With increasing digitization in everyday life, the risk of information "leaking" to an unauthorized user also increases. Various protocols and principles are being developed in order to protect this information and data during the actual transfer from source to destination. One of these technologies is quantum communication, which is based on the foundations of quantum physics, that is, mechanics, and is predicted to have a bright future precisely because of the fact that it is impossible for an unauthorized user to intercept the information in the transmission itself. Quantum communication is a field of applied quantum physics closely related to quantum teleportation and quantum information processing. The most interesting application is the protection of information channels from eavesdropping by an unauthorized user, and this is achieved by applying quantum cryptography. The most developed and well-known application of quantum cryptography is quantum key distribution (QKD). To perform cryptographic tasks or to break cryptographic systems, QKD describes the use of quantum mechanical effects. The working principle of the QKD system is quite simple: two parties, the sender (Alice) and the receiver (Bob) use individual photons that are randomly polarized in a state representing bits 0 and 1 to transmit a series of random numbers that are then used as keys in cryptographic communication. . Both parties are connected to each other by both classical and quantum channels. Alice generates a random stream of qubits that are sent over the quantum channel. When Bob and Alice communicate with each other over the quantum channel — using the classical channel — classical operations are performed to check whether the listener has tried to extract information about the qubit transfer. The presence of an eavesdropper is detected by the imperfect correlation between the two lists of bits obtained after the transmission of the qubit between the sender and the receiver. One important component of practical all-correct encryption schemes is true randomness, which can be easily generated using quantum optics. Applications of quantum communications are in banking, government, industry, military, etc.