On the evening of July 4, Chen Yu’ao, Professor and Executive Dean of the School of Physical Sciences at the University of Science and Technology of China (USTC), revealed on the CCTV talk show Lecture Room that the strontium optical lattice clock under development at USTC enables far more precise measurement of "one second", and is expected to redefine the current official standard for time in the future.

During the program, Chen guided the audience on a virtual tour of USTC’s optical lattice clock laboratory, unpacking the scientific mysteries behind quantum mechanics and time metrology. He explained that quantum mechanics has long woven itself into daily life, with one pivotal application being the time we rely on every single day.

In ancient times, humans tracked time by the rising and setting of the sun and moon. Later, a single day was divided into 24 hours, 1,440 minutes or 86,400 seconds. As science advanced, researchers discovered that Earth’s rotation is inconsistent; tides, crustal movements and other phenomena disrupt the accuracy of this natural pendulum.

In 1967, the 13th General Conference on Weights and Measures (CGPM) defined the second as the duration of 9,192,631,770 periods of radiation emitted during the transition between two specific hyperfine energy levels of an unperturbed caesium-133 atom. Put simply, one second equals roughly 9.2 billion vibrations of a caesium atom. Even today, the time standard powering mobile phones, navigation systems and countless other devices remains based on this benchmark.

By contrast, USTC’s strontium optical lattice clock delivers vastly superior precision for measuring a second. Chen elaborated that electrons emit far higher-frequency light when jumping between energy levels, oscillating nearly 100,000 times faster than caesium atoms — yielding ultra-fine time readings.

What does a strontium optical clock look like? The lab footage revealed no clock faces or hands; instead, rows upon rows of lasers, vacuum chambers and optical components fill the space. Chen offered a vivid analogy: the optical lattice acts as an egg carton woven from light across three-dimensional space, trapping atoms in place. The experiment also demands stringent conditions: a vacuum environment, temperatures close to absolute zero, and precise laser manipulation from multiple directions.

This extreme level of atomic control keeps atoms stable and generates consistent frequency signals. The team has pushed the optical clock’s stability and uncertainty to the 10⁻¹⁹ magnitude.

“To put it in perspective, it would drift less than one second over 30 billion years,” Chen said. “If this optical clock ran continuously for 30 billion years, its recorded time would deviate from absolute real time by less than a single second.”

This ultra-precise time measurement is far more than a laboratory milestone. High-accuracy time standards play an irreplaceable role in aerospace, satellite navigation, deep space exploration and fundamental physics research. Chen noted that the team is advancing miniaturization and engineering of the optical clock, with the long-term goal of mounting it on satellites. In orbit, shielded from terrestrial noise, the device could unlock breakthroughs in fundamental scientific inquiry.

It is reported that the CGPM plans to officially adopt a new definition of the second in 2030. Breakthroughs in China’s optical clock technology demonstrate that the country now possesses the technical capacity to participate in redefining the fundamental unit of time, the second.

Source: Hefei Daily