World-first: Scientists use lutetium to build world’s most accurate atomic clock

Researchers at the Centre for Quantum Technologies (CQT) in Singapore have built the world’s most accurate atomic clock using lutetium at its core. This is not just an achievement in terms of the clock’s performance but also because this is the first time lutetium has been used, when researchers typically prefer ytterbium, strontium, or aluminum to make their atomic clocks.

Atomic clocks are the most precise clocks made so far. They are critical in global operations ranging from navigation to internet traffic, telecommunications to banking transactions, where highly precise timekeeping is necessary. Atomic clocks keep time by measuring transitions between an atom’s electron energy levels using a laser.

The oscillations between the energy levels act like a pendulum to count time, and the approach has been standardized using cesium atoms that are used in atomic clocks that support the Global Positioning System (GPS) and communication networks that we commonly use today.

However, researchers have been trying to improve the accuracy of these systems by using other atoms like ytterbium, strontium, and aluminum, which oscillate faster than cesium and hence can are more accurate.

Turning to lutetium

Researchers at CQT in Singapore turned to lutetium for their atomic clock more than a decade ago since changes in the temperature or magnetic field do not impact the transition.

A team led by Murray Barrett, a principal investigator at CQT and associate professor at the National University of Singapore (NUS), spent much of the past decade precision-engineering the clock setup and testing different properties of the atom.

“The good properties mean that high accuracy can be achieved even in a wide range of environments,” explained Barrett in a press release. “The lutetium clock would be stable even if you went from the hottest place recorded on Earth in Death Valley to the coldest place in the Antarctic plateau.”

The clock consists of a single charged 176Lu+ ion with a transition matched to a laser with a wavelength of 848 nanometers. The researchers also had to invent a new way to define the clock’s transition, something they refer to as ‘hyperfine averaging.’

In their experiments, the team measured the frequency of the lutetium clock to 19 decimal places, with an uncertainty of 1 x 10^ -19, the lowest for an optical atomic clock to date.

Measuring accuracy

When any research team claims to have built the most accurate atomic clock, they verify their claim by comparing its accuracy to the best one out there.

In the case of the lutetium clock, though, the level of precision is so high that it can detect the slowing of time caused by gravity, even when the height difference is a few millimeters and incomparable to the best atomic clocks available.

The researchers therefore built another lutetium clock and compared its ticking to arrive at the uncertainty of 5.7 x 10^ -19, the highest recorded precision thus far. To make more comparisons and develop further applications, the clock needs to leave the lab. Barrett and his team will now work on miniaturizing it so that it can be transported.

The research findings were published in the journal Nature.