Quite a lot of research has already been done on the topic of quantum signal transmission, and even successful tests of this technology have been carried out. However, with all the potential advantages of quantum computers and a quantum information network, they have a significant drawback: a specific unit of information transfer (qubit), for which you need to lay your own communication lines from scratch. But a group of researchers from the Netherlands has made significant progress in this area and managed to use ordinary optical fiber to transmit qubits.
To begin with, let's recall what a qubit is and why it is so good. The name qubit comes from the merger of the words "quantum" and "bit". In other words, the same bit that is used in the classical data transmission system, but it differs in that it has the property of quantum entanglement. And this, if not going into details, allows him to perform an extremely large amount of calculations and transfer data at such speeds that ordinary modern technology never dreamed of.
So, in the course of a series of studies, a group of scientists from the University of Groningen has found a way to create qubits whose radiation is close to the wavelength of light, which allows information to be transmitted using optical fiber. To achieve these results, scientists have created special crystals of silicon carbide with color centers of molybdenum. These centers were irradiated with lasers. After such an impact, the electrons on the outer shell of molybdenum atoms move to a higher energy level, and when they return back, they emit energy in the form of a photon. Further, the experts used a method called Coherent Population Trapping (CPT), which allows creating a superposition of atoms when exposed to two resonant optical fields. As a result of the above actions, it was possible to create a qubit,in which the superposition is maintained for a long time and it emits photons of a certain wavelength.
According to Quantum Information, qubits created at the university transmit information at a wavelength of 1,100 nanometers. In this case, the most commonly used wavelengths for fiber optic networks are 850, 1300, 1310 and 1550 nanometers, but 1100 nanometers is used, unfortunately, extremely rarely. But according to experts, even this is already a big breakthrough and they have come close to creating qubits "operating at waves of 1300 and 1500 nanometers in length."
Vladimir Kuznetsov