Ten years of lab work paid off in a single experiment. An international team of researchers has teleported the polarization state of a single photon from one quantum dot to another physically separate one, using a 270-meter free-space optical link. It is the first time quantum teleportation has been achieved between two independent quantum emitters, and the results were published in the journal Nature Communications.
The experiment was led in part by researchers at Paderborn University in Germany, working alongside a team at the Sapienza University of Rome. Doctoral and postdoctoral researchers at Paderborn spent roughly a decade on optical measurements, data analysis, and evaluation before the milestone was reached.
Quantum teleportation does not move matter. What travels is information — specifically, the quantum state of a particle. In this case, the polarization state of one photon was transferred to another photon at a separate location. The two photons were never the same particle, but through quantum entanglement, the properties of one were effectively reproduced in the other across a meaningful distance.
That distinction matters. Previous experiments in quantum teleportation had used photons originating from the same source. Getting the effect to work between two entirely independent quantum emitters is a harder problem, and solving it removes a major obstacle on the path to scalable quantum networks.
Professor Klaus Jöns, who leads the Hybrid Photonics Quantum Devices research group at Paderborn and sits on the board of the Institute for Photonic Quantum Systems, explained why independent emitters are essential. "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," he said.
Quantum relays are roughly analogous to signal repeaters in conventional fiber-optic networks. They extend the range over which quantum information can be transmitted without losing integrity. Without them, a practical quantum internet — capable of transmitting information with theoretically unbreakable encryption — remains out of reach. This experiment shows that semiconductor quantum dots could serve as the hardware foundation for those relays.
Entanglement is what makes the whole system work. When particles are entangled, measuring or manipulating one instantly affects the other, regardless of the distance between them. In quantum communication, this property allows information to be encoded across multiple particles simultaneously, creating security advantages that classical encryption cannot match. Any attempt to intercept the signal disrupts the entanglement and reveals the intrusion.
The 270-meter free-space link used in this experiment is modest by the standards of a global network, but it demonstrates the principle with independent devices rather than a controlled single-source setup. Researchers describe it as proof that quantum light sources based on semiconductor quantum dots are viable for real-world quantum communication infrastructure.
The collaboration between Paderborn and Rome reflects how long and technically demanding the road to this result was. A decade of foundational work preceded the breakthrough, and the team now looks toward more complex systems. Quantum relays built on this approach could eventually connect distant nodes across cities or between countries, forming the backbone of a communications network secured by the laws of physics rather than computational difficulty alone.
