Optically active spins in van der Waals materials and devices

Layered materials offer a singular, versatile platform for the development of quantum communication and sensing applications based on optically addressable spins. Insulating and semiconducting layered materials host optically addressable spins that can be created via top-down and bottom-up approaches, and recent advances with photonic and electronic devices can achieve in situ manipulation of their optical and spin transitions. Combined with the large variety of naturally occurring and artificially synthesized layered materials, van der Waals (vdW) materials provide extensive opportunities, from novel defect engineering to scalable device engineering. However, challenges include identification of the microscopic configuration of the atomic and electronic structures that give rise to optically addressable spins in these materials, as well as achieving the desired level of reproducibility at defect, material, and device levels simultaneously. Here, we present an overview of the recent advances in these areas, including a discussion of the microscopic origin of some of the quantum emitters in vdW materials, as well as strategies toward developing functional devices based on these systems.