Near-coherent quantum emitters in hexagonal boron nitride with discrete polarization axes

Hexagonal boron nitride (hBN) is a 2-dimensional material that has recently gained attention as a solid-state host of quantum emitters. In particular, the recently discovered B centers show promise for integration in scalable photonic quantum technologies thanks to site-specific defect generation, a reproducible wavelength of 436nm, and room temperature emission. In this work, we perform spectroscopic measurements to characterize such emitters, revealing near lifetime-limited homogeneous linewidths as narrow as 150 MHz for individual emitters and ensembles. Our results constitute an important milestone towards the implementation of hBN quantum emitters in integrated quantum photonics.