Two independent research teams came to the same result, successfully demonstrating the teleportation of cutrite, a three-part unit of quantum information. This is an important achievement in quantum communication, which so far has only dealt with qubits.
The phrase “quantum teleportation” is associated with the science fiction series “Star Trek”, where it was possible to move large-sized objects and even living things over long distances. In reality, everything is not so convenient and large-scale: the states of two entangled particles, for example, the electron’s spin, move. Even if two entangled electrons are at a great distance from each other, manipulations with one cause instant changes in the other. This technology can be used for secure communication.
The first – in April – a physicist from the University of Science and Technology of China (USTC) under the supervision of Guang-Can Guo conducted an experiment on teleportation of kutrites, but publication was later. At the end of June, another team led by Anton Zeilinger of the Austrian Academy of Sciences and Jian-Wei Pan of USTC announced their results in an article published in the journal Physical Review Letters.
Pan, Zeilinger and their colleagues conducted an experiment on quantum communication with the Chinese Mo-tzi satellite at the longest distance – 7600 km in 2017. Two photons were sent to Austria and China, where scientists were able to create an unbreakable password with which they made a secure video call. Any attempt to intervene would leave a noticeable mark, Scientific American writes.
Scientists tried to teleport and more complex states of particles. In 2015, Pan’s associates were able to send two states of a photon: its spin and orbital angular momentum. However, each of these states was binary — the system was still working with qubits. So far, scientists have not teleported more complex conditions.
The classic bit can be either “0” or “1”. Quantum can combine “0” and “1” – that is, be in a superposition of both states. Classic trit is “0”, “1” or “2”, while coutrit is a superposition of all three states. Therefore, they are much more difficult to create.
To create cutrites, both teams used complex optical systems from lasers, beam splitters and barium borate crystals, and then confused the two resulting smokes together. The task was not easy, since light rarely interacts with itself.
Finally, they had to confirm the intricacies of the kutrits with the help of the so-called “Bell state”. This is the condition under which particles are as entangled as possible. It is necessary to understand the exact condition of Bell’s kutrits in order to extract information from them and prove that it was transmitted with high accuracy.
In this last paragraph, the two teams disagree. Guo’s group is convinced that their result is enough to find the experiment successful. A group of Pan and Zeilinger claims that the Chinese colleagues could not achieve a sufficient value for Bell’s condition.
However, both teams agree that they all managed to teleport kutrit, and both have plans to move on: to quartquarts and even more complex particles.