Complex quantum teleportation achieved for the first time

For the first time, Austrian and Chinese researchers have successfully teleported three-dimensional quantum states. Future quantum computers could rely heavily on high-dimensional teleportation.

What was previously merely a theoretical possibility has been empirically shown by researchers from the University of Vienna and Austrian Academy of Sciences. They have been successful in teleporting intricate high-dimensional quantum states along with quantum physicists from the University of Science and Technology of China. This global first is reported by the study teams in the journal Physical Review Letters.

In their investigation, the scientists transferred a photon's quantum state from one faraway photon to another. The only two-level states ("qubits") that have previously been conveyed were "0" or "1" values. However, the researchers were able to transport a three-level state, known as a "qutrit". In contrast to traditional computer science, "0" and "1" are not a "either/or" in quantum physics; they can exist concurrently or in any combination. This has recently been proved in practice by the Austrian-Chinese team using a third option, "2".

new experimental technique

Theoretically feasible multidimensional quantum teleportation has been known since the 1990s. But first, according to Manuel Erhard of the Vienna Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences, "we had to design an experimental method for implementing high-dimensional teleportation, as well as to develop the necessary technology."

The potential routes a photon can travel are programmed with the quantum state that needs to be transported. These routes can be seen as three optical cables. Most intriguingly, a single photon may really exist simultaneously in all three optical fibers according to quantum physics. The team developed a novel experimental technique to transport this three-dimensional quantum state. The so-called Bell measurement is the essential component of quantum teleportation. It is based on a multiport beam splitter, which joins all optical fibers by routing photons through a number of inputs and outputs. The researchers also utilized supplementary photons, which can interfere with other photons and are also fed into the multiple beam splitter.

Without the two photons ever physically touching, the quantum information may be transmitted to another photon distance from the input photon by carefully choosing specific interference patterns. As Erhard underlines, the experimental notion is not restricted to three dimensions and may theoretically be expanded to any number of dimensions.

increased information capacity for quantum computers

As high-dimensional quantum systems can carry more information than qubits, the worldwide research team has also taken a significant step toward real-world applications like a potential quantum internet. The creative potential of the new approach is highlighted by Anton Zeilinger, a quantum physicist at the Austrian Academy of Sciences and the University of Vienna. "This result could help to connect quantum computers with information capacities beyond qubits," he adds.

The involved Chinese researchers think multidimensional quantum teleportation has a lot of potential. According to Jian-Wei Pan of the University of Science and Technology of China, "the fundamentals for the next-generation quantum network systems are based on our foundational research today. On the request of the University of Vienna and the Academy, Pan recently gave a lecture in Vienna.

Future research by quantum physicists will concentrate on how to apply their newly acquired understanding to enable the teleportation of an atom or photon's whole quantum state.