  Long-distance quantum communication relies on the ability to efficiently
generate and prepare single photons at telecom wavelengths. In many
applications these photons must also be indistinguishable such that they
exhibit interference on a beamsplitter, which implements effective
photon-photon interactions. However, deterministic generation of
indistinguishable single photons with high brightness remains a challenging
problem. We demonstrate two-photon interference at telecom wavelengths using an
InAs/InP quantum dot in a nanophotonic cavity. The cavity enhances the quantum
dot emission, resulting in a nearly Gaussian transverse mode profile with high
out-coupling efficiency exceeding 36% after multi-photon correction. We also
observe Purcell enhanced spontaneous emission rate up to 4. Using this source,
we generate linearly polarized, high purity single photons at 1.3 micron
wavelength and demonstrate the indistinguishable nature of the emission using a
two-photon interference measurement, which exhibits indistinguishable
visibilities of 18% without post-selection and 67% with post-selection. Our
results provide a promising approach to generate bright, deterministic single
photons at telecom wavelength for applications in quantum networking and
quantum communication.

Quantum Physics;Optics