Environment-assisted quantum control of a solid-state spin via coherent dark states

Abstract

The interaction of a quantum system with its surroundings is usually detrimental, introducing decoherence. Experiments now show how such interactions can be harnessed to provide all-optical control of the spin state of a quantum dot. Understanding the interplay between a quantum system and its environment lies at the heart of quantum science and its applications. So far most efforts have focused on circumventing decoherence induced by the environment by either protecting the system from the associated noise1,2,3,4,5 or by manipulating the environment directly6,7,8,9. Recently, parallel efforts using the environment as a resource have emerged, which could enable dissipation-driven quantum computation and coupling of distant quantum bits10,11,12,13,14. 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 feedback15,16, to other systems interacting with an adiabatically evolving environment.