Researchers have created an atomic clock, built from the element lutetium, which they say can measure a trillionth of a second accurately and is the most stable one across environments, hardly feeling changes in temperature or magnetic field.
Atomic clocks keep time with reference to an atomic transition—when one of an atom’s electrons swaps energy levels. Frequency of an atomic transition is a fixed property of an atom. A laser is matched to the ‘clock transition’, and the light oscillations act like a pendulum to count time.
While atoms of the element caesium were used in building the first accurate atomic clock in 1955, scientists have been pushing the limits of timekeeping with other elements, including recent record-holders ytterbium, strontium and aluminium, which oscillate much faster than caesium.
The team from the National University of Singapore used lutetium, a dense, silvery-white rare-earth metal with the symbol ‘Lu’ and an atomic number 71.
They said their clock would be able to measure one-trillionth of a second with record-making accuracy.
“I am confident that what we have now is the most accurate clock in the world,” team leader Murray Barrett, a principal investigator at centre for quantum technologies and associate professor in the department of physics at the National University of Singapore, said.
Barrett’s team have been working with the element for over a decade on the hunch that lutetium has the right properties to join the set of top-performing clocks—its strong performance comes from its properties, they said.
Lutetium’s clock transition hardly feels changes in temperature or magnetic field, even as the environmental factors can gently vary the frequency in other elements, the researchers said.
“In the future, I just don’t see how this clock can be beat,” Barrett said.
“The good properties mean that high accuracy can be achieved even in a wide range of environments. 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,” Barrett said.
The researchers added they are the only group working with this element for timekeeping so far.
Their confidence is bolstered by their clock comparison, carried out using a technique known as correlation spectroscopy over 200 hours of measurement, they said.
Each lutetium clock consists of a single charged Lu+ ion having a clock transition matched to a laser with wavelength of 848 nanometers.
“There is a humorous saying that ‘A man with a watch knows what time it is. A man with two watches is never sure’,” first author Kyle Arnold, a senior research scientist from the centre for quantum technologies said.
“It basically tells you that the only way to test the accuracy of a standard is to compare clocks and demonstrate reproducibility,” Arnold said.
