# Quantum-dot based telecom-wavelength quantum relay

## TL;DR

This paper demonstrates a quantum relay using a semiconductor quantum dot emitting entangled photon pairs at telecom wavelengths, achieving high fidelity and robustness, advancing practical quantum communication networks.

## Contribution

First implementation of a telecom-wavelength quantum relay with a semiconductor quantum dot source, showing high fidelity and robustness for quantum communication.

## Key findings

- Maximum fidelity of 94.5% for 4-state protocol
- Operation with arbitrary pure input states, gate fidelity 83.6%
- Compatibility with existing communication infrastructure

## Abstract

The development of quantum relays for long haul and attack-proof quantum communication networks operating with weak coherent laser pulses requires entangled photon sources at telecommunication wavelengths with intrinsic single-photon emission for most practical implementations. Using a semiconductor quantum dot emitting entangled photon pairs in the telecom O-band, we demonstrate for the first time a quantum relay fulfilling both of these conditions. The system achieves a maximum fidelity of 94.5 % for implementation of a standard 4-state protocol with input states generated by a laser. We further investigate robustness against frequency detuning of the narrow-band input and perform process tomography of the teleporter, revealing operation for arbitrary pure input states, with an average gate fidelity of 83.6 %. The results highlight the potential of semiconductor light sources for compact and robust quantum relay technology, compatible with existing communication infrastructures.