Quantum teleportation is a phenomenon in which the quantum states of one particle can be transferred to another, distant particle without anything physical traveling between them. It relies on a property called entanglement, in which measuring the state of one particle immediately affects the state of its entangled partner, regardless of the distance between them.
Writing for the New Scientist, Anil Ananthaswamy explains the phenomenon by employing three hypothetical participants – Alice, Bob and Charlie – with Alice trying to exchange cryptographic keys with Bob.
“First Alice sends a particle (A) to Charlie. Bob, meanwhile, creates a pair of entangled particles (B & C), sends B to Charlie and holds on to C. Charlie receives both A and B, and measures the particles in such a way that it’s impossible to tell which particle was sent by Alice and which by Bob. This so-called Bell state measurement results in the quantum state of particle A being transferred to particle C, which is with Bob.”
Experiments in transferring data via quantum entanglement first started in 1997, culminating in a record distance of information travelling over 143 kilometres of free space between two Canary Islands, which took place in 2012.
Now, however, physicists from Calgary, Canada and Hefei, China had managed to bring the phenomenon out of the lab and into the real world – using fibre optic networks that aren’t used for regular communications, the two teams successfully transferred data over close to 4 and 9 miles, respectively.
In the future, this could lead to inter-city quantum communication networks based on a central quantum computer, or, with the help of quantum repeaters that amplify the signal as it travels over long distances, even networks that span several cities.
“The two experiments can be seen as milestones on the path to a long-term goal, namely to build a fibre-based quantum internet connecting large cities,” says Johannes Kofler of the Max Planck Institute of Quantum Optics in Munich.
Another key use of quantum teleportation is data encryption. For a third party to read two entangled particles would require not only the key, which is sent via the Internet and could conceivably be intercepted, but also the particles themselves.
The breakthrough has been published in two separate papers on September 19 in the journal Nature Photonics.