NUS researchers develop new Lutetium Atomic Clock with record accuracy that could advance precision timekeeping

Measuring time at an exceptionally precise level has become increasingly significant as modern technology and scientific research requires ever more accurate references. Atomic clocks already support systems like satellite navigation, communications infrastructure and transport networks, while scientists are continuing to develop technologies that can measure time with even finer precision.

A team from the National University of Singapore (NUS) has reported a significant advancement using lutetium, a rare-earth element. Scientists at the university’s Centre for Quantum Technologies (CQT) developed the laboratory-based optical atomic clock, with the research published in Nature on September 23.

The researchers determined the clock’s frequency to 19 decimal places and reported an uncertainty of 1 × 10-19. The team stated that this is the lowest uncertainty recorded so far for an optical atomic clock.


The researchers also made two independent clocks rather than depending on a single device. Comparing the two produced an uncertainty of 5.7 × 10-19, offering the team an extra way to analyze the reproducibility of their measurements.

“I am confident that what we have now is the most accurate clock in the world.” Murray Barrett, Principal Investigator, Centre for Quantum Technologies and Associate Professor, National University of Singapore

Why Researchers Chose Lutetium

Atomic clocks establish precise measurements of time within atoms to establish an accurate measurement of time. When a laser is adjusted to the frequency linked with a specific atomic transition, its stable oscillations can offer a timing reference.

The NUS team chose lutetium because it is less susceptible to environmental challenges. Temperature variations and differences in magnetic fields can affect highly sensitive measurements, making the characteristics of the factor important to the clock’s operation.

At the heart of the device is a lutetium ion. Researchers monitor the frequency of light that causes an electron to move into a higher-energy state. They then stabilize a laser around that frequency and use the laser’s oscillations to mark the passage of time.

The work follows more than a decade of research by the team. During that period, the scientists developed a method termed as “hyperfine averaging,” which was utilized to establish the clock transition.

The team says these characteristics allow the clock to help the system retain its accuracy across a wider range of operating conditions.

Two Clocks Provided an Independent Check

Achieving an extremely accurate measurement is only part of the challenge. Scientists also require a method for finding whether the measurement can be reproduced independently.

For that reason, the CQT researchers established two lutetium clocks and compared them. They utilized correlation spectroscopy over 200 hours of measurements to find the outputs from the separate systems.

The two systems agreed to the 19th digit, which the research team described as the most precise clock comparison ever carried out.

The comparison also disclosed another concern that becomes important when measurements reach this level of accuracy: gravity.

Millimetres Can Affect the Measurement

At an uncertainty level of 10-19, tiny variations in elevation can impact how time is measured. The researchers therefore had to find the vertical separation between the two ions to be better than a millimetre.

Their testing featured just how sensitive the system can be. The clock comparison was capable of resolving an almost 5-millimetre difference in height between two clocks placed on the same table.

This sensitivity could make highly accurate clocks useful for investigating variations in gravity. The researchers cite that such technology could contribute to work in areas that includes geophysics, fundamental physics and gravity research.

Possible Role in Redefining the Second

Today’s global time standards currently rely on caesium atomic clocks, which have been utilized since the 1960s. Researchers in the world are investigating optical atomic clocks as they operate at higher frequencies and can offer more accurate measurements.

Beyond timekeeping standards, increasingly accurate clocks could offer opportunities for precision measurement and other scientific applications. The technology is also being explored in association with systems and research that need extremely accurate timing.

More Than 10 Years of Research

The achievement represents over a decade of work by the Singapore research team. The researchers also believe the robustness of the lutetium system could make it suitable for future development beyond a controlled laboratory environment.

The new device was reported to be four times more accurate than the earlier best clock, which used calcium ions.

David Leibrandt, a physicist at the University of California, Los Angeles who works on ultra-precise clocks, described the device’s accuracy as “impressive.”

With the lutetium clock currently illustrating an uncertainty of 1 × 10-19, the researchers are turning their heads to the next stage: developing a smaller, transportable system that could offer this level of accuracy beyond the laboratory.

Source: OpenGov Asia

FAQs:

1. What is an atomic clock?

An atomic clock is a highly precise device used to measure time. It relies on predictable changes within atoms to establish a timing reference.

2. What did the NUS researchers develop?

The researchers developed an optical atomic clock using lutetium. They reported an uncertainty of 1 × 10-19.