  A future quantum internet is expected to generate, distribute, store and
process quantum bits (qubits) over the globe by linking different quantum nodes
via quantum states of light. To facilitate the long-haul operations, quantum
repeaters, the building blocks for a long-distance quantum network, have to be
operated in the telecom wavelengths to take advantage of both the low-loss
fiber network and the well-established technologies for optical communications.
Semiconductors quantum dots (QDs) so far have exhibited exceptional
performances as key elements, i.e., quantum light sources and spin-photon
interfaces, for quantum repeaters, but only in the near-infrared (NIR) regime.
Therefore, the development of high-performance telecom-band QD devices is
highly desirable for a future solid-state quantum internet based on fiber
networks. In this review, we present the physics and the technological
developments towards epitaxial QD devices emitting at the telecom O- and
C-bands for quantum networks by using advanced epitaxial growth for direct
telecom emission, and quantum frequency conversion (QFC) for telecom-band
down-conversion. We also discuss the challenges and opportunities in the future
to realize telecom QD devices with improved performances and expanded
functionalities by taking advantage of hybrid integrations.
