Existing prototypes of quantum communication systems use the simplest, binary code. One photon is one bit, 1 or 0, which is very easy to implement. But this is a real waste when it comes to advanced and knowledge-intensive systems. No, one photon can fit at least twice as much information, and scientists from the University of Ottawa have proven that the principle of 4D quantum encryption works.
Coding in 4D differs from 2D in that a single photon is assigned a two-bit value. It can be 00, 01, 10 and 11 - a total of four different values. To transfer information, the already familiar quantum states of a photon and the same equipment are used - the encryption algorithms simply change. In addition to a noticeable increase in the data transfer rate, this also promises an increase in the noise immunity of communication lines.
But theory is theory, and what is in practice? Canadian scientists climbed onto the roofs of two buildings at a distance of 300 m and placed laboratory equipment in wooden boxes for at least some protection from the weather. Below the big city was noisy, sparkling and radiated radio waves - the air, to put it mildly, was thoroughly clogged. And so, in such conditions, the 4D quantum encryption system managed to transfer information with a loss level of only 11%, much lower than the permissible maximum.
After processing the data, taking into account all correction methods, the 4D system showed a throughput rate of 1.6 times higher than that of 2D. The next step will be to test the operation of systems with three transmitters at a distance of 5.6 km using adaptive optics. And then the equipment will be installed on a drone or helicopter and try to establish communication with a moving object. And then ... they don't think so far away at the University of Ottawa, although they are infinitely glad of the opening prospects.