Computers and traditional communications encode information in bits, either ones or zeros. In the computers and quantum communications, the qubits, or quantum bits, are used, which can be zeros and ones at the same time. This allows to exponentially increase the processing capacity, allowing to solve problems that are currently impossible.
For example, last year, a Chinese quantum computer managed to do a calculation in 200 seconds for which they would have been late 2.5 billion years with a traditional computer. However, these types of devices are very sensitive to vibrations or small changes in temperature, which can spoil your data. This makes transmitting the signal over long distances more difficult because it degrades more easily.
Quantum communication over fiber optic cables
Fortunately, Toshiba researchers have discovered a way to send these types of signals over long distances using fiber optic cables. To do this, they have developed a new dual-band stabilization technology that sends two optical reference signals together with their own qubits, encoded as a phase delay of a weak optical pulse.
The first reference signal is at a wavelength designed to cancel out fluctuations caused by the environment, while the second is at the same wavelength as the qubits and is used to control the phase of light. Thanks to this, they managed to keep the quantum signal constant at just ten nanometers, allowing the quantum Internet at a distance of more than 600 kilometers of fiber optics.
Reaching this distance means multiply the previous record by six, although it is not the absolute record, since they have been able to carry out satellite retransmissions to more than 1,200 kilometers. However, an Internet of the future with ultra-fast communications will require a combination of fiber and satellite, hence this is good news for both.
QKD: encryption for messages impossible to spy on
The team says that the first use they will make of this technology will probably be to Quantum Key Distribution (QKD), an encryption technique that takes advantage of one of the key fundamentals of quantum physics: that if someone looks at the content or the key of the communication, it changes. For this reason, it would be useless for an attacker to gain access to the information, in addition to the fact that the authorities could identify the attempt to access the information.
Due to the instability of quantum signals over long distances, this type of secure communication had only been done in urban areas a few kilometers apart. With this innovation, it would be possible to connect separate cities hundreds and even thousands of kilometers to each other without having to use intermediary nodes.
Furthermore, quantum communication would offer another advantage: that the latency it is greatly reduced by quantum entanglement, since two particles separated from each other can be distantly entangled. However, transmitting information faster than the speed of light is currently impossible, and it is being investigated whether this would be possible with quantum communications.