Quantum Science and the Search for Axion Dark Matter

The dark matter puzzle is one of the most important open problems in modern physics. The ultra-light axion is a well-motivated dark matter candidate, conceived to resolve the strong-CP problem of quantum chromodynamics. Numerous precision experiments are searching for the three non-gravitational interactions of axion-like dark matter. Some of the searches are approaching fundamental quantum limits on their sensitivity. This Perspective describes several approaches that use quantum engineering to circumvent these limits. Squeezing and single-photon counting can enhance searches for the axion-photon interaction. Optimization of quantum spin ensemble properties is needed to realize the full potential of spin-based searches for the electric-dipole-moment and the gradient interactions of axion dark matter. Several metrological and sensing techniques, developed in the field of quantum information science, are finding natural applications in this area of experimental fundamental physics.