  The implementation of fiber-based long-range quantum communication requires
tunable sources of single photons at the telecom C-band. Stable and
easy-to-implement wavelength- tunability of individual sources is crucial to
(i) bring remote sources into resonance, to (ii) define a wavelength standard
and to (iii) ensure scalability to operate a quantum repeater. So far, the most
promising sources for true, telecom single photons are semiconductor quantum
dots, due to their ability to deterministically and reliably emit single and
entangled photons. However, the required wavelength-tunability is hard to
attain. Here, we show a stable wavelength-tunable quantum light source by
integrating strain-released InAs quantum dots on piezoelectric substrates. We
present triggered single-photon emission at 1.55 {\mu}m with a multiphoton
emission probability as low as 0.097, as well as photon pair emission from the
radiative biexciton-exciton cascade. We achieve a tuning range of 0.25 nm which
will allow to spectrally overlap remote quantum dots or tuning distant quantum
dots into resonance with quantum memories. This opens up realistic avenues for
the implementation of photonic quantum information processing applications at
telecom wavelengths.
