Why can't we feel it around? Maybe it's a gimmick. Today we will decrypt China's leading quantum communication.
The so-called quantum is a unit in physics, that is, the smallest unit that can't be divided. It was discovered by German physicist M Planck, who was the pioneer of quantum mechanics. Together with Einstein, he was called the greatest physicist in the 20th century. He was earlier than Einstein, which inspired Einstein a lot. He was also a man of god.
Planck found that energy is actually discontinuous, but consists of several parts. Quantum is the basic unit, and the quantum of light is called photon. For example, for a laser beam, energy is an integer multiple of photons, and this multiple is the frequency. Newton's classical mechanics can't explain microscopic physical phenomena, but quantum mechanics can. Of course, it is not that the macro is Newtonian mechanics and the micro is quantum, but that the essence of the world is quantum.
But in the microscopic field, people are more likely to feel the existence of quantum. Newton's classical mechanics is a quantum approximation of the macroscopic world in the eyes of quantum physicists. Convenient calculation. For example, the macroscopic superconducting superfluid semiconductor is a classical quantum phenomenon. Therefore, in order to lead the future science and technology, quantum mechanics is a new door at present. To understand quantum communication, we must continue to dig deep into this quantum entanglement.
The most interesting thing about quantum theory is quantum entanglement. No matter how near or far a quantum changes its state, the same quantum will change its state. Einstein called it ghost interaction at a distance. Because quantum entanglement violates the speed limit set by relativity for information transmission. Infinite distances can be connected, but there is an upper limit to the speed of light.
At present, the simplest explanation for quantum entanglement is that there are two electrons A B in a closed box, and the states of the electrons may spin up and down, so there are four situations in the paper box. AB spins up, AB spins down, A spins up, B spins down, A spins down, B spins up, but the electrons have a characteristic. Once they are close enough, they will overlap and become opposite states. If A is topspin, then B will become backspin, no matter how far apart. If you don't observe, it's hard to say which of A and B is screwed up and which is screwed down. This is entanglement. If one side of A or B is observed, the entanglement breaks and becomes two independent electrons.
Many people here think that this can realize long-distance instant communication. Sorry, the current quantum communication still relies on ordinary communication means to transmit prepared entangled photons. Therefore, there is no way to realize the superluminal experience, because people holding B electrons thousands of miles away may see B spinning up and down. There is no way to be controlled by A, so information transmission cannot be realized. The current significance of quantum communication lies in encrypting information. For many industries, confidentiality is more important than speed.
At the end of last century, many sciences were trying to prove quantum entanglement. And unremitting efforts, but most of the experiments are full of loopholes, there is no way to prove, but these scientific experiments laid the foundation of quantum communication, and quantum cryptography flourished.
1995 quantum entanglement communication was successfully practiced in Europe, and the global quantum communication competition began. On the technology of foreign scientists' theoretical research, China scientists took the banner of quantum application, and China scientists found that photons in optical fiber can't amplify quantum communication signals, but the propagation of light in vacuum is unrestricted. So we need a transit satellite.
August 20 16, Jiuquan Satellite Launch Center and Long March II carrier rocket sent Mozi quantum satellite into space. Why Mozi? Because Mozi was the first person to suggest that light travels in a straight line, Mozi satellite can be regarded as an enlarged version of quantum entanglement experiment. The experimental distance reaches 1200 km, and the communication is successful. In other words, two quanta with an interval of 1200 km have realized interaction, and the first quantum communication backbone network-Beijing-Shanghai trunk line has also realized intercontinental quantum communication video conference between 6 o'clock. In addition to the four ground receiving stations in China, four ground receiving stations have been established in Vienna and Graz to share the experimental results with overseas scientists.
The difference between quantum communication and traditional communication is that quantum communication has absolute information security, because quantum is not only inseparable, but also cannot be cloned. Simply put, it is stealing news, and it must be copied first. But once quantum communication is disturbed, it will change its state, that is, collapse. People on both sides will know that their communication is being monitored, such as using quantum entanglement to prepare keys. Once this secret key is monitored, the original key will be declared invalid. The sender of information will naturally not use this set of keys to send ciphertext in a formulaic way, so it is meaningless to steal information. At present, physicists have verified the absolute confidentiality of quantum communication from mathematical logic. Among them, quantum key distribution generates quantum cryptography, which is compatible with binary, and opens the door for the application of quantum communication.
Therefore, China has a quantum satellite in orbit, and has carried out the experiment of star-earth entanglement. It means that China has been at the forefront of the world in the field of quantum communication. However, many scientific and technological powers are basically at a standstill in the field of quantum communication, and will also be at a disadvantage in the future information security in the fields of energy, military and finance. Mozi experiment officially got rid of this risk. For people's livelihood, building a communication network that integrates heaven and earth is more conducive to the safe application of the Internet, navigation and new currency.
Once we break through ftl transmission in the future. The power of quantum is no less than today's semiconductor manufacturing technology. So don't worry, when the quantum world is successfully networked, it will be a leap-forward life experience, not a transition from 4G to 5 G.