KIPAC Tea: SPIE Conference Recap & Photon detection for cosmology/astrophysics with qubit-based sensors

Talk Abstract: Axion dark matter searches above ~5 GHz face a fundamental obstacle: the standard quantum limit on linear amplification, where quantum noise overwhelms the vanishingly small axion signal. Single microwave photon detectors (SMPDs) sidestep this limit by counting photons and discarding phase information, accelerating haloscope scan rates by orders of magnitude, opening the well-motivated post-inflation axion mass range to practical search. In this talk, I will introduce the SMPD pioneered by the Saclay Quantronics group and now under development at Stanford/SLAC. I will explain how a superconducting qubit can register the arrival of a single itinerant microwave photon, what limits its dark-count rate and efficiency, and how we are tailoring the design for our local axion experiments.