Environment-assisted quantum control of a solid-state spin via coherent   dark states
  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. 
Jack Hansom, Carsten H. H. Schulte, Claire Le Gall, Clemens   Matthiesen, Edmund Clarke, Maxime Hugues, Jacob M. Taylor and ...
quant-ph cond-mat.mes-hall