  Ultracompact chip-integrated single-photon sources of collimated beams with
polarizationencoded states are crucial for integrated quantum technologies.
However, most of currently available single-photon sources rely on external
bulky optical components to shape the polarization and phase front of emitted
photon beams. Efficient integration of quantum emitters with beam shaping and
polarization encoding functionalities remains so far elusive. Here, we present
ultracompact single-photon sources of linearly polarized vortex beams based on
chip-integrated quantum emitter-coupled metasurfaces, which are meticulously
designed by fully exploiting the potential of nanobrick arrayed metasurfaces.
We first demonstrate on-chip single-photon generation of high-purity linearly
polarized vortex beams with prescribed topological charges of -1, 0, and +1. We
further realize multiplexing of single-photon emission channels with orthogonal
linear polarizations carrying different topological charges and demonstrate
their entanglement. Our work illustrates the potential and feasibility of
ultracompact quantum emitter-coupled metasurfaces as a new quantum optics
platform for realizing chip-integrated high-dimensional single-photon sources.
