Quantum teleportation over 143km smashes distance record

This month, two major studies on quantum teleportation have made it through peer review and been published, breaking previous distance records. Chinese scientists report teleporting photons over 97km and now a team working in the Canaries report doing the same thing, but between the islands — a distance of over 140km. Both experiments were completed earlier this year and have now been published in Nature.

The researchers from the Austrian Academy of Sciences, and the University of Vienna, say their work paves the way for global quantum communications.

Lead scientist Anton Zeilinger said: "Our experiment shows how mature quantum technologies are today and how useful they can be for practical applications. The next step is satellite-based quantum teleportation, which should enable quantum communication on a global scale."

Quantum teleportation is not a physical process as we would normally understand it. Even calling it 'sending' information is misleading, but language can only do so much.

Quantum entanglement

To understand what is going on, first we need to understand entanglement. This is the property that occurs when two or more quantum bits are linked together in such a way that whatever happens to one of them will produce an immediate change in the other. Often, these pairs are made by splitting a single photon into two, creating an entangled pair.

The idea is that we could use very distant entangled photons to send information over very long distances, securely and instantly, thus building a quantum internet. But making that work is harder than writing it down.

Generally, quantum communication is run through familiar optical fibre. But in this case, the distance was so great that the signal loss would be "too severe", according to the researchers. Instead, the team used lasers to send photons directly through the atmosphere.

Xiao-song Ma, one of the scientists involved in the experiment, said: "The realisation of quantum teleportation over a distance of 143km has been a huge technological challenge."

"An important step for our successful teleportation was a method known as 'active feed-forward', which we have used for the first time in a long-distance experiment. It helped us to double the transfer rate".

This method involves the researchers in sending conventional data alongside the quantum information, which enables the recipient to decipher the transferred signal more efficiently.

Zeilinger adds that his research team is now working with colleagues at the Chinese Academy of Sciences to design and develop a quantum satellite mission.