Austrian and Chinese professors were able to communicate by the method of quantum communication.
On Friday, September 29, the presidents of the Austrian and the Chinese Academy of Sciences held the first session of transcontinental communication, the encryption key which is distributed using the methods of quantum cryptography.
During the experiment, set a new distance record for quantum communication over 7400 kilometers, which is shared by Vienna and Beijing. The key instrument used was the companion of Mo zi (Micius, QUESS), famous for the first successful teleportation of the quantum state of particles on Earth orbit.
In the first stage of the experiment using quantum techniques generate a secret key between the satellite and Observatory near Vienna. Then the other key was created between the satellite and Beijing. In the last step the two keys are combined on the satellite and is distributed between cities.
In the future, similar conversations will be held between China and Russia, Germany, Italy and Singapore.
Quantum key distribution is a special method of generation of secret key between sender and recipient information, which makes the interception impossible.
The sender creates a single photon in a random state, which encodes either zero or a unit in a randomly chosen measurement method. For example, vertical and horizontal polarization encode the zero and one in one measurement method, and the two diagonal polarizations correspond to zero and one in the other measurement method. Then the receiver randomly chooses a measurement method of state of a photon.
At the last stage the participants of communication exchange selected methods of cooking and measurement conditions, and if they match, the received bit is written in the secret key encryption. Any attempt of a third party listening to the polarization of a photon will lead to irreversible change in its status, the sender and the receiver detects errors in a partial reconciliation key.
In ground quantum key distribution is limited to the loss of single photons in the environment — for example, in the optical fiber. Therefore limit the transmission distance of the signal — about a hundred kilometers. This distance can be increased using a less “noisy” environment, such as outer space.