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With the advancement of science and technology, humans use the physical effect of quantum transitions to take the frequency of electromagnetic waves radiated by atoms of a substance between specific energy levels as a standard frequency, and use time to derive time, thereby making an "atomic clock". .

The atomic clock is the most accurate clock in the world. Its accuracy depends mainly on the internal structure and motion of the microparticles, and its frequency of construction and motion is extremely stable, so it has a fairly high accuracy. The atomic time measurement standard of China Institute of Metrology has reached 150,000 years of error for 1 second, and the atomic clock of Shaanxi Observatory can reach 300,000 years of error for 1 second, which ranks among the world's first in comparison with the international. Therefore, it is a matter of course that people adopt atomic time as the standard of time.

The atomic clock is the leader of the highest standard of time and frequency with its excellent stability and superior accuracy. The main principle is to use quantum energy level transitions. We often hear on TV: "Quartz technology, world-renowned, leading the world's new trend of watches and clocks." It is the quartz crystal oscillator that helps the atomic clock. It oscillates 5 million times per second and then uses the frequency divider circuit to get a second signal per second. The 60-bit logic circuit is used to obtain the hour, minute, and second signals. This component is called a quartz clock.

In the cesium atomic clock, the frequency of the quartz oscillator is constantly compared with the transition frequency of the helium atom and corrected at any time. Because the frequency of the two is different by 2000 times, it is not easy to directly compare. This requires a special frequency and integrated circuit to increase the frequency of the crystal oscillator by a fixed multiple. This multiple is exactly equal to the frequency ratio of the two, obtained by calculation, and then implemented by the circuit. By comparing the frequency with the frequency of the helium atom transition, the difference is found and a control signal is generated, and the frequency of the quartz crystal oscillator is automatically corrected, and it is "locked" to the helium atomic transition frequency by the circuit system. The crystal oscillator is no longer "free", but is constantly being supervised by the atomic system, resulting in a highly stable atomic clock. How do you "match" the atomic time and the world? Internationally, the time-scale of Coordinated Universal Time is adopted, and its second length conforms to the new second definition, but it is necessary to make its moment close to the world moment through leap seconds. At a certain time, coordinate it by adding one second or one second, commonly known as "leap seconds." The addition and subtraction time is carried out by the International Bureau of Weights and Measures throughout the world, thus unifying World Time and atomic time through satellite and radio waves, called Coordinated Universal Time. (Source: China Metrology Network)