Integrated circuits that process information encoded in individual quantized states of the electromagnetic field are poised to revolutionize information processing, communications, and sensing technologies. An emerging class of such quantum technologies is based on solid-state, on-demand single-photon emitters (SPEs) coupled to optical resonators and waveguides that serve as building blocks for high-density, on-chip quantum circuits (1). To date, the most investigated solid-state SPE systems are epitaxial quantum dots (QDs) that operate primarily at cryogenic temperatures, and color centers in solids. A noteworthy example of the latter is the nitrogen vacancy defect (NV-center) in diamond, which has become a standard for the myriad quantum optics experiments and inspired numerous studies of SPEs (2).
Despite years of research, the existing systems remain inadequate for real-world applications, and the search is on for high-performance emitters hosted by materials that enable integration in solid-state, on-chip devices. In 2015, the SPE playground expanded abruptly with the discovery of cryogenic quantum emitters in two-dimensional (2D) materials (3). In 2016, hexagonal boron nitride (hBN) emerged as a compelling 2D host of SPEs that operate at room temperature (4). The hBN system is somewhat analogous to diamond because it has a wide bandgap of ∼6 eV and can host a broad range of deep trap defects that act as ultrabright, photostable, room-temperature SPEs. However, hBN has the advantage of being atomically thin and therefore offers new possibilities for scientific exploration and device engineering.
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