This achievement is a key step for future quantum communication networks. In the experiment, researchers used a 270m free-space optical link to connect the systems. The findings have been published in the journal Nature Communications.

A Decade of Collaboration Pays Off

At Paderborn University, doctoral and postdoctoral researchers spent about ten years working on optical measurements, data analysis, and evaluation. During this time, Professor Klaus Jöns's group collaborated closely with a team led by Professor Rinaldo Trotta at the Sapienza University of Rome.

"The experiment impressively demonstrates that quantum light sources based on semiconductor quantum dots could serve as a key technology for future quantum communication networks. Successful quantum teleportation between two independent quantum emitters represents a vital step towards scalable quantum relays and thus the practical implementation of a quantum internet," explained Professor Jöns, head of the 'Hybrid Photonics Quantum Devices' research group and a member of the board of the Institute for Photonic Quantum Systems (PhoQS) at Paderborn University.

Why Entanglement Matters for Quantum Communication

Entangled systems made up of multiple quantum particles offer major advantages for communication technologies. Instead of relying on a single state determined by one photon, these systems create interconnected states across multiple particles. This approach is essential for applications in secure communication, data processing, and quantum computing.

Entanglement links specific properties of photons, allowing them to share information. A state represents a unit of information being processed. "Previously, these photons came from one and the same source, i.e. the same emitter. Although there has been significant process made in recent years, using distinct quantum emitters to implement a quantum relay between independent parties had previously remained out of reach," Professor Jöns noted.

Long-Term Strategy and Advanced Technology

About ten years ago, Professors Jöns and Trotta outlined a plan for using quantum dots as sources of entangled photon pairs in communication and teleportation systems. Their latest success confirms that this long-term approach has worked.

"This result shows that our long-term strategic planning has paid off," Professor Jöns said, adding: "The combination of excellent materials science, nanofabrication and optical quantum technology was the key to our success."

Europe-Wide Collaboration Enables Precision Results

The breakthrough relied on contributions from several research centers across Europe. Quantum dots were precisely engineered at Johannes Kepler University Linz, while resonator nanofabrication was carried out by partners at the University of Würzburg. The teleportation experiments themselves took place at Sapienza University of Rome, where scientists connected two buildings using a 270m free-space optical link.

The system used GPS-assisted synchronization, ultra-fast single photon detectors, and stabilization methods to counter atmospheric turbulence. The achieved teleportation state fidelity (i.e. the quality in which quantum states are preserved during teleportation) reached up to 82 ± 1%, exceeding the classical limit by more than 10 standard deviations.

Next Step: Building a Quantum Relay

This accomplishment opens the door to the next goal, demonstrating 'entanglement swapping' between two quantum dots. Achieving this would create the first quantum relay using two deterministic sources of entangled photon pairs. Deterministic sources can reliably produce single photons almost on demand, although developing them has been a major challenge.

Parallel Advances Strengthen Quantum Research

At nearly the same time, another research team from Stuttgart and Saarbrücken reported a similar achievement using frequency conversion. Together, these results mark an important milestone for quantum research in Europe and bring the vision of a functional quantum internet closer to reality.