Quantum Enhancement of Multi-cavity Axion Haloscopes*

The search for axions as the dark matter has intensified over the past several years. This has led to a plethora of experimental proposals and new aiding technologies, which is necessary given the poorly predicted axion mass. For a search to cover a significant range of possible axion masses at benchmark DFSZ sensitivity is a daunting task, as has proven to be the case for even the most successful experimental technique thus far, the cavity haloscope, where coverage is being measured in decades-per-octave. This so-called scan speed problem has produced a pressure on readout technology to accelerate searches, where quantum devices have already played a prominent role as amplifiers. The role of quantum technology is set to expand in the upcoming years, with studies of squeezing and state swapping for single cavity haloscopes already underway, and the possibilities for quantum enhanced readout becoming much broader when considering the next generation of axion haloscopes using multiple cavities. This talk presents opportunities for upcoming multi-cell searches such as ADMX Run 2 and ADMX-EFR to significantly improve their sensitivity through quantum enhanced readout, including through the preparation of multi-mode entangled states and the observation of many-body Bose signatures embedded in the ambient axion field.