Towards Generating Indistinguishable Photons from Solid-State Quantum Emitters at Elevated Temperatures

Indistinguishable photons are a key resource for many optical quantum technologies. Efficient, on-demand single photon sources have been demonstrated using single solid-state quantum emitters, typically epitaxially grown quantum dots in III-V semiconductors. To achieve the highest performance, these sources are typically operated at liquid helium temperatures ($\sim 4~\mathrm{K}$), introducing significant significant size, weight and power (SWAP) considerations that are often impractical for emerging applications such as satelite quantum communications. Here we experimentally verify that coupling a solid-state emitter to a photonic nanocavity can greatly improve photon coherence at higher temperatures where SWAP requirements can be much lower. Using a theoretical model that fully captures the phonon-mediated processes that compromise photon indistinguishability as temperature increases, we reproduce our experimental results and demonstrate the potential to further increase the operating temperature in future generations of optimised devices.