Quantum entanglement can be used for communication, but it needs classical channels. Quantum entanglement itself can never be directly used in communication, which is a conclusion rather than a problem to be solved. At present, there is no possibility of superluminal communication, whether it is neutrino, gravitational wave or quantum communication.

Delay calculation

Where g00 is a component of the gravity field scale. The stronger the gravitational field, the greater the delay of coordinate time relative to eigentime. In the formula, R is the unit vector from the observer to the position of signal source, and X is the unit vector from the observer to the position of mass M. ..

After reading the EPR paper, Schrodinger has many ideas. He wrote a letter to Einstein in German, in which he used the term "reverse time" for the first time? Nkung (he translated it as "entanglement") describes the relationship between two temporarily coupled particles in EPR thought experiments, which remains after they are no longer coupled.

Soon after, Schrodinger published an important paper, defined the term "quantum entanglement" and explored related concepts. Schrodinger realized the importance of this concept. He showed that quantum entanglement is not only a very interesting property of quantum mechanics, but also a characteristic property of quantum mechanics. Quantum entanglement makes a complete cut between quantum mechanics and classical thought.

Like Einstein, Schrodinger is not satisfied with the concept of quantum entanglement, because quantum entanglement seems to violate the speed limit set for information transmission in relativity. Later, Einstein even laughed at quantum entanglement as a ghostly action at a distance.

EPR papers have obviously aroused the interest of many physicists and inspired them to explore the basic theory of quantum mechanics. But beyond that, physicists believe that this topic has nothing to do with modern quantum mechanics. After a long time, the physics circle did not pay special attention to this topic, nor did it find any major defects in EPR papers.

EPR thesis attempts to establish the theory of localized hidden variables to replace the theory of quantum mechanics. 1964, john bell's paper shows that the prediction of quantum mechanics for EPR thought experiment is obviously different from the theory of localized hidden variables.

Generally speaking, if the spins of two particles along different axes are measured, the statistical correlation obtained by quantum mechanics is much stronger than that obtained by the theory of localized hidden variables. Bell inequality gives this difference qualitatively, which should be detected by experiments. So physicists have done many experiments to test Bell's inequality. Baidu baike