Scientists from the Joint Astrophysical Laboratory (JILA), jointly established by the National Institute of Standards and Technology (NIST) and the University of Colorado Boulder, have successfully developed the most accurate atomic clock known to date. This atomic clock not only provides precise timing, but also helps with precise navigation over a wide spatial range and can search for new particles. The relevant paper has been accepted by the latest issue of the Physics Review Letters magazine. The Physicist Organization Network reported earlier this month that as the accuracy of atomic clocks continues to improve, they will demonstrate their expertise in areas such as gravitational wave detection and dark matter detection, potentially helping scientists test fundamental theories such as general relativity with unprecedented precision. For those atomic clock builders, they are not only developing better clocks, but also creating a "key" that reveals the mysteries of the universe, laying the foundation for cutting-edge technology in the future. When an atom transitions from one energy state to a lower energy state, it releases electromagnetic waves. This discontinuous electromagnetic wave frequency is called the transition frequency. The transition frequency of the same atom is fixed. The atomic clock can use the frequency of electromagnetic waves emitted during atomic transitions as a metronome for timing. That is to say, an atomic clock achieves precise timing by measuring the transition frequency of atoms. The earliest atomic clocks used microwave bands to irradiate atoms, causing them to undergo transitions, but the optical frequency was much higher than the microwave frequency, and higher frequencies also meant higher timing accuracy. In 2022, JILA physicist Ye Jun and others developed the most accurate atomic clock at the time by using lasers to capture, cool, and detect atoms. If it ran for 15 billion years, the error would be less than a second. To further improve the accuracy of atomic clocks, in the latest research, Ye Jun and others used shallower and milder laser "nets" to capture thousands of atoms. This greatly reduces two main sources of error: the effects generated by the laser capturing atoms, and the effects generated when atoms are tightly packed and colliding with each other. On this basis, they developed the most accurate atomic clock ever. If this atomic clock runs for 30 billion years, the error is only one second. Measuring high-precision atomic clocks in general relativity at a smaller scale may have a significant impact on scientific research. Ye Jun said that their newly developed atomic clock is very precise, and even at the microscopic scale, it can detect small effects predicted by theories such as general relativity. General relativity holds that due to the existence of matter, space and time undergo curvature. One key prediction is that time itself is influenced by gravity, and the stronger the gravitational field, the slower time passes. In 2010, NIST physicists validated general relativity by comparing two atomic clocks 33 centimeters apart. In their paper published in the journal Nature, Ye Jun and others also pointed out that they have confirmed using the atomic clock that Einstein's theory of general relativity predicts the correct time expansion on the millimeter scale - two tiny atomic clocks, separated by only one millimeter, will also operate at different speeds. The ability to observe the effects of general relativity at the microscopic scale is expected to help physicists unify quantum mechanics with general relativity. Quantum mechanics describes matter at a very small scale, while general relativity can predict the behavior of objects at a very large cosmic scale. Atomic clocks can detect small gravitational effects, providing the possibility for the marriage of general relativity and quantum theory. More precise space navigation can also be achieved with more precise atomic clocks. As humans continue to delve deeper into the solar system, atomic clocks will need to maintain precise timing over long distances. The saying goes that a tiny mistake can lead to a thousand miles of error. Even the slightest mistake in timing can cause navigation errors and have a huge impact on the entire exploration activity. Ye Jun said that if scientists want spacecraft to land accurately on Mars, they need atomic clocks that are several orders of magnitude more precise than the current global positioning system. The newly developed atomic clock is expected to help achieve this goal. In addition, some quantum computers use individual atoms or molecules as their basic information processing units (qubits), and precise manipulation of these atoms or molecules will improve the performance of quantum computers. The technology of precise manipulation of individual atoms within atomic clocks has also found its place here. With the further improvement of atomic clock measurement accuracy, scientists are expected to enhance their understanding of quantum physics through new phenomena. A new understanding of quantum physics, in turn, can promote the development of experimental technology and further improve measurement accuracy. Ye Jun stated that atomic clocks can serve as both a "microscope" to explore the subtle relationship between quantum mechanics and gravity, as well as a "telescope" to explore the depths of the universe and trace gravitational waves and dark matter. From the infinitesimal scale of time flow distorted by gravity to the vast cosmic boundaries dominated by dark matter and dark energy, atomic clocks are no longer a timing device. They have become the "eyes" of scientists, helping them discover more new phenomena and uncover more unsolved mysteries. (Lai Xin She)