https://phys.org/news/2018-11-closer-complex-quantum-teleportation.html

The idea behind it is simple: Instead of just increasing the number of particles involved, the complexity of each system is increased. "The special thing about our experiment is that for the first time, it entangles three photons beyond the conventional two-dimensional nature," explains Manuel Erhard, first author of the study. For this purpose, the Viennese physicists used quantum systems with more than two possible states—in this particular case, the angular momentum of individual light particles. These individual photons now have a higher information capacity than qubits. However, the entanglement of these light particles turned out to be difficult on a conceptual level. The researchers overcame this challenge with a groundbreaking idea: a computer algorithm that autonomously searches for an experimental implementation.

With the help of a computer algorithm called Melvin, the researchers found an experimental setup to produce this type of entanglement. At first, this was very complex, but it worked in principle. After some simplifications, the physicists still faced major technological challenges. The team was able to solve these with state-of-the-art laser technology and a specially developed multi-port. "This multi-port is the heart of our experiment, and combines the three photons so that they are entangled in three dimensions," explains Manuel Erhard.