Precise Frequency Measurement with Ultracold Magnesium Atoms
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Time is the physical quantity determined today with the highest degree of accuracy. Scientists continually aspire to develop more precise clocks. A breakthrough in the modern history of clocks was the realization of the method of separated oscillatory fields by Norman F. Ramsey and its application to microwave atomic clocks based on Cesium.
Unlike atomic clocks (that work at microwave frequencies which can be easily measured with conventional electronics), optical clocks require the measurement of optical frequencies. The breakthrough came with the invention of the optical frequency comb (for which John Hall and T. W. Hänsch were awarded the Nobel prize in 2005) which allows one to directly measure the frequency of light with very high precision. With such a "ruler for light", it is possible to measure any optical frequency, which is immeasurable by conventional electronics. Find more information on the frequency comb here.
The invention of the frequency comb started the era of optical clocks. They were quickly demonstrated, first, in trapped ions and later in trapped neutral atoms. The uncertainty of best optical clocks now is better than one second in 80 million years and they have already surpassed the SI definition of the second in accuracy.
Such an accurate clock is sensitive to the smallest perturbations in the environment, making it an extremely sensitive sensor.
Since the first optical clocks based on alkaline earth atoms were realized, Magnesium seems to be a promising candidate with an expected stability and accuracy higher than the momentary definition of the SI second.
Our work is motivated by the quest for precise time and frequency standards both for technology and fundamental research. Applications of accurate clocks are in global positioning systems, fiber-optical communication networks and the verification of relativistic effects.
We are frequently visited by students to complete their praktikum. If you are interested in arranging a visit to our lab feel free to contact us: fimiqo.uni-hannover.de.