Quantum precision measurement achieves new breakthrough: my country's scientific research team develops "nuclear optical clock"

Recently, Tsinghua University, in collaboration with multiple domestic research teams, took the lead in the world in developing a "nuclear optical clock" that realizes quantum precision measurement from electronic transitions to atomic nuclear transitions, opening up new technical paths for a new generation of high-performance time and frequency benchmarks, deep space exploration and basic physics research. The international journal Nature published the research results today.

"Nuclear optical clocks" are regarded as a new generation of time and frequency standards after atomic microwave clocks and atomic optical clocks, and are the current cutting-edge research direction in the field of quantum precision measurement. The Tsinghua University research team spent nearly five years to innovatively develop 148-nanometer continuous wave vacuum ultraviolet laser technology, and used this light source to accurately drive the nuclear transition of the radioactive isotope thorium-229, stabilizing the laser frequency at this nuclear transition, and thus developed a "nuclear optical clock."

Ding Shiqian, associate professor of the Department of Physics at Tsinghua University and adjunct researcher at the Beijing Institute of Quantum Information Science, said that the old-fashioned pendulum swings almost once every second. You can know how much time has passed by counting how many times the pendulum swings. This "nuclear optical clock" uses the beat of the atomic nucleus as a "pendulum". This beat is much faster than the beat of a wall clock. It is almost 2000 trillion times per second. The time is cut very finely. By counting the number of beats, you can know the precise time.

It is understood that the most accurate atomic optical clock at present is based on the principle of recording the rhythm of electronic transitions inside atoms. However, to achieve extremely high accuracy, it is necessary to finely control various disturbances caused by electric fields, magnetic fields, temperatures, and laser systems. Therefore, the currently highest-performing atomic optical clocks are still mainly operated in laboratories, and their miniaturization and engineering still face challenges. The "nuclear optical clock" shifts the timing reference from electronic transitions to nuclear transitions inside the thorium-229 nucleus.

Ding Shiqian said that the size of the atomic nucleus is only about tens of thousands of times the size of the electron cloud outside the nucleus, which results in a more stable rhythm of the nucleus, and the "nuclear optical clock" developed is expected to be more accurate. On the other hand, it is expected to miniaturize this "nuclear optical clock". After miniaturization, an extremely high-precision timing device can be truly used, not just a tool in the laboratory.

According to reports, the "nuclear optical clock" is expected to be used in fields such as navigation and deep space exploration in the future to conduct more accurate positioning and distance measurement of satellites and spacecraft to serve the country's major needs.