Thanks to a new network service from SURF, developed in collaboration with the National Metrology Institute VSL and the international White Rabbit Collaboration, this extremely precise signal is now accessible via the SURF network. Researchers at Vrije Universiteit Amsterdam are also actively using it.
Linked to VSL's national atomic clock, the signal has a time accuracy of less than a nanosecond and a frequency precision at the level of picoseconds (one trillionth of a second). This makes it possible to perform experiments much faster and more accurately. The time and frequency signal is currently available at eleven locations within the SURF network; expansion to more locations is on the horizon.
From atomic clock to research network
The SURF network is directly connected to VSL's atomic clock, which realizes the official Dutch time scale (UTC). Using so-called White Rabbit technology, this signal is spread across the network via fiber optics, without loss of accuracy. Special, calibrated network switches ensure that time and frequency signals arrive at research equipment with extreme precision. Together, the connected locations form the Dutch time & frequency network for research and education.
Cooperation as key
The creation of this new network service is the result of more than fifteen years of collaboration between researchers, technological experts and network managers. In addition to SURF, VSL and the White Rabbit Collaboration, nine universities and research institutes were involved, including the Vrije Universiteit Amsterdam. Important breakthroughs included transporting time signals over long distances, combining them with regular data traffic and validating extreme accuracy. The project shows that groundbreaking research infrastructure can only come about through intensive multidisciplinary collaboration.
Major time savings and new science
With the new time and frequency signal, some experiments can be performed up to a hundred times faster and more accurately. What used to take months to measure can now be done in a few weeks. Also, observations become sharper, for example in radio astronomy, and advanced equipment for quantum communication can be synchronized to the highest level.
At VU Amsterdam, the network is being used, among other things, for extremely precise measurements of elementary particles, atoms and molecules. In addition, VU researchers are working on improvements to the White Rabbit protocol, with the goal of allowing multiple atomic clocks to work together as one virtual "superatom clock. Together with the University of Amsterdam, VU Amsterdam is also preparing experiments in which height differences are measured at the millimeter level using quantum clocks connected via fiber optics.
'An enormous leap forward'
VU physicist Jeroen Koelemeij was the founding father of Dutch research into time and frequency signals over networks in 2010, thus spearheading SURF's new service. "The possibilities offered by this kind of precision are enormous," he says. "The fact that we now have this available as a national service represents a great leap forward for fundamental and applied research."
Koelemeij also points to a broad societal interest in the background. "Society has become dependent on signals from satellite navigation systems, while we see that those signals are increasingly being disrupted." According to Koelemeij, the crux lies in the role that atomic clocks play in this. "Each navigation satellite has its own atomic clock. By offering the atomic clock not via radio signals from space, but via the network as SURF and VSL are doing now, you could realize a safe alternative to satellite navigation."
Distribution point of the SURF Time&Frequency network in the VU Research Building in Amsterdam (Photo J. Koelemeij).