A minute with your hand on a hot stove undoubtedly lasts longer than a minute in the arms of a loved one — loosely based on a disputed quote attributed to Albert Einstein. In short: time is relative.
Yet measuring time with extraordinary precision is critical for many areas of modern life, from telecommunications and financial systems to scientific research seeking to understand the smallest particles in nature: molecules, atoms and electrons.
At Vrije Universiteit Amsterdam, physicist Jeroen Koelemeij is using ultra-precise timing technology to study molecular vibrations — research that could help deepen our understanding of chemistry, biology and drug development.
“Our understanding of chemistry and biology depends on how well we understand those atoms and molecules. That matters for many areas of society, for example drug development. By looking at how fast atoms and molecules vibrate, we can learn a great deal about their properties and how they function.”
Tapping and probing molecules
To study these vibrations, Koelemeij traps molecules inside a vacuum chamber, isolating them from external influences such as magnetic fields. A laser beam is then fired at the molecules, causing them to vibrate.
The vibrations happen at astonishing speeds. Measuring them accurately requires exceptionally precise timing.
“By firing a laser beam at them, he sets the molecule vibrating and counts the number of vibrations per second,” Koelemeij explains. “We can measure that frequency to as many as twelve decimal places.”
That level of precision depends on an atomic clock. Despite the advanced science behind it, the device itself is surprisingly ordinary in appearance.
“Incidentally, it does not look particularly science-fiction-like — it is a flat grey box that mostly resembles a DVD player.”
Connecting directly to the Netherlands’ national time standard
Until recently, the team relied on the atomic clock housed in their own laboratory. But the next generation of experiments demands even greater precision.
“So far, we have been able to do everything using the atomic clock in our own lab, but for the next generation of experiments we want to measure with 14 to 17 decimal places. You can’t simply buy an atomic clock that precise; you have to build it yourself, and that is very expensive.”
Instead, the researchers turned to VSL, the Netherlands’ national metrology institute in Delft, which maintains the country’s official time standard.
“Every country has its own national metrology institute that maintains the official time standard. In the Netherlands, that is VSL in Delft,” says Koelemeij. “So we needed access to VSL’s atomic clocks, which are 10 to 100 times better than ours. That will allow us to move forward for years to come.”
Using the Time&Frequency service operated by SURF, the Netherlands’ research and education network provider, an optical fibre connection now links the laboratory in Amsterdam directly to VSL’s atomic clocks in Delft.
An optical fibre cable — as thin as a hair and carrying data at the speed of light — effectively brings the clock in Delft into the Amsterdam laboratory itself.
More stable measurements through White Rabbit technology
The connection immediately improved the stability of the team’s measurements.
“The connection was installed last summer. We immediately saw a major improvement: the measurements are now much more stable, and our researchers are very happy with that. What initially looked like an enormous mountain of six months’ worth of measurements, we can now do in a month.”
But transferring ultra-precise timing signals over fibre is not straightforward.
The atomic clock signal takes only a fraction of a millisecond to travel the roughly 100 kilometres between Delft and Amsterdam. At the same time, changes in ambient temperature cause the fibre in the ground to contract and expand, subtly altering the signal timing.
“This creates variations in the signal, making it seem as if the atomic clock in Delft is constantly moving away from us and towards us.”
To solve this challenge, SURF installed specialised White Rabbit network equipment that continuously measures and corrects these variations.
“Thanks to the direct fiber connection to the atomic clock at VSL and White Rabbit technology, our measurements are now much more stable.”
Originally developed and released as open source by CERN in Geneva, White Rabbit technology is now used worldwide in scientific and industrial environments where extreme timing precision is essential.
Beyond molecular research: a more resilient alternative to GPS
While Koelemeij’s work focuses on molecular physics, the same Time&Frequency technology has much broader implications.
One area attracting increasing attention is positioning and navigation technology.
Today, most navigation and timing systems rely on GPS satellites orbiting the Earth. Each satellite carries several atomic clocks and continuously transmits radio signals to receivers on the ground.
“GPS receivers on Earth — for example the one in your phone — pick up these signals,” Koelemeij explains. “Because the satellites are at different distances from your phone, the signals do not arrive at the same time. By calculating the time differences between the signals, your phone determines your location and synchronises its clock with the GPS system.”
GPS systems are highly effective, providing timing accuracy within a few nanoseconds and positioning accuracy within a few metres. But fibre-based timing systems can be even more precise.
“With the SURF network, we can reach fractions of a nanosecond and determine a location down to within 10 centimetres,” Koelemeij explains. “So it is much more accurate.”
The fibre-based approach also avoids some of GPS’s limitations. Satellite signals can be disrupted by buildings, underground environments or shielded laboratories.
More importantly, concerns are growing around the resilience and security of satellite-based infrastructure.
“Countless companies and organisations use GPS for navigation and to know the time. But a major solar flare could fry all those satellites, or they could be hacked or disrupted by hostile parties.”
The consequences of a prolonged GPS outage could affect telecommunications networks, banking systems, transport infrastructure and other essential services.
“SURF’s system offers a robust alternative that is less vulnerable to disruption than GPS. In the future, it may well become essential to our society. For me, that is an important reason to do this research.”
The network infrastructure enabling precision science
Projects like this highlight the increasingly important role research and education networks play in enabling advanced scientific discovery.
The same high-capacity fibre infrastructure used to connect universities and research institutions is now also supporting ultra-precise timing, distributed scientific instruments and new forms of collaboration.
In this case, the network is doing more than moving data between cities. It is transferring time itself with extraordinary precision — helping researchers better understand the molecular building blocks of the natural world while also exploring technologies that could one day strengthen the resilience of critical infrastructure worldwide.
The project highlights how national research and education networks are supporting increasingly specialised scientific applications beyond traditional connectivity.
This is an edited version of a story by Josje Spinhoven first published on the SURF website
Photo: Vera Duivenvoorden
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