What is the basic principle of quantum communication?

Quantum communication refers to a new communication mode that uses quantum entanglement effect to transmit information. Quantum communication is a new interdisciplinary subject developed in recent twenty years, and it is a new research field combining quantum theory with information theory. Quantum communication mainly involves: quantum cryptographic communication, quantum teleportation and quantum dense coding.

Optical quantum communication is mainly based on quantum entangled state theory, and information transmission is realized by quantum teleportation (transmission). According to the experimental verification, no matter how far apart two entangled particles are, as long as one of them changes, the other will change instantly. The process of realizing optical quantum communication by using this characteristic is as follows: a pair of entangled particles are constructed in advance, and the two particles are placed on both sides of the communication to jointly measure the unknown particles and the particles of the sender (an operation), and the particles of the receiver will collapse (change) instantly. Collapse (change) is a state that is symmetrical with the state of the sender's particles after collapse (change), and then the information of joint measurement is transmitted to the receiver through the classical channel, and the receiver performs unitary transformation (equivalent to inverse transformation) on the collapsed particles according to the received information, so that the unknown quantum state exactly the same as that of the sender can be obtained.