  Acceptor dopant atoms in silicon have recently been identified as compelling
candidates for spin-based quantum technologies. Interest in acceptor qubits
ultimately derives from the properties of acceptor bound holes, where
spin-orbit coupling quantizes total angular momentum $J=3/2$ rather than spin,
endowing them with quadrupolar couplings to electric and elastic fields. This
property of single-atom acceptor qubits makes them amenable to electric control
and coupling over long distances using phonon, capacitive, or microwave photon
mediated interactions. Accepted as a contribution within a roadmap for quantum
technologies, this section reviews progress on single-acceptor devices,
observation of ultra-long coherence times of acceptors in isotope purified
silicon, and comments on future challenges in single qubit measurement, long
distance coupling, and scalable acceptor-spin-based technologies.
