NPA Seminar: Karl van Bibber, UC Berkeley, “ALPHA – A Search for the Post-Inflation Axion”

The axion represents both the most natural solution to the Strong-CP problem and a compelling candidate to constitute the dark matter of the Universe. The most sensitive experiments searching for axion dark matter are based on the resonant conversion of axions to photons within a microwave cavity permeated by a magnetic field. The HAYSTAC experiment at Yale has pioneered much technology for the axion haloscope, including the first and to date only use of a squeezed-state receiver circumventing the Standard Quantum Limit to search for the extraordinarily weak signal, expected to be on the order of 10–24 Watt.
Recent simulations for axion production in one cosmological scenario predict its mass to be at much higher frequencies than current experiments, in the 10-50 GHz range, where a new paradigm for the microwave resonator will be required. Such an innovation has recently been proposed in the form of a metamaterial whose plasma frequency can be engineered and tuned, and can be fabricated in arbitrarily large volumes. A new experiment will be constructed and operated in the Wright Lab based on the promising R&D of wire-medium metamaterials and parallel developments in higher frequency quantum amplifiers, by an international collaboration ALPHA. This talk will also venture into the exciting physics program that will begin upon discovery of the post-inflation axion.