Quantum Dot Source generates triggered polarization-entangled Photon Pairs with high Coincidence Rates, Fidelities, and Single-Photon Purity –
Many concepts for future Quantum Networks rely on the distribution of entangled qubits between spatially separated nodes. Photons are particularly well suited as information carriers, as they can transmit over long distances at the speed of light. Photonic entanglement represents a key resource for a wide range of Quantum Communication Applications and also plays a crucial role in Quantum Repeaters, which help to compensate for transmission losses in long-distance networks. The scalability of such networks strongly depends on the availability of efficient sources of entangled photons. While established approaches based on spontaneous parametric down-conversion (SPDC) generate photon pairs only probabilistically, deterministic Quantum Emitters promise significantly higher efficiency and improved scalability.
Semiconductor Quantum Dots are considered a particularly promising platform, as they can naturally generate entangled photon pairs. While Quantum Dots operating in the near-infrared have already demonstrated excellent performance, the development of efficient sources in the telecom C-band – crucial for fibre-based communication networks – remains a challenge. Against this background, researchers from the QR.N consortium at the Stuttgart, Würzburg, and Karlsruhe sites published a paper in Advanced Quantum Technologies in late June 2026.
In the paper, the researchers present a Quantum Dot Source for polarization-entangled photon pairs in the telecom band. The source is based on InAs Quantum Dots integrated into a planar cavity structure. In contrast to other resonator concepts, this approach provides high structural symmetry and thus robust conditions for the generation of entangled photons. Using resonant two-photon excitation, the experiment yields entangled photon pairs with high brightness, high entanglement fidelity, and excellent single-photon purity. These results extend the current state of the art in quantum dot-based sources of entangled photons in the C-band and represent an important step towards efficient photonic components for future Quantum Networks.
