Navn på bevillingshaver

Stefan Alaric Schäffer


DKK 850,000




Internationalisation Fellowships


The project tackles the forefront of measurement science, where atomic clocks have proven themselves to be the most accurate measurement devices available to man. Atomic clocks rely on highly selective transitions in atoms whose energy levels are very long-lived. While this makes the transitions excellent for accurate time-keeping, it also imposes limits on the feedback rate of such clocks. Since atomic clocks are typically based on carefully controlling the frequency of noisy lasers this sets limitations to their performance. By using optical atomic clock transitions in strontium to generate laser light it is possible to achieve a continuous signal independent of delays in feedback time. This can be realized in a so-called superradiant laser operating with a stream of ultra-cold atoms.


Atomic clocks are an essential part of modern technology and used in, e.g., telecommunication, GPS-systems and high-speed timing. Accurate measurements of time allows accurate measurements of distances as well as gravitational potential differences used in geological monitoring. By developing new techniques to overcome current limitations it will be possible to advance the performance of atomic clocks, reducing their complexity, and thus allowing for improved measurement capabilities. Improved accuracy in navigation satellites will allow orders of magnitude increase in the accuracy of navigation systems, improved geological mapping of the underground, and highly accurate quantum sensors for industry applications. A continuous clock signal from a superradiant laser allows real-time sensing.


A continuous superradiant laser relies on the same essential elements as a traditional laser, but the use of narrow transitions in clock atoms require very cold samples. I will use my former experience with generating superradiant lasing pulses in unconfined samples of cold atoms as steppingstone to move to a continuous regime. The atoms are heated during lasing, and a viable solution is thus to use a continuously flowing stream of ultra-cold atoms. Such systems are notoriously hard to realize, but at the University of Amsterdam they have recent, highly successful, results that I will be able to benefit from during my project. Merging our expertise in this field will thus allow us to realize this new type of atomic clock laser and characterize the inner workings of such a machine.

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