  We propose that an optically excited heavy hole in a quantum dot can drive
the surrounding nuclear spins into a quiescent collective state, leading to
significantly prolonged coherence time for the electron spin qubit. This
provides a general paradigm to combat decoherence by environmental control
without involving the active qubit in quantum information processing. It also
serves as a unified solution to some open problems brought about by two recent
experiments [X. Xu et al., Nature 459, 1105 (2009) and C. Latta et al., Nature
Phys. 5, 758 (2009)].
