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Optical atomic clocks are the most precise measurements ever build by the mankind. Accuracy at the level of 10^-18 [1,2] and instability in mid 10^-17 after 1 s of averaging [3] was already presented. With all perturbation under control one can use a clock not only for precise time measurements but also for other physical quantity measurements, e.g. for looking for fundamental constants variations [4] or dark matter in form of topological defects [5]. Atomic clocks are also directly sensitive to the gravitational potential, i.e. they can be used as a gravitational waves detectors [6] and in relativistic geodesy [7,8].
All modern optical atomic clocks are passive, with an oscillator in the form of ultra-stable laser and a frequency discriminator in the form of cold atomic sample. We would like to propose instead an active optical atomic clock [9] as a gravitational detector. Such an active frequency standard would take advantage form both better instability and higher time resolution over already existing optical clocks. Its construction will provide a high degree of mobility, since its performance would not be limited by an instability of a fragile optical cavity.
We will present potential advantages of using active optical clocks as gravitational potential detectors along with gravimeters measuring acceleration. A combination of both devices can remotely detects not only small gravitational anomalies or objects, but also precisely locate them. Moreover, shape and mass distribution can also be derived.
[1] T. Nicholson et al., Nat. Commun. 6, 6896 (2015),
[2] I. Ushijima et al., Nat. Photon. 9, 185 (2015),
[3] M. Schioppo et al., Nat. Photon. 11, 48 (2017),
[4] T. Rosenband et al., Science 319, 1808 (2008),
[5] P. Wcisło et al., Nat. Astronomy 1, 0009 (2016),
[6] S. Kolkowitz et al., Phys. Rev. D, 94, 124043 (2016),
[7] A. Bjerhammar, NOAA Technical Rep. NOS 118 NGS 36 (1986), Available at: http://www.ngs.noaa.gov/PUBS_LIB/RelativisticGeodesy_TR_NOS118_NGS36.pdf,
[8] R. Bondarescu et al., Geophys. J. Int. 191, 78 (2012),
[9] G. A. Kazakov et al., arXiv:1503.03998v1 [physics.atom-ph].
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