Since humans began to track the passage of time, the accuracy of timekeeping devices has continued to improve. Today, the vibration of an atomic clock is a stable periodic event that scientists can observe. Therefore, the most accurate timepiece in the world is the atomic clock. This exquisite instrument uses lasers to measure the vibration of atoms. If the atomic clock has been running since the beginning of the universe, the accumulated error so far is only half a second. If there are more accurate timekeeping methods, it can help humans detect phenomena such as dark matter and gravitational waves. Scientists can also begin to answer some puzzling questions, such as what effect gravity might have on the passage of time, and time itself Does it change with the aging of the universe.
Today, physicists at the Massachusetts Institute of Technology in the United States have designed a new type of atomic clock. Unlike the previous design, it measures not a cloud of randomly oscillating atoms, but multiple atoms that have been quantum entangled. In order to maintain perfect time, it is best to keep track of the oscillations of individual atoms. But the atom is so small that it acts according to the mysterious rules of quantum mechanics: when measured, it behaves like tossing a coin, and only taking the average of multiple flips can give the correct probability. So traditional atomic clocks are designed to measure gases composed of thousands of atoms of the same type in order to estimate their average oscillations.
In quantum mechanics, when several particles interact with each other, because the characteristics of each particle have been integrated into the overall nature, it is impossible to describe the nature of each particle alone, but only the nature of the overall system. This phenomenon is called Quantum entanglement. The research team believes that if the atoms are entangled, their oscillations will tighten around a common frequency, and the deviation will be smaller than if they are not entangled. Therefore, the newly designed atomic clock entangles 350 ytterbium atoms, and the measurable average oscillation is four times higher than that of a clock without entanglement.
Atoms are trapped in an optical cavity composed of two mirrors. When the laser is “squeezed” through the cavity, the atoms are entangled together, and then a second laser is used to measure its frequency as a more accurate atomic clock
