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Scientists Achieve Unprecedented Stability in Atomic Clock

How often do you check the time on your Huawei smartphone or use GPS to locate a new restaurant? It turns out that our modern world heavily relies on a special kind of scientific device for timekeeping called the atomic clock.

January 17, 2024
Editor-in-Chief, The China Academy
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Do you ever wonder how we know the exact time?  Simply by checking your smartphone or a timepiece on your wrist, right? But how do these electronic gadgets make sure the time is correct? We know they all the connect to the internet, but then again, how could the internet know?

Well, it turns out that the internet, and our modern world in general, heavily relies on a special kind of scientific device for timekeeping called the atomic clock, or as scientists like to call it, atomic frequency standards.

Atomic frequency standards are the unsung heroes of our everyday lives, quietly ensuring that time flows seamlessly and our modern world remains in perfect sync. From the precise timing displayed on our smartphones to the flawless navigation provided by GPS, atomic frequency standards work tirelessly behind the scenes. They enable smooth communication in telecommunications, guarantee accurate financial transactions, and empower scientific breakthroughs. With atomic frequency standards as our unwavering guardians of time, our days are organized, our devices are synchronized, and our world effortlessly dances to the beat of perfect precision.

However, creating atomic frequency standards is difficult as they need to be very stable and accurate, measure atomic transitions correctly, reduce noise, and minimize external influences. Stability is crucial. It directly affects how accurate and reliable the frequency measurements are. When a frequency standard is stable, it helps devices work together smoothly, ensures precise scientific experiments, and makes sure things like telecommunications and navigation systems perform well. Stability is especially important for long-term use and when precise timing is needed.

In a significant scientific achievement, researchers from Chinese Academy of Sciences have developed a Rubidium Atomic Frequency Standard (RAFS) with an exceptional level of stability. The breakthrough, detailed in an upcoming publication in the IEEE Transactions on Instrumentation and Measurement, demonstrates a short-term stability in the 10-14 level, a notable improvement.

The RAFS has been widely used as a reliable atomic frequency standard since its development in the 1960s. Over the years, its stability performance has steadily improved, with the best standards achieving stability in the 10-13 level.

In this latest development, the team from CAS has achieved stability in the 10-14 level for the first time. The researchers employed innovative techniques to enhance the signal-to-noise ratio of the atomic discrimination signal, and found ways to make the microwave signal clearer and reduce the interference from the environment on the atomic transitions.

Microwave signals are employed to interrogate the rubidium atoms and measure the atomic transitions. The microwave signals are carefully controlled and sent into the rubidium absorption cell, where the atoms interact with the microwave radiation. By precisely tuning the frequency of the microwave signals, the researchers can target specific atomic transitions and observe the changes in the atoms’ behavior.

They made sure that the microwave signal was more stable and had less unwanted noise, and also worked on minimizing the impact of things like temperature changes or other disturbances on the atoms so that the measurements would be more accurate.

In the design of the RAFS, they used a special lamp that emitted light from rubidium atoms. Xenon gas was used to start the lamp and provide the initial light. The light was then carefully filtered using special techniques to make it cleaner. The device also includes a large microwave chamber and a 40 mm wide cell to improve the detection of the rubidium atoms.

Structure of the physics package

To prevent interference from the environment, they built a sealed box around the important parts of the RAFS. This box protected the critical components from changes in air pressure and other external conditions. They also used a microwave signal with very little unwanted noise at a frequency of 6.834xx GHz to interact with the rubidium atoms and make the measurements even more stable.

The achieved stability of the RAFS was predicted to be 7.6×10-14τ-1/2 based on quantitative analysis. The short-term stability was measured and found to be 9.0×10-14τ-1/2 (1 ~ 100 s) using a hydrogen maser and 9.1×10-14τ-1/2 (1 ~ 100 s) using an optical microwave generator as references. These measured results align with the predicted stability, validating the accuracy of the RAFS.The development of RAFS with stability in the 10-14 level represents a significant milestone in atomic frequency standards. It showcases the continuous progress made in atomic physics and the pursuit of ever more precise timekeeping. As the demand for accurate synchronization continues to grow, the remarkable stability achieved by the RAFS opens up new possibilities for scientific research, technological advancements, and societal applications.



Editor-in-Chief, The China Academy
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