  In this review, we describe the current landscape of emergent quantum
materials for quantum photonic applications. We focus on three specific
solid-state platforms: single emitters in monolayers of transition metal
dichalcogenides, defects in hexagonal boron nitride, and colloidal quantum dots
in perovskites. These platforms share a unique technological accessibility,
enabling the rapid implementation of testbed quantum applications, all while
being on the verge of becoming technologically mature enough for a first
generation of real-world quantum applications.
  The review begins with a comprehensive overview of the current
state-of-the-art for relevant single-photon sources in the solid-state,
introducing the most important performance criteria and experimental
characterization techniques along the way. We then benchmark progress for each
of the three novel materials against more established (yet complex) platforms,
highlighting performance, material-specific advantages, and giving an outlook
on quantum applications. This review will thus provide the reader with a
snapshot on latest developments in the fast-paced field of emergent
single-photon sources in the solid-state, including all the required concepts
and experiments relevant to this technology.
