  Understanding the interplay between a quantum system and its environment lies
at the heart of quantum science and its applications. To-date most efforts have
focused on circumventing decoherence induced by the environment by either
protecting the system from the associated noise or by manipulating the
environment directly. Recently, parallel efforts using the environment as a
resource have emerged, which could enable dissipation-driven quantum
computation and coupling of distant quantum bits. Here, we realize the optical
control of a semiconductor quantum-dot spin by relying on its interaction with
an adiabatically evolving spin environment. The emergence of hyperfine-induced,
quasi-static optical selection rules enables the optical generation of coherent
spin dark states without an external magnetic field. We show that the phase and
amplitude of the lasers implement multi-axis manipulation of the basis spanned
by the dark and bright states, enabling control via projection into a
spin-superposition state. Our approach can be extended, within the scope of
quantum control and feedback, to other systems interacting with an
adiabatically evolving environment.
