  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.
