  Quantum emitters (QEs) in two-dimensional transition metal dichalcogenides
(2D TMDCs) have advanced to the forefront of quantum communication and
transduction research due to their unique potentials in accessing valley
pseudo-spin degree of freedom (DOF) and facile integration into
quantum-photonic, electronic and sensing platforms via the
layer-by-layer-assembly approach. To date, QEs capable of operating in O-C
telecommunication bands have not been demonstrated in TMDCs. Here we report a
deterministic creation of such telecom QEs emitting over the 1080 to 1550 nm
wavelength range via coupling of 2D molybdenum ditelluride (MoTe2) to strain
inducing nano-pillar arrays. Our Hanbury Brown and Twiss experiment conducted
at 10 K reveals clear photon antibunching with 90% single photon purity.
Ultra-long lifetimes, 4-6 orders of magnitude longer than that of the 2D
exciton, are also observed. Polarization analysis further reveals that while
some QEs display cross-linearly polarized doublets with ~1 meV splitting
resulting from the strain induced anisotropic exchange interaction, valley
degeneracy is preserved in other QEs. Valley Zeeman splitting as well as
restoring of valley symmetry in cross-polarized doublets are observed under 8T
magnetic field. In contrast to other telecom QEs, our QEs which offer the
potential to access valley DOF through single photons, could lead to
unprecedented advantages in optical fiber-based quantum networks.
