  A practical way to link separate nodes in quantum networks is to send photons
over the standard telecom fibre network. This requires sub-Poissonian photon
sources in the telecom wavelength band around 1550 nm, where the photon
coherence time has to be sufficient to enable the many interference-based
technologies at the heart of quantum networks. Here, we show that droplet
epitaxy InAs/InP quantum dots emitting in the telecom C-band can provide
photons with coherence times exceeding 1 ns even under non-resonant excitation,
more than a factor two longer than values reported for shorter wavelength
quantum dots under similar conditions. We demonstrate that these coherence
times enable near-optimal interference with a C-band laser qubit, with
visibilities only limited by the quantum dot multiphoton emission. Using
entangled photons, we further show teleportation of such qubits in six
different bases with average fidelity reaching 88.3$\pm$4%. Beyond direct
applications in long-distance quantum communication, the high degree of
coherence in these quantum dots is promising for future spin based telecom
quantum network applications.
