Symmetry-guided search of novel quantum emitters: the role of spatial and spin degrees of freedom

Recent material growth technologies provide control over individual atoms in crystals, allowing us to explore a huge spectrum of materials with applications for quantum technologies, including sensing, communication, and information processing. In these systems, degrees of freedom that have been historically considered detrimental – like spin-orbit coupling and coupling to nuclear-spin-rich environments – can bring forward additional functionality and flexibility in performance. For this reason, this quest for novel engineered materials for quantum-optical applications demands an understanding of the role of different degrees of freedom for the quantum-mechanical behaviour of electrons in these systems.

In this talk, I will show how the combination of material symmetries and spin degrees of freedom can lead to localized spins that are stable, controllable, and optically accessible. This insight is brought forward by our results based on optical and microwave spectroscopy of point defects in silicon carbide and hexagonal boron nitride, where the spin and photo-physical behaviour are determined by non-trivial combinations of spin and spatial degrees of freedom.

Our results show that quantum emitters in solids offer more engineering choices and spread of performance than typically expected, even after 20 years of work on related systems. Relating the microscopic structure of these defect centres to the relevant figures of merit for quantum application allows us to understand seemingly unintuitive results, and to predict how related systems will behave. These approaches may enable engineering of novel and application-specific emitters.