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Logo: Sonderforschungsbereich geo-Q
Logo Leibniz Universität Hannover
Logo: Sonderforschungsbereich geo-Q
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Transportable optical clocks for relativistic geodesy

Trends of the statistical uncertainties
Trends of the statistical uncertainties

Einstein’s general theory of relativity predicts that clocks in a gravitational potential tick slower than clocks outside of it. On Earth, this translates to a relative frequency change of 10−16 per meter of height difference. Comparing the frequency of a “probe” clock with a “reference” clock (both at rest) provides a direct measure of the difference in gravity potential between the two clocks. This novel technique has been dubbed “chronometric leveling” and is a central application of relativistic geodesy. Optical frequency standards have recently demonstrated a fractional frequency uncertainty of 10−17 which enables their use for relativistic geodesy at an absolute level of ten centimeters. The vision of this project is to demonstrate chronometric leveling with transportable clocks and to establish a measurement technique that is directly sensitive to the geopotential. We will demonstrate direct comparisons of the geopotential of 100 km to 1000 km separated sites with a resolution of below 10 cm. This height resolution will be achieved after only a few hours of averaging. With this approach we provide a new capability to connect classical geodetic measurements and to establish anchor measurements for widely spread height grids. As a long term goal, the development of optical clocks operating during their transport will advance these instruments to independent measurement devices that can be used with high flexibility without the necessity of optical links for high accuracy frequency comparisons. We will approach this vision in several steps. In the first step, we will build transportable clocks with a performance comparable to laboratory clocks. Techniques to improve the performance of optical clocks in terms of temporal resolution and reproducibility with respect to geodetic signals and models will be investigated. It will be necessary to develop new experimental approaches to make the outstanding performance of laboratory optical clocks available for devices used in field missions. We will then use these clocks to demonstrate chronometric leveling between distant locations for the first time. This new observable will then be used by experts in geo-Q to show how it can be used together with traditional observables to gain new insights into the Earth system and improve the global geoid to solve e.g. the vertical datum problem. From experience gained during field missions, we will be able to identify, which conceptual and technological measures are necessary for the operation of optical clocks during transport. For the interpretation of clock shifts accumulated during such campaigns it will be necessary to model the transport itself. Relativistic geodesy with transportable clocks is a science driver for ever more accurate and stable clocks. It will enable novel applications in geodesy and improve our understanding of the Earth system.



Scientists working on this project

Jacopo Grotti
email: Jacopo.Grottiptb.de

phone: +49 531 592-4315

Stephan Hannig
email: stephan.hannigquantummetrology.de

phone: +49 531 592-4705

Sophia Herbers
email: Sophia.Herbersptb.de

phone: +49 531 592-4325

Dr. Silvio Koller
email: Silvio.Kollerptb.de

phone: +49 531 592-4325

Johannes Kramer
email: johannes.kramerquantummetrology.de

phone: +49 531 592-4706

Lennart Pelzer
email: lennart.pelzerquantummetrology.de

phone: +49 531 592-4747

Nils Scharnhorst
email: nils.scharnhorstquantummetrology.de

phone: +49 531 592-4722

Selected Publications

Peer-Reviewed Literature

Scharnhorst N., Wübbena J.B., Hannig S., Jakobsen K., Kramer J., Leroux I.D. and Schmidt P.O. (2016): High-bandwidth transfer of phase stability through a fiber frequency comb, Opt. Express 23, 19771–19776
DOI: 10.1364/OE.23.019771
arXiv: 1505.02084

Vogt S., Häfner S., Grotti J., Koller S., Al-Masoudi A., Sterr U. and Lisdat C. (2016): A transportable optical lattice clock, Journal of Physics: Conference Series 723, 012020 more
DOI: 10.1088/1742-6596/723/1/012020

Al-Masoudi A., Dörscher S., Häfner S., Sterr U. and Lisdat C. (2015): Noise and instability of an optical lattice clock, Physical Review A 92, 063814-1-7
DOI: 10.1103/PhysRevA.92.063814
arXiv: 1507.04949

Benkler E., Lisdat C. and Sterr U. (2015): On the relation between uncertainties of weighted frequency averages and the various types of Allan deviations, Metrologia 52, 565 – 574
DOI: 10.1088/0026-1394/52/4/565
arXiv: 1504.00466

Doležal M., Balling P., Nisbet-Jones P. B. R., King S. A., Jones J.M., Klein H.A., Gill P., Lindvall T., Wallin A. E., Merimaa M., Tamm C., Sanner C., Huntemann N., Scharnhorst N., Leroux I.D., Schmidt P.O., Burgermeister T., Mehlstäubler T.E. and Peik E. (2015): Analysis of thermal radiation in ion traps for optical frequency standards, Metrologia 52 (2015) 842-856
DOI: 10.1088/0026-1394/52/6/842
arXiv: 1510.05556

Häfner S., Falke S., Grebing C., Vogt S., Legero T., Merimaa M., Lisdat C. and Sterr U. (2015): 8E-17 fractional laser frequency instability with a long room-temperature cavity, Optics Letters 40, 2112 – 2115
DOI: 10.1364/OL.40.002112
arXiv: 1502.02608

Ludlow A.D., Boyd M.M., Ye J., Peik E. and Schmidt P.O. (2015): Optical atomic clocks, Rev. Mod. Phys. 87, 637–701
DOI: 10.1103/RevModPhys.87.637

Non Peer-Reviewed Literature

Vogt S., Grotti J., Koller S., Häfner S., Herbers S., Al-Masoudi A., Grosche G., Denker H., Sterr U. and Lisdat C. (2016): Using a transportable optical clock for chronometric levelling, Geophysical Research Abstracts, Vol. 18: EGU 2016-16061, EGU General Assembly 2016, Vienna, Austria, 17–22 April 2016 more

Presentations, Talks and Posters

Al-Masoudi A., Dörscher S., Schwarz R., Häfner S., Sterr U and Lisdat C. (2016): A cryogenic lattice clock at PTB, DPG-Frühjahrstagung, Hannover, Germany, 29 February – 04 March, 2016

Lisdat C., Koller S., Grotti J., Vogt S., Al-Masoudi A., Dörscher S., Herbers S., Häfner S. and Sterr U. (2016): Using a transportable optical clock for chronometric levelling, Fall Meeting, AGU, San Francisco, Calif., 12-16 Dec.

Al-Masoudi A., Dörscher S., Falke S., Häfner S., Vogt S., Sterr U. and Lisdat C. (2015): Towards a cryo-lattice clock at PTB, DPG-Frühjahrstagung, Heidelberg, Germany, 23 - 27 March, 2015 more

Al-Masoudi A., Dörscher S., Gerginov V., Weyers S., Grebing C., Lipphardt B., Sterr U. and Lisdat C. (2015): Absolute frequency measurement of the 87Sr lattice clock at PTB, DPG-Frühjahrstagung, Heidelberg, Germany, 23 - 27 March, 2015