Curator's Take
AI Commentary
This article shows that boron‑nitride nanotubes can host bright, room‑temperature single‑photon emitters across the visible spectrum with lifetimes as short as 0.5 ns—roughly twice as fast as the best hBN flakes reported to date. By packing multiple spectrally distinct emitters along a ~25 nm‑diameter tube and demonstrating that surface coating suppresses blinking, the work offers a compact, multi‑wavelength source that can be positioned deterministically in photonic circuits, addressing a long‑standing bottleneck for scalable quantum key distribution hardware. The results complement recent advances in 2D hBN emitters while sidestepping their integration challenges, though further work will be needed to verify long‑term stability and coupling efficiency in realistic device architectures.
— Mark Eatherly
Summary
Quantum information systems such as quantum key distribution and quantum communications require bright, high-purity, stable sources of single photons to act as carriers of quantum information. As such, methods for obtaining single photon emitters (SPEs) in solid-state devices capable of articulating with quantum photonic circuits are a necessary obstacle that must be overcome. Hexagonal boron nitride (hBN) flakes have been extensively studied as a host material for SPEs, though working in two dimensions is accompanied by engineering complexity. However, dimensionality can be reduced through the implementation of boron nitride nanotubes (BNNTs). Here we investigate the potential of BNNTs as room-temperature SPEs using confocal photoluminescence microscopy and Hanbury Brown-Twiss interferometry. Quantum emitters were found in BNNTs spanning the entirety of the visible spectrum, including spectral regions where SPEs within hBN have not been reported. Furthermore, each tube was found to possess multiple SPEs at varying emission wavelengths along the length, exhibiting lifetimes as fast as 0.5 ns, which is about two-fold faster than the fastest hBN SPEs. Additionally, we demonstrate that surface passivation/coating mitigates blinking events, therefore increasing the emitter stability. Thus, BNNTs can function as a single structure supporting a variety of multiwavelength SPE sources, while maintaining a compact radius of ~25 nm, making them ideally suited for deterministic placement and integration within nanophotonic devices such as waveguides and interferometric filters.