GHz (similar to 40 mu eV), not far above the frequencies of current searches.