Engineering quantum light emission from color-centers in atomically thin crystals with phase gradient metasurfaces.

Single-photon sources are elementary building blocks for photonic quantum technologies. However, progress in photonic quantum technologies has been constrained due to a lack of suitable materials with desired optical properties and the challenges in achieving coherent light-matter interaction at the quantum level. Here, we report a new approach for building chip-scale quantum hardware with color-centers in wide bandgap materials, such as hexagonal boron nitride (hBN), interfaced with planar arrays of classical nanoantennas, also known as metasurfaces. We investigated both exfoliated and chemical vapor grown hBN samples at room temperature. We performed photon-photon correlation measurements to isolate centers with single-photon emission characteristics and designed a phase gradient metasurface such that the emission from these color-centers can be efficiently extracted as well as redirected along a preferred direction. Our approach of interfacing these bright emitters with photonic metasurfaces and manipulating their emission characteristics would enable new opportunities for on-chip quantum photonics.