A highly precise terahertz molecular clock

In recent years, many physicists around the world have introduced atomic clocks, systems for measuring the passage of time that depend on the quantum state of atoms. These clocks can have numerous valuable applications, for example in the development of satellite and navigation systems.

Recently, some researchers are also exploring the possible development of atomic clocks, systems that resemble atomic clocks, but are based on simpler molecules. A team from Columbia University and the University of Warsaw recently created a highly accurate molecular clock that can be used to study new physical phenomena.

“Our latest paper is the result of a multi-year effort called a molecular clock,” Tanya Zelevinski, one of the researchers who conducted the study, told Phys.org. “It was inspired by rapid advances in the precision of atomic clocks and the realization that atomic clocks depend on a distinct ‘ticking’ mechanism and can therefore be sensitive to complementary events. One of these ideas is that the fundamental constants of nature can change very little over time. Another possibility is that the gravity between very small objects may be different from what we experience on larger scales.”

The molecular clock developed by Zelevinski and his colleagues is based on the diatomic molecule Sr.₂, structurally resembles two small spheres connected by a spring. The clock specifically uses the vibrational modes of this molecule as a precise frequency reference, which in turn allows it to keep track of time.

“Our clock requires the use of lasers to cool the atoms near absolute zero and place them in an optical trap, induce them to bind into atoms, and shine very precise ‘clock’ lasers at them to actually make the measurements,” Zelevinski explained. “Some of the advantages of the molecular clock include its very low sensitivity to magnetic or electric fields and the very long natural lifetimes of the vibrational modes.”

In their study published in Physical review X, Zelevinski and his colleagues evaluated the precision of their atomic clock in a series of tests, measuring its so-called systematic uncertainty. They found that their proposed design significantly reduced the sources of errors and their clock achieved a total systematic uncertainty of 4.6×10.⁻¹⁴Shows remarkably high precision.

“Our recent work sets a benchmark for the precision of molecular spectroscopy, with an observational measurement of the peak sharpness – or its quality factor – of 3 trillion,” Zelevinski said. “It also highlights the effects that limit this precision, in particular, the eventual loss of molecules through light scattering in which they are trapped. This inspires us to look for improvements in optical trapping strategies.”

The vibrational molecular clock created by this team of researchers could become a standard for terahertz frequency applications, while also potentially informing the construction of new molecular spectroscopy tools. Its design can also be modified, by changing the Sr₂ Molecules with other isotopic variants (with different masses), which may aid the ongoing search for new physical interactions.

“In the future, we hope to apply the atomic clock to understand molecular structure with the greatest precision and to study any possible signatures of non-Newtonian gravity at nanometer size scales,” Zelevinski added.

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