Overview

Since ancient times our ancestors have used the movement of the stars in the sky to measure the passage of time: the hours of the day, the days of the month, the arrival of the seasons, and the age of people. Just a couple of millennia later, our intellect provides us with tools that allow us to measure time with astonishing precision: atomic clocks and methods that involve measuring very small and fast things like electrons. Now an international team of researchers has managed to measure time with a precision never seen before.

The science and other stuff to know

If we divide a second into a thousand trillion parts (that’s a 1 followed by twenty-one 0), we get a zeptosecond. Measuring such an infinitesimally short time is a technological feat since the experiments needed to make such a measurement must be extremely sophisticated.

A team of researchers from the Australian Attosecond Science Facility and the Center for Quantum Dynamics at Griffith University in Australia collaborated with Chinese experts from Shanghai Jiao Tong University to achieve the most precise time measurement ever made. To be exact, the researchers have developed an interferometric technique capable of measuring time delays with zeptosecond (a trillionth of a billionth of a second) resolution.

The experiment was based on measuring the delay of a pulse of ultraviolet light for another within isotopes of a hydrogen molecule. They employed this technique to measure the time delay between extreme ultraviolet light pulses generated by two different isotopes of hydrogen molecules (H2 and D2) interacting with powerful infrared laser pulses.

The delay of one beam to the other is due to “moderately different motions of the lightest and heaviest nuclei,” in the words of the authors of the article published in Ultrafast Science.

“This unprecedented time resolution is achieved through an interferometric measurement, superimposing the delayed light waves and measuring their combined brightness,” said Dr. Mumta Hena Mustary, lead author of the paper, in an official statement from the University of Griffith.

Interferometry is a measurement method that studies wave behavior by employing the notion of wave superposition. In this example, the researchers utilized light pulses to see how the waves’ peaks and troughs reinforced or canceled each other out.

In their experiments, the researchers used a well-known wave pattern to examine the dissonances in the resulting wave pattern and determined that one arrived three attoseconds (three trillionths of a second) later than the other. The waves had been emitted simultaneously by the same source. They did not, however, arrive at the receptor simultaneously because they passed via a molecule that delayed one more than the other.

So what?

According to Griffith experts, this level of precision can expand experimental capabilities. That is, now that they have a clock with enough precision to measure phenomena that occur on scales where a millionth of a second is an eternity, they can study much more fundamental and complex processes, such as the appearance and disappearance of virtual particles caused by quantum fluctuations in the vacuum.

What’s next?

“In the future, this technique can be used to measure the ultrafast dynamics of various light-induced processes in atoms and molecules with unprecedented time resolution,” says Igor Litvinyuk, co-author of the study.